The effect of decreasing mAs on image quality and patient dose in sinus CT.

The aim of this study was to determine the effect of reducing mAs on the diagnostic quality of images and the radiation dose to the orbits in patients undergoing sinus CT. We studied 40 consecutive patients undergoing paranasal sinus CT for inflammatory disease prior to functional endoscopic sinus surgery (FESS). Four groups of 10 patients were scanned at 200 mAs, 150 mAs, 100 mAs and 50 mAs, respectively. Orbital radiation dose was measured using thermoluminescent dosemeters. Images were reviewed independently by two observers who were unaware of the mAs setting used. Image quality was evaluated using a semi-quantitative scoring system for six anatomical structures. The osteomeatal complex, uncinate process, infundibulum, frontal recess, middle turbinate and optic nerve were assessed as: clearly demonstrated (2 points); demonstrated but not clearly visualized (1 point); or not seen (0 points). No significant difference was shown between any of the four groups in terms of image quality according to the scoring system used in this study. Mean radiation dose to the orbit was reduced by 77%, from 13.5 mGy at 200 mAs to 3.1 mGy at 50 mAs (p<0.05). CT of the sinuses can be performed in patients prior to FESS at greatly reduced mAs without loss of diagnostic quality of the images. This is important in reducing the radiation dose to the lens.

MRI of pancreatic neuroendocrine tumours.

Neuroendocrine tumours of the pancreas are rare and are frequently difficult to demonstrate. Several imaging modalities have been used to demonstrate these tumours, but recent reports have suggested that MRI may have an important role in their localization. We review the spectrum of MRI appearances of pancreatic neuroendocrine tumours.

Rapid MRI assessment of renal space-occupying lesions.

The aim of this study was to determine whether rapidly acquired MRI sequences, taking less than 5 min imaging time, can accurately characterise renal masses. All patients found to have a renal space-occupying lesion on CT or asked to participate in a prospective study using rapidly acquired MRI. The MRI technique was performed on a GE Signa (General Electric, Milwaukee, Wis.) 1.5 T magnet using breath-hold coronal and axial T1 GRASS (fast spoiled gradient-recalled acquisition into steady state, FSPGR30/90) and axial T2 fast spin-echo sequences. The results were analysed by two radiologists unaware of the CT or ultrasound findings. The CT/US was independently viewed by a third radiologist. Lesions were characterised as simple cysts, indeterminate or solid. The MR and CT/US results were correlated and the sensitivity and specificity of MR for the characterisation of simple cysts and solid renal masses calculated. A total of 144 lesions (68 patients; 29 women 39 men, age range 32-78 years, average age 60 years) were studied: 111 simple cysts; 3 hyperdense cysts; 26 renal cell carcinomas; and 4 indeterminate lesions on CT/US. There was agreement between the CT/US and MRI in 82% of cases. All renal cell carcinomas were correctly characterised on MRI. Of simple cysts, 79% were correctly identified using this technique. Breath-hold MRI performed in less than 5 min can accurately characterise the majority of renal masses. It is 100% sensitive in the characterisation of renal carcinoma, and it correctly identified approximately 80% of simple cysts. If used at the time a renal mass is detected on MRI, it would reduce the need for further investigation of the majority of incidentally detected lesions which are simple cysts.

Primary hyperaldosteronism (Conn syndrome): MR imaging findings.

PURPOSE: To describe the magnetic resonance (MR) imaging features of the adrenal glands in primary hyperaldosteronism and assess MR imaging in the detection and characterization of aldosterone-producing adenoma (APA). MATERIALS AND METHODS: The authors retrospectively reviewed the cases of 20 patients (13 female and seven male patients; age range, 14-67 years; median age, 46 years) with primary hyperaldosteronism who underwent 1.5-T MR imaging between 1995 and 1998. All patients underwent transverse T1- and T2-weighted imaging, and chemical shift imaging was performed in 17 patients. Imaging results were correlated with findings at biochemical testing, venous sampling, or surgery. RESULTS: Among the 20 patients, 10 (50%) had APA and 10 (50%) bilateral adrenal hyperplasia (BAH). In the detection of APA, MR imaging had a sensitivity of 70%, specificity of 100%, and accuracy of 85%. APAs (mean size, 20 x 16 mm) were iso- or hypointense relative to the liver on T1-weighted images and slightly hyperintense on T2-weighted images. With chemical shift imaging, the signal intensity decreased on the out-of-phase images in six of seven (86%) patients with APA and in eight of nine (89%) patients with BAH. CONCLUSION: MR imaging has a high specificity in the detection of APA. As with nonhyperfunctioning adenoma, APA and BAH show evidence of intracellular lipid at chemical shift imaging.

Role of MR imaging in the selection of patients with early cervical carcinoma for fertility-preserving surgery: initial experience.

PURPOSE: To assess whether magnetic resonance (MR) imaging can be used for reliable prediction of proximal extension of cervical carcinoma into the myometrium. MATERIALS AND METHODS: Thirty patients with early cervical carcinoma underwent MR imaging with use of a 1.5-T magnet prior to surgery. The MR images were analyzed by two radiologists, unaware of the histopathologic findings, for the relationship of the tumor to the internal os and extension of the tumor into the myometrium. Findings at MR imaging were compared with those at histopathologic examination. RESULTS: At MR imaging, 24 patients were considered not to have tumor extension proximal to the internal os and into the myometrium. All tumors were confirmed histopathologically. In six patients thought to have myometrial tumor invasion at MR imaging, five tumors were confirmed histopathologically; in one, tumor extended up to the internal os but did not involve the myometrium. CONCLUSION: This is a small study, but MR imaging appears accurate in the prediction of myometrial tumor involvement and in showing the relationship of cervical carcinoma to the internal os and, hence, the patient's suitability for trachelectomy.

Demonstration of hepatic steatosis by computerized tomography in patients receiving 5-fluorouracil-based therapy for advanced colorectal cancer.

The frequency and severity of fatty infiltration of the liver in patients receiving 5-fluorouracil (5-FU) and folinic acid has not been documented systematically. Its development can result in difficulty assessing disease progression, and treatment may be altered inappropriately. Twenty-seven patients with colon cancer and liver metastases receiving 5-FU and folinic acid were studied with computerized tomography (CT) before treatment and after six or 12 cycles of chemotherapy. Forty-seven per cent of patients developed hepatic steatosis during treatment. There was no correlation between development of hepatic steatosis and the dose of chemotherapy or the liver function tests. Hepatic steatosis occurs commonly in patients receiving 5-FU and folinic acid and can be severe. Its development can make hepatic metastases difficult to assess and if its benign nature is not appreciated treatment may be inappropriately altered.

State-of-the-art CT and MRI of the adrenal gland.

Both CT and MRI have achieved high accuracy in the investigation of patients suspected of having adrenal pathology. The choice of technique will depend on several factors discussed in the review. The advent of spiral CT has allowed the examination to be tailored to demonstrating the adrenal with very high spatial resolution and it remains the most widely used initial technique. This review concentrates on new techniques for evaluating the incidentally discovered adrenal mass and differentiating between adrenal adenomas and metastases.

Pheochromocytoma: effect of nonionic contrast medium in CT on circulating catecholamine levels.

PURPOSE: To study the catecholamine-releasing effect of peripheral intravenous administration of the nonionic contrast medium iohexol in patients with pheochromocytomas. MATERIALS AND METHODS: Ten patients (eight women, two men; mean age, 44 years; age range, 25-70 years) with pheochromocytomas and related tumors and six healthy volunteers (five men, one woman; mean age, 31 years; age range, 27-35 years) were examined. Plasma catecholamine levels were measured at intervals for 60 minutes after the injection of 0.9% saline or iohexol on 2 separate days. All 10 patients intravenously received the specific alpha-adrenergic blocker phenoxybenzamine hydrochloride (0.5 mg/kg in 250 mL of 5% dextrose infused over 2 hours) 24 hours before iohexol-enhanced computed tomography. RESULTS: There was no statistically significant increase in epinephrine or norepinephrine levels in the patients or the control subjects. CONCLUSION: While it may be prudent to administer oral alpha- and beta-adrenoceptor antagonists in all patients with a biochemically proved pheochromocytoma to control their symptoms and to prevent a spontaneous adrenergic crisis, specific blockade may not be required before contrast medium-enhanced scanning with iohexol. Although the sample size of this study is relatively small, the results do suggest that in an incidentally detected, clinically silent adrenal mass that may or may not be hypersecreting, the nonionic contrast medium iohexol may be used for scanning without blockade.