Teruhito Mochizuki

Cardiac imaging using 256-detector row four-dimensional CT: preliminary clinical report

PurposeAlong with the increase of detector rows on the z-axis and a faster gantry rotation speed, the spatial and temporal resolutions of the multislice computed tomography (CT) have been improved for noninvasive coronary artery imaging. We investigated the feasibility of the second specification prototype 256-detector row four-dimensional CT for assessing coronary artery and cardiac function.Materials and methodsThe subjects were five patients with coronary artery disease. Contrast medium (40–60 ml) was intravenously administered at the rate of 3–4 ml/s. The patients whole heart was scanned for 1.5 s to cover at least one cardiac cycle during breathholding without electrocardiographic gating. Parameters used were 0.5 mm slice thickness, 0.5 s/rotation, 120 Kv, and 350 mA, with a half-scan reconstruction algorithm (temporal resolution 250 ms). Twenty-six transaxial datasets were reconstructed at intervals of 50 ms.ResultsThe assessability of the coronary arteries in AHA segments 1, 2, 3, 5, 6, 7, 9, and 11 was visually evaluated, resulting in 29 of 32 (90.9%) segments being assessable. Functional assessment was also performed using animated movies without banding artifacts in all cases.ConclusionsThe 256-detector row four-dimensional CT can assess the coronary artery and cardiac function using data during 1.5 s without banding artifacts.

Quantification of Myocardial Perfusion by Contrast-Enhanced 64-MDCT: Characterization of Ischemic Myocardium

OBJECTIVE Assessment of hemodynamic changes in ischemic cardiac segments at rest using CT has yet to be performed. We hypothesized that variations in subendocardial perfusion during the cardiac cycle might be related to the appearances of ischemia. The purpose of this study was to investigate myocardial perfusion in ischemic segments using contrast-enhanced 64-MDCT. SUBJECTS AND METHODS We performed cardiac MDCT at rest and stress/rest (201)Tl myocardial perfusion scintigraphy (MPS) in 34 patients with suspected coronary artery disease. We reconstructed 2D long- and short-axis cardiac images in diastolic and systolic phases using raw data from coronary CT angiography. The attenuation value (in Hounsfield units) in the myocardium was used as an estimate of myocardial perfusion. We measured the subendocardial intensity of 17 segments according to the American Heart Association classification. Systolic perfusion or diastolic perfusion was calculated by dividing the subendocardial intensity at systole or diastole, respectively, for each segment by the mean value across all segments for each patient. We used stress/rest MPS to evaluate the variation in myocardial perfusion at systole and diastole for the segments diagnosed as ischemic or nonischemic. RESULTS Systolic perfusion for ischemic segments was significantly lower than that for nonischemic segments in 15 of 17 segments. The difference between systolic perfusion and diastolic perfusion in ischemic segments was significantly lower than that in nonischemic segments (14 of 17 segments). There was no significant difference in diastolic perfusion between ischemic and nonischemic segments (15 of 17 segments). CONCLUSION Our results suggest that a pattern of subendocardial hypoperfusion at systole and normal perfusion at diastole characterizes ischemic myocardium.

Detection of lung cancer using single-exposure dual-energy subtraction chest radiography

PurposeThe aim of this study was to evaluate the detectability of lung cancer by chest radiography with a single-exposure dual-energy subtraction (ES) method.Materials and methodsFive radiologists read two sets of chest radiographs from 77 patients (66.5 ± 9.6 years old) with histologically proven lung cancer measuring ≤3.0 cm and those from 77 normal subjects (65.7 ± 9.0 years old). The observer tests were performed in two sessions: standard computed radiography (CR) images only and a combination of CR and ES images. Receiver-operating characteristic analysis was used for statistical analysis. All tumors were classified into three groups according to the appearance on thin-section CT: (1) nonsolid: tumor shadow disappearance rate (TDR) was 100%; (2) partly solid: TDR was ≥50 but <100%; (3) solid: TDR was <50%.ResultsOverall, detectability with the ES method was significantly better than that without ES (mean Az value increased from 0.7673 to 0.8265, P < 0.05). In the subgroup analysis of the nonsolid group and the solid group detectability did not change using the ES method, whereas in the partly solid group detectability with the ES method was significantly better than that without ES (mean Az value increased from 0.7162 to 0.8209, P < 0.005).ConclusionThe ES method improves the detectability of lung cancer by chest radiography, especially of the partly solid group.

Evaluation of tumor blood flow in musculoskeletal lesions: dynamic contrast-enhanced MR imaging and its possibility when monitoring the response to preoperative chemotherapy—work in progress

PurposeThe objective of this study was to calculate tumor blood flow (TBF) in musculoskeletal lesions and to evaluate the usefulness of this parameter in differentiating malignant from benign lesions and monitoring the treatment response to preoperative chemotherapy.Materials and methodsAltogether, 33 patients with musculoskeletal lesions underwent a total of 50 dynamic magnetic resonance imaging (MRI) examinations, including 28 on 9 patients undergoing preoperative chemotherapy. TBF was calculated using deconvolution analysis. Steepest slope (SS) was determined from the time–intensity curve during the first pass of contrast medium.ResultsTBF ranged from 2.7 to 178.6 mL/100 mL/min in benign lesions and from 15.4 to 296.3 mL/100 mL/min in malignant lesions. SS ranged from 0.5%/s to 31.8%/s for benign lesions and from 3.1%/s to 64.8%/sec for malignant lesions. TBF and SS did not differ significantly between benign and malignant lesions. Among the nine patients who underwent preoperative chemotherapy, TBF after chemotherapy was lower in good responders (11.7, 11.0, 7.9 mL/100 mL/min) (n = 3, tumor necrosis ≥90%) than in poor responders (23.4–141.5 mL/100 mL/min) (n = 6, tumor necrosis <90%).ConclusionTBF and SS cannot reliably differentiate malignant from benign lesions. However, they have potential utility in evaluating the preoperative treatment response in patients with malignant musculoskeletal tumors.

Quantitative assessment of regional left ventricular wall thickness and thickening using 16 multidetector-row computed tomography : comparison with cine magnetic resonance imaging

PurposeThe purpose of this study was to investigate the feasibility of retrospective electrocardiography-gated multidetector-row computed tomography (MDCT) in the assessment left ventricular (LV) wall thickness and thickening and to test its validity compared to cine magnetic resonance imaging (MRI) as a standard of reference.Materials and methodsWe enrolled 19 patients who underwent both cardiac MDCT and cine MRI. End-diastolic wall thickness (EDWT) and end-systolic wall thickness (ESWT) were measured in 16 myocardial segments. Percent systolic wall thickening (%SWT) was generated from the EDWT and ESWT. Nondiagnostic myocardial segments were excluded. Correlation and agreement between MDCT and cine MRI were analyzed.ResultsSegmental assessability values were 86.2% (262/304) and 92.1% (280/304) for MDCT and cine MRI, respectively. In assessable segments by both modalities (80.9%, 246/304), a significant correlation between MDCT and MRI was found (r = 0.89, 0.85, and 0.61, for EDWT, ESWT, and %SWT, respectively; all P < 0.05). Mean EDWT and ESWT values by MDCT were slightly lower than those by cine MRI (9.8 ± 3.6 vs. 10.0 ± 3.7 mm and 13.8 ± 4.4 vs. 14.1 ± 4.3 mm, respectively; both P < 0.01). Bland-Altman analysis revealed acceptable limits of agreement between MDCT and Cine MRI.ConclusionMDCT is a feasible method to assess regional LV wall thickness and systolic thickening.

Analysis of microvascularity after reperfused acute myocardial infarction using the maximum slope method of contrast-enhanced magnetic resonance imaging.

PurposeThe aim of this study was to analyze microvas-cularity after reperfused acute myocardial infarction (AMI) using the maximum slope method of contrastenhanced cardiac magnetic resonance imaging (CMR).Materials and methodsCMR and resting 201T1 single photon emission computed tomography (SPECT) images were obtained in 30 consecutive patients after reperfused AMI and 10 controls. After bolus injection of gadolinium diethylenetriamine pentaacetic acid, first-pass CMR images were obtained using the True-FISP sequence. Time-intensity curves were generated by measuring the signal intensity in the myocardium and left ventricle. The arterial input function was obtained from the left ventricular time-intensity curve. On the basis of the maximum slope method, the microvascular index (MVI) was calculated by dividing the maximum initial upslope of the myocardium by the initial upslope of the left ventricle.ResultsThe MVI was significantly lower in the segments related to the occluded coronary artery. MVIs in segments with 201Tl uptake of 50%–59% of peak were significantly lower than in those with 201Tl uptake of 60%–69%. MVIs in segments with 201Tl uptake of <50% of peak were significantly lower than in those with 201Tl uptake of 50%–59%.ConclusionThis study presents a method that directly assesses microvascularity after reperfused AMI.