Gary M. Glazer

Practical approaches to the evaluation of signal‐to‐noise ratio performance with parallel imaging: Application with cardiac imaging and a 32‐channel cardiac coil

In this work, two practical methods for the measurement of signal‐to‐noise‐ratio (SNR) performance in parallel imaging are described. Phantoms and human studies were performed with a 32‐channel cardiac coil in the context of ultrafast cardiac CINE imaging at 1.5 T using steady‐state free precession (SSFP) and TSENSE. SNR and g‐factor phantom measurements using a “multiple acquisition” method were compared to measurements from a “difference method”. Excellent agreement was seen between the two methods, and the g‐factor shows qualitative agreement with theoretical predictions from the literature. Examples of high temporal (42.6 ms) and spatial (2.1 × 2.1 × 8 mm3) resolution cardiac CINE SSFP images acquired from human volunteers using TSENSE are shown for acceleration factors up to 7. Image quality agrees qualitatively with phantom SNR measurements, suggesting an optimum acceleration of 4. With this acceleration, a cardiac function study consisting of 6 image planes (3 short‐axis views, 3 long‐axis views) was obtained in an 18‐heartbeat breath‐hold. Magn Reson Med, 2005.

Integration of magnetic resonance imaging into radiation therapy treatment planning: i. technical considerations

This paper presents the results of a feasibility study specifically addressing the technical and operational difficulties in making quantitative use of Magnetic Resonance Imaging (MRI) in radiation therapy treatment planning (RTTP). Selected radiotherapy patients have been studied with both CT and MRI as part of the treatment planning process. Both sets of images, along with mechanically-obtained external contour and simulator film data, are entered into the treatment planning system. All of the capabilities of the fully three dimensional planning system U-MPlan are available to both the CT and MRI images, in which any image can be used as the backdrop for interactive beam positioning, beam portal simulation, and dose distribution displays for external beam and brachytherapy applications in both 2- and 3-dimensionally-oriented displays. The study has shown that to use MRI data for RTTP, one must (a) use careful patient positioning and marking, (b) transfer information from CT to MRI and vice versa, (c) determine the geometrical consistency between the CT and MR data sets, (d) investigate the unwarping of distorted MR images, and (e) have the ability to use non-axial images for determination of beam treatment technique, dose calculations, and plan evaluation.

A model for faculty mentoring in academic radiology.

RATIONALE AND OBJECTIVES The purpose of this report is to describe the development and implementation of a faculty mentoring program in radiology designed to promote the career development of junior faculty and enhance communication in the department. MATERIALS AND METHODS The mentoring program was implemented in five stages: organizational readiness, participant recruitment, mentor matching and orientation, implementation, and evaluation. Evaluations were based on Likert scale ratings and qualitative feedback. A retrospective analysis was also conducted of the annual performance reviews of junior faculty in the areas of research, teaching, patient care, and overall performance. RESULTS An average of 83% (19 of 23) of the junior faculty participated in the pilot phase of the mentoring program. During five rounds of testing, the median rating (1 indicates not important; 10, extremely important) from responding junior faculty was 10 for overall value of individual mentoring meetings; the median rating for the mentors responding was 8.75. Research and academic development were identified as the areas of greatest importance to the faculty. Research and patient care were most improved as assessed by faculty peers during performance reviews. The schedule of semiannual formal mentoring meetings was reported to be optimal. CONCLUSION The program was implemented to the satisfaction of junior faculty and mentors, and longitudinal performance suggests positive effects. Issues to be contended with include confidentiality and the time needed for mentoring beyond already saturated schedules. Overall, the authors propose that mentoring programs can be an asset to academic radiology departments and a key factor in maintaining their vitality.

The Invisible Radiologist

In the early years of the profession, radiologists had direct contact with patients but gradually became less visible to them as changes occurred in professional status, medical economics, and development of advanced technology and academic medical centers.

MR evaluation of liver iron overload

Children and young adults with hemolytic anemias requiring frequent transfusions develop increased liver iron content. We evaluated 15 chronically transfused children with sickle cell disease to determine whether spin-echo magnetic resonance (MR) imaging was useful in assessing the degree of iron overload. Quantitative MR parameters were correlated with liver biopsy iron determinations and serum ferritin levels. The best predictor of liver iron was the ratio of the intensities between the liver and paraspinal musculature on somewhat T1 weighted sequence (repetition time 0.5 s, echo time 28 ms). R2 = 0.58. Magnetic resonance was able to separate those patients with liver iron levels >100 μg/mg (intensity ratio ∼0.4). from those with levels <100 μg/mg (intensity ratios near I). However. MR was unable to quantitate liver iron in patients with values ranging from 100 to 400 μg/mg since similar intensity ratios were present in this range. Thus. MR provides a qualitative rather than quantitative assessment of liver iron overload.

Multiple pulmonary nodules detected by computed tomography: diagnostic implications.

Prior to the advent of CT, the radiographic demonstration of multiple nonmiliary lung nodules usually indicated the presence of metastases or, less likely, granulomas. The increased sensitivity of CT at detecting small parenchymal pulmonary densities is accompanied by loss of specificity, creating uncertainty as to the significance of nodules detected at CT in any individual patient. During a 1 year period we reviewed all CT scans in our institution demonstrating three or more focal lung densities, noting these parameters: number of densities, maximum lesion size, presence of calcification as determined visually, and lesion morphology (linear or nodular). Of 137 patients with three or more focal lung densities at CT, nodule diagnosis was established on pathologic or clinical grounds in 114. Metastases accounted for 73%, with primary colon and lung malignancies and lymphoma the most common causes. Malignant nodules were statistically significantly larger, more numerous, and more rounded, whereas calcification was significantly associated with benign disease. However, no single criterion or combination of criteria was foolproof. Based on our results, we offer recommendations for further evaluation of nodules in several common clinical settings.

Interobserver variability in CT and MR staging of lung cancer

Objective Our goal was to assess the interobserver variability in staging non-small cell lung cancer using CT and MRI. Materials and Methods As part of the Radiologic Diagnostic Oncology Group (RDOG) study of lung cancer staging, the CT and MR examinations of 40 patients suspected of having non-small cell bronchogenic carcinoma were blindly interpreted by four expert observers. The primary tumor and lymph node stages in the 40 study subjects were similar to the final proportions reported in the RDOG study. Assessed abnormalities included the presence of a lung nodule, chest wall invasion, mediastinal invasion, bronchial involvement, lymph node metastasis in specific node stations, and T and N classifications. Percent agreement and α-values were calculated for each of these determinations. Results Depending on the finding assessed and the method of analysis, average agreement rates ranged from 58 to 90% for CT and from 61 to 96% for MRI. Average α-values were largely between 0.40 and 0.60 when dichotomous analysis was used; weighted α-values were similar. With a single exception, no significant differences were found for α-values calculated for CT and MRI. Conclusion Although interobserver agreement rates are good for determining T and N classification in patients with lung cancer, variability in image interpretation is frequent, even among experienced observers.

In vivo MRSI of hyperpolarized [1-13C]pyruvate metabolism in rat hepatocellular carcinoma

Hepatocellular carcinoma (HCC), the primary form of human adult liver malignancy, is a highly aggressive tumor with average survival rates that are currently less than 1 year following diagnosis. Most patients with HCC are diagnosed at an advanced stage, and no efficient marker exists for the prediction of prognosis and/or response(s) to therapy. We have reported previously a high level of [1‐13C]alanine in an orthotopic HCC using single‐voxel hyperpolarized [1‐13C]pyruvate MRS. In the present study, we implemented a three‐dimensional MRSI sequence to investigate this potential hallmark of cellular metabolism in rat livers bearing HCC (n = 7 buffalo rats). In addition, quantitative real‐time polymerase chain reaction was used to determine the mRNA levels of lactate dehydrogenase A, nicotinamide adenine (phosphate) dinucleotide dehydrogenase quinone 1 and alanine transaminase. The enzyme levels were significantly higher in tumor than in normal liver tissues within each rat, and were associated with the in vivo MRSI signal of [1‐13C]alanine and [1‐13C]lactate after a bolus intravenous injection of [1‐13C]pyruvate. Histopathological analysis of these tumors confirmed the successful growth of HCC as a nodule in buffalo rat livers, revealing malignancy and hypervascular architecture. More importantly, the results demonstrated that the metabolic fate of [1‐13C]pyruvate conversion to [1‐13C]alanine significantly superseded that of [1‐13C]pyruvate conversion to [1‐13C]lactate, potentially serving as a marker of HCC tumors. Copyright

Scintigraphic localization of adrenal lesions in primary aldosteronism.

Dexamethasone suppression adrenal cortical scintiscanning was performed in 87 patients with primary aldosteronism. Fifty patients had adrenal cortical adenomas and 37 had bilateral adrenal hyperplasia. The diagnosis of adrenal cortical adenoma was confirmed by surgery in 49 of 50, and bilateral adrenal hyperplasia was confirmed by adrenal vein aldosterone sampling in 33 and at operation in four. Dexamethasone suppression adrenal scintigraphy correctly identified the lesion(s) in 82 of the 87 patients. There were three false-negative and two false-positive adrenal cortical scintiscanning results. Computed tomography was performed in 33 patients and correctly identified 14 of 23 patients with adrenal cortical adenomas and two of 10 patients with bilateral adrenal hyperplasia and bilateral enlarged adrenals, whereas the remaining eight were considered to have normal findings. These data indicate that, when properly performed, adrenal cortical scintigraphy is an accurate and efficacious modality for the localization of adrenal cortical adenomas and in the differentiation of adrenal cortical adenoma from bilateral adrenal hyperplasia in primary aldosteronism.

Adrenal localization in the adrenocorticotropic hormone-independent Cushing syndrome.

STUDY OBJECTIVE To assess the efficacy of 131I-6-beta-iodomethylnorcholesterol scintigraphy in the adrenocorticotropic hormone-independent Cushing syndrome and to compare this with computed tomography. DESIGN Retrospective analysis of case series from 1977 to 1987. SETTING Referral to the Division of Nuclear Medicine at a tertiary-care university medical center. PATIENTS Twenty-four patients with a pathologically-confirmed diagnosis of the adrenocorticotropic hormone-independent Cushing syndrome had 131I-6-beta-iodomethylnorcholesterol scintigraphy and, in most cases, computed tomography. MEASUREMENTS AND MAIN RESULTS Using 131I-6-beta-iodomethylnorcholesterol scintigraphy, adenomas were accurately seen as focal, unilateral tracer uptake in 14 of 14 patients. In carcinoma, the classic scintigraphic pattern of bilateral nonvisualization was observed in 3 of 4 patients, with ipsilateral uptake of tracer in 1 patient with a histologically well-differentiated malignancy. Computed tomography done during the same interval depicted abnormal adrenals in all cases of adenoma and carcinoma. In cortical nodular hyperplasia, however, computed tomography identified abnormal pairs of adrenals in only one of four cases studied, whereas scintigraphy showed typical patterns of bilateral increased uptake in all of the cases. CONCLUSION 131I-6-beta-iodomethylnorcholesterol scintigraphy accurately shows the location and nature of adrenal dysfunction in the adrenocorticotropic hormone-independent Cushing syndrome and may be particularly useful in identifying the bilateral adrenal involvement in cortical nodular hyperplasia.