Faculty Bibliography

Introduction: An inflammatory response to various diseases, including acute myocardial ischemia, cardiac transplantation rejection and acute myocarditis, results in water accumulation in the myocardium. Excess water accumulation results in myocardial edema, which can lead to various conditions including myocardial stiffness, diastolic dysfunction, and tissue swelling [1]. Conventional T₂-weighted (T₂w) MRI can be used to qualitatively (Table Presented) detect myocardial edema, but often yield non-uniform signal due to surface coil effects [2]. We propose to quantitatively detect myocardial edema using a breath-hold T2 mapping pulse sequence based on multi-echo, spin-echo (ME-SE) imaging [3]. Purpose: To quantitatively assess myocardial edema using a breath-hold, ME-SE T₂ mapping pulse sequence in patients with clinical evidence of cardiac disease. Methods: We imaged 7 female patients with various types of heart disease (see Table 1 for clinical history) on a 1.5 T MR scanner (Siemens;Avanto), using both the conventional T₂w and ME-SE T₂ mapping pulse sequences in 3 short-axis views of the heart. The relevant imaging parameters for the T₂ mapping pulse sequence are: spatial resolution = 2 mm x 2 mm x 8 mm, echo-spacing = 4.5 ms, turbo-factor = 4, number of images = 8, and breath-hold duration = 13 s. Conventional T₂w images were qualitatively evaluated by a cardiologist for presence of myocardial edema. For the ME-SE data, myocardial contours were segmented manually using shortaxis planes, and the corresponding pixel-by-pixel T₂ maps were calculated by non-linear least square fitting of the monoexponential relaxation curve. T₂ values were averaged over the entire myocardium. The clinical reading and T₂ data analysis were performed independently. For the ME-SE data, an upper limit cutoff T₂ value of 62.9 ms (5 standard deviations above the mean) was chosen based on prior ME-SE data obtained from a control group [3]. The accuracy of quantitative detection of myocardial edema was correlated with qualitative evaluation. Results: Figure 1 shows T₂w images and corresponding T₂ maps from a patient diagnosed with myocardial edema compared to those from a patient without edema. Three out of seven patients were diagnosed with myocardial edema based on increased signal intensity on conventional T₂w images and based on increased T₂(Table 1). Conclusion: This study demonstrates the feasibility of quantitatively detecting myocardial edema using a breath-hold ME-SE T₂ mapping pulse sequence. Clinical evaluation for myocardial edema is challenging with conventional T₂w imaging due to surface coil effects and lack of a normal myocardium reference signal. Future directions for this research include correlating increased T₂ values with specific cardiac conditions and evaluating the clinical utility of this quantitative technique for assessment of myocardial edema. (Figure Presented)

AIM: To compare the evaluation times and accuracy of unidirectional panoramic three-dimensional (3D) endoluminal interpretation to traditional two-dimensional (2D) and bidirectional 3D endoluminal techniques. MATERIALS AND METHODS: Sixty-nine patients underwent computed tomography colonography (CTC) after bowel cleansing. Forty-five had no polyps and 24 had at least one polyp > or = 6 mm. Patients underwent same-day colonoscopy with segmental unblinding. Three experienced abdominal radiologists evaluated the data using one of three primary interpretation techniques: (1) 2D; (2) bidirectional 3D; (3) panoramic 3D. Mixed model analysis of variance and logistic regression for correlated data were used to compare techniques with respect to time and sensitivity and specificity. RESULTS: Mean evaluation times were 8.6, 14.6, and 12.1 min, for 2D, 3D, and panoramic, respectively. 2D was faster than either 3D technique (p < 0.0001), and the panoramic technique was faster than bidirectional 3D (p = 0.0139). The overall sensitivity of each technique per polyp and per patient was 68.4 and 76.7% for 2D, 78.9 and 93.3% for 3D; and 78.9 and 86.7% for panoramic 3D. CONCLUSION: 2D interpretation was the fastest overall, the panoramic technique was significantly faster than the bidirectional with similar sensitivity and specificity. The sensitivity for a single reader was significantly lower using the 2D technique. Each reader should select the technique with which they are most successful

OBJECTIVE: The purpose of this study is to compare the diagnostic accuracy of liver apparent diffusion coefficient (ADC) versus normalized liver ADC using the spleen as a reference organ for the diagnosis of liver fibrosis and cirrhosis. MATERIALS AND METHODS: Fifty-six patients, 34 with liver disease and 22 control subjects, were assessed with breath-hold single-shot echo-planar diffusion-weighted imaging using b values of 0, 50, and 500 s/mm(2). Liver ADC and normalized liver ADC (defined as the ratio of liver ADC to spleen ADC) were compared between patients stratified by fibrosis stage. Receiver operating characteristic (ROC) analysis was used to determine the performance of ADC and normalized liver ADC for prediction of liver fibrosis and cirrhosis. Reproducibility was assessed by measuring coefficient of variation (n = 7). RESULTS: Liver ADC failed to distinguish individual stages of fibrosis, except between stages 0 and 4. There were significant differences in normalized liver ADC between control livers and intermediate stages of fibrosis (stages 2-3) and cirrhosis (stage 4) and between stages 1 and 4, and there was a trend toward significance between stages 0 and 1 (p = 0.051) and stages 1 and 3 (p = 0.06). ROC analysis showed that normalized liver ADC was superior to liver ADC for detection of stage >/= 2 (area under the ROC curve, 0.864 vs 0.655; p = 0.013) and stage >/=3 (0.805 vs 0.689; p = 0.015), without a difference for diagnosing cirrhosis (0.935 vs 0.720; p = 0.185). Normalized liver ADC had higher reproducibility than ADC (mean coefficient of variation, 3.5% vs 12.6%). CONCLUSION: Our results suggest that normalizing liver ADC with spleen ADC improves diagnostic accuracy for detection of liver fibrosis and cirrhosis when using breath-hold diffusion-weighted imaging, with better reproducibility

BACKGROUND: Dual-source computed tomography (DSCT) provides diagnostic quality images of the coronary arteries over a wide range of heart rates (HRs). Current dose reduction techniques, including electrocardiographic (ECG) dose modulation and prospective triggering, are optimized for use in patients with relatively slow (<70 beats/min) HRs by limiting radiation dose to the ideal phases of image acquisition. OBJECTIVE: We evaluated coronary vessel image quality (IQ) at different reconstruction phases in patients with fast HRs (>80 beats/min) to assess potential feasibility of prospective triggering techniques on DSCT. METHODS: Patients (n=101) underwent 64-slice DSCT with retrospective ECG-gating without beta-blocker premedication. Image reconstructions were performed at 10% R-R wave phase intervals (0%-90%). Patients were grouped by mean HR: group A, <60 beats/min (n=22); group B, 60-80 beats/min (n=57); group C, >80 beats/min (n=22). Coronary artery IQ was assessed by 2 readers in consensus on a 5-point scale. RESULTS: Optimal IQ occurred at 70% phase for all arteries in groups A and B. In group C, optimal IQ occurred at 30% and 40% phases. The 70% phase achieved diagnostic IQ in 97% of group A and 86% of group B. A widened reconstruction window (30%-50%) was necessary for diagnostic IQ in a similar high proportion (84%) of group C. CONCLUSION: Optimal IQ occurs during late-systolic phases for patients with fast HRs (>80 beats/min). Late-systolic phase prospective triggering is potentially feasible in these patients; however, given the widened reconstruction windows required, a higher radiation dose may be required compared with patients with slower HRs (<80 beats/min)

The multidetector coronary computed tomography angiogram findings of a rare variant crossed left circumflex and left anterior descending artery are presented. In this patient, multidetector coronary computed tomography angiogram enabled clear delineation of the aberrant coronary artery anatomy, including an estimation of patency during systole and diastole. To our knowledge, this is only the second reported case of this particular coronary artery anomaly in the world literature

OBJECTIVE: Dual-source CT improves temporal resolution, and theoretically improves the diagnostic image quality of coronary artery examinations without requiring preexamination beta-blockade. The purpose of our study was to show the improved diagnostic image quality of dual-source CT compared with single-source CT despite the absence of preexamination beta-blockade in the dual-source CT group. MATERIALS AND METHODS: We performed a retrospective analysis of consecutive patients who underwent coronary artery evaluation with either single-source CT or dual-source CT at our institution between February 2005 and October 2006. Examination reports were analyzed for the presence of image artifacts, and image quality was graded on a 3-point scale (no, mild, or severe artifact). Type of artifact (motion, calcium, quantum mottle) was also noted. RESULTS: Examinations (339 single-source CT and 126 dual-source CT) of 465 patients were analyzed. Artifact was reported in 39.8% of examinations using single-source CT and in 29.4% of examinations using dual-source CT (p < 0.05). The number of examinations with motion artifact was significantly higher with single-source CT than with dual-source CT (15.9% vs 4.8%; p < 0.001) despite significantly higher heart rates in the dual-source CT group (59.4 +/- 8.4 vs 68.6 +/- 14.6 beats per minute; p < 0.001). No patients in the dual-source CT group received preexamination beta-blockade compared with 81% of patients in the single-source CT group. The presence of severe (nondiagnostic) calcium artifact was also significantly reduced in the dual-source CT group (13.0% vs 3.2%; p < 0.001). CONCLUSION: Dual-source CT provides significantly better diagnostic image quality than single-source CT despite higher heart rates in the dual-source CT group. These findings support the use of dual-source CT for coronary artery imaging without the need for preexamination beta-blockade

This study aims to assess the feasibility of a protocol to diagnose renovascular disease using dual MR renography (MRR) acquisitions: before and after administration of angiotensin converting enzyme inhibitor (ACEi). Results of our simulation study aimed at testing the reproducibility of glomerular filtration rate (GFR) and renal plasma flow (RPF) demonstrate that for a fixed overall dose of 12 ml gadolinium-based contrast material (500 mmol/L), the second dose should be approximately twice as large as the first dose. A three-compartment model for analyzing the second-injection data was shown to appropriately handle the tracer residue from the first injection. The optimized protocol was applied to 18 hypertensive patients without renovascular disease, showing minimal systematic difference in GFR measurements before and after ACEi of 0.8+/-4.4 ml/min or 2.7%+/-14.9%. For 10 kidneys with significant renal artery stenosis, GFR decreased significantly after ACEi (P < 0.001, T-value = 3.79), and the difference in GFR measurements before and after ACEi averaged 8.3+/-6.9 ml/min or 26.2%+/-43.9%. Dual-injection MRI with optimized dose distribution appears promising for ACEi renography by offering measures of GFR changes with clinically acceptable precision and accuracy. Key words: angiotensin converting enzyme inhibitor, glomerular filtration rate, renovascular disease, compartmental modeling