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Case reports of five patients with pneumatosis intestinalis diagnosed by computed tomography (CT) are presented. Etiology, differential diagnoses, and clinical consequences arising from CT imaging are discussed. In four of the patients, pneumatosis was found to be secondary to gastric ulcer, colon carcinoma, metastasis in the mesentery, and trauma-induced mesenteric ischemia. In one patient, the etiology remained elusive. Using CT, both the extent and the distribution pattern of pneumatosis could be depicted, allowing for differentiation of primary and secondary forms and assessment of prognosis. Evaluation with a lung window is a pre-requisite for reliable diagnosis of pneumatosis with CT. The presence of gas in the mesenteric or portal venous system in mesenteric ischemia is indicative of an unfavorable prognosis.

MRI appears to be a reliable method to monitor LITT effects in patients with BPH.

The behavior of the signal intensity in MRI of human lungs was investigated during inhalation of pure oxygen. Nine volunteers were examined, five using a breath-hold and four using a non-breath-hold technique. Four coronal slices were acquired in each volunteer using an inversion recovery turbo spin-echo sequence. The inversion time of the sequence was optimized for maximum contrast. Breathing of pure oxygen and room air was alternated in the volunteers. Breath-hold and non-breath-hold cases were compared. Breathing pure oxygen lead to a statistically significant signal intensity increase (up to 18%) compared to breathing room air. In addition, T 1 maps were acquired during breathing 100% oxygen and room air. Inhalation of pure oxygen reduced the mean Key words: MRI; lung imaging; oxygen enhanced imaging; pulmonary diffusion capacityBecause of various advances in MRI technology, MRI of the lungs has recently gained interest. Modern MRI scanners with high gradient slew rates allow for good visualization of lung anatomy (1). Contrast-enhanced angiography has boosted lung imaging because it facilitates imaging the vessel tree up to 7-order branches (2-4). Another new and exciting technique uses hyperpolarized noble gases, such as 3 He or 129 Xe to image the airways of the lungs (5-7), which allows for the elucidation of lung ventilation. Most recently, Edelman et al. described a method for functional lung imaging that utilizes 100% O 2 (8). The basic principle of this new method is T 1 shortening of the proton spins when dissolved O 2 molecules are present. O 2 molecules are weakly paramagnetic with a magnetic moment of 2.8 Bohr magnetons (9,10). Because the indirect effect of O 2 on the proton spins in blood is measured with the new MR method and not directly the O 2 molecules, which remain in the alveoli, the diffusion of O 2 from the alveoli to the capillaries of the lungs can be imaged. T 1 shortening of blood protons due to O 2 during breathing of 100% O 2 will lead to a change of signal intensity (SI) in the lungs compared to breathing room air. However, another effect of breathing 100% O 2 is the SI enhancement of the lung parenchyma (8). Therefore, the diffusion of oxygen molecules from the alveoli into the capillaries is only one parameter that specifies the MR signal in oxygen-enhanced lung imaging. Areas in the lungs with a small diffusion capacity, including lung regions with ventilation and/or perfusion disorders, might show reduced or no SI increase during breathing 100% O 2 . However, perfusion is not the most important parameter of the new MRI method using 100% O 2 . The ability to image spatially resolved O 2 diffusion from the alveoli into the capillaries is the most important and interesting aspect of this new MRI method because this cannot be done with nuclear medicine techniques. One must keep in mind, however, that other parameters, such as perfusion, ventilation, and SI enhancement of lung parenchyma, also influence the SI change that can be seen in the oxygen-enhanced images. To reflect the...

The aim of this study was to investigate the value of a contrast-enhanced 3D MR angiography in detecting postoperative vascular complications after kidney transplantation in comparison with digital subtraction angiography (DSA). Forty-one patients who underwent a kidney transplantation were examined with MR angiography and DSA. Contrast-enhanced MR angiography was performed as a dynamic measurement with one precontrast and three postcontrast measurements. Maximum intensity projection reconstructions were performed for all postcontrast data sets after DSA. The results were evaluated by two independent observers who were unaware of the DSA results. Twenty-three hemodynamically significant arterial stenoses were identified with DSA in the iliac arteries ( n=7), the renal allograft arteries ( n=12), and in their first branches ( n=4). For a patient-based analysis the sensitivity and specificity, respectively, for observer 1 were 100 and 97%, and for observer 2, 100 and 93%. Respective data were 100 and 100% after a consensus evaluation by two observers. Complications involving the renal veins were detected in 2 cases and perfusion defects of the kidney parenchyma were detected in 4 cases. Contrast-enhanced MR angiography is a reliable method in identifying postoperative arterial stenoses after kidney transplantation. In addition, dynamic MR angiography can be helpful in detecting venous complications and perfusion defects in kidney allografts.