The circulation time and the mechanical acceleration time (MA time) of an automatic injector were simulated using pharmacokinetic analysis. The addition method and transfer-function method, which are mathematical techniques used for analyzing the test bolus method in multi-detector computed tomography, were used to verify the accuracy of estimation of the time-enhancement curve (TEC) of the main bolus. The TEC estimated using the addition method, and the TEC of the main bolus matched completely only if the MA time of the automatic injector was set to 0 seconds. Moreover, the estimation accuracy of the TEC deteriorated when the MA time was set according to the TEC estimated by the addition method. In contrast, the TEC estimated using the transfer-function method, except when the MA time of the automatic injector was 0 seconds, had higher accuracy than the TEC estimated using the addition method. In this study, the addition method, a number of additions of TEC, and MA time of the automatic injector were found to have a negative effect on the estimation accuracy of the main bolus. The use of the transfer-function method for determining the TEC and the MA time has a positive effect on the estimation accuracy of the main bolus.
Objective: To study whether the actual radiation exposure is different between computed tomography (CT) scanners and medical centers when the same patient is scanned, we investigated the actual effective doses for a whole body (Chest-Pelvis) CT scan in a multicenter study. Materials and Methods: Data from subjects were collected using 12 CT scanners at six medical centers in Yamagata city. Effective-dose data were acquired by scanning the same phantom (ATOM Dosimetry Phantoms Model702-B) using 120 kV tube voltage. Effective doses were calculated using corrected data from a radiophotoluminescent glass dosimeter (GD-302M). GD-302M had energy- dependent issues, which needed to be corrected. Also, differences in sensitivity based on arrangement within the phantom were insignificant. Results: The mean effective energy was 48.6 keV (range, 42.5–55.4 keV), and the mean effective dose was 16.3 mSv (range, 8.9–26.0 mSv). The mean effective dose with a hybrid type iterative reconstruction was 10.7 mSv (range, 8.9–16.4 mSv), but the mean effective dose without any iterative reconstruction was 20.3 mSv (range, 16.2–26.0 mSv). We found an approximate linear correlation between dose length product (DLP) on operation consoles and the effective dose. Conclusion: We suggest that the actual radiation exposure was different at each medical center when the same patient is scanned.
Purpose: The purpose of this study was to investigate the injection pressure reduction effect of the novel indwelling needle (Becton, Dickinson and Company). Method: We evaluated the period of 651 patients who underwent dynamic computed tomography. We compared the maximum injection pressure. The contrast medium was administered at 320, 350, and 370 mgI/ml. Result: The maximum injection pressure of the novel indwelling needle in 22 G was decreased 10% compared with SC5 in all contrast media. The maximum injection pressure of BDN in 20 G decreases 8% compared with SC5 at 370 mgI/ml, but there was no reduction at 320 mgI/ml and 350 mgI/ml. Conclusion: Our analysis demonstrated that BDN significantly reduced the injection pressure especially in 22 G and using high concentration contrast medium in 20 G.
The purpose of this study is to measure the hemodynamics on the effect of Valsalva maneuver aiming at pulmonary thromboembolism (PTE) using 2-dimensional (2D) phase contrast imaging of magnetic resonance image (MRI), Philips Ingenia 3.0-tesla (T). The maximal inspiration reduced the blood flow rate in various degrees at all measurement positions, superior vena cava (SVC), inferior vena cava (IVC), pulmonary artery (PA), ascending aorta (AA), and descending aorta (DA). This result suggests that the contrast effect in the PA might become weak during general PA phase to give a substantial influence of Valsalva maneuver in the condition after maximum inspiration. A contrast-enhanced computed tomography (CT) examination aiming at detection for PTE should be scanned without an advance maximum inspiration.
Purpose: This study aimed to evaluate the statistical noise of motion-frozen (MF) image generated by gated myocardial perfusion single photon emission computed tomography (SPECT) imaging using IQ · SPECT and to determine the optimal acquisition and reconstruction parameters for MF image using IQ · SPECT. Methods: A movement cardiac phantom and static cardiac phantom were used to acquire the MF images. The acquisition times used were different in 8 and 16 frames per R-R interval, and varying reconstruction parameters (subset and iteration) were used. We determined the %CV value, contrast, and normalized mean square error (NMSE) to evaluate the image quality. Results: The %CV value for a MF image with IQ · SPECT was lower than that for a conventional non-gated myocardial perfusion SPECT (MPS) image with low energy high resolution (LEHR). With regard to the acquisition parameters, the contrast did not change when the acquisition time was increased in 8 and 16 frames per R-R interval. NMSE converged in 56 beats/view in 8 frames per R-R interval. With regard to the reconstruction parameters, the contrast and the %CV value of the anterior and septal wall converged in update 40. The minimum NMSE in subsets 1, 2, and 3 were almost similar. Conclusions: Uniformity in the MF image with IQ · SPECT was higher than that in the conventional image. The results of this MF image with IQ · SPECT study suggest that the optimal acquisition parameter should be 56 beats/view in 8 frames per R-R interval, and the optimal reconstruction parameters should be subset 3 and iteration 14.
The specific binding ratio (SBR) was first reported by Tossici-Bolt et al. for quantitative indicators for dopamine transporter (DAT) imaging. It is defined as the ratio of the specific binding concentration of the striatum to the non-specific binding concentration of the whole brain other than the striatum. The non-specific binding concentration is calculated based on the region of interest (ROI), which is set 20 mm inside the outer contour, defined by a threshold technique. Tossici-Bolt et al. used a 50% threshold, but sometimes we couldn’t define the ROI of non-specific binding concentration (reference region) and calculate SBR appropriately with a 50% threshold. Therefore, we sought a new method for determining the reference region when calculating SBR. We used data from 20 patients who had undergone DAT imaging in our hospital, to calculate the non-specific binding concentration by the following methods, the threshold to define a reference region was fixed at some specific values (the fixing method) and reference region was visually optimized by an examiner at every examination (the visual optimization method). First, we assessed the reference region of each method visually, and afterward, we quantitatively compared SBR calculated based on each method. In the visual assessment, the scores of the fixing method at 30% and visual optimization method were higher than the scores of the fixing method at other values, with or without scatter correction. In the quantitative assessment, the SBR obtained by visual optimization of the reference region, based on consensus of three radiological technologists, was used as a baseline (the standard method). The values of SBR showed good agreement between the standard method and both the fixing method at 30% and the visual optimization method, with or without scatter correction. Therefore, the fixing method at 30% and the visual optimization method were equally suitable for determining the reference region.
Brain imaging techniques, such as computed tomography (CT), magnetic resonance imaging (MRI), single photon emission computed tomography (SPECT), and positron emission tomography (PET), can provide essential and objective information for the early and differential diagnosis of dementia. Amyloid PET is especially useful to evaluate the amyloid-β pathological process as a biomarker of Alzheimer’s disease. This article reviews critical points about technical considerations on the scanning and image analysis methods for amyloid PET. Each amyloid PET agent has its own proper administration instructions and recommended uptake time, scan duration, and the method of image display and interpretation. In addition, we have introduced general scanning information, including subject positioning, reconstruction parameters, and quantitative and statistical image analysis. We believe that this article could make amyloid PET a more reliable tool in clinical study and practice.
Recently, intensity-modulated radiation therapy (IMRT) is used worldwide, highly accurate verification of the location using image-guided radiation therapy (IGRT) has become critical. However, the use of cone-beam computed tomography (CBCT) to ascertain the location each time raises concerns about its influence on radiotherapy dosage and increased radiation exposure. The purpose of this study was to measure the absorbed dose using nine kilovoltage (kV) devices and two megavoltage (MV) devices (total 11 devices) at eight facilities, compare the absorbed dose among the devices, and assess the characteristics of the respective devices to ensure optimal clinical operation. For the measurement of the absorbed dose, a farmer-type ionization chamber dosimeter, calibrated using a 60Co and an IMRT dose verification phantom manufactured from water-equivalent material RW3, was used to measure the absorbed dose at nine points in the phantom for two regions, the pelvic and cephalic region. The average absorbed dose of the pelvic region was 3.09±0.21 cGy in kV-CBCT (OBI), 1.16±0.16 cGy in kV-CBCT (XVI), 5.64±1.48 cGy in MV-CBCT (4 MV), and 6.33±1.54 cGy in MV-CBCT (6 MV). The average absorbed dose of the cephalic region was 0.38±0.03 cGy in kV-CBCT (OBI), 0.23±0.06 cGy in kV-CBCT (XVI), 4.02±0.72 cGy in MV-CBCT (4 MV), and 4.46±0.77 cGy in MV-CBCT (6 MV). There was a difference in the absorbed dose at the measured points as well as in the dose distribution in the phantom cross section. No major difference was observed in the absorbed dose among identical devices, but a difference was identified among the devices installed at multiple facilities. Therefore, the angle of rotation should be paid attention to when CBCT is taken, and the image-taking conditions should be determined. In addition, it is important to handle the devices only after ascertaining the absorbed dose of each device.