Pancreatic carcinoma and fast MR imaging: technical considerations for signal intensity difference measurements

Magnetic resonance imaging of the canine abdomen: effect of pulse sequence on diagnostic quality

Motion artifact is an important limiting factor for abdominal magnetic resonance imaging (MRI) in veterinary patients. The purpose of this study was to determine the effects of pulse sequence on abdominal MRI diagnostic quality in dogs. Ten normal dogs were each scanned using 16 MRI pulse sequences. Sequences included breath-holding sequences, respiratory navigation sequences, and traditional spin-echo sequences. Four observers independently scored diagnostic quality for each sequence based on the appearance of specific organs, overall diagnostic quality, and degree of artifactual interference. Signal-to-noise ratio and contrast-to-noise ratio were also calculated for each sequence. The sequence with the highest overall mean diagnostic quality score was the dorsal T2 turbo spin echo (TSE) with fat saturation and breath-holding. The sequence with the lowest mean diagnostic quality score was the dorsal T2 fast spin echo. The sequence with the highest signal-to-noise ratio for all evaluated organs was the sagittal T1 spin echo. Signal-to-noise and contrast-to-noise ratios did not correlate with subjective assessment of overall diagnostic quality for the majority of the sequences evaluated (P < 0.05). The three sequences considered to have the highest diagnostic quality for the cranial abdomen were the dorsal T2 TSE with fat saturation and breath-hold, transverse T1 turbo fast low-angle shot gradient echo with breath-hold, and dorsal T2 half-Fourier acquisition single shot TSE with respiratory navigation. These sequences had short acquisition times, yielded studies of similar diagnostic quality, provided complementary information, and are therefore recommended for routine canine abdominal MRI protocols.

Evaluation of steady state free precession imaging of the pancreas

The aim of this work was to assess the diagnostic value of fast steady state free precession (SSFP) for the detection, characterization, and delineation of pancreatic lesions. Forty-eight patients referred for magnetic resonance (MR) imaging of the pancreas were included in the study. In addition to the standard protocol, axial pre-contrast SSFP slices of the pancreas were acquired. The standard of reference was defined as based on all imaging data other than SSFP, histopathology, surgery, and/or clinical follow-up. A randomized consensus reading of the SSFP data sets was retrospectively conducted by two board-certified radiologists. The presence of pancreatic lesions, local infiltration, and lymph node metastases was evaluated. Sensitivity and specificity were calculated and a receiver operating characteristic (ROC) analysis was performed. The overall sensitivity and specificity of SSFP were 0.93 and 0.77, respectively. Comparable values were achieved for lymph node detection (0.88/0.91) and assessment of vascular infiltration (0.94/0.91). The mean area under the ROC curve (Az) was 0.91. Owing to its potential to detect vascular infiltration and the rapid acquisition time, SSFP imaging should be supplemented as part of a standard MR protocol of the pancreas.

Respiration-induced movement of the upper abdominal organs: a pitfall for the three-dimensional conformal radiation treatment of pancreatic cancer

Respiration-induced movement of the upper abdominal organs (pancreas, liver and kidneys) was assessed in 12 subjects using dynamic magnetic resonance imaging. The movement of each organ in the cranio-caudal, the lateral and the anterior-posterior direction was deduced from the movement of the center of gravity on two-dimensional images. This center of gravity was computed from the volume delineated on sequential 8-mm slices of both sagittal and coronal dynamic series. The largest movements were noticed in the cranio-caudal direction for pancreas and liver (23.7+/-15.9 mm and 24.4+/-16.4 mm). The kidneys showed smaller movements in the cranio-caudal direction (left kidney 16.9+/-6.7 mm and right kidney 16.1+/-7.9 mm). The movements of the different organs in the anterior-posterior and lateral directions were less pronounced. It is of the greatest importance to be aware of these movements in the planning of a conformal radiation treatment for pancreatic cancer.

Diagnosis and staging of pancreatic cancer: comparison of mangafodipir trisodium-enhanced MR imaging and contrast-enhanced helical hydro-CT

OBJECTIVE

The purpose of this study was to compare mangafodipir trisodium-enhanced MR imaging performed with a phased array coil and contrast-enhanced single-detector helical CT for accuracy in the detection and local staging of pancreatic adenocarcinoma and in the differentiation between cancer and focal pancreatitis.

SUBJECTS AND METHODS

Forty-two patients with suspected pancreatic masses underwent contrast-enhanced helical CT and mangafodipir trisodium-enhanced MR imaging at 1.5 T. The images were assessed for the presence or absence of tumors; characterization of masses; and presence of vascular invasion, lymph node metastases, or liver metastases. Imaging findings were correlated with findings at laparotomy, laparoscopy, biopsy, or follow-up.

RESULTS

Focal masses were present in 36 patients (cancer, n = 26; focal pancreatitis, n = 7; other, n = 3). The sensitivity for lesion detection of MR imaging was 100% and of CT, 94%. Two small malignant lesions were missed on CT. For the diagnosis of tumor nonresectability, the sensitivity of MR imaging and CT was 90% and 80%, respectively. Liver metastases were missed on MR imaging in one of the eight patients and on CT in four. For differentiation between adenocarcinoma and nonadenocarcinoma, the sensitivity of MR imaging was 100% (positive predictive value, 90%; negative predictive value, 100%), and the sensitivity of CT was 92% (positive predictive value, 80%; negative predictive value, 67%). Receiver operating characteristic analysis revealed that the mean area under the curve for MR imaging was 0.920 and for CT, 0.832 (not significant).

CONCLUSION

Mangafodipir trisodium-enhanced MR imaging is as accurate as contrast-enhanced helical CT for the detection and staging of pancreatic cancer but offers improved detection of small pancreatic metastases and of liver metastases compared with CT.