Preoperative MR imaging in hyperparathyroidism: results and factors affecting parathyroid detection.

OBJECTIVE: To determine the sensitivity of MR imaging for the detection of abnormal parathyroid glands in patients with biochemical evidence of hyperparathyroidism and to identify the factors affecting detection. SUBJECTS AND METHODS: Between 1985, 82 patients with biochemical proof of hyperparathyroidism were referred for MR imaging of the parathyroid glands prior to surgery. Axial T1- (600/20 [TR/TE]) and T2-weighted (2500/40, 80) spin-echo images were obtained using an anterior neck surface coil. The interpretation of the MR image was compared with the findings at surgery and also correlated with gland histology, volume, and weight. Cases in which a false-positive or false-negative diagnosis was made were reviewed to determine the factors affecting detection. RESULTS: MR imaging detected 71 of 92 (77%) surgically proven abnormal glands (sensitivity, 77%; 95% confidence interval (CI), 68-86%) and misdiagnosed five (1.6%) of 314 normal glands as abnormal. There was no difference in the detection of enlarged glands in patients presenting for the first time (n = 71) (sensitivity, 77%; 95% CI, 66-86%) compared with patients with recurrent hyperparathyroidism (n = 12) (sensitivity, 77%; 95% CI, 46-95%). There was no significant difference in the detection of adenomas (sensitivity, 77%; 95% CI, 65-86%) compared with hyperplasia (sensitivity, 71%; 95% CI, 42-92%). Of five patients with ectopic parathyroid glands (1.6%), four had had previous surgery. All five glands were successfully located (three mediastinal, two in the neck). Factors contributing to a false-negative MR imaging diagnosis included small gland size and thyroid disease. Four of five false-positive diagnoses were due to enlarged lymph nodes being mistaken for parathyroid glands. CONCLUSIONS: MR imaging is an accurate technique for investigation of hyperparathyroidism. Pitfalls include low sensitivity for the identification of small glands, misinterpretation of enlarged lymph nodes as parathyroid adenomas, and misinterpretation because of thyroid disease. MR imaging is particularly useful in the investigation of patients who remain hypercalcemic following initial surgery.

Magnetic resonance angiography of the distal lower extremity.

OBJECTIVE: To assess magnetic resonance angiography (MRA) for demonstration of arterial patency in the ankle and foot of patients with peripheral vascular disease. METHODS: Peripheral MRA of the ankle and foot was performed on 34 limbs of 31 insulin-dependent diabetics. 2-D time-of-flight MRA (TR 33 ms/TE 7.7 ms/inferior saturation band) was performed with 16 cm field of view. Pre- or intra-operative angiographic correlation was available in all cases. RESULTS: In 24 limbs MRA was compared to conventional angiography. MRA showed more patient run-off vessel segments (120) than angiography (100). In 10 limbs MRA was compared to intraoperative angiography and for the detection of patent vessel segments showed a sensitivity of 87.5% (42/48) with a 95% confidence interval of 75% to 95% and a specificity of 95% (38/40) with a 95% confidence interval of 83% to 99%. Pitfalls included difficulty in visualizing flow at the bifurcation of the peroneal artery, in the plantar arch and retrograde flow in the lateral plantar artery. CONCLUSIONS: MRA is sensitive for the detection of patent arteries in the ankle and foot but artefacts may cause overdiagnosis of focal stenoses or occlusions.

Magnetic resonance cholangiography.

MR cholangiography offers a noninvasive method of obtaining images of the biliary system without the use of a contrast agent. There is no radiation exposure. Pulse sequences can be chosen to obtain bright bile or black bile cholangiograms. Image processing algorithms can be selected to obtain a three-dimensional representation of biliary anatomy and pathology, and those images can be rotated in any plane so that ductal anatomy and pathology can be seen to best advantage. In patients with a nonobstructed biliary system, the RHD, LHD, CHD, CBD, and distal PD are usually visible. In patients with choledocholithiasis, the CE-FAST technique has demonstrated higher diagnostic accuracy than the FSE approach, although TRAP image reconstruction probably would improve the accuracy of the FSE technique in detecting stones. In patients with malignant biliary obstruction, FSE is considerably more accurate in determining the cause of obstruction than is CE-FAST. Furthermore, MR cholangiography compares favorably with ERCP, prompting one author to suggest that, in selected patients, MR cholangiography might be used instead of direct cholangiography or to direct invasive techniques. With continued technologic advancements, MR cholangiography will no doubt improve as well. In particular, the possibility of a breath-hold, multicoil, FSE cholangiogram, obtained with the stronger gradients on an echo planar system, potentially combines the key advantages of CE-FAST and conventional FSE techniques. It may be that in the not-too-distant future, all patients with obstructive jaundice will be imaged first with MR imaging. In addition to the typical axial images of the abdomen required for staging, an MR cholangiogram will be obtained in a matter of a few seconds. An MR angiogram will also be performed to determine vascular anatomy and pathology. MR spectroscopy might also be used to obtain additional diagnostic information. All of this would be done in less than an hour, noninvasively, and with no radiation. Some patients would then require percutaneous transhepatic cholangiography or ERCP. Others would undergo MR-guided biopsy. Eventually, still other patients might go directly to surgery.

Prostatic and periprostatic cysts: findings on MR imaging.

Cysts of the prostate or perioprostatic tissues are uncommon and include congenital müllerian or utricular cysts, prostatic retention cysts, cysts of benign prostatic hyperplasia, cystic carcinoma, parasitic and infectious cysts, as well as cysts of the ejaculatory apparatus or seminal vesicles. The radiological diagnosis of prostatic or periprostatic cysts can be difficult because of the resolution needed to define the relationship of a cyst to surrounding structures, such as the vas deferens, seminal vesicles, and ejaculatory ducts [1]. Prostatic cysts are easily identified on MR images by virtue of their high signal on T2-weighted images and can be characterized because of their typical locations and the high resolution and multiple imaging planes provided by MR [2]. Because these conditions are usually managed conservatively, pathologic proof is not possible in all cases, and the diagnosis is often made on the basis of clinical features and imaging appearance. The purpose of this essay is to illustrate the findings on MR imaging.

Preliminary evaluation of iron phytate (inositol hexaphosphate) as a gastrointestinal MR contrast agent.

A simple, effective, safe, and well-tolerated contrast agent is needed as a bowel marker for magnetic resonance (MR) imaging. The authors tested a variety of foodstuffs admixed with ferric iron as potential gastrointestinal MR contrast agents. Phytate (inositol hexaphosphate) more than doubled the relaxivity of solutions of ferric iron. Because of the improved relaxivity of iron phytate, the concentration of iron could be reduced substantially relative to free ferric iron (eg, ferric chloride or ferric ammonium citrate). Imaging studies were performed in five volunteers to determine the optimal dose of iron phytate and in five additional volunteers to test its effectiveness. A 200 mg/L concentration of ferric iron with phytate functions as an effective gastrointestinal MR contrast agent for T1-weighted abdominal MR imaging, significantly improving bowel contrast (P < .01). Blood studies after contrast agent administration showed no appreciable increase in serum iron. Compared with standard chelate complexes that decrease the relaxivity of a given paramagnetic ion, phytate not only decreases the absorption of the iron but increases its relaxivity.

CT findings after hepatic chemoembolization.

Hepatic arterial chemoembolization (CE) with a mixture of particulate collagen and chemotherapeutic agents was evaluated as therapy for hepatic metastases from colorectal carcinoma. This article describes the characteristics sequential pattern of change seen on liver CT scans following CE. Thirty CT scans were performed on seven patients who had undergone a total of 11 CE procedures. All patients had baseline, immediate postprocedural, and follow-up CT exams at 1 to 2 month intervals following CE. Immediate post-procedural CT scans mapped the area of embolization owing to the density of the contrast mixed with the CE agents. Some lesions seen easily on baseline were more difficult to see as they became isodense with normal liver. Reflux of embolic material into the cystic artery and gallbladder wall was also observed on postprocedural scans in three patients. In all patients, early follow-up scans (1 month after CE) demonstrated changes in lesions seen on baseline scans consistent with tumor necrosis. This was corroborated by a decrease in carcinoembryonic antigen (CEA) levels. In three patients, however, low attenuation regions developed in areas in which there had been no lesion before. The significance of these is uncertain, but the low CEA values and the subsequent evolution in appearance of these sites on CT suggest that they were regions of hepatic ischemia/infarction as opposed to heretofore unidentifiable metastases, now "unmasked." Intermediate follow-up scans (2-3 months) revealed maximal effect on tumor volume, with a decrease of > or = 25% in five of seven patients (71%). Late follow-up scans (> or = 3 months after the last CE) confirmed recurrent disease and new lesions in all cases.

Factors influencing women to undergo screening mammography.

Despite the fact that mammography is a valuable tool for early detection of breast cancer, the majority of age-eligible American women do not avail themselves of screening mammography. To better understand why women do or do not undergo mammography and to further develop guidelines for promoting breast cancer screening, the authors investigated what impact personal factors, attitudes, and health-related behaviors have on compliance with screening mammography by surveying 521 women for information related to health behavior, health concerns, sense of well-being, satisfaction with health care, and knowledge about breast cancer. Women who underwent mammography were more likely to have a regular physician, to practice breast self-examination, to be less concerned over the cost of mammography, to be generally satisfied with their health care, to believe they have a greater sense of control over their health, and to be more knowledgeable about mammography and breast cancer. Age, health behavior, sense of well-being, locus of control, and breast cancer experience helped differentiate between women who had undergone mammography and those who had not.