Resolution brings women's health into focus

A massive machine with a large appendage greeted me when I first encountered ultrasound in 1977 as a first-year radiology resident at the Massachusetts General Hospital in Boston. We dragged the attached articulated arm back and forth across the patient's belly multiple times to create an image that mimicked the surface of the moon. This modality intrigued me because it required skill in both creating and interpreting the images. I had served as a surgical intern before I begun training in imaging, so I also found the contact with the patient and the ability to combine elements of history-taking with the physical examination somehow less sterile and more gratifying than many remote imaging modalities. By 1980, all gynecological ultrasound examinations were performed in real time and the resolution and frame rates of the ultrasound machines improved rapidly. In the early 80s, a pelvic ultrasound examination required the patient to have a very full bladder in order to provide an acoustic window to the uterus and ovaries (Figure 1a). If the bladder was not sufficiently full, bowel gas artifacts filled the image and obscured the uterus, and if the bladder was overdistended, the pelvic organs would be flattened posteriorly, further limiting resolution. The imaging detail was quite limited, allowing detection of only large masses. The interrogation of lesions in the cul-de-sac required the patient to tolerate, with a full bladder, a water enema during scanning, in order to generate bubbles in the rectosigmoid colon to determine whether the mass was separate from the bowel. The emergence of the transvaginal probe in the mid 80s afforded great relief to both doctors and patients, who could finally empty their bladder! The transvaginal approach used higher-frequency transducers with better resolution, furnishing far more detail (Figure 1b). As such, it finally enabled us to visualize the details of ovarian cysts, small fibroids, endometrial abnormalities, the cervix and the cul-de-sac1. Moreover, the transvaginal method allowed us to monitor ovarian follicular development in patients with infertility, as well as procedures used in in-vitro fertilization. Concerned about the possible discomfort associated with the intracavitary probe, I volunteered as the first subject in my practice before I was willing to subject my patients to this imposition. The introduction of Doppler in 1989 was another key turning point in gynecological imaging, offering more information about the content, vascularity and hence etiology of adnexal masses2 (Figure 2). Color Doppler provided a vascular map of the masses and pulsed Doppler revealed the increased flow velocity typical of malignant lesions. During the 90s, we saw increasingly improved grayscale images thanks to higher-frequency transducers, improved penetration, harmonic imaging and improved spatial resolution. When the uterine cavity was abnormal or unclear on standard views, we introduced saline to outline any endometrial abnormalities in detail (Figure 3). The vastly superior quality of images coupled with vascular mapping and the ability to visualize the pelvic organs in real time revolutionized gynecological imaging and led to many innovations over the ensuing three decades. New areas of study included endometriosis, which soon led to the realization that deep infiltration of endometriosis could be detected sonographically3 (Figure 4). Guerriero et al. showed that ultrasound could detect accurately the extent of endometriosis outside the ovaries and demonstrate the implants of endometriosis on the bowel wall, uterosacral ligaments, rectovaginal septum, as well as the bladder wall in the anterior compartment3. Performing the examination in real time led to the development of the tenderness-guided4 and the sliding-sign5 techniques, which helped greatly in the assessment of patients presenting with pelvic pain. In 1999, a multicenter research group, the International Ovarian Tumor Analysis (IOTA) group, was founded with the aim to develop standardized terminology and to determine methods for discriminating between malignant and benign masses using grayscale and Doppler criteria6. Their findings and those of other groups revolutionized the use of transvaginal ultrasound and Doppler for recognizing all types of ovarian and uterine pathology. We now possess well-accepted methods for scoring specific grayscale and Doppler characteristic findings, resulting in vast improvement in the accuracy of identifying pelvic malignancies6, 7 (Figure 5). The most recent addition to the ultrasound armamentarium is the development of volume or three-/four-dimensional ultrasound. For the first time, it was possible to generate images from an ultrasound volume, which offered the ability to rescan a patient virtually using saved volumes and visualize any plane or section, including those reconstructed within the volume. Since traditional two-dimensional transvaginal ultrasound can generate images from only the vaginal point of view, certain crucial views of the pelvis could not be displayed but only viewed in the mind's eye of the practitioner. Suddenly, volume ultrasound allowed us to image any reconstructed ultrasound view of the pelvis, such as the coronal view of the uterus which shows the fundus, cervix and both cornua simultaneously. The coronal view revolutionized our ability to diagnose Müllerian duct anomalies, submucosal fibroids, perforation of an intrauterine device (IUD), hydrosalpinges and much more8 (Figure 6). We were able to create images that had never been generated by ultrasound before; we were able to gaze at the dark side of the moon9. Volume imaging also made possible to review volumes saved by a different practitioner and rescan the raw data, thus minimizing operator dependency, a problem that has persistently plagued the ultrasound community. We were finally able to measure the true width of the uterine cavity and find that one IUD size didn't fit all10! In conclusion, ultrasound has evolved from providing quasi uninterpretable pointillistic patterns of black dots on a white background to a contemporary tool able to visualize pelvic structures with considerable clarity and diagnostic detail. The constant innovations that have enabled the flourishing of the art of ultrasound not only represent a triumph of technology but have afforded a major advance in women's health.