Basic as well as detailed neurosonograms can be performed by offline analysis of three-dimensional fetal brain volumes.

OBJECTIVES: To evaluate the feasibility and the processing time of offline analysis of three-dimensional (3D) brain volumes to perform a basic, as well as a detailed, targeted, fetal neurosonogram. METHODS: 3D fetal brain volumes were obtained in 103 consecutive healthy fetuses that underwent routine anatomical survey at 20-23 postmenstrual weeks. Transabdominal gray-scale and power Doppler volumes of the fetal brain were acquired by one of three experienced sonographers (an average of seven volumes per fetus). Acquisition was first attempted in the sagittal and coronal planes. When the fetal position did not enable easy and rapid access to these planes, axial acquisition at the level of the biparietal diameter was performed. Offline analysis of each volume was performed by two of the authors in a blinded manner. A systematic technique of 'volume manipulation' was used to identify a list of 25 brain dimensions/structures comprising a complete basic evaluation, intracranial biometry and a detailed targeted fetal neurosonogram. The feasibility and reproducibility of obtaining diagnostic-quality images of the different structures was evaluated, and processing times were recorded, by the two examiners. RESULTS: Diagnostic-quality visualization was feasible in all of the 25 structures, with an excellent visualization rate (85-100%) reported in 18 structures, a good visualization rate (69-97%) reported in five structures and a low visualization rate (38-54%) reported in two structures, by the two examiners. An average of 4.3 and 5.4 volumes were used to complete the examination by the two examiners, with a mean processing time of 7.2 and 8.8 minutes, respectively. The overall agreement rate for diagnostic visualization of the different brain structures between the two examiners was 89.9%, with a kappa coefficient of 0.5 (P < 0.001). CONCLUSIONS: In experienced hands, offline analysis of 3D brain volumes is a reproducible modality that can identify all structures necessary to complete both a basic and a detailed second-trimester fetal neurosonogram.

Transrectal scanning: an alternative when transvaginal scanning is not feasible.

OBJECTIVE: In scanning the female pelvis the clear images of transvaginal sonography (TVS) result from placing the transducer close to the region of interest. The advantages of TVS over transabdominal sonography (TAS) and transperineal sonography are well documented. Transrectal scanning is proposed mostly for ultrasound guidance in draining a pelvic abscess. Our aim was to investigate the applicability of transrectal scanning (TRS) for cases in which TVS is impossible. METHODS: Forty-two patients with an absolute or a relative contraindication to TVS were scanned transabdominally and transrectally. The TRS was performed using a transvaginal probe, which was lubricated and slowly advanced into the rectum. The technique used was similar to that of TVS. Images were compared for resolution and quality. RESULTS: All scans were completed without significant patient discomfort or complaints. TRS was clearly superior to TAS in 31 cases. In nine cases TAS furnished some clinical information but TRS yielded better images. Only in one such case was TAS similar in quality to TRS. In four obese patients TAS did not reveal sufficient pelvic anatomy to generate a clinical diagnosis, whereas TRS revealed two sets of normal ovaries and two patients with ovarian cysts. In the two cases with vaginal agenesis TRS revealed the diagnosis of Rokitansky-Küster syndrome. In three of the four patients with ruptured membranes the cervix could be measured precisely. CONCLUSION: Transrectal scanning should be used liberally after proper patient selection and counseling. The images obtained are superior to TAS and comparable to those obtained by TVS.