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.
Following the trend of the digitalization of the modalities used for diagnostic imaging, the devices for such imaging have increasingly included monitors. The present study was undertaken to evaluate the usefulness of soft-copy (liquid crystal display; LCD) images of phantoms of small adenocarcinomas using receiver operating characteristic (ROC) analysis of two different display systems: LCD and hard copy (film). A two-tailed paired t-test and the jackknife method (parametric methods) were performed, and no significant differences were found in the area under the ROC curve (AUC) for the pulmonary fields, lungs, ribs, or mediastinum between the film and LCD display systems, and the detectability did not differ between the film and LCD monitors. A Mann-WhitneyU test, which is a non-parametric method that applies to the analysis of a small sample, also showed no significant differences in the AUC. The results of this study suggest that LCDs can replace hard-copy film as a display system if the signals.
Pneumoconiosis is diagnosed as categories 0–4 according to the Pneumoconiosis Law. Physicians have difficulty precisely categorizing many chest images. Therefore, we have developed a computerized method for automatically categorizing pneumoconiosis from chest radiographs. First, we extracted the rib edge regions from lung ROIs. Second, texture features were extracted using a dot enhancement filter, line enhancement filter, and grey level co-occurrence matrix. Third, the rib edge regions were removed from these processed images. Finally, we used a support vector machine for feature analysis. In a consistency test, 56 cases (69.7%) were classified correctly, and 45 cases (61.8%) were classified correctly in a validation test. These results show that the proposed features and removal of the rib edge are effective in classifying the profusion of opacities that indicate pneumoconiosis.
MR angiography (MRA) for pediatric moyamoya disease is important as a non-invasive examination to diagnose blood flow in the brain. Generally, the conventional 3D-TOF MRA is used for moyamoya disease. However, retrobulbar and subcutaneous fat of the head show high intensity signals. We found that using the conventional MRA to diagnose the details of brain blood flow is difficult and that it cannot differentiate moyamoya vessels and fat. It similarly obscures the ophthalmic artery and superficial temporal artery that overlap with fat in the direction of the maximum intensity projection (MIP). Therefore, we devised an MRA technique with fat suppression to diagnose blood flow in moyamoya disease patients: MR angiography with the principle of selective excitation technique (PROSET). The scan time does not need to be increased. We studied the TOF effect in constant and pulsatile flows and the water selective excitation method with the binominal pulse (PROSET) for the fat suppression effect for moyamoya disease. The results showed that PROSET-MRA achieved better image results than conventional MRA. The development of collaterals of the superficial temporal artery and occipital artery in pre- and post-operation moyamoya disease could be clearly visualized and evaluated. The PROSET-MRA method is useful for evaluating pre- and post-operation (encephalo-duro-arterio-synangiosis, encephalo-myo-synangiosis) blood flow reconstruction for patients who have moyamoya disease.
We devised a method for visualizing the distal portion of lumbar spinal nerve roots in the direction of the long axis using a three-dimensional balanced sequence with inversion recovery pulse, and we established the imaging parameters. This pulse sequence was used with the following parameters: 260 mm field of view, 4.8 ms repetition time, 2.4 ms echo time, 90 degree flip angle, 1.5 mm slice thickness (0.75 mm overlap), and low-high radial k-space profile order. We assessed the signal intensity and contrast for the phantom and healthy volunteer images with different inversion times (TI). Moreover, we evaluated this method by using the optimal TI in clinical cases. The optimal TI obtained from the phantom and human studies was 600 ms. In clinical cases, this method with 600 ms of TI provided the best definition in images of abnormal pathway and compression of the lumbar spinal nerve roots. Our imaging method makes it possible to clearly and noninvasively visualize the lumbar spinal nerve roots.
To evaluate the usefulness of hybrid iterative reconstruction (iDose) for quantification of calcium content in the coronary artery on 64-detector computed tomography (CT), an anthropomorphic cardiac CT phantom containing cylinders with known calcium content was scanned at tube current-time products of 15, 20, 25, and 50 mAs using 64-detector CT. The images obtained at 15, 20, 25, and 50 mAs were reconstructed using filtered back projection (FBP), and those at 15, 20, and 25 mAs were also reconstructed using iDose. Then the volume and mass of the calcium content in the cylinders were calculated and compared with the true values. The Agatston score was also evaluated. The Agatston score and mass of calcium obtained at 50 mAs using FBP were 656.92 and 159.91 mg, respectively. In contrast, those obtained at 25 mAs using iDose were 641.91 and 159.05 mg, respectively. No significant differences were found in the calcium measurements obtained using FBP and iDose. In addition, the Agatston score and mass of calcium obtained at 15 mAs and 20 mAs using iDose were not significantly different from those obtained at 25 mAs with iDose. By using iDose, accurate quantification of calcium in the coronary artery can be achieved at 15 mAs using 64-detector CT. The radiation dose can be significantly reduced in coronary artery calcium scoring without impairing the detection and quantification of coronary calcification.
Purpose: In carotid artery stenosis, precisely assessing the vessel cross-sectional area and diameter is important because this result determines the treatment strategy for patients. The purpose of our study was to evaluate the vessel sizes of normal and stenotic carotid arteries using time-of-flight magnetic resonance angiography (TOF-MRA) and X-ray CT angiography (CTA). Method and materials: The TOF-MRA and the CTA data were obtained using 3D TOF-MRA on a 1.5-T MR scanner (1.0 mm slice thickness) and dynamic contrast-enhanced multi-detector row CT (0.5 mm slice thickness). In thirty-three normal patients (20 men, 13 women, mean age of 66.9±9.0 years) and eighteen patients with carotid artery stenosis (12 men, 6 women, mean age of 74.4±6.4 years), we measured the vessel cross-sectional areas and the diameters of the internal and common carotid arteries (ICAs and CCAs) using TOF-MRA and CTA and a vessel-analytic program of the workstation. Results: The mean cross-sectional areas and diameters of normal ICAs and CCAs determined using TOF-MRA were significantly smaller than those determined using CTA. The percentages of area and diameter stenoses found using TOF-MRA were 7.7 and 14.3% higher than those found using CTA. In six cases in the stenotic group, the stenotic artery showed no signal using TOF-MRA, but the CTA depicted it. Conclusion: In both normal and stenotic carotid arteries, TOF-MRA underestimates vessel size more than CTA does.
A questionnaire survey about mammography in Hokkaido was mailed to 121 facilities from August to September 2009. We surveyed the conditions of digital mammography with regard to quality control (QC) and average glandular dose at 79 facilities in Hokkaido in 2009, and the results of the survey were compared with those of 2004. We found that digital mammography techniques were widely used across Hokkaido and that computed radiography (CR) systems were quite widespread, with 70% of facilities having them. The average glandular dose ranged from 1.04 to 2.3 mGy (mean: 1.73 mGy) for digital equipment. The results revealed several problems. Although the use of 1-, 2-, and 3-megapixel (MP) liquid crystal displays (LCDs) was not uncommon, 5-MP LCDs were used in most cases when reading digital mammograms. Facilities that have mammography equipment are unlikely to have quality control instruments for mammography. Although daily QC is performed in most facilities, further quality control for digital mammography should be developed, including that for monitors. In a second study, we evaluated the 1 Shot Phantom M Plus (1 Shot Phantom), which enables objective evaluation by providing for one physical measurement rather than a subjective visual analysis. The results indicated that the 1 Shot Phantom was very useful for digital mammography systems in daily QC testing because it enabled objectivity.