Four-dimensional flow magnetic resonance imaging for assessment of hemodynamic changes in the portal venous system before and after balloon-occluded retrograde transvenous obliteration: a pilot feasibility study.

BACKGROUND: The effectiveness of four-dimensional (4D) flow magnetic resonance imaging (MRI) for assessing hemodynamic changes before and after balloon-occluded retrograde transvenous obliteration (BRTO) remains unclear. PURPOSE: To evaluate the feasibility of 4D flow MRI for assessing hemodynamic changes in the portal venous system before and after BRTO. MATERIAL AND METHODS: We included 10 patients (7 men, 3 women; mean age = 67 years) with liver cirrhosis who had a high risk of gastric variceal bleeding or hepatic encephalopathy. Non-contrast 4D flow MRI of the upper abdomen was performed before and after BRTO. In addition, we compared the blood flow rates in the portal vein (PV), superior mesenteric vein (SMV), splenic vein (SV), left renal vein, and inferior vena cava before and after BRTO. Moreover, the flow directions of the SMV and SV before and after BRTO were assessed using both portography and 4D flow MRI. RESULTS: There was a significant post-BRTO increase in the blood flow rate in the PV and SV (P < 0.05). There was no significant post-BRTO change in the blood flow rates in the SMV, inferior vena cava, and left renal vein. In four patients, portography confirmed that hepatofugal flow in the SV and SMV changed to hepatopetal flow after BRTO. Moreover, 4D flow MRI correctly assessed the flow directions in the SMV and SV in 70%-100% of the patients. CONCLUSION: 4D flow MRI can be used to detect hemodynamic changes in the portal venous system before and after BRTO.

Age-related change and gender differences in pelvic morphology of healthy children.

BACKGROUND: An increasing number of studies about the hip joint morphology with childhood-specific hip diseases have been reported. But there have been few reports on pelvic morphology of healthy children. The purpose of this study was to assess the pelvic morphology of healthy children in detail and clarify the age-related change and gender difference of it. METHODS: We retrospectively assessed the pelvic morphology of 97 healthy children (3-18 years old) using their pelvic computed tomography (CT) data. Superior iliac angle (SIA), inferior iliac angle (IIA), and ischiopubic angle (IPA) as the parameters of pelvic winging, and acetabular anteversion and anterior acetabular sector angle (AASA), posterior acetabular sector angle (PASA), superior acetabular sector angle (SASA) as the parameters of acetabular coverage, are measured. Pearson's correlation coefficient was used for examining the correlation between the each measurement and the age of cases. Multiple linear regression analysis was performed to investigate the possibility of association of age and sex with each measurement. RESULTS: In female, it was found that IIA, AASA, PASA, SASA were significantly correlated with the age of the cases. And in male, SIA, IIA, IPA, AASA, PASA were significantly correlated with the age. Multiple linear regression analysis revealed the significant difference of the distribution between males and females was observed in IIA, IPA, AVcen, PASA, and these measurements were lager for female. CONCLUSIONS: In this study, we revealed the age-related change and gender difference of the pelvic morphology of healthy children, and this could be useful information in evaluating the hip with what appears to be an abnormal acetabular anteversion and acetabular inclination in the patients with childhood specific hip disease. Additionally, it will also help us to make operation plans pertaining to the hip.

Diagnostic performance and image quality of low-tube voltage and low-contrast medium dose protocol with hybrid iterative reconstruction for hepatic dynamic CT.

OBJECTIVE: To evaluate the diagnostic performance and image quality of the low-tube voltage and low-contrast medium dose protocol for hepatic dynamic CT. METHODS: This retrospective study was conducted between January and May 2018. All patients underwent hepatic dynamic CT using one of the two protocols: tube voltage, 80 kVp and contrast dose, 370   mgI/kg with hybrid iterative reconstruction or tube voltage, 120 kVp and contrast dose, 600  mgI/kg with filtered back projection. Two radiologists independently scored lesion conspicuity and image quality. Another radiologist measured the CT numbers of abdominal organs, muscles, and hepatocellular carcinoma (HCC) in each phase. Lesion detectability, HCC diagnostic ability, and image quality of the arterial phase were compared between the two protocols using the non-inferiority test. CT numbers and HCC-to-liver contrast were compared between the protocols using the Mann-Whitney U test. RESULTS: 424 patients (70.5 ± 10.1 years) were evaluated. The 80-kVp protocol showed non-inferiority in lesion detectability and diagnostic ability for HCC (sensitivity, 85.7-89.3%; specificity, 96.3-98.6%) compared with the 120-kVp protocol (sensitivity, 91.0-93.3%; specificity, 93.6-97.3%) (p < 0.001-0.038). The ratio of fair image quality in the 80-kVp protocol also showed non-inferiority compared with that in the 120-kVp protocol in assessments by both readers (p < 0.001). HCC-to-liver contrast showed no significant differences for all phases (p = 0.309-0.705) between the two protocols. CONCLUSION: The 80-kVp protocol with hybrid iterative reconstruction for hepatic dynamic CT can decrease iodine doses while maintaining diagnostic performance and image quality compared with the 120-kVp protocol. ADVANCES IN KNOWLEDGE: The 80- and 120-kVp protocols showed equivalent hepatic lesion detectability, diagnostic ability for HCC, image quality, and HCC-to-liver contrast.The 80-kVp protocol showed a 38.3% reduction in iodine dose compared with the 120-kVp protocol.

Adaptive change in temporomandibular joint tissue and mandibular morphology following surgically induced anterior disc displacement by bFGF injection in a rabbit model.

PURPOSE: The purpose of this study was to examine the effect of injecting basic fibroblast growth factor following surgical induced anterior disc displacement in temporomandibular joints (TMJ). MATERIALS AND METHODS: Adult male Japanese white rabbits (n = 16; 2.0-2.5 kg; 10 weeks old) were assigned to experimental and control groups. In the experimental group, anterior disc displacement was induced in the bilateral TMJ. Recombinant human basic fibroblast growth factor (rh bFGF) 0.1 µg/1 µL aqueous solution was injected into the left retro-discal connective tissue close to the disc (ADL group), and saline alone was injected into the same site on the right (ADR group). In the control group, a sham operation without disc position change was performed in the bilateral TMJ (CR group and CL group). Four animals from the experimental (ADR and ADL) and control (CR and CL) groups were sacrificed at 1 and 12 weeks postoperatively to evaluate the mandibular morphology and computed tomographic (CT) value of the condylar head, using 3 dimensional computed tomography. Furthermore, cartilage layers and disc tissue were examined histologically. RESULTS: Regarding CT value at the 0° site of the condylar surface, ADR showed the lowest value after 1 week (P = 0.0325). However, there were no significant differences among the 4 groups regarding CT values at the other degree sites after 1 and 12 weeks. Regarding mandibular length, ADR showed the lowest value after 12 weeks (P = 0.0079). In condylar width, ADR showed the lowest value after 1 week (P = 0.0097). CONCLUSION: This study suggested that surgically induced anterior disc displacement could affect condylar morphology in the early stage, and could decrease mandibular length in the late stage. However, bFGF injection into the TMJ might prevent the degenerative change derived from anterior disc displacement and inhibition of sequential mandibular growth.

[New diagnostic imaging for navigation surgery].

Progress in diagnostic computed tomography (CT) and magnetic resonance (MR) imaging has been remarkable. Multidetector-row CT provides thin-slice images through the upper abdomen, multiphase abdominal imaging, and 3D images of high quality including CT angiography and multiplanar reformation. The development of MR units provides diffusion-weighted images for detecting abdominal tumors, and the steady-state coherent echo method can be used for imaging of vessels without using contrast media. The 3D images provided in CT and MR imaging facilitate anatomic understanding of tumors and vessels and are useful for preoperative navigation. However, we must be careful when using 3D images for diagnosis, because the subjectivity of the 3D image creator may affect the results. Therefore the original axial images should also be referred to.

[Estimation of operator dose by dose area product meter].

Because of the more advanced and more complex procedures in interventional radiology (IVR), longer treatment times have become necessary. Therefore, it is important to determine the exposure doses received by operators and patients. Operator doses arising from the use of X-rays are mainly due to scattered radiation. The purpose of this study was to assess the feasibility of estimating operator dose by dose area product (DAP), which shows the total X-ray output from the collimator. DAP showed a strong correlation with the space dose from the fundamental examination. In clinical practice, we measured the exposure doses of the neck, left shoulder, left hand, and right finger using a thermoluminescence dosimeter (TLD). These then were compared with the DAP. The results indicated that the dose equivalents (H70 microm) of the neck and left shoulder were strongly correlated with DAP (r=0.85, 0.86), whereas the H70 microm of the left hand and right finger were less closely correlated (r=0.40, 0.48). In comparison with the fluoroscopic time, the dose equivalents showed a better correlation with DAP in all the evaluated parts. The effective doses for the operator were strongly correlated with DAP (r=0.87). When measurements are not available, dose equivalents and operator effective doses can be estimated by the DAP, as indicated by the strong correlations recognized in this study.

A new irradiation unit constructed of self-moving gantry-CT and linac.

PURPOSE: To improve reproducibility in stereotactic irradiation (STI) without using noninvasive immobilization devices or body frames, we have developed an integrated computed tomography (CT)-linac irradiation system connecting CT scanner and linac via a common treatment couch. METHODS AND MATERIALS: This system consists of a linac, a CT scanner, and a common treatment couch. The linac and the CT gantry are positioned on opposite ends of the couch so that, by rotating the treatment couch, linac radiotherapy or CT scanning can be performed. The rotational axis of the linac gantry is coaxial with that of the CT gantry, and the position of the linac isocenter on the couch matches the origin of the coordinate system for CT scanning when the couch is rotated 180 degrees toward the CT side. Instead of the couch moving into the gantry, as in conventional CT, in this case the table is fixed and scanning is accomplished by moving the gantry. We evaluated the rotational accuracy of the common couch and the scan-position accuracy of the self-moving gantry CT. RESULTS: The positional accuracy of the common couch was 0.20, 0.18, and 0.39 mm in the lateral, longitudinal, and vertical directions, respectively. The scan-position accuracy of the CT gantry was less than 0.4 mm in the lateral, longitudinal, and vertical directions. CONCLUSION: This irradiation system has a high accuracy and is useful for noninvasive STI and for verification of the position of a target in three-dimensional conformal radiotherapy.

A new irradiation system for lung cancer combining linear accelerator, computed tomography, patient self-breath-holding, and patient-directed beam-control without respiratory monitoring devices.

PURPOSE: To introduce and assess a new irradiation technique for lung cancer that utilizes a linear accelerator and computed tomography (CT) scanner combination, along with a novel switching mechanism, which enables patients to synchronize the duration of irradiation with self-breath-holding without respiratory monitoring devices. MATERIALS AND METHODS: A newly developed treatment unit, a linear accelerator combined with a CT scanner (CT-linac), was used for irradiation. A novel switching mechanism, connected directly to the console of the linear accelerator, enabled the patient to control the radiation beam to correspond with the duration of self-breath-holding during a session determined by a radiation technologist. Twenty patients with lung cancer were enrolled in this study. All patients were instructed in the technique of breath-holding during the inspiration phase using visualization of respiratory motion through fluoroscopy as a teaching aid. CT scans under patients' self-breath-holding were repeated three times, and differences in tumor position on CT images were measured. The reproducibility of tumor position was visually evaluated on electronic portal images (EPI). RESULTS: Mean maximum differences in tumor position under patients' self-breath-holding were 2.2 mm in the cranial-caudal direction, 1.4 mm in the anterior-posterior direction, and 1.3 mm in the right-left direction. Switching of the radiation beam was delayed less than 0.1 s behind patient switching. EPIs were used to determine that reproducibility of tumor position was satisfactorily accurate. CONCLUSIONS: The reproducibility of tumor position, during patient self-breath-holding synchronized with patient-initiated radiation and without a respiratory monitoring device, was sufficiently accurate. This novel irradiation technique for lung tumors using a combination CT-linac offers reduced PTV, sufficient reproducibility, and decreased duration of treatment.

CT evaluation of patient deep inspiration self-breath-holding: how precisely can patients reproduce the tumor position in the absence of respiratory monitoring devices?

The aim of the present study was to evaluate the reproducibility of tumor position under patient deep inspiration self-breath-holding in the absence of respiratory monitoring devices, as well as to compare the reproducibility of deep inspiration self-breath-holding on the verbal command of a radiation technologist (Passive mode) with that initiated by patients' own estimation (Active mode). Twenty patients with lung cancer were shown how the tumor and diaphragm move during the respiration cycle. Patients were instructed to hold their breath during deep inspiration and reproduce identical tumor position as well as possible either by the Active mode or by the Passive mode. After patients had practiced self-breath-holding during deep inspiration, a set of three CT scans was obtained for each of the two modes of self-breath-holding (6 CT scans total) to obtain randomly timed images of 2 mm thickness in the vicinity of the tumor. The first three scans were performed during breath-hold using the Active mode, and next three scans were using the Passive mode. Maximum difference in tumor position for the three CT scans was then calculated along three axes: cranial-caudal (C-C); anterior-posterior (A-P); and right-left (R-L). In the 20 patients who underwent analysis of self-breath-holding, mean maximum difference in tumor position obtained under breath-hold using the Active and the Passive modes were: 2.2 and 3.1 mm along the C-C axis; 1.4 and 2.4 mm along the A-P axis; and 1.3 and 2.2 mm along the R-L axis, respectively. These differences in all axes were significantly smaller (p<0.05) for the Active mode than for the Passive mode. Most tumors displayed maximal respiratory movement along the C-C axis, and minimal movement along the R-L axis, but tumors located in the upper lung displayed maximal movement along the A-P axis. Significant correlation (p<0.05) was observed between differences along three axes in either mode of breath-hold. In conclusion, the reproducibility of tumor position under self-breath-holding by patients during deep inspiration after sufficient practice and in the absence of respiratory monitoring devices was satisfactorily accurate, and differences in tumor position were smaller under breath-holding using the Active mode than using the Passive mode. We believe this new technique is likely to prove extremely useful for the irradiation of lung tumors with a small internal margin and for reduced proportion of high-dose irradiated normal lung to total lung volume.

[Consideration of the newly standardized interventional reference point].

The interventional reference point is standardized by the International Electrotechnical Commission (IEC), and is adapted to adult cardiovascular studies. We examined the precision of the indicated incident dose at the interventional reference point. As a fundamental examination, we compared entrance phantom dose and incident dose at the interventional reference point. We also compared the entrance skin dose of patients with incident dose at the interventional reference point and evaluated the possibility of clinical application. Results showed that the incident dose at the interventional reference point indicated an underestimation of 0.77 times to an overestimation of 2.2 times when representing entrance surface dose. In clinical application, the incident dose at the interventional reference point calculated from the dose area product tended to overestimate by about 1.17 times the entrance skin dose measured by thermoluminescence dosimeter (TLD). Furthermore, the evaluation varied according to the angles of the C-arm of the x-ray system. A interventional reference point is a useful standard for simple, real-time dose measurement by the indirect method. It is important to understand the characteristics of the indicated incident dose at the interventional reference point in clinical use.

Determination of a standard deviation that could minimize radiation exposure in an automatic exposure control for pulmonary thin-section computed tomography.

PURPOSE: The aim of this study was to determine a standard deviation (SD) that most reduces the radiation dose without sacrificing the diagnostic accuracy of thin-section computed tomography (CT) for clinical use. MATERIALS AND METHODS: A total of 120 patients were examined by multidetector CT. They were assigned to one of four SD groups: 8, 9, 11, and 12. Each SD group consisted of 30 patients. The CT images of the same patients with SD10 that had formerly been examined were used for comparison. Two radiologists independently evaluated the degrees of image noise and diagnostic acceptability of the pulmonary diseases using a point score grading system. We compared the scores between each SD and the SD10 group. RESULTS: Generally, image noise was significantly more prominent in the higher-SD groups. The mean score of diagnostic acceptability was significantly lower in the SD12 group (4.2 ± 1.6) than in the SD10 group (4.6 ± 1.1) group (P < 0.001), whereas no difference was present between the SD8 (4.9 ± 0.7), SD9 (4.8 ± 1.0), and SD11 (4.4 ± 1.5) groups and the SD10 group (4.7 ± 1.1, 4.6 ± 1.4, 4.6 ± 1.1, respectively). CONCLUSION: Thin-section CT with SD12 is not acceptable. SD11 seems to be the setting with the lowest radiation dose while providing acceptable imaging quality for pulmonary thin-section CT.

[Optimization of radiographic conditions for computed tomography (CT) during hepatic angiography by interventional radiology-CT angio system].

Many cases in which the skin complication are caused by increased exposure dose to skin by interventional radiology (IVR) are reported. Therefore, the decrease of patient exposure dose at IVR is important. Patient exposure dose by using IVR-computed tomography (CT) unit is defined as the sum of exposure dose from both angiography and CT scanner. The dose decrease with the CT device was examined in this article. Since the images available during angiography have a high contrast compared to conventional CT scan, best applied standard deviation (SD) values are evaluated by using CT auto exposure control (CT-AEC). Although exposure dose decreased by varying SD values, contrast resolution was kept high. As a result, it became possible to adjust the dose from CT device to about a third by setting a proper CT-AEC value, which led to decrease of the total exposure dose.