2Transvaginal sonography gives more accurate and more detailed information on pelvic organs and masses than vaginal examination. It is preferable to set an ultrasound scanner with a transvaginal probe by each gynecological examination table (Fig. 1.1).
A transvaginal probe consists of a head, shaft and a grip (Figs 1.2A to C). A straight-type probe (Figs 1.2A and B) may be easier to manipulate for obtaining a desirable tomographic image than a bending-type probe (Fig. 1.2C).
Figs 1.2A to C: Transvaginal probes: (A) A straight-type mechanical sector probe. (B) A straight-type convex probe. (C) A bending-type convex probe: (H) head, (S) shaft, (G) grip
A mechanical sector probe (Fig. 1.3A) or a convex (curved-array) prove (Figs 1.3B and C) is used as a transvaginal probe.
CONVEX PROBES
A convex probe performs electronic beam focusing and dynamic focusing, and the depth of the focal zone is selectable (Fig. 1.4). There are many grating lobes on both sides of the main lobe from a convex probe. These grating lobes as well as side lobes cause artifacts (Fig. 1.4). A convex probe has the capability of color, power and pulsed Doppler as well as B-mode imaging (Figs 1.5A and B).
Figs 1.3A to C: Probe heads: (A) A mechanical sector probe. (B) A convex probe. (C) A convex probe for obliquely forward scanning
Fig. 1.4: An image of a simple cyst obtained with a convex probe. The focal zone (depth) is indicated by a semicircle (arrow) on the left side. Grating and side lobes from the probe make many artifacts (arrowheads) and the inner outline of the cyst is not shown clearly
Figs 1.5A and B: Images of an ovary obtained with a convex probe: (A) A B-mode image. (B) A power Doppler image of the same section showing blood flows surrounding the corpus luteum
Mechanical Sector Probes
Figure 1.6 illustrates the principle of a mechanical sector probe. The tip of a mechanical sector probe is a small hemisphere and thus a mechanical sector probe can be easily inserted into the vagina. This is especially preferable for examining virgins and old women with atrophic vaginae. The scan angle can be easily widened to more than 200 degrees. The focal zone is fixed at a constant depth determined by the shape of the transducer and there appears no mark indicating the focal zone (Fig. 1.7). A mechanical sector probe is superior to a convex probe in B-mode image quality, mainly because there is no grating lobe (compare Figs 1.4 and 1.7).
Fig. 1.6: Principle of the scanning of a mechanical sector probe. The head is filled with acoustically transparent liquid and two transducers rotate in it at high speed. One transducer is for a low-frequency and the other for a high-frequency. The ultrasonic frequency is changeable by switching the active transducer
Fig. 1.7: An image of a simple cyst obtained with a mechanical sector probe (the same cyst in Figure 1.4). The focal zone is not indicated on the image because it is fixed. The inner outline of the cyst is clearer than in Figure 1.4, because a mechanical sector probe has no grating lobe and causes less artifacts
THREE-DIMENSIONAL TRANSVAGINAL PROBES
A three-dimensional (3D) transvaginal probe is used in 3D ultrasound (Figs 1.8A to C). The head of the probe houses either a convex probe or a mechanical sector probe which swings to acquire 3D data as a large number of consecutive tomograms (Fig. 1.9).
Figs 1.8A to C: Three-dimensional transvaginal probes: (A) A mechanical sector probe is housed in the head. (B and C) A convex probe is housed in the head
Fig. 1.9: Principle of three-dimensional scanning: A mechanical sector probe or a convex probe housed in the probe head swings and a bunch of tomographic images is acquired automatically for 3D data set construction
Figs 1.10A and B: (A) A needle guide and a transvaginal probe. (B) The transvaginal probe prepared with a condom, the needle guide and a long needle for aspiration
ACCESSORIES OF A TRANSVAGINAL PROBE
A needle guide is attached to a transvaginal probe in transvaginal ultrasound-guided follicular/cyst aspiration for ease and safety (Figs 1.10A and B).
BASIS OF TRANSVAGINAL SCANNING
Preparing the Patient and the Probe
- Explain transvaginal sonography to the patient, especially when she has not undergone transvaginal sonography to ease her fear.
- Let the patient urinate to vacate the bladder to bring the uterine body closer to the vaginal fornix (Figs 1.11A and B).
- See the position and direction of the uterus and intrapelvic masses by vaginal examination or by transabdominal sonography before the transvaginal scanning.
- Wipe the head of the probe. Put a clean condom or a probe cover on the probe after putting ultrasonic jelly on the head or into the condom.
Probe Insertion and Rotation
- Wet the tip of the condom with clean water or put some cream on it to insert the probe into the vagina smoothly.
- Insert the probe into the vagina slowly and obtain a sagittal (longitudinal) section of the uterus (Figs 1.12A and B).
- Make sure that the direction of the image is always fixed not to lose or confuse the orientation. When the probe is rotated counterclockwise from 12 o'clock to 9 o'clock (Fig. 1.13), a transverse section of the uterus (parallel to the abdominal wall), is displayed such that the right side of the patient is displayed on the left side of the image and the left side of the patient on the right side of the image.
Basic Techniques in Transvaginal Scanning
- Figure 1.14A shows a sagittal section of a retroverted uterus, when the probe head is inserted into the anterior vaginal fornix.The cervix prevents the uterine body from being seen satisfactorily. When the probe head is moved into the posterior vaginal fornix, the uterine body comes closer to the probe head and its clear image is obtained (Fig. 1. 14B).When an ovary is far from the vaginal fornix, the ovary is not depicted clearly (Figs 1.15A and B). In this case, the probe should be inserted further more to push the vaginal fornix. The ovary comes closer to the probe head and a clear image can be obtained (Fig. 1.15C). When an ovary is in the cul-de-sac (the pouch of Douglas), the probe head must be put in the posterior vaginal fornix to obtain a clear ovarian image (Figs 1.16A and B).Figs 1.15 A to C: (A) An ovary (arrowheads) with a follicle is barely seen with low-frequency ultrasound. (B) The ovary cannot be seen with high-frequency ultrasound due to its poor penetration. (C) When the probe is pressed against the vaginal fornix, the ovary comes closer to the probe head and a clear ovarian image can be obtained with high-frequency ultrasound
- Select the ultrasound frequency appropriately when using a frequency-selectable probe.Figure 1.17A shows a dermoid cyst imaged with low-frequency ultrasound. A solid-type dermoid cyst tends to be overlooked with high-frequency ultrasound because of its low tissue penetration (Fig. 1.17B).
- Adjust the depth of the focal zone properly to obtain a clear image when a convex probe is used (Figs 1.18A and B).
- Consider the pressure to the object by the probe head. Soft objects such as an ovarian cyst or the uterine cervix in pregnancy are temporarily deformed by pressing excessively with the probe (Figs 1.19A and B).
- Palpate the uterus or ovaries with the probe head, when the patient complains of a lower abdominal pain.An adhesion or a touch of two organs or masses may be distinguished by moving them around with the probe head (Figs 1.20A and B).
- Use a negative contrast medium (saline) for outlining the uterine cavity clearly (Figs 1.21A and B). This technique is called sonohysterography.Figs 1.20A and B: (A) A solid mass (M) seems a pedunculated myoma because it seems to rise from the uterine fundus (arrowhead). (B) The uterus and the mass separate from each other and the uterine contour (arrowheads) is clearly depicted by pressing between the two with the probe, leading a conclusion that the mass is not a myoma of the uterus
TRANSRECTAL SONOGRAPHY
Introduction
The rectum is a hollow viscous connecting the sigmoid colon to the anal canal. It lies posterior to the female genital organs, which include the vagina, cervix and uterus. It is situated anatomically more or less parallel to the vagina, hence, the uterus will be in most cases anteverted anteflexed on the rectum (Fig. 1.22).
PROBES, PLANES AND ORIENTATION (FIG. 1.23)
The anatomical proximity and similarity of the rectum to the vagina imposes much of the similarities between transrectal sonography (TRS) and transvaginal sonography (TVS) in relation to their probe designs, basic probe movements, scanning planes and orientation difficulties.18
Both TRS and TVS probes are designed as elongated finger-like instruments that fit their respected hollow organs, with diameters less than other older instruments such as the vaginal speculum or the rectoscope.
Both TRS and TVS share the five basic probe movements, which include: sliding, rocking, tilting, rotating and compressing.
Using the transabdominal sonography (TAS) approach, we can obtain an infinite number of sagittal, coronal and transverse planes of the examined structures. Using, on the other hand, TVS or TRS can only yield a midsagittal and coronal planes, but no transverse planes. Any attempt to obtain parasagittal planes will ultimately cause some discomfort to the patient and only yield oblique views (Fig. 1.24).
Whether the ultrasound examination is done in the supine or the lateral decubitus positions, a problem of orientation will be faced since the sonographic waves are sent in a direction different from that of the displayed image on the monitor (Fig. 1.25).
INDICATIONS OF TRS (TABLE 1.1)
Transrectal sonography (TRS) was first introduced in the field of gynecology as an alternative to TVS in cases where TVS was impossible to perform, or when it produced unsatisfactory results.20
Children and young adolescents are also candidates of TRS rather than TVS due to the psychological trauma that may occur due to the vaginal examination and due to the anatomical limitations imposed by the narrow and short vagina. Anatomical characteristics of that age group like the higher ovarian level and the higher ratio of cervical to uterine sizes should be kept in mind (Fig. 1.26).21
Some congenital genital tract abnormalities may also make TVS impossible. These include vaginal atresia, transverse vaginal septum, Rokitansky-Küster-Hauser syndrome, hematocolpometrium, etc. (Fig. 1.27).
TRS was also found to be effective in cervical carcinoma staging, detection of vulvovaginal lesions and in the examination of rectocanal pathologies such as fistulas, sphincter trauma and neoplastic lesions (Fig. 1.28).
The use of TRS has been studied in the immediate postpartum period to detect sphincter injuries (Fig. 1.29), and the adequacy of primary repair.23
TRS is also found to be of value in addition to TVS in some cases such as retroverted uteri, ovarian lesions distant from vagina (Fig. 1.30), fundal uterine pathologies (Figs 1.31A and B), and suspected ectopic pregnancies.
In cases of retroverted uteri, TRS may give a better view, as it is sometimes difficult to depict the endometrium and measure its thickness using TVS. This is due to the fact that sonographic waves are aligned with the endometrium in the case of TVS, while they are perpendicular to the endometrium in the case of TRS (Fig. 1.32).
Furthermore, TRS is frequently used as a monitoring tool during interventions such as dilatation and curettage (Fig. 1.33), intrauterine contraceptive device insertion and removal (Fig. 1.34), cervical cerclage to localize the level of internal os, and in intrauterine radiotherapy tandem insertion.
Technique and Preparation
For TRS, we use disposable plastic speculums with the blades directed sideways rather than the usual anteroposterior position. This helps to obtain a better view (Fig. 1.35).
AUTHORS' RESULTS
The authors had carried out a study at their center comparing the reliability of TAS with that of TRS. (These results have not been published yet). In this study, they examined 74 patients using TAS and TRS. The findings included polycystic ovaries (Fig. 1.36), ovarian cysts (Figs 1.37A and B), myomas, hematocolpometra, Rokitansky-Küster-Hauser syndrome, streak ovaries and endometrial polyps (Figs 1.38A and B and Table 1.2).
|
In this study, TRS was found to be superior to TAS in 72 cases and similar to TAS in one case.