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Three-dimensional gadolinium-enhanced MR angiography is a rapid and accurate method that can at times image only a limited amount of anatomy during an examination. We evaluated a technique that doubled the anatomy imaged by obtaining two separate gadolinium-enhanced MR angiograms during a single examination.Twenty-three patients referred for MR evaluation of aortic or peripheral vascular disease underwent two successive gadolinium-enhanced three-dimensional MR angiographic examinations during a single MR examination. An injection of 15 ml of gadopentetate dimeglumine was used for the first MR angiogram, and 25 ml was used for the second MR angiogram. The angiograms were quantitatively and qualitatively evaluated to determine the effect of residual gadolinium from the initial MR angiogram on the second angiogram.The two studies depicted either the entire aorta to the femoral arteries (n = 10) or the distal aorta to the popliteal arteries (n = 13). The total mean gadolinium dose was 0.245 mmol/kg per patient. An average of 15 min elapsed between injections. The value of arterial signal-to-noise ratio (mean, 48.8 versus 56.4) and artery-to-vein contrast-to-noise ratio (mean, 45.5 versus 49.0) increased between the first and second angiograms, respectively. Residual gadolinium elevated the values for venous signal-to-noise ratio (mean, 2.3 versus 7.2) and background-to-muscle signal-to-noise ratio (mean, 5.5 versus 10.1) on the second MR angiogram. Qualitative evaluation by three observers showed no significant differences in diagnostic usefulness or overall image quality between the first and second MR angiograms.The use of two low-dose gadolinium-enhanced three-dimensional MR angiograms during a single examination is a feasible approach to increase anatomic coverage when performing gadolinium-enhanced three-dimensional MR angiography of the aorta and peripheral vessels. Although background enhancement is slightly elevated on the second angiogram, such enhancement does not significantly change diagnostic usefulness or overall image quality.

Colonic adenocarcinoma is an uncommon but aggressive neoplasm in patients under the age of 40. The goals of this study were to evaluate the utility of computed tomography (CT) in preoperative staging and detection of postoperative recurrences in young patients with colon cancer and to evaluate the pattern of recurrent disease. We reviewed 51 cases of adenocarcinoma in patients aged 40 years and younger. CT preoperatively staged 21 (72%) of 29 patients correctly and had a 100% positive predictive value for metastatic disease. Recurrent disease occurred in 23 (76%) of 30 nonstage D patients with at least 2 years of disease-free follow-up. CT accurately detected 21 (91%) of 23 cases of recurrent disease. Local recurrences were detected in 20 (87%) of 23 patients. Isolated local disease was the most frequent pattern of recurrence, seen in 17 (74%) of 23 patients. Hepatic metastases were rare and occurred in nine (13%) of 51 patients. Young patients with colon cancer have an increased prevalence of isolated local recurrences and decreased rate of hepatic metastases than the older population. In order to detect early, and therefore resectable recurrent disease, CT examinations should be obtained early and often in the postoperative period.

Recent reports have raised general awareness that cardiac computed tomography (CT) has the potential for relatively high effective radiation doses. While the actual amount of risk this poses to the patient is controversial, the increasing concern has led to a great deal of research on new CT techniques capable of imaging the heart at substantially lower radiation doses than was available only a few years ago. Methods of dose reduction include optimised selection of user-defined parameters, such as tube current and voltage, as well as use of new technologies, such as prospective triggering and iterative reconstruction. These techniques have each been shown to lead to substantial reduction in radiation dose without loss of diagnostic accuracy. This article will review the most frequently used and widely available methods for radiation dose reduction in cardiac CT and give practical advice on their use and limitations.