Purpose: Detailed strategy for regional hemodynamics is significant for knowledge of plaque development on vascular diseases such as atherosclerosis. The aim of this study was to derive relation between atherosclerosis and hemodynamics at human carotid bifurcation by the use of computational fluid dynamics (CFD), and to provide more accurate hemodynamic information. Methods: Blood velocity datasets at common carotid artery were obtained by phase-contrast cine magnetic resonance imaging (PC cine MRI). Carotid bifurcation model was computed for systolic, mid-diastolic, and end-diastolic phase. Comparison of wall shear stress (WSS) was performed for each cardiac phase. Results: PC cine MRI provided velocity measurement for common carotid artery with various cardiac phases. The blood velocity had acute variation from 0.21 m/s to 1.07 m/s at systolic phase. The variation of WSS during cardiac phase was presented at carotid bifurcation model. High shear stress area was observed at dividing wall for all cardiac phases. The systole-diastole WSS ratio was 10.15 at internal carotid side of bifurcation. And low shear stress (<0.5 Pa) was observed at internal carotid side of bifurcation. Conclusion: Bifurcation area represented low shear stress and changed significantly WSS. The specific area with significant change in shear stress and low shear stress had good agreement with predilection sites of atherosclerosis. The result suggested that hemodynamics was related to atherosclerosis, and CFD analysis with various cardiac phases that were provided by PC cine MRI was allowed to determine an accurate analysis condition. This led to the representation of hemodynamics in vivo.
Previous studies have shown that extreme value statistics are useful for quantitative evaluations of streak artifacts on multi-detector computed tomography (MDCT). However, we hypothesized that the scanning direction of the extreme value would affect the quantitative value obtained using the conventional method. In this study, we developed the region of interest rotation method and calculating the extreme value, and we investigated the usefulness of this method in comparison with the conventional approach. For our examination, the high absorber was placed around a water phantom and a head and chest phantom. In the new method, linearity was confirmed in the Gumbel plot of all the phantoms. On the other hand, the value of the location parameter was significantly different according to the scanning direction with the conventional method. In conclusion, compared to the conventional method, the isotropic method of evaluation does not depend on the direction of streak artifact occurrence in the new method.
Purpose: To design an evaluation method for lumbar spine and hip joint function using dynamic radiography using a flat-panel detector (FPD) system. Method: Sixteen healthy subjects (males; age range, 22-60 years; median, 27 years) and 9 patients (7 males and 2 females; age range, 67-85 years; median, 73 years) with L4 degenerative spondylolisthesis were examined using a dynamic FPD system (CANON Inc.). Sequential images were captured with the subjects in the standing position with maximal forward bending followed by backward bending for 10 s. The lateral lumbar radiographs were obtained at 2 frames/s (fps). The flexion-extension angles of L1 and S1 were measured on those images. Results and discussion: The range of motion (ROM) of the lumbar joints was significantly larger in the healthy group (82.4±8.7°) than in the disease group (50.4±8.5°; p<0.05). The ROM of the pelvic region was significantly smaller in the healthy group (26.9±17.1°) than in the disease group (53.1±17.6°; p<0.05). The healthy subjects exhibited a normal lumbar-pelvic rhythm. In the disease group, hip joint movements tended to be completed earlier compared with those in the healthy group. In the disease group, the loss of lumbar flexibility was compensated by an increase in hip joint motion due to the lumbar disease. Conclusion: The dynamic FPD system is a convenient imaging modality for the diagnosis of lumbar diseases through the assessment of locomotive function in the lumbar spine and hip joints.
In magnetic resonance imaging (MRI) of brain, fast spin echo-fluid attenuated inversion recovery (FSE-FLAIR) is widely used to detect high intensity areas (HIAs). The way of getting FLAIR contrast at high speed includes echo planar imaging-FLAIR (EPI-FLAIR), and in EPI-FLAIR there are single shot EPI-FLAIR (SS-EPI-FLAIR) and multi shot EPI-FLAIR (MS-EPI-FLAIR). There were negative opinions for the reports of SS-EPI-FLAIR, and it is reported that SS-EPI-FLAIR is able to acquire image quality that is equal to FSE-FLAIR in a shorter time, recently. But there are few reports that utilized contrast of MS-EPI-FLAIR. Our object was to compare HIA detectability in FSE-FLAIR and MS-EPI-FLAIR in equal imaging time, and to evaluate a basic characteristic. We dissolved indigestive dextrin in the aqua destillata and created a 0-46 wt% phantom. The concentration that correspond to T1, T2 value of brain white matter was 42 wt%. We calculated contrast by using signal intensities of each phantom, and compared contrast by signal intensities of each phantom, and compared the contrast of MS-EPI-FLAIR and FSE-FLAIR. In the range of 18-46 wt%, the contrast of MS-EPI-FLAIR was positive value, and that of FSE-FLAIR was 26-42 wt%. By the statistical test, contrast of MS-EPI-FLAIR in 18-26% was significantly different for FSE-FLAIR. In conclusion, it was suggestive that MS-EPI-FLAIR is able to detect HIA equally or sharply.
When an inhomogeneous medium such as bone, whose composition or density are clearly different from that of soft tissue of human body, exist in irradiated body, a subjective contrast of X-ray image changes by the location of these inhomogeneous medium. This cause due to the change of behavior of scattered photons in the body depends on the location of inhomogeneous medium besides due to the influence of a penumbra. But this mechanism is not explained clearly yet. In this paper, it was analyzed by means of the Monte Carlo simulation that what kind of difference occurs to a subjective contrast by the difference in location of inhomogeneous medium in water phantom and that a change in behavior of scattered photons in the phantom influences a subjective contrast by what kind of mechanism. In this case the inhomogeneous medium is bone, whose effective atomic number and density are higher than that of water, the subjective contrast of X-ray image degrades when bone is located near the entrance surface (upper position) than located near the exit surface (lower position). This is caused by the number of scattered photons, originated in primary photons incident upon the zone besides the region from entrance surface to exit surface including inhomogeneous medium and incident on the area of shadow of inhomogeneous medium on the image detector, is greater in case of the upper position than in case of the lower position. In the lower position, many of these scattered photons are interacted in bone located near the exit surface by the photo-electric absorption and only a small amount is incident on the image detector.
We investigated dose reduction ability of an iterative reconstruction technology for low-dose computed tomography (CT) for lung cancer screening. The Sinogram Affirmed Iterative Reconstruction (SAFIRE) provided in a multi slice CT system, Somatom Definition Flash (Siemens Healthcare) was used. An anthropomorphic chest phantom (N-1, Kyoto Kagaku) was scanned at volume CT dose index (CTDIvol) of 0.50-11.86 mGy with 120 kV. For noise (standard deviation) and contrast-to-noise ratio (CNR) measurements, CTP486 and CTP515 modules in the Catphan (The Phantom Laboratory) were scanned. Radiological technologists were participated in the perceptual comparison. SAFIRE reduced the SD values by approximately 50% compared with filter back projection (FBP). The estimated dose reduction rates by SAFIRE determined from the perceptual comparison was approximately 23%, while 75% dose reduction rate was expected from the SD value reduction of 50%.
In the dopamine transporter scintigraphy there are two quantitative analysis softwares, DaTView and DaTQUANT. The quantitative value of both software has to be treated independently because there is a difference between them in the point of how to set the region of interest on the striatum and the background, calculation formula of quantitation. And also DaTQUANT has a capability of performing anatomical standardization which DaTView does not have. The aim of this study was to evaluate the accuracy of registration on DaTQUANT using a phantom, and to evaluate the correlation between the quantitative values between DaTView and DaTQUANT using clinical data. As a result, the accuracy of registration was acceptable. Regardless of the degree of accumulation in the striatum, there was a high correlation to each analysis software (r>0.85).
In recent years, aortic aneurysm treatment with stent graft grafting in the X-ray fluoroscopy is increasing. This is an endovascular therapy, because it is a treatment which includes the risk of radiation damage, having to deal with radiation damage, to know in advance is important. In this study, in order to grasp the trend of exposure stent graft implantation in a hybrid operating room (OR) system, focusing on clinical data (entrance skin dose and fluoroscopy time), was to count the total. In TEVAR and EVAR, fluoroscopy time became 13.40±7.27 minutes, 23.67±11.76 minutes, ESD became 0.87±0.41 mGy, 1.11±0.57 mGy. (fluoroscopy time of EVAR was 2.0 times than TEVAR. DAP of EVAR was 1.2 times than TEVAR.) When using the device, adapted lesions and usage are different. This means that care changes in exposure-related factors. In this study, exposure trends of the stent graft implantation was able to grasp. It can be a helpful way to reduce/optimize the radiation dose in a hybrid OR system.
Workloads of radiological technologists under different conditions of heights of radiographic table and/or X-ray tube assembly were calculated using a software for preventing musculoskeletal complaint to investigate optimal working environment for general X-ray examinations. In the patient positioning, compressive force of lumbar disc decreased at higher radiographic table within the range of 45-90 cm. On the other hand, workload of the shoulder joint increased with increase in the height of radiographic table. Load of the shoulder joint similarly increased as the height of the X-ray tube assembly increased. Compressive force of lumbar disc reduced by approximately 10-30% as the height ratio of the radiographic table to body height increased by approximately 40%, compared to the lowest table of 45 cm. Muscle load of a 50-years-old woman was approximately double compared to a 30-year-old man, even in the same workload. It is important to keep suitable height of radiographic table for reduction of the workloads of lumbar rather than shoulder joint, because floating-type radiographic table is generally used.
Phase contrast MRI (PC-MRI) is a useful tool for evaluating valvular pathology. In addition, PC-MRI can provide a noninvasive assessment of blood flow in an arbitrary cross section. However, the blood flow measurement with breath-hold or free breath PC-MRI may be different from each other because of intrathoracic pressure changing and variable image position. The aim of this study was to find both the optimal breath-hold technique and the image position. Quantitative flow images were acquired in four planes (ascending aorta: Ao, sino-tubular junction: STJ, valsalva sinus: valsalva, left ventricular outflow tract: LVOT), in healthy subjects (n=10). The study protocol was divided into two parts: (1) stroke volume (SV) measured in each slice positions by using inspiration, expiration, and navigation method during normal breathing and (2) SV measured at each breath-hold techniques in the Ao, STJ, valsalva, and LVOT. As a result, (1) SV of the respective measurement positions were not significant by using inspiration, expiration, and navigation method and (2) LVOT SV was significantly lower than Ao, STJ, and valsalva.
We developed a custom-designed phantom for bone single photon emission computed tomography (SPECT)-specific radioactivity distribution and linear attenuation coefficient. The aim of this study was to evaluate the accuracy of the phantom. The lumbar phantom consisted of the trunk of a body phantom (background) containing a cylinder (vertebral body), a sphere (tumor), and a T-shaped container (processus). The vertebral body, tumor, and processus phantoms contained a K2HPO4 solution of bone equivalent density and 50, 300 and 50 kBq/mL of 99mTc, respectively. The body phantom contained 8 kBq/mL of 99mTc solution. SPECT images were acquired using low-energy high-resolution collimation, a 128×128 matrix and 120 projections over 360° with a dwell time of 15 sec/view×4 times. Thereafter, CT images were acquired at 130 kV and 70 ref mAs using adaptive dose modulation. The SPECT data were reconstructed with ordered subset expectation maximization with three-dimensional, scatter, and CT-based attenuation correction. Count ratio, linear attenuation coefficient (LAC), and full-width at half-maximum (FWHM) were measured. Count ratios between the background, the vertebral body, and the tumor in SPECT images were 463.8: 2888.0: 15150.3 (1: 6.23: 32.7). The LAC of the background and vertebral body in the CT-derived attenuation map were 0.155 cm-1 and 0.284 cm-1, respectively, and the FWHM measured from the processus was 15.27 mm. The precise counts and LAC indicated that the phantom was accurate and could serve as a tool for evaluating acquisition, reconstruction parameters, and quantitation in bone SPECT images.
Although measurement and management of angiographic entrance skin dose (ESD) are deemed extremely important, accurate determination of maximum ESD and its location is generally difficult because of the dependence on therapeutic technique and position. Following our development of body-mounted gear bearing radiophotoluminescence glass dosimeter (RPLD) arrays for direct measurement of ESD in cranial and cardiovascular angiography and interventional radiology (IVR), our focus next turned to the limited number of facilities equipped to read RPLD outputs and the need for methods to effectively provide feedback to clinical facilities. As described here, we first constructed an RPLD reading facility capable of sending and receiving RPLDs by post, offering the potential to enable utilization of the developed gear at all hospitals in Japan that perform angiography and IVR. We next developed specialized web-based system to generate dose maps from RPLD dose data, thereby enabling any facility to perform trial system analysis, evaluation, and implementation; and investigated the results and related problems.