Effect of flip angle for optimization of image quality of gadoxetate disodium-enhanced biliary imaging at 1.5 T.

OBJECTIVE: The purpose of this study was to perform a qualitative and quantitative comparison of image quality of gadoxetate disodium-enhanced imaging of the biliary system acquired using different flip angles (FAs). MATERIALS AND METHODS: Thirty-two patients (21 men and 11 women; mean [± SD] age, 51 ± 16 years) who underwent gadoxetate disodium-enhanced 1.5-T MRI were included. A 3D fat-suppressed T1-weighted gradient-echo sequence was acquired during the hepatobiliary phase using FAs of 12°, 25°, and 40°. One radiologist, who was blinded to FA, measured signal-to-noise ratios (SNRs) and contrast-to-noise ratios (CNRs) of the biliary tree. Two other blinded radiologists assessed subjective biliary duct clarity, overall image quality, background signal suppression, and ghosting artifact from the biliary tree using a scale of 1 to 4. RESULTS: SNRs and CNRs of the common bile duct were significantly higher for FAs of 25° (227.5 ± 113.2 and 191.0 ± 102.2, respectively) and 40° (239.6 ± 118.7 and 201.7 ± 107.7, respectively) than for 12° (168.9 ± 73.9 and 126.7 ± 59.7, respectively; all p < 0.001). There were no significant differences in SNR or CNR between FAs of 25° and 40° (p ≥ 0.360). Clarity of first-, second-, and third-order intrahepatic ducts, background signal suppression, and overall image quality were significantly higher for both readers for FAs of 25° and 40° than for 12° (all p ≤ 0.031). None of these comparisons was significantly different for either reader between FAs 25° and 40° (all p ≥ 0.091), aside from improved depiction of third-order ducts at 40° for one reader (p = 0.030). Biliary ghosting artifact was significantly worse at 40° than at 12° for both readers (p ≤ 0.016). CONCLUSION: The use of an FA larger than the clinical standard of approximately 12° has the potential to improve the image quality of gadoxetate disodium-enhanced biliary imaging.

Pelvic ultrasound immediately following MDCT in female patients with abdominal/pelvic pain: is it always necessary?

To determine the added value of reimaging the female pelvis with ultrasound (US) immediately following multidetector CT (MDCT) in the emergent setting. CT and US exams of 70 patients who underwent MDCT for evaluation of abdominal/pelvic pain followed by pelvic ultrasound within 48 h were retrospectively reviewed by three readers. Initially, only the CT images were reviewed followed by evaluation of CT images in conjunction with US images. Diagnostic confidence was recorded for each reading and an exact Wilcoxon signed rank test was performed to compare the two. Changes in diagnosis based on combined CT and US readings versus CT readings alone were identified. Confidence intervals (95%) were derived for the percentage of times US reimaging can be expected to lead to a change in diagnosis relative to the diagnosis based on CT interpretation alone. Ultrasound changed the diagnosis for the ovaries/adnexa 8.1% of the time (three reader average); the majority being cases of a suspected CT abnormality found to be normal on US. Ultrasound changed the diagnosis for the uterus 11.9% of the time (three reader average); the majority related to the endometrial canal. The 95% confidence intervals for the ovaries/adnexa and uterus were 5-12.5% and 8-17%, respectively. Ten cases of a normal CT were followed by a normal US with 100% agreement across all three readers. Experienced readers correctly diagnosed ruptured ovarian cysts and tubo-ovarian abscesses (TOA) based on CT alone with 100% agreement. US reimaging after MDCT of the abdomen and pelvis is not helpful: (1) following a normal CT of the pelvic organs or (2) when CT findings are diagnostic and/or characteristic of certain entities such as ruptured cysts and TOA. Reimaging with ultrasound is warranted for (1) less-experienced readers to improve diagnostic confidence or when CT findings are not definitive, (2) further evaluation of suspected endometrial abnormalities. A distinction should be made between the need for immediate vs. follow-up imaging with US after CT.

Normal or abnormal? Demystifying uterine and cervical contrast enhancement at multidetector CT.

Computed tomography (CT) is not generally advocated as the first-line imaging examination for disorders of the female pelvis. However, multidetector CT is often the modality of choice for evaluating nongynecologic pelvic abnormalities, particularly in emergent settings, in which all the pelvic organs are invariably assessed. Incidental findings of uterine and cervical contrast enhancement in such settings may easily be mistaken for abnormalities, given the broad spectrum of anatomic variants and enhancement patterns that may be seen in the normal uterus and cervix. The authors' review of CT and magnetic resonance (MR) imaging enhancement patterns, augmented by case examples from their clinical radiology practice, provides a solid foundation for understanding the spectrum of normal uterine and cervical appearances and avoiding potential pitfalls in the diagnosis of benign cervical lesions, adenomyosis, infection, malignancy, and postpartum effects. This information should help radiologists more confidently differentiate between normal and abnormal CT findings and, when CT findings are not definitive, offer appropriate recommendations for follow-up ultrasonography or MR imaging.

Commonly encountered foreign bodies and devices in the female pelvis: MDCT appearances.

OBJECTIVE: The objective of this article is to illustrate the MDCT appearances of several commonly encountered foreign bodies and devices in the female pelvis. CONCLUSION: The presence of a foreign body or device in the female pelvis can be a potential source of confusion to radiologists, particularly to the inexperienced reader. Familiarity with the normal appearances and locations of these devices on MDCT allows their accurate identification and detection of associated complications.