Review of Radiology Rajat Jain, Virendra Jain
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1GENERAL RADIOLOGY

General Radiology1

 
GENERAL
Radiation: Energy that comes from a source and travel through some material or through space.
Can be:
(1) Ionizing
(2) Non-ionizing
Electromagnetic radiations
(a) UV-rays
(a) X-rays
(b) Visible rays
(b) ˠ-rays
(c) Infra red-rays
(c) Cosmic rays
(d) microwaves
Particulate radiations
(e) radiowaves
(a) α-rays
(b) β-rays
(c) Protons
(d) neutrons
Various diagnostic modalities and procedures and radiations
Ionizing Radiations
Non-Ionizing
X-Rays are used in
g-Rays are used in
MRI
1. CT-scan
PET
USG
2. Radiography
Bone-scan
Thermography
3. DEXA
Radionuclelide Scan
Doppler
4. IVP/IVU
SPECT
MRCP
5. HSG
6. Bronchography
7. ERCP
8. Fluoroscopy
zoom view
 
4X-Ray Tube
Wilhelm Conrad Roentgen, a German physicist, discovered X-rays on November 8, 1895.
  • Awarded the first Nobel Prize for Physics in 1901.
  • Considered as Father of radiology
  • International radiology day = 8th November
 
PARTS OF X-RAY TUBE
  • Glass Envelope: Provides protected and vaccumated environment to the tube.
    • Target window: It is the thinning of glass in lower part of glass envelope which allows X-ray to come out of tube
  • Cathode: Negatively charged electrode and consist of filament, supporting wires, and focusing cups
    • Filament:
An electric current is passed through the filament and it gets heated to a very high temperature (approx 2200°C) which makes the metal sufficiently violent to enable a fraction of free electrons to leave the surface despite net attractive pull of the lattice of the positive ions.
  • Anode: it is the positively charged electrode and the most important part is target, which is usually made of tungsten. The electrons are repelled by the negative cathode and attracted by the positive cathode. Because of the vacuum, they are not hindered in any way and bombarded the target with a velocity around half of the velocity of light. X-rays are produced when fast moving electrons are stopped by impact on a metal target. The kinetic energy of the electrons is converted into X-rays (1%) and into heat (99%).
    • The production of X-rays is largely because of two processes:
      • Interaction with the inner shell electron (k shell) a.k.a photoelectric effect resulting in productions of characteristics radiations.
      • Interaction with the nucleus a.k.a Bremsstrah-lung reaction. It is the most important reaction (80%) responsible for X-ray production in most of the tube except Mammography where photoelectric effect predominates
5Two types of anode are available:
  • Stationary
  • Rotating
 
FILTER
  • To block the low energy radiation
  • To decrease radiation dose to the patient without effecting image quality
  • Mostly made up of aluminum
  • The target window also acts as an inherent filter in the tube.
 
Collimator
  • Beam – restricting device
  • It restrict the scattered radiation
  • It also gives direction to the beam.
zoom view
 
Grid
  • Made up of lead
  • These are parallel arranged lead stripes placed between patient and cassette
  • Blocks scatter radiation from reaching to the film to improve image quality
  • Radiation dose to the patient is slightly increased as the useful radiation are slightly blocked by the grid.
Cassette: un Conventional Radiography, It is a Screen Film System
  • Screen: Calcium tungstate
  • It converts X-ray into light
 
Film
  • Made of photosensitive material, mostly silver bromide
  • Single coated film: If Agbr is present only on one surface, most commonly used
  • Double coated film is used in screen film system and in dental radiography.
 
Contrast
  • It is the ability to see something in relation to the background
  • Influenced by both KVP and MAS
  • Most important factor to influence contrast is KVP
6
Kilo volt peak (KVP)
Milli ampere second (MAS)
  • Related with voltage
  • Current x exposure time
  • Directly proportional to the energy of the beam
  • No effect on energy
  • Directly proportional to penetration
  • No effect on penetration
  • Inversly proportional to contrast
  • Determines the number of photon in a given area
  • Determines the background blackening
  • Directly proportional to contrast
RADIATION UNITS
 
 
Exposure Dose
  • The unit of radiation exposure is the Roentgen (R), defined as an amount of X-rays or gamma rays that will liberate a charge of 2.58 x 10–4 C/kg of air, under standard temperature and pressure
  • The SI unit for radiation exposure is Coulombs/kg. Change dose = 2.58 × 10–4 C/kg.
  • Conventional unit: Roentgen.
Dose
Conventional
SI Unit
1. Exposure dose
Roentgen
Coulombs/kg
2. Absorbed dose
Rad
Gray
3. Equivalent dose
Rem
Sievert
4. Effective dose
-
Sievert
5. radiactivity
Curie
Bacquerel
 
Radiation Absorbed Dose
  • The unit rad is defined as the radiation necessary to deposit energy of 100 ergs in 1 gram of irradiated material.
  • The SI unit for absorbed dose is Gray. One Gray is the amount of radiation necessary to deposit 1 joule of energy in 1 kg of material.
  • 1 Gray = 100 rad.
S no.
Types of radiations
quality factor
1
X, gamma, or beta radiation
1
2
Alpha particles and multiple charged particles
20
3
Neutrons
10
4
High energy protons
10
 
Equivalent Dose
It represents the biological impact of various types of radiation.
  • HT = WR × D, where HT is the equivalent dose, WR is the quality factor and D is the absorbed dose in Rads or Gray.
  • The radiation dose equivalent for which the unit was rem, has now been replaced by ‘Sievert’ in the SI units (systeme internationale).
  • 1 Sievert = 100 rems.
Tissue
Weighting factor
Gonads
0.2
Active bone marrow, Colon, Lungs, Stomach
0.12
Bladder, Breast, Esophagus, Liver, Thyroid
0.05
Bone surfaces, Skin
0.01
 
7Effective Dose
  • It assigns the various tissues/organs the proportional risk of stochastic effect to irradiation, compared to uniform whole body radiation by same equivalent dose.
  • It takes into account Tissue Weighting Factor (WT) which depends on the susceptibility of a particular tissue to the stochastic effect by radiation. It is also expressed in Sieverts.
  • HE = WT x HT, where HE is the effective dose, HT is the equivalent dose, and WT is the tissue weighting factor. Equivalent dose × Tissue wt-factor = effective dose.
SI unit: Sievert or milli sievert (mSv).
Harmful Effects of Radiation
  • Ionization of molecule- Free radical generation – damage to DNA.
    Note: M/C radiation side effect: Skin erythema.
  • Be directly proportional to dose, i.e. deterministic (certainty) effects
    • Related with certainty to a known dose of radiation
    • Dose threshold exists
    • Severity is dose related
    • e.g. skin effects, epilation, lens opacities, etc.
  • Not directly proportional to dose, i.e. stochastic effects.
    • Random events without threshold
    • Probability increases with dose
    • ‘ALL OR NONE’ phenomenon
    • Severity may not be dose related Dose-dependent/Deterministic side effect dose related severity dose threshold exist:
    • e.g. genetic side effects, teratogencity, mutations, etc.
Radiation protection for patient
10-Day Rule:
  • In a female of reproductive age group, any modality which gives ionising radiation should be performed with in first 10 days of menstrual cycle. (because there is no ovulation) – to prevent radiation to an undiagnosed pregnancy.
8ALARA approach: As low as Reasonably achievable radiation dose. For patient
Occupation workers
General public
Limit
Annual equivalents
Limit
Annual equivalents
ICRP
20 mSv/yr over 5 years
20 mSv
1 mSv/yr over 5 years
1 mSv
NCRP
Cumulative dose = Age in yrs x 10 mSv
50 mSv
5 mSv for 5-year period
1 mSv
AERB
100 mSv for 5-year period
30 mSv
1 mSv/yr for 5 years
1 mSv
Note: Radiation workers protect themselves from radiation by
  • Aprons (made of lead) thickness = 0.5 mm (according to AERB, it should have at least lead equivalance of 0.25 mm). increase thickness, increases the weight of the apron.
  • Lead-free apron: Tin, Antimony, and Bismuth.
  • TLD (thermoluminiscent dosimeter): It is a badge which monitors radiation used by radiation worker.
  • Checked every 3-month.
Amount of radiation exposure in a CT scan is dependent on the body part to be examined for example in CT head, it is 2.3 MSV and in CT abdomen it is 10 MSV.
A CT chest has radiation exposure of almost equal to 400 chest radiographs.
Digital Radiography
  • Digitizing conventional film
  • Computed radiography (CR)
  • Direct radiography (DR)
zoom view
 
9Computed Radiography
Conventional x-ray
Phosphor plate (PSP)
Latent image
Laser beam
Emission of light
Ultra-sensitive PMT
Electronic signal (digital)
CRT or Hard copy
 
Direct Radiography
X-ray
Patient
Flat panel detector
Electrical energy
Digital image
zoom view
Computed radiography (CR)
Digital radiography (DR)
Steps required
Advantages
Manipulation and positioning of image receptor for cross table projections is possible (useful in trauma)
Disadvantages
Mammography
Mammography uses lower kV (for higher image contrast) and higher mA (for shorter exposure times) compared with the technique for chest and abdominal examinations.
  • Small focal spot size (0.2–0.5 mm)
  • Beryllium Window
  • Target-Filter combination
    • Molybdenum (preferred); Rhodium; Tungsten
    • Mammography is usually done after 40 years because in Young age, breast has dense glandular parenchyma. Where it is difficult to see the lesion on mammography and glandular tissue is more sensitive to radiation.
    • USG is done for palpable legion and done to differentiate between solid and cystic lesion and to rule out breast abscess.
 
Two Views
  • Mediolateral (more important because of the more coverage area)
  • Craniocaudal
Note: Mammography has 10–40 times more radiation exposure than CXR.
BIRADS classification for mammography lesion:
(Breast imaging Reporting and systematic).
Grade
Interpretation
Management
0
Incomplete evalution
Complete it
1
Normal
None (CRS) continue routine screening
2
Benign calcified fibro
None (CRS)
3
Probably benign (< 2%)
Short follow-up
4
Suspicous
Indeterminate
5
Highly suspicious (> 15%)
Biopsy
6
Biopsy proven malignancy
To look for contralateral breast and multi- centric disease in the same breast
11
Ultrasound
Advantage
Disadvantage
  • Works on the principal of pizeoelectric effect: generation of sound waves by passing electricity. The electricity is passed through crystal, vibration of which generates sound waves.
  • Most commonly used crystal: Lead zirconate Titanate (PZT)
  • Medical used frequency: 2–20 MHz
  • A handheld transducer is applied to the body. This transducer both sends US waves into the body and receives reflected sound waves. This information is communicated via cable to the US scanner, and the image is generated on a monitor.
  • Real-time B-scans allow body structures which are moving to be investigated.
Note: Posterior structure better seen on transesophageal echocardiography.
Note: 5-layer of GIT seen on endoscopic US.
 
Clinical Transducer
For thick, deep body parts (Abdomen, obstetric) = 3.5 to 5 MHz.
For small body parts (Orbit, Thyroid, breast) = 7.5 to 10 MHz.
Intracavitary Transducers (7.5−20 Hz)
Endovaginal—Pelvis
Endorectal—Prostate
Transesophageal—Heart
Intravascular—Blood vessels
Endoscopic ultrasound—Pancreatic lesion, local staging of esophageal cancer, rectal cancer.
zoom view
 
Methods of Display
  • A-Mode (AMPLITUDE): Amplitude of the returning signals is plotted in a graphical form against their distance from transducer/depth. Commonly used for orbital biometry.
  • 12B-Mode (BRIGHTNESS): The amplitude of returning signals is given grey scale value based on a scale and is represented in the display to form a image of the scan plane. Most commonly used mode
  • M-Mode (MOTION): Detects any rhythmic motion occurring in the scan plane without any amplitude considerations. Used for valvulular morphology and motion.
 
Nomenclature of USG Images
  • Regions which reflect a lot of sound to the transducer are termed as echogenic or hyperechoic and by convention are viewed as bright or white areas.
  • Regions which do not reflect many sound waves are termed as hypoechoic and are viewed as dark or black areas.
  • The regions which have similar pattern to normal viscera or soft tissue are labeled as isoechoic.
Fat, calculus, bones, and stones are extremely echogenic on USG.
Fluid is absolutely black on USG and is termed as anechoic.
Posterior acoustic enhancement: Increased brightness beyond the objects that transmit a lot of sound waves, e.g. cysts.
Posterior acoustic shadowing has the opposite effect-decreased brightness seen beyond objects that reflect a great deal of sound. e.g. stones (refer to the image shown with B mode USG).
 
Ultrasonography is Investigation of Choice for
  • Hydrocephalus in infants
  • Retinal detachment
  • Minimal pleural effusion
  • Minimal pericardial effusion
  • CHPS
  • Gallstones
  • Acute cholecystitis (although theoretically HIDA scan is best)
  • Screening for Rotator cuff injuries (initial investigation)
  • Renal colic in pregnancy
  • Minimal ascites
  • Pararenal fluid collection post renal transplant
  • 13Obstetrics indications
  • Scrotal pathologies
  • Varicose veins
  • DDH (developmental dysplasia of hip)
Advance Applications of USG
 
Doppler
Doppler US: For moving structure, i.e. blood. It can be used for
  1. Presence/absence of flow
  2. Direction of flow
    Note: Blood flow toward the probe = Red
  3. Blood flow away from probe = Blue
    Note: Green color in Doppler is seen in turbulent blood flow due to mixing of red and blue
  4. Velocity of flow
  5. Pattern of flow
Doppler can be used to asses velocity of the blood flow which is important in assessing the stenosis in a vessel. As there is a stenosis, velocity increases at the point of stenosis.
Note: the vessel transducer angle should be less than 60 degree for proper velocity calculation on USG.
 
Pattern of Flow
Every vessel in the body has a specific pattern of flow which can be detected on Doppler
  • The peripheral arteries in the body has a high resistance due to peripheral vascular resistance and commonly shows triphasic pattern.
    • In case of arterial vasoconstriction, the peripheral resistance increase and flow becomes biphasic.
    • In case of peripheral vasodilation, the peripheral resistance decreases and flow becomes monophasic with pulsatility.
    • In case of arterial obstruction, there is significant loss of pressure and the flow distal to obstruction becomes monophasic (tardus pavus).
  • The visceral arteries (hepatic artery, renal artery, umbilical artery) in the body has low resistance and usually has low resistance flow, which is monophasic pattern with pulsation.
    • In cases of IUGR, as there is increase in the placental resistance, diastolic flow decreases 14and the S/D ratio increases (normal S/D ratio is < 2.5. It is increased to > 3.0 in IUGR).
    • When the placental resistance increases further, diastolic flow decreases further and a time comes when the diastolic force becomes equal to the placental resistance and no flow is seen in doppler, this is called as absent diastolic flow and is a sign of severe IUGR.
    • When the placental resistancee in increased further, there is reversal of flow in diastole and it is the sign of impending fetal death.
  • The veins in the body has continuous flow with out pulsations, a.k.a monophasic pattern without pulsations.
Elastography
Elastography is a new method which applies a distorting force (stress) to a tissue to move it by few millimetres, and create an image of the tissue’s response (strain) by comparing the two. In principle, any imaging method can be used: ultrasound has the advantage that the transducer can be used to apply the stress and of working in real time while magnetic resonance has also been used successfully.
For ultra-sound, the transducer is usually used to apply the stress manually and the strain is detected by tracking the speckle pattern as it changes during probe-induced distortion. The information used to create the images is similar to that gained from clinical palpation except that it is much more sensitive, especially to deeper structures. It has already found clinical applications in the breast, liver, and prostate, and is an active research area. The important uses of elastography include:
  • Assessment of degree of fibrosis in liver
  • To differentiate benign lesion from malignant lesion in liver, breasts, and prostate.
CT SCAN
The first CT machine used for clinical purposes, developed by the late Sir Godfrey Hounsfield, was installed at the Atkinson Morley Hospital, London, in the early 1970s. In the initial days only sequential acquisition was possible. In 1980s, the development of slip-ring technology enabled continuous revolution of the X-ray unit, which not only reduced the acquisition time per axial image to 1 sec, but also allowed helical 15data to be acquired. The next step of development occurred in the late 1990s, when detectors were split into multiple thin rows along the z-axis to permit acquisition of multiple sections simultaneously (multidetector CT). This decreased acquisition time yet further and made it possible to routinely use thin sections. As a result, multi-detector CT is nowadays able to provide near isotropic volumetric data sets in which spatial resolution is similar in all planes. 2000s saw the introduction of cardiac CT which is based on ECG-synchronization to freeze cardiac motion. The number of detector rows increased from 4 to somewhere between 64 and 320 rows, depending on the manufacturer. Rapid tube rotation (<0.3s) and dual-source systems with two X-ray tubes were developed to optimize cardiac imaging.
Basic Principle of CT is Linear Attenuation of X-Rays
  • CT No./HU value: Numerical value, given to a tissue depending on degree of attenuation of X-ray by that tissue
    Substance
    HU value
    Air
    –1000
    Fat
    –50 to –100
    Water
    0
    Muscle
    10–40
    Blood
    ~60
    Contrast
    130
    Bone
    >400
  • Slice thickness: Thickness of tissue scanned in one rotation
    zoom view
  • Increase in the pitch leads to decrease in the scan duration and radiation but reduces the scan quality.
  • Decrease in the pitch leads to increase in the scan duration and radiation but improves the scan quality.
16Advantage of Multislice CT/Multidetector C7
  • Faster acquisition
  • Coverage of larger area
  • Less movement artefacts
  • Isotropic multi-planar reformats
  • Improved vascular and cardiac imaging
  • Potential for faster throughput of patients.
 
DUAL SOURCE CT
zoom view
Two X-ray sources are used operating at different potential (Kv). The interaction between the two with tissues in the body is different and by comparing those differences in the two images, radiologists can differentiate, characterize, isolate and distinguish body tissues and fluid, leading to breakthroughs in medical imaging.
Applications
Bottom-line inference
Pulmonary nodule characterization
Fatty liver quantification for liver donors
Characterization of liver lesions
Characterization of an adrenal mass
Coronary in-stent stenosis
Bone subtraction for CTA post processing
Kidney-stone differentiation
Iron deposition in liver
One densitometry
Not useful
Useful, present application
Limited data
Useful (more validation needed)
Further data needed
Few data available
Useful results from initial patient studies
More data needed
MRI is superior to CT in this respect
Better tests are available
 
Advantage
  • Ability to scan at any heart rate
  • No need to use beta-blockers
  • Better temporal resolution - 83 ms
  • Trauma, oncology, obese patient
 
HIGH RESOLUTION CT SCAN (HRCT)
It is a type of CT technique done for some specific diseases like
  • Interstitial lung disease
  • Bronchiectasis
  • 17Miliary tuberculosis
  • Temporal bone evaluation
  • CSF leaks
 
Principle
  • Thin slice-thickness or collimation
  • Narrow field of view
  • Bone algorithm for image reconstruction
 
RADIATION DOSE IN A CT SCAN
CTDI (CT Dose Index): CT dose index (CTDI) is a standardized measure of radiation dose output of a CT scanner which allows the user to compare radiation output of different CT scanners.
CTDI represents the average absorbed dose, along the z-axis, from a series of contiguous irradiations. It is measured from one axial CT scan (one rotation of the X-ray tube), and is calculated by dividing the integrated absorbed dose by the nominal total beam collimation. The CTDI is always measured in the axial scan mode for a single rotation of the X-ray source, and theoretically estimates the average dose within the central region of a scan volume consisting of multiple, contiguous CT scans [Multiple Scan Average Dose (MSAD)] for the case where the scan length is sufficient for the central dose to approach its asymptotic upper limit.
 
Dose Length Product (DLP)
DLP (mGy-cm) = CTDIvol (mGy) x scan length (cm)
The DLP reflects the total energy absorbed (and thus the potential biological effect) attributable to the complete scan acquisition. Thus, an abdomen-only CT exam might have the same CTDIvol as an abdomen/pelvis CT exam, but the latter exam would have a greater DLP, proportional to the greater z-extent of the scan volume.
MRI
Magnetic resonance imaging (MRI) is a non-invasive method of mapping structure and various aspects of function within the body by producing images by the virtue of gyromagnetic property of protons, with the greatest advantage of not using ionizing radiation for imaging.
18Principle of MRI: Nuclear magnetic resonance: Purcell and Bloch
Invention of MRI: Lauterbeur and Mansfield
Functional MRI: Ogawa and Rosen
Magnetic resonance is a phenomenon whereby the nuclei of certain atoms, when placed in a magnetic field, absorb and emit energy at a specific or resonant frequency.
Nuclei suitable for MRI contain odd no of protons and/or neutrons. Almost all clinical MR images are produced using the simplest of all nuclei, that of hydrogen (comprising a single proton), which is present in virtually all biological material and exhibits relatively high MR sensitivity.
 
Parts of MRI
  • Maxwell Coil - Gradient coil used to create magnetic field gradients along the direction of the main magnetic field
  • Radio frequency coils: to generate stronger magnetic field along the scan field.
  • Faraday cage/shield/Hoffman Box – blocks out external static electric fields. Made up of copper [Cu]
  • Superconductors – Electromagnets (determines the strength of magnet) measured in tesla.
 
How Image is Acquired in MRI
  • In the absence of magnetic field all protons have random movement
  • Under the influence of magnetic field, alignment of proton takes place
  • Realignment occurs under the influence of radiofrequency pulse
  • After switching off the radiofrequency pulse, the atoms return to their original position and release energy in the form of electrical voltage signal
  • When proton releases energy to surrounding lattice, it is called as spin lattice relaxation or T1 relaxation
  • When proton releases energy to the surrounding spin, it is called as spin-spin relaxation or T2 relaxation
  • This electrical signal (produced in receiver coil) is digitized and analyzed in a computer, to produce MR images.
19Using T1 and T2 relaxation time,two types of images are broadly acquired using this principal; T1 weighted MR and T2 weighted MR.
 
Contraindications of MRI
It is a common saying that MRI means “metal results in injury” however it is not true in current scenario and there are many metallic devices compatible with MRI and students should be aware of those, particularly devices made up of TITANIUM which are very much compatible with MRI.
Few important devices or conditions where MRI is usually contraindicated are:
  • Cardiac pacemakers
  • Cochlear implants
  • Intraoccular Metallic foreign body
  • Electronically, magnetically, and mechanically acti-vated implants
  • Ferromagnetic or electronically operated active devices like defibrillators
  • Aneurysmal clips
  • Prosthetic heart valves
  • Insulin pumps and nerve stimulators
  • Stapedial implants
  • Claustrophobia
  • First trimester of pregnancy
Note: even in the devices mentioned above, MRI can be performed depending upon the make of the device, e.g. some pacemakers are MRI compatible at lower strength magnet, i.e. up to 1.5 Tesla so it is always advised to check the compatibility of the device before saying NO to MRI.
 
MRI can be Safely Performed in
  • Orthopedic implants (usually made of titanium). in cases of implants made of stainless steel, MRI can still be done however, heating is a problem so it is usually recommended for a shorter time and on a lower strength magnet. In permanent tattoos also because of the heavy metal dyes, heating may be an issue.
  • Pregnancy after 1st trimester. Safety profile of MRI is not established in first trimester so, should not be done in 1st trimester.
  • 20Cholecystectomy clips, sternal sutures
  • IUCD
  • Non metallic foreign bodies
  • Breast implants (investigation of choice is MRI)
  • Pediatric patients (MRI is usually preferred because of lack of ionising radiation however, it is usually done under sedation due to uncooperative behavior
  • Coronary stents usually drug eluting stents are used and MRI can be done after 3 months.
zoom view
T2W axial image of brain
SPECIAL SEQUENCES OF MRI
 
FLAIR: Fluid Attenuated Inversion Recovery Sequence (Flair = T2-water)
zoom view
T1W axial image of brain
It is type of T2 weight MRI where the water is suppressed to make pathology more visible. it is predominantly used at places where water is the confounding factor and limiting the contrast, e.g. brain.
 
Uses
  • For better appreciation of pathologies in brain (most of the pathology being white
  • To differentiate arachnoid cyst from epidermoid cyst (arachnoid is a CSF filled cyst and becomes black on FLAIR, where as epidermoid is not).
zoom view
FLAIR coronal image of brain
 
STIR (Short Tau Inversion Recovery Sequence)
STIR can be easily remembered as T2- Fat means patho-logy will remain white whereas Fat will become black.
It is predominantly used at places where fat is the confounding factor and limiting the contrast, e.g. rest of the body and musculoskeletal imaging.
 
Uses
zoom view
STIR coronal image of pelvis
Identification of bone marrow edema in diseases like stress fracture, avascular necrosis, Perthes disease, etc. for better appreciation of diseases in body where presence of Fat is reducing the contrast due to background whiteness.
 
Contrast Enhanced MRI (CEMRI)
Gadolinium containing compunds are most commonly used contrast agents in MRI.
21Presence of gadolinium caused reduction in both T1 and T2 relaxation time which leads to increases in signal on T1-weighted MRI and decreases in signal on T2 weighted MRI. As human eyes appreciate white color better, post contrast MRI images are always acquired as T1-weighted MRI.
 
MRCP (Magnetic Resonance Cholangio-pancreatography)
MRCP images are heavily T2-weighted sequences which demonstrate fluid-filled structures as areas of very high signal intensity and are very commonly used to show the biliary and pancreatic ducts in magnetic resonance cholangiopancreatography (MRCP). Being non-invasive and no need of external contrast, it is considered as a preferred investigation to diagnose pathologies of biliary duct and pancreatic duct in comparison to diagnostic endoscopic retrograde cholangiopancreatography (ERCP).
 
MR Angiography
Visualization of vessels using MRI.
This technique is unique due to the fact that the beautiful angiographic images can be obtained without external administration of contrast. The technique used in MRI for angiography is called TOF (time of flight). it is a very commonly used angiographic technique now days and is the preferred imaging technique to assess renal artery stenosis and an intracerebral aneurysm. It is also preferred investigation to look for carotid artery stenosis.
 
Diffusion Weighted MRI (DWI)
It is a special type of MRI technique which assesses the random (brownian) motion of the water molecule, which is a normal phenomenon. In some disease, there is reduction in the brownian motion of the water molecule, which is called as restricted diffusion. Areas of restricted diffusion are seen as white on DWI.
 
Common Causes of Restricted Diffusion
  • Acute ischemic infarct (most common cause)
  • Abscess
  • High cellular tumors
  • Epidermoid cyst
 
22Gradient Echo Images
Used to see calcification and hamorrahge on MRI.
 
Spectroscopy
It is a new technique of MRI to assess certain metabolites in the body tissues. Metabolic changes occur earlier than the structural changes and Since routine MRI picks up structure changes, new techniques have been developed for the early diagnosis of the diseases. Commonly studied metabolites are
  • N acetyl asperate (NAA)
    • neuronal marker
    • assess neural integrity
    • decrease in most of the brain disorders except Canavan’s disease
  • Choline
    • present in cell membrane
    • marker of cell membrane turnover
    • increased in malignancies
  • Creatine
    • Present in ATP
    • Marker of energy stores
    • Reference marker, used to see the relative concentration of metabolites as it is a stable workers and doesn’t change much during diseases.
  • Lipid peak. Tubeculomas are rich in caseous necrosis and presence of lipid peak is a useful way to differentiate tuberculoma from cysticercosis which will be seen in tuberculoma and not in neurocysticercosis.
 
MRI is Usually a Preferred Investigation for
  • For all brain tumors (contrast enhanced MRI)
  • For extent of pancoast tumor (due to neural involvement)
  • Ventricular function (most accurate investigation)
  • Posterior mediastinal mass (neurogenic in origin)
  • Bony metastais in spine (bone scan is preferred at other places)
  • Chronic subarachnoid hemorrahge
  • Traumatic paraplegia due to neural involvement
  • Extent of pott’s spine (for diagnosis Bx is the best)
  • Stress fracture, Perthe’s disease, avascular necrosis, early osteomyelitis (bone marrow edema)
  • 23Pregnancy after first trimester (not for obstetrics problem but for other abdominal pathologies). For antenatal scanning, USG is still preferred over MRI
  • Spinal cord pathologies
  • Gynecological malignancies
  • Uterine anomalies
MRI
CT Scan
USG
Ionizing radiation
No
Yes
Moderate - high radiation
No
Principal
Magentic moment of protons (gyro magnetism
Linear attenuation of X-rays
Pizeo elctric effect
Time for scanning
10 minutes to hour
Less than a minute
Variable
Bony details
Cortical bone is not well seen but bone marrow is very well seen
Cortical bone is very well seen
Not well seen. Structure posterior to bone are not seen due to acoustic shadowing
Soft tissue structure
Very well seen and differentiated
Seen but not well characterized
Very well seen
Multiplanar capability
Images can be acquired in any planes
Scans are acquired in axial planes and later can be reconstructed in any planes on MDCT
Yes depending on the position of the probe
Real time imaging
Mostly not
No
Yes
Portable
Usually not
Usually not
Yes
Cost
Very costly
Costly
Cheap
Uses
  • For neural tisuues
  • For bone marrow
  • Cartilage
  • Ligaments
  • Tendons
  • Soft tissues
  • Cortical bone
  • Acute hematoma in brain
  • Calculi
  • Calcifications
  • Air
  • Guiding biopsies in lung
Fluid containing structures
Guidning biopsies
24CONTRAST AGENTS IN RADIOLOGY
 
MRI CONTRAST AGENTS
Gadolinium chelates are most commonly used contrast agents in MRI studies. Due to lack of iodine, these compounds are relatively safe without any significant risk of anaphylaxis or allergic reactions unlike iodinated contrasts.
Being paramagnetic in nature, they predominantly acs by reduction of the T1 and T2 relaxation time.
The most common side effects of these agents are mild headache and a metallic taste.
Pregnant patients should not receive gadolinium chelates. Many of the agents are known to be able to cross the blood-placental barrier, and their effect on the fetus is unknown.
Nephrogenic systemic fibrosis is a scleroderma like dermatopathy that is known to precipitate due to use of gadolinium chelates in patients with compromised renal function.
Risk factors are
  • Increased dose of gadolinium
  • Repeated doses
  • Use of linear gadolinium chelates particularly gadodiamide (omniscan).
 
European Guidelines for Prevention of Nephrogenic Systemic Fibrosis
Patients at a high risk for nephrogenic systemic fibrosis
  • Chronic kidney disease (CKD) 4 and 5 (GFR <30 mL/min), including those who require dialysis and those who have reduced renal function who have had or are awaiting renal transplant.
    Low Risk
  • CKD 3 (GFR 30–59 mL/min) and
  • Children younger than 1-year-old, because of their immature renal function.
    Not at risk
  • Normal renal function
    Contrast agents with highest risk for NSF
  • Gadodiamide
  • Gadopentetate dimeglumine
  • Gadoversetamide
25The use of these agents is contraindicated in patients who have CKD4 and 5 (GFR <30 mL/min), including those who require dialysis and patients who have reduced renal function who have had or are awaiting kidney transplantation.
They should be used with caution in patients who have CKD 3 (GFR 30–59 mL/min) and children younger than 1-year-old.
Serum creatinine (eGFR) levels should always be measured before using these three agents.
The intermediate-risk group includes the following agents:
  • Gadobenate dimeglumine
  • Gadofosveset trisodium
  • Gadoxetate disodium
The determination of eGFR levels is not mandatory before using these agents.
The low-risk group includes the following agents:
  • Gadobutrol
  • Gadoterate meglumine
  • Gadoteridol
The measurement of eGFR levels before administration is not mandatory.
 
USG Contrast Agents
  • Gas filled microbubbles with diameter ranges from 0.1 to 10 μm.
  • Inert gas enclosed in a phospholipidic, albumin, or polymer shell.
 
MOA
  • Increases the backscattering echo intensity, proportional to the change in acoustic impedance between the blood, and the gas making the bubbles.
  • Seen as a increase in color, power and spectral Doppler signal strength or gray scale image intensity.
    e.g. Albumex, levovist, echogen.
 
Uses
  • In the liver
    • Characterization of focal liver lesions
    • Can detect flow in portal vein or collaterals in patients with cirrhosis
    • Improves evaluation of TIPSS stent for patency and stenosis
    • 26Small intrahepatic collaterals in patients with Budd-Chiari syndrome
  • Better visualization of vessels in doppler.
Note: At least 100 mL of air required to cause air embolism but in USG-contrast we give only 0.5 mL air.
Iodinated Water Soluble Contrast Media
Iodinated water soluble contrast agents
Name of the contrast agent
Ionic monomers
Ionic dimers
Non-ionic monomers
Non-ionic dimers
Iodine particle ratio
3:2
6:2
3:1
6:1
Osmolality
HOCM
LOCM
LOCM
IOCM
e.g.
(UROGRAFFIN, GASTROGRAFFIN)- Diatrizoate -Iothalamate
-Ioxaglate
-Iohexol (IOHEXOL)
-Iomeron
-Iopamidol
-Ipromide
-Ioversol
-Xenetix
-Iodixanol
(VISIPAQUE)
Uses
Preferred for non vascular use
Not available
Most preferred contrast for vascular administration
-The best for patients with asso- ciated renal disease
 
Contrast Reactions
  • Idiosyncratic anaphylactoid reactions (DOC is adrenaline)
  • Non-idiosyncratic reactions.
 
Contrast-induced Nephropathy
Contrast-induced nephrotoxicity (CIN) is a sudden deterioration in renal function following the recent intravascular administration of iodinated contrast medium in the absence of another nephrotoxic event.
 
Diagnosis
There are no standard criteria for the diagnosis of CIN; criteria used in the past have included percent change in 27the baseline serum creatinine (an increase of variously 25% to 50%) and absolute elevation from baseline serum creatinine (e.g., an increase of variously 0.5 to 2.0 mg/dL). One of the most commonly used criteria has been an absolute increase of 0.5 mg/dL.
 
Pathogenesis
The exact pathophysiology of CIN is not understood and the Nephrotoxicity of contrast media is likely to be due to decreased renal perfusion due to renal vasoconstriction due to high osmolality of the contrast media.
Symptoms: Usually asymptomatic. Creatinine peaks in 3–5 days. In severe oliguric patients: peaks in 5–7 days
 
Risk Factors for CIN
  • Pre-existing renal impairment (S.creat > 1.3 mg/dL, GFR < 60 mL/min)
  • Dehydration
  • CHF
  • Use of nephrotoxic drugs (NSAID, aminoglycosides)
  • Hypersensitivity disease (multiple myeloma)
  • Hypertension
  • Hyperuricemia (as in active gout)
  • Proteinuria (> 0.5 gm/dL)
  • DM, age > 70 years
 
Prevention of Contrast Induced Nephropathy in High Risk Patients
  • Avoidance of Iodinated Contrast Medium:
  • Contrast media selection: Increased osmotic overload on the diseased kidney is considered to be the major etiology of CIN so; these can be significantly reduced by substituting IOCM/LOCM for the very hypertonic HOCM.
  • Hydration: Adequate hydration is considered to be the single most effective way to prevent CIN. The ideal infusion rate and volume is unknown. One possible protocol would be 0.9% saline at 100 mL/hr, beginning 6 to 12 hours before and continuing 4 to 12 hours after intravascular iodinated contrast medium administration. Oral hydration has also been utilized, but with less demonstrated effectiveness.
  • Sodium bicarbonate: It has been found to be useful in prevention from CIN according to some studies.
  • N Acetyl Cystine: The role is controversial. There is evidence that it reduces serum creatinine in normal 28volunteers without changing cystatin-C (cystatin-C is reported to be a better marker of GFR than serum creatinine). This raises the possibility that N-acetylcysteine might be simply lowering serum creatinine without actually preventing renal injury. N-acetylcysteine should not be considered a substitute for appropriate pre-procedural patient screening and adequate hydration.
  • Diuretics: Mannitol and Furosemide: There is no reported benefit and neither mannitol nor furosemide is recommended for CIN risk reduction.
  • Other Agents: The evidence for other theoretically renal-protective medications, such as theophylline, endothelin-1, and fenoldopam is even less convincing. Use of these agents to reduce the risk of CIN is not recommended.
  • hemodialysis has not shown to be of much effect in prevention from CIN. hemofillteration has some benefit.
 
Patient on Metformin
Remember: Metformin + Chronic Renal Insufficiency + I/v contrast = Lactic Acidosis
Category 1
Category 2
Category 3
Normal renal function with no known co-morbidities
No reason to discontinue Metformin
Normal renal function with known co-morbidities +, then suspend Metformin for 48 hrs
If the patient had normal renal function at baseline, was clinically stable, and had no intercurrent risk factors for renal damage (e.g. treatment with aminoglycosides, major surgery, heart failure, sepsis, repeat administration of large amounts of contrast media), metformin can be restarted
Renal dysfunction then suspend Metformin for 48 hrs and restart only if repeat KFT is normal
29BARIUM STUDIES
Barium sulfate is commonly used for evaluation of GIT because it is an inert substance and not absorbed from the GIT. It also causes mucosal coating and helps in assessing mucosal details.
  • Barium swallow: done for dysphagia to rule out stricture or mass) replaced by endoscopy for these indications. Now commonly done for motility disorder.
  • Barium meal: abdominal pain (to rule out gastric or duodenal ulcer disease), replaced by endoscopy.
  • Small bowel follow-through: diarrhea or constipation (to rule out Crohn’s disease or other small bowel pathologic conditions). Replaced by barium enteroclysis commonly called as small bowel enema and now a days with another technique called as CT enterography.
  • Barium enema: rectal bleeding (to rule out a polyp or mass). Still performed but at some places, CT virtual colonoscopy is done.
 
Contraindications of Barium Sulfate in GIT Studies
  • Small bowel obstruction (ionic contrast are preferred)
  • Intestinal perforation (ionic contrasts are preferred)
  • Tracheoesophageal fistula (non ionic contrasts are preferred because of the risk of pulmonary edema with ionic contrast due to very high osmolarity).
 
Myelography
  • Contrast agent is injected into the SUBARACHNOID space following a lumbar puncture.
  • Non ionic contrast agents are preferred due to the risk of arachnoiditis with previously used contrast agents.
  • Most common side effect of myelography is headache
  • Most severe side effect is arachnoiditis.
30QUESTIONS
  1. CT or Hounsfield numbers depend upon:
    1. Mass density
    2. Electron density
    3. Atomic number
    4. Atomic mass
  1. Which of the following statement is true?
    1. By reducing KVP by 50% radiation dose is reduced to half
    2. In pediatric patients dose should be reduced
    3. CT dose index is not useful for control exposure in multislice CT
    4. kV has no control over CT dose index
  1. Investigation of choice in parathyroid pathology is:
    1. CT scan
    2. Gallium scan
    3. Thallium scan
    4. Tc-thallium subtraction scan
  1. Which artery is dissected most commonly following arteriography by femoral route?
    1. Celiac trunk
    2. Superior mesenteric artery
    3. Inferior mesenteric artery
    4. Gastroduodenal artery
  1. Earliest investigation for diagnosis of Ankylosing spondylitis:
    1. MRI STIR sequence
    2. Bone scan
    3. CT scan
    4. X-ray
    5. USG
  1. How much area is covered by spiral CT in 30 seconds?
    1. Entire organ
    2. Entire abdomen
    3. Entire trunk
    4. Whole body
  1. In CT scan, Hounsfield units depends on:
    1. Electron density
    2. Mass density
    3. Effective atomic number
    4. Linear attenuation coefficient
  1. X-ray view of choice for lumbar spondylosis is/are:
    1. PA view
    2. PA view
    3. Lateral view
    4. Left oblique view
    5. Right oblique view
  1. High resolution CT of the lung is a specialized CT technique for greater detail of lung parenchyma and it utilizes:
    1. Special lung filters
    2. Thick collimation
    3. Bone algorithm for image reconstruction
    4. Large filed of view
  1. Which of the following is non-ionising radiation?
    1. X-ray
    2. β-rays
    3. α-rays
    4. Microwave
    5. g-rays
  1. Time sector scanning of neonates is preferred because of the following reason. Most practical reason:
    1. Open fontanelles
    2. Inexpensive
    3. Children more co-operative
    4. Better resolution
  1. PET stands for:
    1. Positive electron tomography
    2. Proton-electron therapy
    3. 31Positron emission tomography
    4. Photon emmitting tomography
  1. What modification is needed for proper radiographic image in a heavy bony built person?
    1. ↑ed ma
    2. ↑kvp
    3. ↑ed exposure time
    4. ↑ed developing time
  1. Maximum radiation exposure occurs in:
    1. Bone scan
    2. X-ray
    3. MRI
    4. CT scan
  1. USG is definitive investigation of:
    1. Vasa previa
    2. Abruption placenta
    3. Placenta previa
    4. Imperforate hymen
  1. Investigation of choice in whole body imaging in metastasis is:
    1. Magnetic resonance imaging
    2. Angiography
    3. Venography
    4. CT scan
  1. Gyromagnetic property of proton is seen in:
    1. MRI
    2. CT
    3. PET scan
    4. USG
  1. Most reliable test for spinal tuberculosis:
    1. Raised ESR
    2. PPD skin test
    3. CT guided biopsy
    4. MRI
  1. In magnetic resonance imaging, paramagnetic substances cause:
    1. Shortening of both T1 and T2 relaxation times
    2. Shortening of T2 relaxation time only
    3. Shortening of T1 relaxation time only
    4. No effect on T1 or T2 relaxation times
  1. SI unit of absorbed dose of radiation is:
    1. Roentgen
    2. Gray
    3. Sievert
    4. Coulomb
  1. Frequency of ultrasound waves in USG:
    1. 2000 Hz
    2. 5000 Hz
    3. <2 MHz
    4. >2 MHz
  1. Which of the following is a non-Iodine containing contrast?
    1. Gadolinium
    2. Visipaque
    3. lopamidol
    4. Diatrizoate
  1. In computed tomography (CT), the attenuation value are measured in Hounsfield units (HU). An attenuation value of ‘0’ (zero) HV corresponds to:
    1. Water
    2. Very dense bone structure
    3. AIR
    4. Fat
  1. The best contrast to perform an lVU in the contemporary era is:
    1. Iodinated ionic water soluble contrast
    2. Iodinated nonionic water soluble contrast
    3. Gadolinium based contrast
    4. Lipidol
  1. All of the following are true about iodinated intravascular contrast media except:
    1. They are used in digital subtraction angiography
    2. They are radio-opaque
    3. They can cause anaphylactic reactions
    4. They are used in magnetic resonance imaging
    5. They are excreted mainly by the kidneys
  1. 32BIRADS stands for:
    1. Breast Imaging reporting and data system
    2. Best imaging reporting and data system
    3. Brain imaging reporting and data system
    4. Best imaging reporting and data system
  1. Doppler effect is due to:
    1. Change in frequency in relation to the movement of source or observer
    2. Change in attenuation
    3. Change in absorption
    4. Change in reverberation
  1. Diagnosis of pulmonary embolism is primarily made by:
    1. Multidetector CT contrast
    2. Angiography
    3. Ventilation perfusion scan
    4. CXR
  1. Alpha particle is similar to:
    1. Electron
    2. Proton
    3. Neutron
    4. Helium nucleus
  1. Neural tube defect is best detected by:
    1. USG
    2. Chromosomal analysis
    3. Amniocentesis
    4. Placentography
  1. Light rays and X-rays have same:
    1. Velocity
    2. Wavelength
    3. Energy
    4. Frequency
  1. The magnetic field in a MRI machine is measured in:
    1. Hounsfield curt
    2. Tesla
    3. Watt/sec
    4. None of the above
  1. The basic principle behind ultrasound probe technology is:
    1. Piezoelectric effect
    2. Photoelectric effect
    3. Calorimetric effect
    4. Raman effect
  1. PACS in medical imaging stands for:
    1. Portal archiving common system
    2. Photo archiving computerized system
    3. Picture archiving communication system
    4. Planning archiving communication scheme
  1. Wavelength of light is:
    1. 400-700 nm
    2. SOD-800 nm
    3. 700-900 nm
    4. 300-600 nm
  1. CAT was invented by:
    1. Hounsfield
    2. Roentgen
    3. Cormack
    4. Tesla
  1. The study using barium for small intestine is known as:
    1. Barium meal follow through
    2. Barium swallow
    3. Barium enema
    4. None of the above
  1. Which is not echogenic while doing ultrasonography?
    1. Bile
    2. Gas
    3. Bone
    4. Gallstones
  1. The dark areas in a conventional radiographic film are due to particulate deposits of:
    1. Carbon
    2. Iron
    3. Silver
    4. Copper
  1. IV contrast is not used in:
    1. CECT
    2. MRI
    3. IVP
    4. Myelography
  1. Maximum scattering in X-ray plate occurs in:
    1. Carbon
    2. Mercury
    3. H+
    4. Ca++
  1. 33Radiation produced by nuclear decay/disintegration:
    1. Gamma rays
    2. X-rays
    3. Alpha rays
    4. Cosmic rays
  1. Contrast used in CT:
    1. Gadolinium
    2. Technitium
    3. Iodine
    4. Chromium
  1. Investigation of choice to see gallbladder:
    1. CT
    2. USG
    3. Plain X-ray
    4. Oral cholecystogram
  1. Radiocontrast is contraindicated in all except:
    1. Renal failure
    2. History of previous severe allergic reaction
    3. Dehydration
    4. Morbid obesity
  1. The wavelength of X-ray is:
    1. Greater than that of light
    2. Lesser than that of light
    3. Equal to that of light
    4. None of the above
  1. Slice of tissue X-rays is:
    1. Tomography
    2. Mammography
    3. Contrast studies
    4. All of the above
  1. Contrast agent used in PET scan is:
    1. FDG
    2. Gallium
    3. Gadolinium
    4. Iodine
  1. In which of the following form of imaging, harmonic imaging is related:
    1. Sonography
    2. Digital radiography
    3. MRCP
    4. Nuclear imaging
  1. Not a contraindication to MRI is:
    1. Cochlear prosthesis
    2. Foley’s catheter
    3. Penile implants
    4. Metallic intraocular implants
  1. The CT scanner room are coated with:
    1. Lead
    2. Glass
    3. Tungsten
    4. Iron
  1. “Time of Flight” technique is employed in:
    1. Spiral CT
    2. MR angiography
    3. CT angiography
    4. Digital radiography
  1. Which of the following is not ionizing?
    1. Beta radiation
    2. Alpha radiation
    3. Gamma radiation
    4. UV radiation
  1. USG wave travel in human body at the rate of:
    1. 1500 m/s
    2. 2500 m/s
    3. 3500 m/s
    4. None of above
  1. Rad is burned to produce:
    1. 10 ergs/g
    2. 100 ergs/g
    3. 0.1 erg/g
    4. 1000 ergs/kg
  1. Ultrasound frequency used for diagnostic purposes in obstetrics:
    1. 1-20 MHz
    2. 20-40 MHz
    3. 40-60 MHz
    4. 60-80 MHz
    5. 80-100 MHz
  1. All of them use nonionizing radiation except:
    1. Ultrasonography
    2. Thermography
    3. MRI
    4. Radiography
  1. X-rays are produced when:
    1. Electron beam strike the nucleus of the atom
    2. 34Electron beam strikes the anode
    3. Electron beam reacts with the electromagnetic field
    4. Electron beam strikes the cathode
  1. X-rays are modified:
    1. Protons
    2. Electrons
    3. Neutrons
    4. Positrons
  1. Contrast in X-rays is predominantly dependent on:
    1. KV
    2. MA
    3. Duration of exposure
    4. Distance between source and object
  1. Negative contrast medium is:
    1. Difficult for X-rays to penetrate
    2. Easily penetrated by X-rays
    3. High in atomic number
    4. Opaque to X-rays
  1. The contract used for MRI includes:
    1. Perfluorocarbons
    2. Ferric ammonium citrate
    3. Gadolinium diethylmethylamine
    4. All of the above
  1. NMR based in the principle of:
    1. Electron beam
    2. Proton beam
    3. Magnetic field
    4. Neutron beam
  1. MRI is not better than CT for detection of:
    1. Ligament injury
    2. Soft tissue tumors
    3. Meningeal pathology
    4. Calcified lesions
  1. All of the following about MRI are correct except:
    1. MRI is contraindicated in patients with pacemakers
    2. MRI is useful for evaluating bone marrow
    3. MRI is better for calcified lesions
    4. MRI is useful for localizing small lesions in the brain
  1. Patient with a metallic foreign body investigation is not done:
    1. MRI
    2. USG
    3. X-ray
    4. CT
  1. The EEG cabins should be completely shielded by continuous sheet of wire mesh of copper to avoid the noise from external electromagnetic disturbances. Such a shielding is called as:
    1. Maxwen cage
    2. Edison’s cage
    3. Faraday cage
    4. Ohm’s cage
  1. Ionizing radiation is the substance which ionizes the atoms when it passes. It is harmful for biological matter. Which of the following is non-ionizing modality?
    1. Conventional X-rays
    2. Computerized tomography
    3. Magnetic resonance imaging
    4. Isotopic scanning
  1. Investigation of choice for focal neurologic deficit in emergency room is:
    1. CT
    2. MRI
    3. Lumbar puncture
    4. USG
  1. Fracture of nose, which view X-ray taken:
    1. Waters view
    2. Caldwdl’s view
    3. Lateral view
    4. Occlusive anterior view
  1. Which of the following statements about contrast in radiography is true?
    1. Ionic monomers have three iodine atoms per two particles in solution
    2. High osmolar contrast agents may be ionic or nonionic
    3. Gadolinum may cross the blood brain barrier
    4. Iohexol is a high osmolar contrast media
  1. 35Doppler effect results from change in:
    1. Amplitude of sound
    2. Frequency of sound
    3. Direction of sound
    4. None of the above
  1. Investigation of choice for subdural hemorrhage is:
    1. Angiography
    2. NCCT
    3. CECT
    4. MRI
  1. Which of the following contrast agents is preferred in a patient with decreased renal function to avoid contrast nephropathy?
    1. Acetylcysteine
    2. Fenoldopam
    3. Mannitol
    4. Low osmolar contrast
  1. High resolution computed tomography of the chest is the ideal modality for evaluating:
    1. Pleural effusion
    2. Interstitial lung disease
    3. Lung mass
    4. Mediastinal adenopathy
  1. Investigation of choice in congenital uterine anomaly is:
    1. MRl
    2. CT
    3. HSG
    4. Hysteroscopy
  1. Best investigation for pericardial effusion is:
    1. MRI
    2. CT
    3. X-ray
    4. Echocardiography
  1. Barium swallow is used for:
    1. Colon
    2. Esophagus
    3. Duodenum
    4. Jejunum
  1. Rhese view is used for:
    1. Superior orbital foramen
    2. Inferior orbital foramen
    3. Optic foramen
    4. Sella turcica
  1. Becquerel is equal (disintegration/sec) to:
    1. 3.7 × 1010
    2. 2.7 × 1010
    3. 1.7 × 1010
    4. 3.7 × 10-2
    5. 1
  1. Which one of the following has the maximum ionization potential?
    1. Electron
    2. Proton
    3. Helium ion
    4. Gamma-Photon
  1. Which of the following techniques uses Piezo-electric effect?
    1. MR spectroscopy
    2. Xeroradiography
    3. Ultrasonography
    4. Conventional tomography
  1. Investigation of choice in choledocholithiasis:
    1. CT
    2. PET scan
    3. USG
    4. MRCP
  1. Investigation of choice for DVT is:
    1. Doppler USG
    2. Angiography
    3. CT scan
    4. MRI
  1. A 8-year-old child was injected contrast in hand for CECT chest. Immediately he developed swelling in the arm which gradually increased. After 4 hours, there was numbness and pain, and he was not allowing the doctor to flex the hand. Pulse is present. What should be done?
    1. High dose prednisolone
    2. Arterial thrombectomy
    3. Immediate fasciotomy
    4. Angiography
  1. Radionuclide scan done for parathyroid adenoma is:
    1. Sestamibi
    2. Iodine-123 scan .
    3. 99m-Tc-sulphurcolloid
    4. Galliun scan
  1. 36Use of water-soluble contrast medium is:
    1. Constipation
    2. Perforation
    3. Ileocecal tuberculosis
    4. Gastroesophageal reflux
  1. Which of the following liver metastasis appears hypoechoic on ultrasonography?
    1. Breast cancer
    2. Colon cancer
    3. Renal cancer
    4. Mucinous adenocarcinoma
  1. X-ray artifact is:
    1. A radiolucent area
    2. Any abnormal opacity in the radiograph
    3. Produced when patient moves while taking the shoot
    4. Any of the above
  1. Decubitus view is useful in diagnosing:
    1. Pleural effusion
    2. Pleural effusion with dependent hemithorax
    3. Pericardial effusion
    4. Middle lobe consolidation
  1. X-rays were discovered by:
    1. Godfrey Hounsfield
    2. Roentgen
    3. Coulomb
    4. Sievert
  1. Grid is a device used for:
    1. Reducing scattered radiation
    2. Reducing patient’s exposure time
    3. Reducing the contrast of the X-ray
    4. All of the above
  1. The active ingredient of X-ray film is:
    1. Silver chloride
    2. Silver bromide
    3. Silver nitrate
    4. Gold chloride
  1. The best X-ray view for minimal pleural effusion:
    1. AP
    2. PA
    3. Lateral
    4. Lateral decubitus
  1. Half life of Tc99 is:
    1. 6 hours
    2. 3 days
    3. 10 months
    4. 12 years
  1. Interlobar pleural effusion can be detected in best way in:
    1. Lateral decubitus
    2. Reverse lordotic
    3. Lateral oblique
    4. Posterior oblique
  1. Piezoelectric crystals are made use of in which modality that is safe from radiation also?
    1. MRI
    2. US
    3. CT
    4. All of above
  1. Radioisotope used in PET scan is:
    1. Tecnnetium 99m
    2. Iodine 123
    3. Iodine 131
    4. Fluoride 18
  1. Most common radiological feature of sarcoidosis in Indian patients:
    1. Normal chest X-ray
    2. Bilateral hilar lymphadenopathy
    3. Bilateral hilar lymphadenopathy with parenchymal infiltrate
    4. Only parenchymal infiltrate
  1. Which one of the following imaging modalities is most sensitive for evaluation of extra-adrenal Pheochromocytoma?
    1. Ultrasound
    2. CT
    3. MRI
    4. MIBG scan
  1. The diagnostic procedure not done in case of pheochromocytoma:
    1. CT scan
    2. MRI
    3. FNAC
    4. MIBG scan
  1. 37True about electromagnetic radiations are all except:
    1. Pair production occur for low energy
    2. Infrared is an EM radiation
    3. Compton scattering occur for intermediate energy
    4. X-ray is EM radiation
  1. Earliest diagnosis of cerbral infarct can be done by:
    1. NCCT
    2. CECT
    3. Diffusion weighted MRI
    4. FLAIR MRI
  1. Best investigation for diagnosing abdominal aortic aneurysm is:
    1. USG
    2. CT angiography
    3. Classical radiography
    4. Noncontrast CT scan
  1. Fluorescein angiography is used to examine:
    1. Ciliary vasculature
    2. Retinal vasculature
    3. Corneal vasculature
    4. Conjunctival vasculature
  1. Hounsfiled unit of fat ranges from:
    1. 1 to 20
    2. 100–1000
    3. -10 to –100
    4. 100–300
  1. Chest X-ray, most common view is:
    1. AP
    2. PA
    3. RAO
    4. LAO
  1. Which of the following is the gold standard for imaging of swallowing disorders?
    1. Dynamic MRI
    2. Barium swallow
    3. Videofluoroscopy
    4. X-ray
  1. 1 Gray is equal to:
    1. 1 Roentgen
    2. 1 Rad
    3. 100 Rad
    4. 1 Rem
  1. Inferior rib notching is seen in:
    1. Coarctation of aorta
    2. SLE
    3. RA
    4. Scleroderma
  1. Most sensitive test for ureteric stone is:
    1. CECT
    2. MRI
    3. USG
    4. NCCT
  1. Contrasts used in USG:
    1. Urografin
    2. Ultragraffin
    3. Sonavist
    4. Conray
    5. Barium
  1. Best view for collapse of middle lobe lung is:
    1. Lateral
    2. AP
    3. Oblique
    4. Lordotic
  1. On imaging diffuse axonal injury is characterized by:
    1. Multiple small petechial hemorrhage
    2. Patch ill, defined low density lesion mixed with small hyperdense petechial hemorrhage
    3. Crescentic extra-axial hematoma
    4. White matter lucencies
  1. Miliary nodules are seen in all except
    1. Silicosis
    2. TB
    3. Aspergillosis
    4. Anthracosis
  1. Hour glass appearance of stomach is seen in:
    1. Linitis plastica
    2. Gastric ulcer
    3. Duodenal ulcer
    4. Gastric carcinoma
  1. Which of the following is the investigation of choice for dissecting aortic aneurysm?
    1. CECT
    2. PET
    3. MRI
    4. TEE
  1. 38Ultrasonogram is the primary modality of choice in obstetrics and in surgery. Frequency of the ultrasound used to image the breast, thyroid and testis are:
    1. 2–5 MHz
    2. 5–10 MHz
    3. 1–2 MHz
    4. 20–25 MHz
  1. In a 90-year-old man with pyonephrosis and with pacemaker and Sr. creatinine of 3 mg/dL, which of the following should be used:
    1. CECT
    2. NCCT
    3. MRI
    4. X-ray
 
Multiple Correct Answers
  1. Energy linear acceleration used in:
    1. X-ray
    2. Cathode rays
    3. Photon rays
    4. α-rays
    5. g-rays
  1. Which of the following do not use radiation?
    1. MRI
    2. CT
    3. USG
    4. SPECT
    5. PET
  1. True about virtual colonoscopy are A/E:
    1. Provide endoluminal view
    2. Biopsy can be taken
    3. CT and MRI used
    4. Used even when conventional colonoscopy fails
    5. Used for screening of carcinomacolon
  1. Radiological findings of eosinophilic granuloma is/are:
    1. Hilar involvement
    2. Miliary shadowing
    3. Honey comb appearance
    4. White out lung
    5. Splitting of pleura
  1. Tracheal bifurcation on X-ray corsponds to
    1. T5T6
    2. T4T5
    3. Sternal angle
    4. Thoracic inlet
  1. Radiation hazard is absent in:
    1. MRI
    2. Doppler USG
    3. Digital substraction angiography
    4. Tc 99 scan
  1. Attenuation value (Hounsfield unit) of < zero (i.e. negative) on CT is seen in:
    1. Muscle
    2. Bone
    3. Fat
    4. Air
    5. Blood
39ANSWER KEYS
1. Ans. a. Mass density
2. Ans. b. In pediatric patients dose should be reduced
3. Ans. d. Tc-thallium subtraction scan
4. Ans. c. Inferior mesenteric artery
5. Ans. a. MRI STIR sequence
6. Ans. d. Whole body
7. Ans. d. Linear attenuation coefficient
8. Ans. c. Lateral view
9. Ans. c. Bone algorithm for image reconstruction
10. Ans. d. Microwave
11. Ans. a. Open fontanelles
12. Ans. c. Position emission tomography
13. Ans. b. ↑kVp
Its a wrongly framed question friends, idealy the body part of CT should have been mentioned.
14. Ans. d. CT scan
15. Ans. c. Placenta previa
16. Ans. d. PET scan
17. Ans. a. MRI
18. Ans. c. CT guided biopsy
19. Ans. a. Shortening of both T1 and T2 relaxation times
20. Ans. b. Gray
21. Ans. d. >2 MHz
22. Ans. a. Gadolinium
23. Ans. a. Water
24. Ans. b. Iodinated nonionic water soluble contrast
25. Ans. d. They are used in magnetic resonance imaging
26. Ans. a. Breast imaging reporting and data system
27. Ans. a. Change in frequency in relation to the movement of source or observer
28. Ans. a. Multidetector CT contrast
29. Ans. d. Helium nucleus
30. Ans. a. USG
31. Ans. a. Velocity
32. Ans. a. Hounsfield curt
33. Ans. a. Piezoelectric effect
34. Ans. c. Picture archiving communication system
35. Ans. a. 400-700 nm
36. Ans. a. Hounsfield
37. Ans. a. Barium meal follow through
38. Ans. a. Bile
39. Ans. c. Silver
40. Ans. d. Myelography
41. Ans. b. Mercury
As we all know that Scattering of the radiation is the function of Compton effect and Compton effect is proportional to the no of electron per unit volume which is equal to no of electron/ volume = physical density(m/v) × electron density (number of electrons per unit mass).
Electrone density is proportional to Z/A (as number of atoms per unit mass is proportional to 1/A and number of electrons per atom is proportional to Z)
A- is atomic mass, Z is atomic number.
Electrone density is maximum for H+ (Z/A = 1/1), while rest of the elements have Z/A ~ 0.5.
Physical density of various elements are as follows:
Mercury – 13.5 gm/cm3
Hydrogen – 0.000082
Carbon – 3.513 (diamond); 2.2 (graphite)
Calcium – 1.54
40So if we look at the combine picture, though hydrogen has most favorable z/A ratio for Compton effect, the difference in mass density so so much that virtually, Compton effect become proportional to the mass density.
Hence the answer should be Mercury (Hg)
42. Ans. a. Gamma rays
43. Ans. c. Iodine
44. Ans. b. USG
45. Ans. d. Morbid obesity
46. Ans. b. Lesser than that of light
47. Ans. a. Tomography
48. Ans. a. FDG
49. Ans. a. Sonography
50. Ans. b. Foley’s catheter
51. Ans. a. Lead
52. Ans. b. MR angiography
53. Ans. d. UV radiation
54. Ans. a. 1500 m/s
55. Ans. b. 100 ergs/g
56. Ans. a. 1-20 MHz
57. Ans. d. Radiography
58. Ans. a. Electron beam strikes the anode
59. Ans. b. Electrons
60. Ans. a. kV
61. Ans. b. Easily penetrated by X-rays
62. Ans. c. Gadolinium diethylmethylamine
63. Ans. b. Proton beam
64. Ans. d. Calcified lesions
65. Ans. c. MRI is better for calcified lesions
66. Ans. a. MRI
67. Ans. c. Faraday cage
68. Ans. c. Magnetic resonance imaging
69. Ans. a. CT
70. Ans. c. Lateral view
71. Ans. a. Ionic monomers have three iodine atoms per two particles in solution
72. Ans. b. Frequency of sound
73. Ans. b. NCCT
74. Ans. d. Low osmolar contrast
75. Ans. b. Interstitial lung disease
76. Ans. a. MRl
77. Ans. d. Echocardiography
78. Ans. b. Esophagus
79. Ans. c. Optic foramen
80. Ans. e. 1
81. Ans. c. Helium ion
82. Ans. c. Ultrasonography
83. Ans. d. MRCP
84. Ans. a. Doppler USG
85. Ans. c. Immediate fasciotomy
86. Ans. a. Sestamibi
87. Ans. b. Perforation
88. Ans. c. Renal cancer
89. Ans. c. Produced when patient moves while taking the shoot
90. Ans. b. Pleural effusion with dependent hemithorax
91. Ans. b. Roentgen
92. Ans. a. Reducing scattered radiation
93. Ans. b. Silver bromide
94. Ans. d. Lateral decubitus
95. Ans. a. 6 hours
96. Ans. b. Reverse lordotic
97. Ans. b. US
98. Ans. d. Fluoride 18
99. Ans. b. Bilateral hilar lymphadenopathy
100. Ans. d. MIBG scan
101. Ans. c. FNAC
102. Ans. a. Pair production occur for low energy
103. Ans. c. Diffusion weighted MRI
104. Ans. b. CT angiography
105. Ans. b. Retinal vasculature
41106. Ans. a. –10 to –1000
107. Ans. b. PA
108. Ans. b. Barium swallow
109. Ans. c. 100 Rad
110. Ans. a. Coarctation of aorta
111. Ans. d. NCCT
112. Ans. c. Sonavist
113. Ans. d. Lordotic
114. Ans. b. Patch ill, defined low density lesion mixed with small hyperdense of petechial hemorrhage
115. Ans. c. Aspergillosis
116. Ans. b. Gastric ulcer
117. Ans. a. CECT
118. Ans. b. 5–10 MHz
119. Ans. b. NCCT
 
Multiple Correct Answers
120. Ans. a. X-ray, b. Cathode rays
121. Ans. a. MRI, c. USG
122. Ans. a. Provide endoluminal view and e. Used for screening of carcinoma colon
123. Ans. a. Hilar involvement, b. Miliary shadowing, c. Honey comb appearance, d. White out lung, e. Splitting of pleura
124. Ans. b. T4T5
Most of the standard radiology textbooks and 40th edition of Gray’s anatomy says the bifurcation is at T4T5 level which however descend to T6 level on deep inspiration.
41st edition of Gray’s anatomy says that bifurcation is at upper half of T6 vertebra level which however descend to T6 level on deep inspiration which looks like a controversial statement
125. Ans. a. MRI, b. Doppler USG
126. Ans. c. Fat, d. Air