The prevalence of pancreatic cysts at single-shot fast SE MR imaging-especially cysts with a diameter smaller than 10 mm-is similar to that of pancreatic cysts at autopsy and higher than that of pancreatic cysts at transabdominal ultrasonography. Prevalence is especially high in patients with pancreatitis.
Dynamic contrast-enhanced subtraction MR imaging can provide information about testicular perfusion on the basis of contrast enhancement and can be used to differentiate testicular diseases from scrotal disorders.
Purpose: To assess whether measuring the pattern of pancreatic enhancement on gadolinium chelate dynamic magnetic resonance imaging (MRI) is helpful for diagnosis of suspected early or mild chronic pancreatitis. Materials and Methods:In this retrospective study, 24 patients with suspected early or mild chronic pancreatitis, classified by imaging criteria of equivocal chronic pancreatitis (ultrasound, computed tomography [CT] or ERCP) grading, had dynamic MRI that included unenhanced, arterial dominant, early venous, and late venous phases of contrast enhancement. Twenty patients without pancreatic diseases also had the dynamic sequence as a control group. The signal intensity was measured at the pancreatic head, body, and tail on all phases, and for each, the signal intensity ratio (SIR, the signal intensity in postcontrast divided by that in precontrast) was calculated. Two radiologists independently reviewed the images of the patients with suspected early or mild chronic pancreatitis for pancreatic morphologic abnormalities without knowing the results of signal intensity measurements.Results: On unenhanced images, there was no significant difference of signal intensity between control and pancreatitis groups (P Ͻ 0.05). In the pancreatitis group, but not in the control group, the unenhanced signal intensity of the pancreatic head and body were significantly higher than that of the tail (P Ͻ 0.05). In the control group, the greatest enhancement (highest SIR) after injection was in the arterial phase (1.89 Ϯ 0.31), significantly higher than that in the early venous phase (1.68 Ϯ 0.17, P Ͻ 0.01) and in the late venous phase (1.61 Ϯ 0.15, P Ͻ 0.001). The pancreatitis group, however, had an arterial phase SIR (1.65 Ϯ 0.23) that was significantly lower than its early venous phase SIR (1.75 Ϯ 0.22, P Ͻ 0.05) and lower than the arterial phase SIR of the control group (P Ͻ 0.01). The presence of an SIR less than 1.73 in the arterial phase and/or a delayed peak enhancement after contrast agent administration had a sensitivity and specificity of diagnosing early or mild chronic pancreatitis of 92% and 75%, respectively. This sensitivity was significantly higher than the sensitivity of 50% for diagnosis based on morphologic abnormalities (P Ͻ 0.05). Conclusion:Measuring pancreatic signal intensity on gadolinium chelate dynamic MRI is helpful for diagnosing early or mild chronic pancreatitis, especially before apparent pancreatic morphologic or signal intensity changes are present.
Rapid advances in techniques of magnetic resonance (MR) imaging have enabled diagnosis of acute gynecologic conditions, which are characterized by sudden onset of lower abdominal pain, fever, genital bleeding, intraperitoneal bleeding, or symptoms of shock. The chemical-selective fat-suppression technique not only helps establish the characteristics of lesions that contain fat components but also increases the conspicuity of inflammatory lesions. When a T2-weighted image is obtained with a very long effective echo time (>250 msec), even a small amount of ascites can be easily identified and the contrast between urine and complex fluid becomes more conspicuous. T2*-weighted images are useful for identification of hemorrhagic lesions by demonstrating deoxyhemoglobin and hemosiderin. Contrast material-enhanced dynamic subtraction MR imaging performed with a three-dimensional fast field-echo sequence and a rapid bolus injection of gadopentetate dimeglumine allows evaluation of lesion vascularity and the anatomic relationship between pelvic vessels and a lesion and allows identification of the bleeding point by demonstrating extravasation of contrast material. To optimize the MR imaging examination, attention should be given to the parameters of each pulse sequence and proper combination of the sequences.
Rapid advances in techniques of contrast material-enhanced magnetic resonance (MR) angiography have enabled evaluation of the entire aorta and the main arteries. Dynamic subtraction MR angiography consists of first-pass imaging of long segments of arteries by using a three-dimensional fast field echo sequence with multiple rapid bolus injections of a small dose of gadopentetate dimeglumine. Subtraction enables clear demonstration of the enhanced vascular lumen by eliminating background signal. Improved temporal resolution and repeated sequences after gadopentetate dimeglumine administration allow demonstration of arteries and veins separately. Double subtraction postprocessing can be used to eliminate arterial enhancement in demonstration of the portal and systemic veins. Additional postprocessing can be used to demonstrate arteries in a single image in patients with aortic dissection or a prolonged circulation time. To optimize the examination, the pulse sequence, injection dose, injection rate, timing of the start of data acquisition, imaging time, breath holding, section thickness, and coil selection should be considered. This technique is flexible enough to be applied in a variety of clinical settings, including atherosclerotic occlusive disease, aneurysm of aortoiliac arteries, bypass graft, Takayasu arteritis, aortic dissection, antiphospholipid antibody syndrome, renal artery disease, pelvic vascular disease, and the portomesenteric venous system.
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