A cross-national investigation of CT, MRI, PET, mammography, and radiation therapy resources and utilization.

PURPOSE: This study aimed to analyze the domestic and international landscape of imaging diagnostics and treatments, focusing on Japan, to provide current insights for policymaking, clinical practice enhancement, and international collaboration. METHODS: Data from 1996 to 2021 were collected from Japan's Ministry of Health, Labor and Welfare database for medical device counts of CT, MRI, PET, mammography, and radiotherapy. The National Database of Health Insurance Claims and Specific Health Checkups of Japan was utilized for examination numbers. An international comparison was made with data from 41 countries using the Organization for Economic Cooperation and Development (OECD) database. RESULTS: The data included a total of 108,596 CT devices, 47,233 MRI devices, 2998 PET devices, 20,641 MMG devices, and 8023 RT devices during the survey period. Upon international comparison, Japan ranked first in CT and MRI devices per million people and second in examination numbers per 1000 people. The number of PET devices per million people exceeded OECD averages; however, the number of examinations per 1000 people was below the OECD average in 2020 (Japan: 4.0, OECD: 4.9). Although Japan exceeded OECD averages in mammography device counts (Japan: 33.8, OECD: 24.5 in 2020), radiotherapy device counts were similar to OECD averages (Japan: 8.3, OECD: 7.9 in 2020). CONCLUSION: We have analyzed the utilization of equipment in the context of diagnostic imaging and radiotherapy in Japan. Since the initial survey year, all devices have shown an upward trend. However, it is essential not only to increase the number of devices and examinations but also to address the chronic shortage of radiologists and allied health professionals. Based on the insights gained from this study, understanding the actual status of diagnostic imaging and radiation therapy equipment is critical for grasping the domestic situation and may contribute to improving the quality of healthcare in Japan.

Pacemaker Malfunction During Passive Proton Beam Therapy for Localized Prostate Cancer: Case Reports and a Literature Review.

We report two cases of pacemaker malfunction occurring during proton beam therapy (PBT) for localized prostate cancer treatment. The first case involved mode changes in the pacemaker, while the second exhibited prolongation of the RR interval. Remarkably, both cases did not manifest significant clinical changes. Our findings indicate that careful consideration should be given to passive PBT in patients with localized prostate cancer who have pacemakers, like the considerations in patients with thoracic and abdominal cancers. Moreover, our report highlights the importance of recognizing potential cardiac implantable electronic devices malfunction in various PBT scenarios.

Computed tomographic pulmonary angiography: Three cases of low-tube-voltage acquisition with a slow injection of contrast medium.

Acute pulmonary thromboembolism occurring during cancer treatment has been increasing with the number of cancer patients and chemotherapy cases. Computed tomographic pulmonary angiography (CTPA) for evaluating the pulmonary artery is generally performed using rapid injection of contrast medium. However, intravenous catheters for contrast medium injection might cause extravasation due to rapid injection. This case series describes three patients who underwent contrast-enhanced computed tomography combined with low-tube-voltage imaging and slow injection. Low-tube-voltage slow-injection CTPA can be an effective technique for obtaining high contrast enhancement while accommodating fragile veins and low injection rates.

Inaccurate table height setting affects the organ-specific radiation dose in computed tomography.

PURPOSE: We aimed to prove that the locally absorbed doses in tissues and organs are affected by inaccurate table height in computed tomography. MATERIALS AND METHODS: We compared the volume CT dose index (CTDIvol) and the absorbed doses using an anthropomorphic phantom combined with a breast phantom. The phantom was set at the gantry center, from which the table height was changed every 20 mm between-40 mm and 40 mm. Data acquisition was performed using auto table height correction (AHC) for each table height. The CTDIvol was obtained from the CT console and the tube current value for each image slice (DICOM tag: 0018, 1151). The absorbed dose was measured by a glass dosimeter that was implanted at various positions in the phantom. RESULTS: The tube current values in the lung were lower at a table height of + 40 mm than those at other heights. The CTDIvol was slightly lower at + 40 mm than at the center (12.78 mGy vs. 13.42 mGy, p < 0.05). The CTDIvol values were almost the same at the other table heights (13.30-13.40 mGy). The absorbed doses at the lens and mammary gland were significantly different from those at the gantry center (-27.27%-17.77% and -24.31%-12.83%, respectively). Compared with the center, both the lens and mammary gland had higher absorbed doses at a table height of -40 mm. CONCLUSION: The absorbed dose was affected by the table height, but the CTDIvol was maintained by AHC. The operator should appropriately position patients even when using AHC.

Ultrahigh-Resolution Computed Tomography Improves Preoperative Computed Tomography Angiography for Deep Inferior Epigastric Artery Perforator Flap Reconstruction.

OBJECTIVE: The aim of the study was to compare computed tomography (CT) angiography (CTA) imaging of deep inferior epigastric artery perforator (DIEP) using the ultrahigh-resolution CT (UHRCT) and conventional multidetector CT (MDCT). METHODS: This retrospective study enrolled 20 patients who underwent CTA of DIEP flap with UHRCT and MDCT. Computed tomography values were measured at 4 large vessels (thoracic aorta, abdominal aorta, common iliac artery, and external iliac artery) and 5 peripheral vessels (proximal and distal internal thoracic artery, proximal and distal deep inferior epigastric artery, and DIEP). RESULTS: There were no significant differences in mean CT values of the major vessel between UHRCT and MDCT. Ultrahigh-resolution CT shows higher CT values of the peripheral vessels than MDCT (P < 0.05 for all). The median CT values of the DIEP in UHRCT were approximately 3 times higher than those in MDCT (P < 0.001). CONCLUSIONS: Ultrahigh-resolution CT provides higher-quality CTA of DIEP compared with MDCT.

Comparison of five-phase computed tomography images of type 1 autoimmune pancreatitis and pancreatic cancer: Emphasis on cases with atypical images.

BACKGROUND/OBJECTIVES: International consensus diagnostic criteria (ICDC) include characteristic images of autoimmune pancreatitis (AIP); however, reports on atypical cases are increasing. The aims of this study were to compare CT findings between AIP and pancreatic cancer (PC), and to analyze type 1 AIPs showing atypical images. METHODS: Five-phase CT images were compared between 80 type 1-AIP lesions and 80 size- and location-matched PCs in the case-control study. Atypical AIPs were diagnosed based on the four ICDC items. RESULTS: ICDC items were recognized in most AIP lesions; pancreatic enlargement (87.7%), narrowing of the main pancreatic duct (98.8%), delayed enhancement (100%), and no marked upstream-duct dilation (97.5%). CT values of AIPs increased rapidly until the pancreatic phase and decreased afterward, while those of PCs gradually increased until the delayed phase (P < 0.0001). Atypical images were recognized in 14.8% of AIPs, commonly without pancreatic enlargement (18.5 mm) and sometimes mimicking intraductal neoplasms. The CT values and their ratios were different between atypical AIPs and size-matched PCs most significantly in the pancreatic phase, but similar in the delayed phase. CONCLUSIONS: Ordinary type 1 AIPs can be diagnosed with the ICDC, but atypical AIPs represented a small fraction. "Delayed enhancement" is characteristic to ordinary AIPs, however, "pancreatic-phase enhancement" is more diagnostic for atypical AIPs.

Radiation dose and image quality of CT fluoroscopy with partial exposure mode.

PURPOSE: The present study aimed to evaluate the scan technique of computed tomography (CT)-guided puncture procedures using partial exposure mode (PEM) on the radiation dose of the operator's hand and image quality. METHODS: Radiation dose was evaluated using three types of scanning methods: one-shot scan (OS), OS with a bismuth shield added (OSBismuth), and a half-scan (i.e., PEM) capable of an adjustable exposure angle. Dose evaluation was performed using a torso phantom, while a circular phantom simulating the liver parenchyma and lesions was used for image quality evaluation. For each scanning method, four measurements were made to determine the radiation dose to the operator's hand and the dose distribution on the surface of the patient's torso; the output-dose profile was determined from five measurements. Image quality was evaluated in terms of contrast and contrast-to-noise ratio (CNR). Analysis of variance (ANOVA) or Friedman test were used for comparison between groups as appropriate. The post hoc tests were Tukey's honestly difference (HSD) test for parametric data or Wilcoxon signed rank test with Bonferroni correction for nonparametric data. RESULTS: The PEM yielded a radiation dose to the operator's hand that was 84% (0.35 vs. 2.33 mGy) lower than that of the OS. The dose to the patient's torso was reduced by 35% and 68% for the OSBismuth and PEM, respectively, relative to that of the OS. Compared with the CNR of the other two scanning methods (OS, 2.9±0.1; OSBismuth, 2.9±0.1), the PEM increased the standard deviation and decreased the CNR (2.1±0.04, Tukey's HSD, P < 0.001 for all). Images acquired with PEM showed visibility equivalent to that of other scanning methods when window conditions were adjusted. CONCLUSION: This study demonstrated that CT-guided puncture procedure using PEM effectively reduces the operator's exposure to radiation while minimizing image quality deterioration.

Wedged field using the half-field method with a flattening filter-free photon beam.

In this study, we propose a novel wedged field using a half-field flattening filter-free beam without a metallic filter or a moving jaw, and investigate the characteristics of the proposed technique. Dose distributions of the proposed method were first determined in virtual-water or anthropomorphic phantom using a radiotherapy planning system. We evaluated the wedge angle as a function of the field size, collimator rotation, and depth. The wedge angle at 10 MV was observed to be greater than that at 6 MV. The minimum angles at 6 and 10 MV were 17.7° and 40.4°, respectively, while the maximum angles were 33.9° and 48.4°, respectively. We determined that the wedge angle depended on the nominal beam energy and field size, and we verified that the proposed method is capable of delivering a gradient dose distribution and reducing treatment time.

Contrast Enhancement in Breast Cancer and Background Mammary-Gland Tissue During the Super-Early Phase of Dynamic Breast Magnetic Resonance Imaging.

RATIONALE AND OBJECTIVES: We aimed to compare the contrast enhancement between tumor and mammary-gland tissue to distinguish lesions in the super-early phase, during which minimal contrast media uptake is observed in mammary-gland tissue. MATERIALS AND METHODS: Dynamic magnetic resonance imaging, including the super-early phase with bolus tracking (BT) method (to determine the optimal imaging start time), was performed by using identical parameters to obtain transverse fat-suppressed T1-weighted images of both breasts. The percent enhancement (PE) and the contrast ratio (CR) indicators for tumor and mammary-gland tissue were assessed in each dynamic phase. RESULTS: The PE values of the tumor were 62.4% and 151.6%, and those of the mammary gland were 0.3% and 20.7% in the super-early and early phases, respectively. Therefore, virtually no background parenchymal enhancement was observed in the super-early phase. The variation in the PE values during the super-early phase was significantly smaller when the values were determined with the BT method (P < .05). The CR was highest in the early phase, and the CR in the super-early phase was lower than in the other phases. Early-phase PE and CR were significantly higher in invasive cancer cases than in noninvasive cancer cases (P < .01). A significant difference in the imaging start time was observed for the anatomic side factor by the BT method. CONCLUSION: Background parenchymal enhancement almost never appeared in the super-early phase, but the CR was lower in the super-early phase than in the early phase. The BT method allowed for an optimal imaging start time for the super-early phase and yielded images with less deviation of contrast enhancement.

Radiation dose optimization for the bolus tracking technique in abdominal computed tomography: usefulness of real-time iterative reconstruction for monitoring scan.

The purpose of this study was to optimize the monitoring dose, obtained using the conventional filtered back projection (FBP) method and iterative reconstruction algorithms, for the bolus tracking technique. A phantom study was performed to assess the effect of the scan start time in patients grouped according to different body weights. An oval torso phantom was used for simulating the time enhancement curve of the bolus tracking technique. To reproduce image noise levels in the two body weight groups, the phantom diameter was adjusted with a water-equivalent material. The tube currents were 10, 20, 30, and 50 mA. The monitoring scan was performed with the conventional FBP method and real-time adaptive iterative dose reduction by three-dimensional processing (AIDR 3D). The results at different doses were compared with those at 50 mA. The volume computed tomography dose index was 1.31, 2.65, 3.93, and 6.56 mGy at tube currents of 10, 20, 30, and 50 mA, respectively. The scan start time, reconstructed using FBP, was significantly faster at 10 and 20 mA in group A (50-59 kg) and at 20 mA in group B (≥80 kg). The CT values in the region of interest could not be measured at 10 mA because of artifacts. With real-time AIDR 3D, both groups showed no significant differences between the measurements obtained at 30 or 20 mA and those obtained at 50 mA. Our study demonstrated that the real-time AIDR 3D algorithm improved the accuracy of the CT measurements with the bolus tracking technique.

Operator Dose Measurements and Image Quality Assessment in Computed Tomography Fluoroscopy Using Bismuth Sheet.

OBJECTIVE: The purpose of this study was to assess the dose reduction and the image quality using bismuth sheets during the computed tomography fluoroscopy (CTF). MATERIALS AND METHODS: The bismuth sheets of 1-mm thick were put on the upper mylar ring to reduce the frontal X-ray. The dose rates of an operator were measured using a torso phantom in the patient position during the CTF. The torso phantom was set on the gantry rotation center (center) and the lower position from the center (off-center). The image quality of the CTF image was assessed using an original phantom that mimics the normal liver parenchyma and the low attenuation lesions. The image contrast and contrast-to-noise ratio (CNR) were compared with and without the bismuth sheets. RESULTS: The bismuth sheets reduced the dose rate of the operator, regardless of whether the torso phantom was set at the center or the off-center. The reduction rate of exposure at the center and the off-center were 42.3% and 34.5%, respectively. There were no significant differences in the image contrast and the CNR, although the bismuth sheets increased the CT values of the liver parenchyma and the low attenuation lesions. CONCLUSION: The bismuth sheets were effective for the reduction of exposure to the operator without degrading the image quality of CTF images.

Clinical application of 320-row multidetector computed tomography for a dynamic three-dimensional vascular study: imaging findings and initial experience.

The 320-row multidetector computed tomography (MDCT) is now used by both cardiologists and neurosurgeons. It enables dynamic 3D-CT angiography, because the wide-area detector eliminates helical scanning, thus achieving very fast scanning times for single 3D-CT volume data. Some microvascular surgeons are familiar with 64-row MDCT for perforator studies, but there are few reports of studies using 320-row MDCT. This MDCT system was used to follow the dynamic blood flow of small vessels. It is considered to have a great potential in the clinical field of microvascular surgery.