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Despite expert reader analyses, subjective evaluations of liver lesion signal characteristics are prone to inaccuracy and lack certainty and consistency when intermediate TEs (50/160 ms) are used. Quantitative measurements of T2 relaxation times should be performed to accurately and confidently differentiate benign from malignant liver lesions. Use of a higher T2 threshold than previously recommended is required to avoid misclassification of malignancies.

Despite expert reviewer analyses, subjective evaluations of blood attenuation characteristics are prone to inaccuracy and show poor interobserver agreement. Quantitative measurements of CT density in Hounsfield units should be performed to accurately differentiate an anemic from a nonanemic state when serum hemoglobin levels are not readily available.

Radiology research involves comparisons that deal with the presence or absence of various imaging signs and the accuracy of a diagnosis. In this article, the authors describe the statistical tests that should be used when the data are not distributed normally or when they are categorical variables. These nonparametric tests are used to analyze a 2 x 2 contingency table of categorical data. The tests include the chi2 test, Fisher exact test, and McNemar test. When the data are continuous, different nonparametric tests are used to compare paired samples, such as the Mann-Whitney U test (equivalent to the Wilcoxon rank sum test), the Wilcoxon signed rank test, and the sign test. These nonparametric tests are considered alternatives to the parametric t tests, especially in circumstances in which the assumptions of t tests are not valid. For radiologists to properly weigh the evidence in the literature, they must have a basic understanding of the purpose, assumptions, and limitations of each of these statistical tests.

We found no statistically significant difference in the prevalence of renal artery stenosis between patients with accessory renal arteries and those without accessory renal arteries. Assuming that the presence of two separate causes of hypertension in the same patient would be unlikely, this finding implies that accessory renal arteries are a vascular anomaly and not a direct cause of hypertension. The findings are potentially relevant in refuting the theory of accessory renal arteries as an anatomically treatable cause of hypertension.

This brief report outlines the novel use of whole body coronal turbo short tau inversion recovery (STIR) imaging to localize a primary tumor in patients with known metastatic disease without a previously identified source. ATTEMPTS TO IDENTIFY the source of metastases in patients without a known primary tumor are often time consuming, expensive, and ultimately unsuccessful (1). We report the novel use of whole body turbo short tau inversion recovery (STIR) MRI, as a n alternative to radiographs, CT, and scintigraphy, to identify the source of skeletal metastases in patients without a previously recognized primary source. METHODS AND MATERIALSOf 60 patients referred for staging whole body turbo STIR MRI over an 18-month period. 56 patients had known primary tumors. Four patients with documented metastatic disease (skeletal metastases, three patients: retroperitoneal lymphadenopathy, one patient), were referred without a known primary tumor. In each case, review of chest radiograph and abdominal CT failed to identify a primary tumor before whole body turbo STIR MRI. MR TechniqueMRI was performed on a 1.5-T Philips Gyrosran imager (Philips Medical Systems, Shelton, CT). In each case, coronal images were acquired using the body coil, maximum field of view (45-50 cm), and a turbo STIR sequence (TR = 4,000 msec: TE = 40 msec, inversion time [TI] = 160 msec: echo train length [ETL] = 6; echo spacing = 12 msec: acquisition time = 3 minutrs 43 seconds [images of the thorax were respiratory gated, increasing acquisition lo a n average of 8 minutes]), allowing uniform fat saturation and enhanced conspicuity of skeletal, visceral, and soft tissue lesions. In each case, 16 coronal slices were acquired for a TR of 4,000-msec, slice thickness dictated by body habitus (mean, 8 mm: with an interslice gap of .5 mm), and complete body coverage achieved by a maximum of four overlapping coronal body coil acquisitions (mean total scan time, 40 minutes). In each case, coronal images were obliqued to the long axis of the spine prescribed off a sagittal localizrr. In each case, positioning of the upper extremities was dictated by patient habitus. In patients with cachexia, the arms were easily placed over the thorax and abdomen. In larger patients, the arms were placed above the head, requiring an additional coronal acquisition (an additional 4 minutes scan time). RESULTS Case 1A 42-year-old male presented with shoulder pain. A chest radiograph dem-

Objective The purpose of this study was to determine which imaging characteristics can be used as prognostic indicators in conjunction with β‐human chorionic gonadotropin (β‐hCG) levels in the treatment of ectopic pregnancy (EP) with single‐dose methotrexate (MTX). Methods A retrospective study was performed on 62 patients (age range, 16–47 years; mean, 29 years) treated with MTX for EP from November 2000 to August 2003. The transvaginal sonographic findings in each case were analyzed for the presence and size of an extraovarian mass or a pseudogestational sac, amount of free fluid, presence of a yolk sac, and fetal heart motion. Patient age and β‐hCG level were also noted. Success of treatment was defined as a single dose of MTX that resulted in appropriate lowering of β‐hCG levels. Results Of 62 patients, 17 (27%) had single‐dose MTX treatment failure. A yolk sac was identified in 15 (88%) of the 17 treatment failures and in none of the cases in which treatment was successful (positive predictive value, 100%). The average β‐hCG level in the cohort of patients who had single‐dose treatment failure was 3282 mIU/mL compared with 1544 mIU/mL in the treatment success cohort. The presence of fetal heart motion was seen in only 1 patient, and this patient had treatment failure. The age of the patient, size of the extraovarian mass, presence of a pseudogestational sac, and amount of free fluid did not correlate with outcome. Conclusions The presence of a yolk sac was always associated with treatment failure in single‐dose MTX treatment of EP and was the most reliable predictor of failure among all features analyzed. The β‐hCG level was a useful adjunct. A prediction rule was created correlating the probability of treatment success with the β‐hCG level.

Renal masses that are interpreted as suspicious on CT may lack MR enhancement because of hemorrhage effects; heterogeneity of their T2 appearance is thus critical in differentiating malignancy from benign disease. Odds-ratio calculations give an adjusted estimate of a 3.36-fold increase (95% confidence interval, 1.8-6.27) in the likelihood of malignancy when masses are heterogeneous on T2-weighted images and a 29-fold increase (95% confidence interval, 3.67-241.8) for predicting malignancy when enhancement is present.