[Estimation of the Average Glandular Dose Using the Mammary Gland Image Analysis in Mammography].

Currently, the glandular dose is evaluated quantitatively on the basis of the measured data using phantom, and not in a dose based on the mammary gland structure of an individual patient. However, mammary gland structures of the patients are different from each other and mammary gland dose of an individual patient cannot be obtained by the existing methods. In this study, we present an automated estimation method of mammary gland dose by means of mammary structure which is measured automatically using mammogram. In this method, mammary gland structure is extracted by Gabor filter; mammary region is segmented by the automated thresholding. For the evaluation, mammograms of 100 patients diagnosed with category 1 were collected. Using these mammograms we compared the mammary gland ratio measured by proposed method and visual evaluation. As a result, 78% of the total cases were matched. Furthermore, the mammary gland ratio and average glandular dose among the patients with same breast thickness was matched well. These results show that the proposed method may be useful for the estimation of average glandular dose for the individual patients.

Preliminary study on the automated skull fracture detection in CT images using black-hat transform.

Linear skull fracture, following head trauma, may reach major blood vessels, such as the middle meningeal artery or sinus venosus, and may cause epidural hematoma. However, hematoma is likely to be missed in the initial interpretation because it spreads only gradually. In addition, the fracture lines that run along the scan slice plane are often missed during initial interpretation. In this study, we develop a novel method for automated detection of the linear skull fracture using head computed tomography (CT) images and conduct a basic evaluation using digital phantom and head phantom that enclose genuine human bones. In the proposed method, the bone region is first extracted using morphological processing of the head CT images. Then, the cranial vault is determined from the CT scout view image. The skull has low-density cancellous bone between the hard two-layer high-density compact bones. Because the fracture lines of compact bones are more clearly recognized as compared to cancellous bones, the bone surface is then extracted by performing three-dimensional (3D) Laplacian filtering. Finally, linear structures are extracted by applying the black-hat transform to the bone surface image. In the experiments, we evaluated the proposed method using digital phantom and CT images of the head phantom. From the experiments using digital phantom, we were able to detect a crack line with a width of 0.35 mm. In the experiments using head phantom, we were able to clearly detect the crack lines in the phantom. These results indicate that our proposed method will be useful for the automated detection of skull fracture in CT images.

Plaque Characterization by Coronary Computed Tomography Angiography and the Likelihood of Acute Coronary Events in Mid-Term Follow-Up.

BACKGROUND: Coronary computed tomography angiography (CTA)-verified positive remodeling and low attenuation plaques are considered morphological characteristics of high-risk plaque (HRP) and predict short-term risk of acute coronary syndrome (ACS). OBJECTIVES: This study evaluated whether plaque characteristics by CTA predict mid-term likelihood of ACS. METHODS: The presence of HRP and significant stenosis (SS) of ≥70% were evaluated in 3,158 patients undergoing CTA. Serial CTA was performed in 449 patients, and plaque progression (PP) was evaluated. Outcomes (fatal and nonfatal ACS) were recorded during follow-up (mean 3.9 ± 2.4 years). RESULTS: ACS occurred in 88 (2.8%) patients: 48 (16.3%) of 294 HRP(+) and 40 (1.4%) of 2,864 HRP(-) patients. ACS was also significantly more frequent in SS(+) (36 of 659; 5.5%) than SS(-) patients (52 of 2,499; 2.1%). HRP(+)/SS(+) (19%) and HRP(+)/SS(-) (15%) had higher rates of ACS compared with no-plaque patients (0.6%). Although ACS incidence was relatively low in HRP(-) patients, the cumulative number of patients with ACS developing from HRP(-) lesions (n = 43) was similar to ACS patients with HRP(+) lesions (n = 45). In patients with serial CTA, PP also was an independent predictor of ACS, with HRP (27%; p < 0.0001) and without HRP (10%) compared with HRP(-)/PP(-) patients (0.3%). CONCLUSIONS: CTA-verified HRP was an independent predictor of ACS. However, the cumulative number of ACS patients with HRP(-) was similar to patients with HRP(+). Additionally, plaque progression detected by serial CTA was an independent predictor of ACS.

Adding coronary computed tomography angiography to invasive coronary angiography improves prediction of cardiac events.

BACKGROUND: The additive value of plaque characteristics determined by computed tomography angiography (CTA) in patients undergoing invasive coronary angiography (ICA) has not been established. METHODS AND RESULTS: We studied 676 patients undergoing ICA and CTA within 3 months. The luminal diameter narrowing based on ICA and the presence of high risk plaque (HRP) based on CTA were assessed in all coronary artery segments except for those after or before scheduled treatment. We followed their cardiac events including cardiac death, acute coronary syndrome (ACS), and revascularization for de novo lesions ≥3 months after ICA. The incidence of coronary events was higher in the segments including >25% luminal narrowing than in those without (2.94% vs. 0.31%, P<0.0001), and higher in the segments containing HRP than in those without (12.6 vs. 0.46%, P<0.0001). Greater than 25% residual luminal narrowing and the presence of HRP were identified as independent predictors of cardiac events after risk adjustment for age, gender, and history of ACS (hazard ratio [HR], 3.22; 95% confidence interval [CI]: 1.29-10.76; P=0.0092, HR, 2.64; 95% CI: 1.59-4.35; P=0.0002, respectively). Adding the presence of HRP to a model including age, gender, ACS history, and >25% residual stenosis improved the prediction of cardiac events. CONCLUSIONS: Assessment of coronary plaque characteristics on CTA improves the prediction of cardiac events in patients undergoing ICA.

Characteristics of plaque progression detected by serial coronary computed tomography angiography.

We previously reported that serial coronary computed tomography angiography (CTA) had a potential to evaluate the interval change of plaque morphology of coronary arteries. The aim of this study was to evaluate variables associated with the plaque progression by serial CTA. We included 148 patients (age 66.3 ± 9.8 years, male 81.1 %, median scan interval 12 months) with coronary artery disease undergoing serial CTA. Each coronary artery was compared visually between baseline and follow-up CTA to detect plaque progression. Baseline characteristics between progression and nonprogression patients did not demonstrate any significant differences. Logistic analysis revealed that only low-density lipoprotein cholesterol (LDL-C) ≥100 mg/dl at follow-up was associated with plaque progression (odds ratio 2.59, 95 % confidence interval 1.12-6.34, P = 0.0263). Cutoff value of LDL-C for plaque progression at follow-up was 103.0 mg/dl based on receiver-operator characteristic curves analyses. Of the 36 progressive lesions in 32 patients, plaque composition at baseline included 13 lesions (36.1 %) of noncalcified plaque, 1 lesion (2.8 %) of calcified plaque, 12 lesions (33.3 %) of partially calcified plaque, and the remaining 10 lesions (27.8 %) had no plaque at baseline and revealed de novo plaques at follow-up. There were 9 lesions (25 %) with high-risk plaque (HRP) characteristics at baseline and 18 lesions (50 %) with HRP at follow-up. Plaque progression of coronary arteries by serial CTA was associated with LDL-C ≥100 mg/dl at follow-up regardless of baseline LDL-C level. There was no specific finding to predict plaque progression on the baseline plaque characteristics.

A combination of anatomical and functional evaluations improves the prediction of cardiac event in patients with coronary artery bypass.

OBJECTIVE: To study the usefulness of combined risk stratification of coronary CT angiography (CTA) and myocardial perfusion imaging (MPI) in patients with previous coronary-artery-bypass grafting (CABG). DESIGN: A retrospective, observational, single centre study. SETTING AND PATIENTS: 204 patients (84.3% men, mean age 68.7±7.6) undergoing CTA and MPI. MAIN OUTCOME MEASURES: CTA defined unprotected coronary territories (UCT; 0, 1, 2 or 3) by evaluating the number of significant stenoses which were defined as the left main trunk ≥50% diameter stenosis, other native vessel stenosis ≥70% or graft stenosis ≥70%. Using a cut-off value with receiver-operating characteristics analysis, all patients were divided into four groups: group A (UCT=0, summed stress score (SSS)<4), group B (UCT≥1, SSS<4), group C (UCT=0, SSS≥4) and group D (UCT≥1, SSS≥4). RESULTS: Cardiac events, as a composite end point including cardiac death, non-fatal myocardial infarction, unstable angina requiring revascularisation and heart-failure hospitalisation, were observed in 27 patients for a median follow-up of 27.5 months. The annual event rates were 1.1%, 2%, 5.7% and 12.9% of patients in groups A, B, C and D, respectively (log rank p value <0.0001). Adding UCT or SSS to a model with significant clinical factors including left ventricular ejection fraction, time since CABG and Euro SCORE II improved the prediction of events, while adding UCT and SSS to the model improved it greatly with increasing C-index, net reclassification improvement and integrated discrimination improvement. CONCLUSIONS: The combination of anatomical and functional evaluations non-invasively enhances the predictive accuracy of cardiac events in patients with CABG.

Morphologic and functional assessment of coronary artery disease--potential application of computed tomography angiography and myocardial perfusion imaging.

BACKGROUND: The role of combined evaluation of myocardial perfusion imaging (MPI; by single-photon emission computed tomography) and computed tomography angiography (CTA) for risk stratification of coronary artery disease was evaluated. For CTA, the extent of luminal stenosis, and also the features of high-risk plaques (HRP, including positive remodeling and low attenuation) were evaluated. METHODS AND RESULTS: A total of 304 patients (65 ± 11 years, male 72%, median follow-up: 24 months) who underwent CTA and MPI were enrolled in the study. Summed stress scores and summed difference scores (SDS) for MPI, stenosis, and HRP were evaluated, and event rates were compared. Cardiac events were defined as acute coronary event including cardiac death or non-fatal acute myocardial infarction, and unstable angina requiring revascularization. Of 304 patients, 51 (16.8%) underwent early revascularization. In the remaining 253 patients, an event occurred in 11 (4.3%). HRP (hazard ratio [HR], 4.75, P=0.00171) and stenosis (+) with SDS >0 (HR, 4.58, P=0.0461) were significant independent predictors of cardiac event. The event rate for stenosis (+) with SDS >0 was significantly higher than others (log-rank P=0.0490). The event rates were significantly different between HRP(+) and HRP(-) (16.1% vs. 2.7%, log-rank P=0.0013). CONCLUSIONS: HRP on CTA was an independent predictor of acute coronary events, as was stenosis (+) with SDS >0, and HRP had increased prognostic value over stenosis and abnormal MPI findings.

Coronary plaque characteristics in patients with mild chronic kidney disease. Analysis by 320-row area detector computed tomography.

BACKGROUND: The differences in the coronary plaque characteristics between patients with mild chronic kidney disease (CKD) (estimated glomerular filtration rate [eGFR] 30-59 ml·min(-1) · 1.73 m(-2)) and those without CKD (eGFR ≥60) by 320-row area detector computed tomography (CT) have not been studied. METHODS AND RESULTS: We enrolled 487 patients undergoing coronary CT angiography with suspected stable coronary artery disease (mean age: 66.6±10.8 years, 131 with mild CKD) and analyzed 6,352 segments. All coronary plaques were characterized for the presence of vessel remodeling, plaque consistency and the disposition of coronary calcification, and a plaque with positive vessel remodeling and/or low-attenuation was defined as high risk. The number of diseased segments per patient was higher in mild CKD patients than in those without CKD (4.61±3.83 vs. 2.95±3.11, P<0.0001). The prevalence of severe stenosis (≥70% luminal diameter) was significantly higher in cases of mild CKD than in no CKD (35.1% vs. 19.4%, P=0.0003), but there was no significant difference in the prevalence of high-risk plaque (13.0% vs. 9.8%, P=0.3189). CONCLUSIONS: The severity of coronary artery stenosis was higher in the patients with mild CKD, though there was no significant difference in the prevalence of high-risk plaque. We suggest that the high risk of coronary events in patients with CKD is related to the severity of stenosis rather than to the characteristics of plaque.

[A new method for measuring temporal resolution in electrocardiogram-gated reconstruction image with area-detector computed tomography].

The purpose of this study was to design and construct a phantom for using motion artifact in the electrocardiogram (ECG)-gated reconstruction image. In addition, the temporal resolution under various conditions was estimated. A stepping motor was used to move the phantom over an arc in a reciprocating manner. The program for controlling the stepping motor permitted the stationary period and the heart rate to be adjusted as desired. Images of the phantom were obtained using a 320-row area-detector computed tomography (ADCT) system under various conditions using the ECG-gated reconstruction method. For estimation, the reconstruction phase was continuously changed and the motion artifacts were quantitatively assessed. The temporal resolution was calculated from the number of motion-free images. Changes in the temporal resolution according to heart rate, rotation time, the number of reconstruction segments and acquisition position in z-axis were also investigated. The measured temporal resolution of ECG-gated half reconstruction is 180 ms, which is in good agreement with the nominal temporal resolution of 175 ms. The measured temporal resolution of ECG-gated segmental reconstruction is in good agreement with the nominal temporal resolution in most cases. The estimated temporal resolution improved to approach the nominal temporal resolution as the number of reconstruction segments was increased. Temporal resolution in changing acquisition position is equal. This study shows that we could design a new phantom for estimating temporal resolution.

Coronary CT angiographic characteristics of culprit lesions in acute coronary syndromes not related to plaque rupture as defined by optical coherence tomography and angioscopy.

AIMS: Pathological and clinical optical coherence tomography (OCT) studies have indicated that acute coronary syndrome (ACS) lesions have either ruptured fibrous caps (RFC-ACS) or intact fibrous caps (IFC-ACS). Although computed tomographic (CT) angiographic characteristics of RFC-ACS include low-attenuation plaques and positive plaque remodelling, features associated with IFC-ACS have not been previously described. The aim of this study was to assess the CT characteristics of IFC-ACS lesions. METHODS AND RESULTS: Seventy-four patients with ACS/stable angina consented to multimodality imaging, of which 66 underwent CT angiography. Of these, 57 culprit lesions in 57 patients were evaluated with sufficient image quality from all four of OCT, angioscopy, intravascular ultrasound, and CT angiography. Intraluminal thrombus was assessed by OCT/angioscopy, and culprit lesions further classified by OCT-based demonstration of fibrous cap integrity. Of 35 culprit lesions with ACS, OCT revealed IFC with thrombus in 10 (29%) and RFC in the remaining 25 (71%); all 22 lesions with stable angina had intact fibrous caps. Fibrous caps were significantly thinner in RFC-ACS than IFC-ACS and stable angina (45 ± 12, 131 ± 57, and 321 ± 146 µm, respectively; P = 0.001). CT angiography revealed that low-attenuation plaques were more frequently observed in RFC-ACS than IFC-ACS and stable angina (88, 40, and 18%; P = 0.001) lesions. Similarly, positive remodelling was more predominantly seen in RFC-ACS than IFC-ACS and stable angina (96, 20, and 14%; P = 0.001). However, none of the specific CT angiography features clearly distinguished IFC-ACS from stable lesions. CONCLUSION: In contrast to the situation with RFC-ACS, distinct culprit lesion characteristics associated with non-rupture-related mechanisms are not identified by CT angiography. It will therefore not be possible to differentiate plaques likely to develop IFC-ACS from stable plaques.

[Evaluation of 320-row area detector computed tomography (ADCT) coronary angiography for patients with atrial fibrillation].

The aim of this study was to evaluate 320-row area detector CT (ADCT) for patients with atrial fibrillation (Af) based on simulated exposure using electrocardiogram RR intervals and comparison with the findings of coronary CT angiography (CCTA) using 64-row multi slice CT (MSCT). The probability of including RR intervals of 900 ms or more was calculated when the acquisition time was varied from 1 to 4 beats. Overall, 51 patients with Af who underwent CCTA were examined. The exposure time for CCTA, the total dose length product (DLP) for the examination, and the image quality (scored 0 to 3: poor to excellent) were compared between ADCT and MSCT. The probability of including RR intervals of 900 ms or more was highly significantly increased at 3 beats of acquisition time. The exposure time using ADCT was reduced by 75% compared with MSCT (ADCT/MSCT: 2.8/11.3 s), and the total DLP was reduced by 40% (ADCT/MSCT: 1398/2277 mGy·cm). Moreover, ADCT provided diagnosable images in all cases, and the mean image quality score for ADCT was significantly higher than that for MSCT (ADCT/MSCT: 2.8/2.4). Thus, 320-row ADCT at 3 beats of acquisition time can provide CCTA images of acceptable quality for patients with Af.

Serial coronary CT angiography-verified changes in plaque characteristics as an end point: evaluation of effect of statin intervention.

OBJECTIVES: This study sought to assess, by serial computed tomography angiography (CTA), the effect of statin treatment on coronary plaque morphology. BACKGROUND: In addition to the assessment of luminal stenosis, CTA also allows characterization of plaque morphology. Large, positively remodeled plaques with large necrotic cores have been reported as indicators of plaque instability. METHODS: CTA was performed in 32 patients (26 men, ages 64.3 +/- 8.5 years). Of these, 24 received fluvastatin after the baseline study; 8 subjects who refused statin treatment were followed as the control subjects. Serial imaging was performed after a median interval of 12 months. All vessels were examined in every subject, and a 10-mm-long segment was identified for comparison before and after intervention. Total plaque volume, low attenuation plaque (LAP) volume, lumen volume, and remodeling index were calculated. RESULTS: In the statin-treated patients, the total plaque volume (92.3 +/- 37.7 vs. 76.4 +/- 26.5 mm(3), p < 0.01) and LAP volume (4.9 +/- 7.8 vs. 1.3 +/- 2.3 mm(3), p = 0.01) were significantly reduced over time; however, there was no change in the lumen volume (63.9 +/- 25.3 vs. 65.2 +/- 26.2 mm(3), p = 0.59). On the other hand, no change was observed in the CTA characteristics in the control subjects, including total plaque volume (94.4 +/- 21.2 vs. 98.4 +/- 28.6 mm(3), p = 0.48), LAP volume (2.1 +/- 3.0 vs. 2.3 +/- 3.6 mm(3), p = 0.91), and lumen volume (80.5 +/- 20.7 vs. 75.0 +/- 16.3 mm(3), p = 0.26). The plaque volume change (-15.9 +/- 22.2 vs. 4.0 +/- 14.0 mm(3), p = 0.01) and LAP volume change (-3.7 +/- 7.0 vs. 0.2 +/- 1.5 mm(3), p < 0.01) were significantly greater in the statin than the control group. The lumen volume (1.3 +/- 15.6 vs. -5.5 +/- 13.1 mm(3), p = 0.24) and remodeling index (-2.4 +/- 6.8% vs. -0.3 +/- 6.5%, p = 0.53) did not show the significant differences between the 2 groups. The decrease in the plaque volume was due to reduction in the LAP volume (R = 0.83, p < 0.01), and was not related to any changes in the lumen volume (R = 0.21, p = 0.24). CONCLUSIONS: This preliminary study suggests that serial CTA evaluation of coronary plaques allows for the assessment of interval change in the plaque morphology. Statin treatment results in decreases in the plaque and necrotic core volume. The features known to be associated with plaque instability.

Accuracy of 64-slice multidetector computed tomography for diseased coronary artery graft detection.

BACKGROUND: Sixty-four-slice multidetector computed tomography (64-MDCT) has been shown to be a feasible modality for diagnosing coronary artery disease. We studied the accuracy of 64-MDCT in the detection of diseased grafts and also evaluated its limitations. METHODS: This study comprised 19 patients who underwent coronary artery bypass grafting and both invasive coronary angiography (ICA) and 64-MDCT. The 64-MDCT images were analyzed for bypass graft occlusion and significant stenosis (>50%) of the anastomosis, and the results were compared with those of ICA. RESULTS: A total of 90 anastomoses, including 25 proximal anastomoses, were evaluated. Of 65 distal anastomoses, including 5 previously occluded grafts in redo cases, 12 distal anastomoses were identified by 64-MDCT as occluded. In comparison, only 10 grafts were identified as occluded by ICA. The sensitivity, specificity, positive predictive value, and negative predictive value for patency were 100% (10 of 10), 96.5% (55 of 57), 83.3% (10 of 12), and 100% (55 of 55), respectively. The ICA patent grafts were evaluated with respect to stenosis. Invasive coronary angiography identified significant stenosis at only 1 site, whereas 64-MDCT showed significant stenosis at 6 sites. The sensitivity, specificity, positive predictive value, and negative predictive value for stenoses were 100% (1 of 1), 93.1% (67 of 72), 16.7% (1 of 6), and 100% (67 of 67), respectively. CONCLUSIONS: Although 64-MDCT demonstrated diagnostic accuracy in evaluating bypass grafts, limitations of this method include false positive results in cases of competitive flow between the graft and the native coronary artery.

Computed tomographic angiography characteristics of atherosclerotic plaques subsequently resulting in acute coronary syndrome.

OBJECTIVES: In a computed tomographic (CT) angiography study, we identified the characteristics of atherosclerotic lesions that were associated with subsequent development of acute coronary syndrome (ACS). BACKGROUND: The CT characteristics of culprit lesions in ACS include positive vessel remodeling (PR) and low-attenuation plaques (LAP). These 2 features have been observed in the lesions that have already resulted in ACS, but their prospective relation to ACS has not been previously described. METHODS: In 1,059 patients who underwent CT angiography, atherosclerotic lesions were analyzed for the presence of 2 features: PR and LAP. The remodeling index, and plaque and LAP areas and volumes were calculated. The plaque characteristics of lesions resulting in ACS during the follow-up of 27 +/- 10 months were evaluated. RESULTS: Of the 45 patients showing plaques with both PR and LAP (2-feature positive plaques), ACS developed in 10 (22.2%), compared with 1 (3.7%) of the 27 patients with plaques displaying either feature (1-feature positive plaques). In only 4 (0.5%) of the 820 patients with neither PR nor LAP (2-feature negative plaques) did ACS develop. None of the 167 patients with normal angiograms had acute coronary events (p < 0.001). ACS was independently predicted by PR and/or LAP (hazard ratio: 22.8, 95% confidence interval: 6.9 to 75.2, p < 0.001). Among 2- or 1-feature positive segments, those resulting in ACS demonstrated significantly larger remodeling index (126.7 +/- 3.9% vs. 113.4 +/- 1.6%, p = 0.003), plaque volume (134.9 +/- 14.1 mm(3) vs. 57.8 +/- 5.7 mm(3), p < 0.001), LAP volume (20.4 +/- 3.4 mm(3) vs. 1.1 +/- 1.4 mm(3), p < 0.001), and percent LAP/total plaque area (21.4 +/- 3.7 mm(2) vs. 7.7 +/- 1.5 mm(2), p = 0.001) compared with segments not resulting in ACS. CONCLUSIONS: The patients demonstrating positively remodeled coronary segments with low-attenuation plaques on CT angiography were at a higher risk of ACS developing over time when compared with patients having lesions without these characteristics.

Whole-brain perfusion CT performed with a prototype 256-detector row CT system: initial experience.

PURPOSE: To preliminarily evaluate the feasibility and potential diagnostic utility of whole-brain perfusion computed tomography (CT) performed with a prototype 256-detector row CT system over an extended range covering the entire brain to assess ischemic cerebrovascular disease. MATERIALS AND METHODS: Institutional review board approval and informed consent were obtained. Eleven cases in 10 subjects (six men, four women; mean age, 64.3 years) with intra- or extracranial stenosis were retrospectively evaluated with whole-brain perfusion CT. Three readers independently evaluated perfusion CT data. The diagnostic performance of perfusion CT was visually evaluated with a three-point scale used to assess three factors. Differences between four axial perfusion CT images obtained at the basal ganglia level (hereafter, four-section images) and whole-brain perfusion CT images were assessed with the paired t test. In four subjects, the interval between perfusion CT and single photon emission computed tomography (SPECT) was 1-17 days (mean, 10.3 days). Correlation between perfusion CT findings and SPECT findings was assessed with the Spearman correlation coefficient. RESULTS: Three-dimensional perfusion CT images and axial, coronal, and sagittal whole-brain perfusion CT images were displayed, and the extent of ischemia was assessed. Mean visual evaluation scores were significantly higher for whole-brain images than for four-section images (4.27 +/- 0.76 [standard deviation] vs 2.55 +/- 0.87). The cerebral blood flow ratios of the ischemic lesions relative to normal regions scanned with perfusion CT (x) and SPECT (y) showed a significant positive correlation (R(2) = 0.76, y = 0.44 x + 0.37, P < .001). CONCLUSION: Perfusion CT performed with a 256-detector row CT system can be used to assess the entire brain with administration of one contrast medium bolus. Thus, ischemic regions can be identified with one examination, which has the potential to improve diagnostic utility.

Development of variable pitch factor scanning for multislice computed tomography.

RATIONALE AND OBJECTIVES: The latest multislice computed tomography (MSCT) scanners permit the chest and abdomen to be scanned continuously. However, conventionally, it has been necessary to perform scanning twice using different pitch factors for the cardiac and abdominal regions. We have developed a new scanning technique known as variable pitch factor scanning, in which the table speed is changed during scanning to obtain continuous images from the heart to the abdomen in a single scan, and have evaluated its physical characteristics. MATERIALS AND METHODS: A bead phantom, a comb phantom, and a gold wire placed at an angle were scanned using a 64-row MSCT scanner. The variation in the spatial resolution and continuity of images in the body axis direction because of changes in the pitch factor were evaluated. RESULTS: Because reconstruction taking the cone angle into consideration was employed, the spatial resolution in the body axis direction was unchanged and the continuity of images in the body axis direction was maintained at a certain level even when the pitch factor was changed. CONCLUSION: Variable pitch factor scanning is a useful technique for obtaining continuous images from the heart to the abdomen in a single scan.

[Automatic selection of optimal cardiac-phase in coronary CT angiography--its clinical usefulness for patients with atrial fibrillation].

The optimal cardiac phases for coronary CT angiography (CTA) are end-systole and mid-diastole, in which cardiac movement is slow. In conventional methods, these cardiac phases are determined by visual selection. We have compared the images in the optimal cardiac phases that were selected by the conventional method and cardiac-phase search software (Phase Navi), and examined the clinical usefulness of Phase Navi in patients with atrial fibrillation. The subjects were 38 patients (regular rhythm: 20, atrial fibrillation: 18). The continuity scores of patients with regular rhythm (Phase Navi, conventional methods) were 2.4+/-0.3-2.5+/-0.3 in end-systole and 2.4+/-0.5-2.4+/-0.4 in mid-diastole. The scores of patients with atrial fibrillation (Phase Navi, conventional methods) were 2.3+/-0.4-2.3+/-0.4 in end-systole, and 2.2+/-0.5-2.1+/-0.6 in mid-diastole. Because the continuity scores of the optimal images from Phase Navi were similar to those from the conventional method, Phase Navi had clinical usefulness in patients with atrial fibrillation.

Multislice computed tomographic characteristics of coronary lesions in acute coronary syndromes.

OBJECTIVES: To evaluate the feasibility of noninvasive assessment of the characteristics of disrupted atherosclerotic plaques, the authors interrogated the culprit lesions in acute coronary syndromes (ACS) by multislice computed tomography (CT). BACKGROUND: Disrupted atherosclerotic plaques responsible for ACS histopathologically demonstrate large lipid cores and positive vascular remodeling. It is expected that plaques vulnerable to rupture should bear similar imaging signatures by CT. METHODS: Either 0.5-mm x 16-slice or 64-slice CT was performed in 38 patients with ACS and compared with 33 patients with stable angina pectoris (SAP) before percutaneous coronary intervention. The coronary plaques in ACS and SAP were evaluated for the CT plaque characteristics, including vessel remodeling, consistency of noncalcified plaque (NCP <30 HU or 30 HU

Atherosclerotic plaque characterization by 0.5-mm-slice multislice computed tomographic imaging.

BACKGROUND: It has been proposed that 0.5-mm-slice multislice computed tomography (MSCT) is a noninvasive tool for the detection of atherosclerotic plaque, but the validity of such an assessment has not been demonstrated by an invasive investigation. The present study was performed to compare the 0.5-mm-slice MSCT density of plaques with intravascular ultrasound (IVUS) findings. METHODS AND RESULTS: Atherosclerotic plaques were characterized in 37 consecutive patients undergoing percutaneous interventions. Based on the IVUS echogenecity, the plaques were classified as soft (n=18), fibrous (n=40) or calcified (n=40). In these 98 plaques, 0.5-mm-slice MSCT plaque density was calculated in 443 regions-of-interest, including 331 lesional foci and 112 luminal cross-sections, and represented as Hounsfield units (HU). MSCT density of the 3 types of plaque was 11+/-12 HU, 78+/-21 HU, and 516 +/-198 HU respectively. Computed tomography density of the (contrast-filled) lumen was 258+/-43 HU. There were statistically highly significant differences in the densitometric characteristics among the 4 groups (soft, fibrous, calcified plaque and lumen) by nonparametric Kruskal-Wallis test (p<0.0001). CONCLUSIONS: The IVUS-based coronary plaque configuration can be accurately identified by 0.5-mm slice MSCT. Noninvasive assessment of plaque characterization will ensure emphasis on the vessel wall beyond the vascular lumen.