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PURPOSE: To use fiducial markers containing manganese 55 to rapidly localize carbon 13 ((13)C) RF coils for correcting images for B(1) variation. METHODS: Hollow high-density polyethylene spheres were filled with 3M sodium permanganate and affixed to a rectangular (13)C-tuned RF coil. The relative positions of the markers and coil conductors were mapped using CT. Marker positions were measured by MRI using a series of 1D projections and automated peak detection. Once the coil location was determined, coil sensitivity was estimated using a quasistatic calculation. Simulations were performed to determine the minimum number of projections required for robust localization. Phantom experiments were used to confirm the accuracy of marker localization as well as the calculated coil sensitivity. Finally, in vivo validation was performed using hyperpolarized (13)C pyruvate in a rat model. RESULTS: In simulations, our algorithm was accurate in determining marker positions when at least 6 projections were used (RMSE 1.4 ± 0.9 mm). These estimates were verified in phantom experiments, where markers locations were determined with an RMS accuracy of 1.3 mm. A minimum SNR of 4 was required for automated detection to perform accurately. Computed coil sensitivity had a median error of 17% when taken over the entire measured area and 5.7% over a central region. In a rat, correction for nonuniform reception and flip angle was able to normalize the signals arising from asymmetrically positioned kidneys. CONCLUSION: Manganese 55 fiducial markers are an inexpensive and reliable method for rapidly localizing (13)C RF coils and correcting (13)C images for B(1) variation without user intervention.

OBJECTIVE. The purpose of this study was to compare ultrasound and CT in the diagnostic evaluation of right upper quadrant pain in adults in the emergency department. MATERIALS AND METHODS. A retrospective review was conducted of adult emergency department encounters for right upper quadrant pain over a 5-year period, excluding those for prior cholecystectomy, current pregnancy, and trauma. Imaging study reports were reviewed for gallbladder and nongallbladder explanations of right upper quadrant pain and were considered positive for cholecystitis when two or more supportive features were present. Encounter outcomes were evaluated on the basis of pathology data and clinical management. RESULTS. Among the encounters, 2859 met the study inclusion criteria, and 18% met the study definition of cholecystitis by pathologic or clinical criteria. The following metrics showed no statistically significant difference between ultrasound and CT, respectively: sensitivity, 61% and 55%; specificity, 91% and 92%; positive predictive value, 63% and 63%; and negative predictive value, 91% and 90%. Both modalities were performed in 20% of encounters. In the subgroup analysis, ultrasound showed an acute nongallbladder abnormality that was missed at a preceding CT examination in only 1 of 238 cases (0.4%). CT showed an acute nongallbladder abnormality missed at a preceding ultrasound examination in 103 of 322 cases (32%). CONCLUSION. CT is noninferior to ultrasound in both ruling in and ruling out the diagnosis of cholecystitis in adult patients undergoing emergency evaluation of right upper quadrant pain and offers the advantage of depicting acute nongallbladder abnormalities.

The purposes of this study are (1) to utilize multivariable logistic regression in order to evaluate which image feature combination is most predictive in the diagnosis of cholecystitis for computed tomography (CT) and ultrasound (US) in adult ED patients and (2) to use these results to compare the accuracy of CT and US.For RUQ pain patients undergoing US and CT at the same visit, multiple image features were evaluated independently by 2 radiologists blinded to additional data. Inter-reader variability was measured with the Kappa statistic. Sonographic Murphy's sign (SMS) information was obtained from original reports. Multivariable logistic regression was utilized to develop optimal predictive models for each modality. For US, models with/without SMS were compared to establish its relative value.446 patients met inclusion criteria. For CT, the combination of cholelithiasis, short-axis gallbladder diameter 3 cm, pericholecystic fluid or inflammation, and mural thickening 3 mm provided the optimal model for both readers. For US, the optimal model included cholelithiasis, short-axis diameter 3 cm, mural heterogeneity/striation, and sludge/debris for both readers. Kappa = 0.79-0.96 for included image features. For both readers, CT and US models had equivalent diagnostic performances; the SMS did not contribute significantly to US models.For a diagnosis of cholecystitis in the ED, (1) the optimal image feature combination for CT is cholelithiasis, short-axis diameter 3 cm, pericholecystic fluid or inflammation, mural thickening 3 mm; and cholelithiasis, short-axis diameter 3 cm, mural heterogeneity/striation, sludge/debris for US; (2) CT and US have equivalent diagnostic performance; (3) inter-reader reliability is substantial to excellent for utilized image features; (4) the SMS does not affect US model accuracy.

PurposeTo use fiducial markers containing manganese 55 to rapidly localize carbon 13 (13 C) RF coils for correcting images for B1 variation.MethodsHollow high-density polyethylene spheres were filled with 3M sodium permanganate and affixed to a rectangular 13 C-tuned RF coil. The relative positions of the markers and coil conductors were mapped using CT. Marker positions were measured by MRI using a series of 1D projections and automated peak detection. Once the coil location was determined, coil sensitivity was estimated using a quasi-static calculation. Simulations were performed to determine the minimum number of projections required for robust localization. Phantom experiments were used to confirm the accuracy of marker localization as well as the calculated coil sensitivity. Finally, in vivo validation was performed using hyperpolarized 13 C pyruvate in a rat model.ResultsIn simulations, our algorithm was accurate in determining marker positions when at least 6 projections were used (RMSE 1.4 ± 0.9 mm). These estimates were verified in phantom experiments, where markers locations were determined with an RMS accuracy of 1.3 mm. A minimum SNR of 4 was required for automated detection to perform accurately. Computed coil sensitivity had a median error of 17% when taken over the entire measured area and 5.7% over a central region. In a rat, correction for nonuniform reception and flip angle was able to normalize the signals arising from asymmetrically positioned kidneys.ConclusionManganese 55 fiducial markers are an inexpensive and reliable method for rapidly localizing 13 C RF coils and correcting 13 C images for B1 variation without user intervention.

Abdominal and pelvic hernias may be indolent and detected incidentally, manifest acutely with pain and distress, or cause chronic discomfort. Physical examination findings are often ambiguous and insufficient for optimal triage. Therefore, accurate anatomic delineation and identification of complications are critical for effective treatment planning. Imaging, particularly computed tomography, provides a vital understanding of the hernia's location and size, involved viscera, and severity of associated complications. Reader familiarity with the imaging appearances and anatomic landmarks of hernias is important for correct diagnosis, which may impact preoperative planning and reduce morbidity. This article reviews the appearance of anatomic structures in the abdominal wall and pelvis that are important for diagnosing common and uncommon abdominal and pelvic hernias, and it highlights key imaging features that are helpful for differentiating hernias, mimics, and their complications. Online DICOM image stacks are available for this article . ©RSNA, 2017.