The 10 most-cited articles in Japanese Journal of Radiological Technology, 2017

Ray-summation (raysum) images reconstructed from computed tomography (CT) volume data resemble digital radiography (DR) images. Therefore, they have a potential to be used instead of DR images.The aim of this study was to compare the physical image quality evaluated by signal-difference-to-noise ratio (SDNR) and clinical usefulness between raysum and DR images. We employed an oval water phantom simulating adult abdomen for image quality measurement. Raysum images were reconstructed from CT volume data using an assumed x-ray quality of 70 keV. DR images were obtained using an indirect-type flat panel detector system. The normalized noise-power spectrum (NNPS) for various same dose indices (DR: entrance surface dose, CT: CT dose index volume) were measured from raysum and DR images. SDNRs were calculated from the results of NNPSs, modulation transfer function (MTF), and cartilage material contrast. Five experienced observers visually compared each pair of a clinical raysum image and a DR image for nine clinical cases (head, finger, pelvis, and foot). MTF of raysum was significantly…

Purpose: Several cross-calibration schemes have been proposed to produce quantitative values in bone SPECT imaging. Differences in the radionuclide sources and geometric conditions can decrease the accuracy of cross-calibration factor (CCF). The present study aimed to validate the effects of calibration schemes using different sources under various geometric conditions. Methods: Temporal variations as well as variations in acquisition counts and the shapes of 57Co standard and 99mTc point sources and a 99mTc disk source were determined. The effects of the geometric conditions of the source-to-camera distance (SCD) and lateral distance on the CCF were investigated by moving the camera or source away from the origin. The system planar sensitivity of NEMA incorporated into a Symbia Intevo SPECT/CT device (Siemens®) was defined as reference values. Results: The temporal variation in CCF using the 57Co source was relatively stable within the range of 0.7% to 2.3%, whereas the 99mTc source ranged from 2.7% to 7.3%. In terms of source shape, the 57Co standard point source was the most…

During percutaneous coronary intervention (PCI) for chronic total occlusion (CTO), longer fluoroscopic time as compared with PCI for non-CTO lesions may cause skin injury by increased radiation. We have performed a multi-center observational study comparing the exposed dose during the PCI of CTO (CTO group) and during the PCI of non-CTO lesions (non-CTO group). Exposure doses were assessed in 313 patients with CTO and 3,310 patients with non-CTO lesions. Total fluoroscopy time (59.0 ±35.5 vs 26.8 ±18.8 min, p<0.0001) and the total air kerma (2.76±2.11 vs 1.27±0.94 Gy, p<0.0001) were significantly greater in the CTO group than in the non-CTO group. The maximum air kerma of the CTO group was 13.62 Gy. Informed consent about the risk of transient depilation and the transient erythema is required for the case with radiation dose over 3 Gy. The frequency of the patient who received radiation >3 Gy was significantly higher in the CTO group as compared with the non-CTO group (34.1% vs 4.9%). Therefore, informed consent before an operation and postoperative follow-up are indispensable for…

Depiction of the fine vessel can provide useful preoperative information for patients with uterine cervical cancer. Although angiography can visualize vessels in detail, it is invasive. MR-angiography is a minimally invasive method to depict vessels, but the resolution of images is insufficient for preoperative evaluation. In this study, we used less invasive three-dimensional CT angiography (3D-CTA) and reconstructed images of adaptive iterative dose resolution 3D (AIDR 3D) with display field of view (D-FOV), which are suitable for arteries with large and small diameters, and created the fusion images. Created images allowed the observation of vessel branch in wide area compared with angiography, and it was less invasive. We evaluated the utility of 3D-CTA for visualizing fine vessels branching from uterine artery as preoperative evaluation for radial hysterectomy. 3D-CTA was obtained in nine patients. Conventional reconstruction and magnification reconstruction (D-FOV: 320‒360 mm, 150 mm) was made using arterial phase. Normal volume rendering image (N-VR) was made from…

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.

The low-contrast detectability of computed tomography (CT) images is commonly evaluated by the contrast-to-noise ratio (CNR) because of its convenience to measure. However, the correlation between CNR and visual detectability is poor because the CNR is a simple index determined by both the contrast of the object and the standard deviation of the image noise. On the other hand, the signal-to-noise ratio (SNR), especially SNR based on the statistical decision theory model (SNRS, D) and SNR based on the matched-filter model (SNRM) are considered superior to CNR. In this study, we investigated a new physical image quality index for evaluating low-contrast detectability (SNRA), which is approximately derived from SNRS, D and SNRM. The new index, which was calculated using the object size, contrast of the object and the noise power spectrum, provided good approximations when the diameter of the rod object was equal and >5 mm. The diameter dependency of the SNRA was also found to provide better sensitivity than the sensitivities of CNR and object-specific CNR, similar to SNRS, D and SNRM.…

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…

In dynamic multi-leaf collimator (MLC) intensity-modulated radiotherapy (IMRT), the accuracy of delivered dose is influenced by the positional accuracy of the moving MLC. In order to assess the accuracy of the delivered dose during dynamic MLC IMRT, the delivered dose error in dynamic MLC IMRT using the MLC speed control with dose rate change was investigated. Sweeping gap sequence irradiation was performed with constant MLC leaf speed at 0.6 to 5 cm/s or changed MLC speed (4 steps). The positional accuracy of the moving MLC was evaluated from the trajectory log file. Absorbed dose measurements with sweeping field (Field size: 10 cm×10 cm, MLC leaf speed: 0.6 to 2.7 cm/s, MLC leaf gap width: 0.2 to 2.0 cm) were performed. The delivered dose error at each gap width was evaluated according to MLC leaf speed change. MLC positional errors and changes in delivered dose according to MLC leaf speed were within 0.07 mm and 0.6%, respectively, for all measurements. Beam hold-off did not occur under any conditions. We confirmed that TrueBeam can regulate MLC leaf speed below the maximum limit…