Development of a dose-rate dosimeter using a silicon photodiode for a medical linear accelerator in a 10 MV flattening filter-free mode

This study was aimed at developing a dose-rate dosimeter to measure the instantaneous dose rate of a commercially available medical linear accelerator. A dose-rate dosimeter composed of a silicon photodiode (Si-PD), a complementary metal-oxide semiconductor single operational amplifier, a resistor of 20 MΩ, a capacitor of 100 pF, and a mini-substrate measuring 16 × 16 mm2 was evaluated. Voltage outputs from the proposed dosimeter were measured using an analog-to-digital converter on a microcomputer. A custom-made x-ray tube generator at an energy of 120 kV with a tube current ranging from 0.1 to 2.0 mA was used for the dose-rate calibration. Dose-rate calibration was performed 83.3 mm from an x-ray source using a commercially available semiconductor dosimeter. The developed Si-PD dosimeter could measure up to 0.6 Gy/s at a distance of 19.3 mm from the x-ray source. Measurements were also performed using a medical linear accelerator in a 10 MV flattening filter-free mode at depths of 0, 25, 50, and 100 mm with an irradiation field of 100 × 100 mm2 at a constant distance of 1000 mm from the source to the dosimeter. A peak voltage variation corresponding to the instantaneous dose rate was observed using a sampling period of 1.0 ms, and the peak voltages decreased with the depth. The detected pulse numbers were 512, 484, 491, and 511 at depths of 0, 25, 50, and 100 mm, respectively.

Ultra-high-resolution CT vs. invasive angiography for detecting hemodynamically significant coronary artery disease: Rationale and methods of the CORE-PRECISION multicenter study

BACKGROUND

Direct coronary arterial evaluation via computed tomography (CT) angiography is the most accurate noninvasive test for the diagnosis of coronary artery disease (CAD). However, diagnostic accuracy is limited in the setting of severe coronary calcification or stents. Ultra-high-resolution CT (UHR-CT) may overcome this limitation, but no rigorous study has tested this hypothesis.

METHODS

The CORE-PRECISION is an international, multicenter, prospective diagnostic accuracy study testing the non-inferiority of UHR-CT compared to invasive coronary angiography (ICA) for identifying patients with hemodynamically significant CAD. The study will enroll 150 patients with history of CAD, defined as prior documentation of lumen obstruction, stenting, or a calcium score ≥400, who will undergo UHR-CT before clinically prompted ICA. Assessment of hemodynamically significant CAD by UHR-CT and ICA will follow clinical standards. The reference standard will be the quantitative flow ratio (QFR) with <0.8 defined as abnormal. All data will be analyzed in independent core laboratories.

RESULTS

The primary outcome will be the comparative diagnostic accuracy of UHR-CT vs. ICA for detecting hemodynamically significant CAD on a patient level. Secondary analyses will focus on vessel level diagnostic accuracy, quantitative stenosis analysis, automated contour detection, in-depth plaque analysis, and others.

CONCLUSION

CORE-PRECISION aims to investigate if UHR-CT is non-inferior to ICA for detecting hemodynamically significant CAD in high-risk patients, including those with severe coronary calcification or stents. We anticipate this study to provide valuable insights into the utility of UHR-CT in this challenging population and for its potential to establish a new standard for CAD assessment.

Association between preoperative cortical magnetic susceptibility and postoperative changes in the cerebral blood flow on cognitive improvement following carotid endarterectomy

INTRODUCTION

While patients who experience improved cognition following carotid endarterectomy (CEA) typically demonstrate restored brain perfusion after the procedure, it is worth noting that less than 50% of patients in whom postoperative cerebral blood flow (CBF) restoration is achieved actually show improved cognition after postoperatively. This suggests that factors beyond the mere restoration of CBF may play a role in postoperative cognitive improvement. Increased iron deposition in the cerebral cortex may cause neural damage, and quantitative susceptibility mapping (QSM) obtained using magnetic resonance imaging (MRI) quantifies magnetic susceptibility in the cerebral cortex, allowing for the assessment of iron deposition in vivo. The purpose of the present study was to determine whether preoperative cortical magnetic susceptibility as well as postoperative changes in CBF are associated with cognitive improvement after CEA.

METHODS

Brain MRI with a three-dimensional gradient echo sequence was preoperatively performed in 53 patients undergoing CEA for ipsilateral internal carotid artery stenosis (≥70%), and QSM with brain surface correction and vein removal was obtained. Cortical magnetic susceptibility was measured in the cerebral hemisphere ipsilateral to surgery on QSM. Preoperatively and at two months after the surgery, brain perfusion single-photon emission computed tomography (SPECT) and neuropsychological assessments were conducted. Using these collected data, we evaluated alterations in CBF within the affected hemisphere and assessed cognitive improvements following the operation.

RESULTS

A logistic regression analysis showed that a postoperative greater increase in CBF (95% confidence interval [CI], 1.06-1.90; p = 0.0186) and preoperative lower cortical magnetic susceptibility (95% CI, 0.03-0.74; p = 0.0201) were significantly associated with postoperatively improved cognition. Although sensitivity, specificity, and positive- and negative-predictive values with the cutoff value lying closest to the upper left corner of a receiver operating characteristic curve for the prediction of postoperatively improved cognition did not differ between postoperative changes in CBF and preoperative cortical magnetic susceptibility, the specificity and the positive-predictive value were significantly greater for the combination of postoperative changes in CBF and preoperative cortical magnetic susceptibility (specificity, 95% CI, 93-100%; positive-predictive value 95% CI, 68-100%) than for the former parameter alone (specificity, 95% CI, 63-88%; positive-predictive value 95% CI, 20-64%).

CONCLUSION

Preoperative cortical magnetic susceptibility as well as postoperative changes in CBF are associated with cognitive improvement after CEA.

Management for iatrogenic femoral pseudoaneurysms by embolisation of the aneurysmal neck from the contralateral femoral artery: A report of five cases

Femoral pseudoaneurysms are typically associated with femoral arterial catheterisation. Treating iatrogenic morbidity requires curing the disease, without causing any additional complications. Occlusion of the aneurysmal neck is ideal to seal post-catheterised pseudoaneurysms along with maintaining the femoral arterial flow. However, few reports have suggested neck embolisation for post-catheterised pseudoaneurysms. We describe five cases of iatrogenic femoral pseudoaneurysms in patients successfully treated with embolisation through the aneurysmal neck. This technique may be an alternative therapeutic option in managing femoral pseudoaneurysms.

Super-resolution deep learning reconstruction at coronary computed tomography angiography to evaluate the coronary arteries and in-stent lumen: an initial experience

A super-resolution deep learning reconstruction (SR-DLR) algorithm trained using data acquired on the ultrahigh spatial resolution computed tomography (UHRCT) has the potential to provide better image quality of coronary arteries on the whole-heart, single-rotation cardiac coverage on a 320-detector row CT scanner. However, the advantages of SR-DLR at coronary computed tomography angiography (CCTA) have not been fully investigated. The present study aimed to compare the image quality of the coronary arteries and in-stent lumen between SR-DLR and model-based iterative reconstruction (MBIR). We prospectively enrolled 70 patients (median age, 69 years; interquartile range [IQR], 59-75 years; 50 men) who underwent CCTA using a 320-detector row CT scanner between January and August 2022. The image noise in the ascending aorta, left atrium, and septal wall of the ventricle was measured, and the signal-to-noise ratio (SNR) and contrast-to-noise ratio (CNR) in the proximal coronary arteries were calculated. Of the twenty stents, stent strut thickness and luminal diameter were quantitatively evaluated. The image noise on SR-DLR was significantly lower than that on MBIR (median 22.1 HU; IQR, 19.3-24.9 HU vs. 27.4 HU; IQR, 24.2-31.2 HU, p < 0.01), whereas the SNR (median 16.3; IQR, 11.8-21.8 vs. 13.7; IQR, 9.9-18.4, p = 0.01) and CNR (median 24.4; IQR, 15.5-30.2 vs. 19.2; IQR, 14.1-23.2, p < 0.01) on SR-DLR were significantly higher than that on MBIR. Stent struts were significantly thinner (median, 0.68 mm; IQR, 0.61-0.78 mm vs. 0.81 mm; IQR, 0.72-0.96 mm, p < 0.01) and in-stent lumens were significantly larger (median, 1.84 mm; IQR, 1.65-2.26 mm vs. 1.52 mm; IQR, 1.28-2.25 mm, p < 0.01) on SR-DLR than on MBIR. Although further large-scale studies using invasive coronary angiography as the reference standard, comparative studies with UHRCT, and studies in more challenging population for CCTA are needed, this study's initial experience with SR-DLR would improve the utility of CCTA in daily clinical practice due to the better image quality of the coronary arteries and in-stent lumen at CCTA compared with conventional MBIR.

Improved Diagnosis of Adjacent Organ Invasion of Extrahepatic Cholangiocarcinoma by Adding Arterial and Delayed Phases

PURPOSE

To clarify the role of dynamic computed tomography (CT) in diagnosing extrahepatic cholangiocarcinoma (eCCA) involving adjacent organs.

MATERIAL AND METHODS

We retrospectively analyzed patients diagnosed with eCCA in Iwate Medical University Hospital (Morioka, Japan) during January 2011-December 2021 who underwent dynamic contrast-enhanced CT before biliary intervention, surgery, or chemotherapy. For surgical cases, two radiologists independently reviewed CT images in the portal, dual (adding arterial phase), and triple (adding delayed phase) phases. The mean attenuations of the abdominal aorta, portal vein (PV), hepatic parenchyma, pancreatic parenchyma, and eCCA were measured. The biliary segment-wise longitudinal tumour extent, arterial and PV invasion, organ invasion (liver, pancreas, and duodenum), and regional lymph node metastasis were assessed on a five-point scale. Image performances were compared using the sensitivity, specificity, and area under the curve (AUC).

RESULTS

We included 120 patients (mean age, 71.7 ± 8.9; 84 males). The PV and liver differed most from the bile duct tumour in the portal phase. The abdominal aorta and pancreas differed most from eCCA in the arterial phase. For 80 patients evaluated on the five-point scale, adding phases increased the AUC for pancreatic, duodenal, and arterial invasion for each observer (observer 1, 0.79-0.93, p<0.01, 0.71-0.86, p = 0.04, 0.74-0.99, p = 0.02; observer 2, 0.88-0.96, p = 0.01, 0.73-0.94, p<0.01, 0.80-0.99 p = 0.04; respectively). The AUC for biliary segment-wise longitudinal tumor extent, hepatic, and PV invasion remained unchanged with additional phases.

CONCLUSIONS

Portal-phase information is sufficient to evaluate the segmental extent of bile duct and liver/PV invasion. Arterial- and delayed-phase information can help evaluate pancreatic, duodenal, and arterial invasion.

A Comparison of Retrospective ECG-Gated CT and Surgical or Angiographical Findings in Acute Aortic Syndrome

The best cardiac phases in retrospective ECG-gated CT for detecting an intimal tear (IT) in aortic dissection (AD) and an ulcer-like projection (ULP) in an intramural hematoma (IMH) have not been established. This study aimed to compare the detection accuracy of diastolic-phase and systolic-phase ECG-gated CT for IT in AD and ULP in IMH, with subsequent surgical or angiographical confirmation as the reference standard.In total, 81 patients (67.6 ± 11.8 years; 41 men) who underwent emergency ECG-gated CT and subsequent open surgery or thoracic endovascular aortic repair for AD (n = 52) or IMH (n = 29) were included. The accuracies of detecting IT and ULP were compared among only diastolic-phase, only systolic-phase, and both diastolic-phase and systolic-phase methods of retrospective ECG-gated CT; surgical or angiographical findings were used as the reference standard. The detection accuracy for IT and ULP using only diastolic-phase, only systolic-phase, and both diastolic-phase and systolic-phase methods of ECG-gated CT was 93% [95% CI: 87-97], 94% [95% CI: 88-97], and 95% [95% CI: 90-97], respectively. There were no significant differences in detection accuracy among the 3 acquisition methods (P = 0.55). Similarly, there were no significant differences in the accuracy of detecting IT in AD (P = 0.55) and ULP in IMH (P > 0.99) among only diastolic-phase, only systolic-phase, and both diastolic- and systolic-phase ECG-gated CT.Retrospective ECG-gated CT for detecting IT in AD and ULP in IMH yields highly accurate findings. There were no significant differences seen among only diastolic-phase, only systolic-phase, and both diastolic-phase and systolic-phase ECG-gated CT.

Electron beam detection in radiotherapy using a capacitor dosimeter equipped with a silicon photodiode

In this study, a newly developed capacitor dosimeter was evaluated using electron beams commonly utilized in radiotherapy. The capacitor dosimeter comprised a silicon photodiode, 0.47-μF capacitor, and dedicated terminal (dock). Before electron beam irradiation, the dosimeter was charged using the dock. The doses were measured without using a cable by reducing the charging voltages using the currents from the photodiode during irradiation. A commercially available parallel-plane-type ionization chamber and solid-water phantom were used for dose calibration with an electron energy of 6 MeV. In addition, the depth doses were measured using a solid-water phantom at electron energies of 6, 9, and 12 MeV. The doses were proportional to the discharging voltages, and the maximum dose difference in the calibrated doses measured using a two-point calibration was approximately 5% in the range of 0.25-1.98 Gy. The depth dependencies at energies of 6, 9, and 12 MeV corresponded to those measured using the ionization chamber.

Metastatic patellar bone tumor due to gastric cancer resembling a primary or secondary aneurysmal bone cyst: A case report

INTRODUCTION AND IMPORTANCE

Patellar bone tumors are very rare, and most are benign or of intermediate type. In this report, we describe our experience of a metastatic patellar bone tumor caused by gastric cancer, which resembled a very rare primary or secondary aneurysmal bone cyst and review the literature.

CASE PRESENTATION

A 65-year-old man presented with severe pain in the patellar region and marked limitation of the knee joint range of motion. He had a history of gastric cancer; however, epidemiological, clinical, and imaging findings led us to strongly suspect an aneurysm-like bone cyst. Thus, we performed bone tumor curettage and autologous artificial bone grafting without biopsy because of the severe pain. Pathology results showed gastric cancer metastasis; hence, patellectomy and patellar tendon augmentation with femoral fascia were performed. The Musculoskeletal Tumor Society (MSTS) score was taken postoperatively to assess pain and function.

CLINICAL DISCUSSION

We experienced a very rare gastric cancer-related metastatic patellar bone tumor, which resembled a primary or secondary aneurysmal bone cyst in frequency and imaging findings. Patellectomy was ultimately performed, and the patient's MSTS score improved markedly.

CONCLUSION

Despite its very low frequency, patellar metastatic bone tumors must be taken into account without being misled by the frequency or imaging findings and a biopsy should necessarily be performed.

Evaluation of peripheral enhancement on contrast-enhanced computed tomography and corresponding pathological findings in colorectal liver metastases after preoperative chemotherapy

Purpose

To correlate peripheral enhancement on contrast-enhanced computed tomography (CE-CT) in patients with post-chemotherapy colorectal liver metastases (CRLM) with the corresponding pathological findings.

Material and methods

Forty-four patients with CRLM who underwent hepatic resection after preoperative chemotherapy between 2008 and 2013 were included. Two radiologists blinded to the histopathology findings performed a consensus categorization of the marginal contrast effects of CRLM on CE-CT as follows: Group 1, smooth margin without enhancement; Group 2, smooth margin with an enhanced rim; and Group 3, fuzzy margin with/without an enhanced rim. The Kruskal-Wallis test was used to compare the imaging findings with the histological findings.

Results

The percentage of infarct-like necrosis was significantly higher in those with CRLM with smooth margins than in those with CRLM with fuzzy margins (p < 0.001, r = 0.62). The percentage of viable cells was lowest in CRLM with smooth margins without enhancement (p < 0.001, r = 0.60).

Conclusions

Our findings suggest that the type of necrosis is related to the nature of the margins, and the presence of residual cells is related to peripheral enhancement.

Reliability of respiratory-gated real-time two-dimensional cine incorporating deep learning reconstruction for the assessment of ventricular function in an adult population

This study aimed to assess the image quality and accuracy of respiratory-gated real-time two-dimensional (2D) cine incorporating deep learning reconstruction (DLR) for the quantification of biventricular volumes and function compared with those of the standard reference, that is, breath-hold 2D balanced steady-state free precession (bSSFP) cine, in an adult population. Twenty-four patients (15 men, mean age 50.7 ± 16.5 years) underwent cardiac magnetic resonance for clinical indications, and 2D DLR and bSSFP cine were acquired on the short-axis view. The image quality scores were based on three main criteria: blood-to-myocardial contrast, endocardial edge delineation, and presence of motion artifacts throughout the cardiac cycle. Biventricular end-diastolic volume (EDV), end-systolic volume (ESV), stroke volume (SV), ejection fraction (EF), and left ventricular mass (LVM) were analyzed. The 2D DLR cine had significantly shorter scan time than bSSFP (41.0 ± 11.3 s vs. 327.6 ± 65.8 s; p < 0.0001). Despite an analysis of endocardial edge definition and motion artifacts showed significant impairment using DLR cine compared with bSSFP (p < 0.01), the two sequences demonstrated no significant difference in terms of biventricular EDV, ESV, SV, and EF (p > 0.05). Moreover, the linear regression yielded good agreement between the two techniques (r ≥ 0.76). However, the LVM was underestimated for DLR cine (109.8 ± 34.6 g) compared with that for bSSFP (116.2 ± 40.2 g; p = 0.0291). Respiratory-gated 2D DLR cine is a reliable technique that could be used in the evaluation of biventricular volumes and function in an adult population.

Research Note: Expression of IGF-1 and IGF-1 Receptor Proteins in Skeletal Muscle Fiber Types in Chickens with Hepatic Fibrosis

We investigated the expression of insulin-like growth factor 1 (IGF-1) and IGF-1 type 1 receptor (IGF-1R) in skeletal muscle fiber types in chickens with hepatic fibrosis induced by bile duct ligation (BDL). Eleven hens, approximately 104 weeks old, were randomly assigned to BDL (n = 4) and sham surgery (SHAM; n = 7) groups. In BDL hens, histopathology revealed marked bile duct proliferation and liver fibrosis. The cross-sectional area (CSA) of myofibers from both the pectoralis (PCT) muscles significantly decreased in the BDL group compared with the SHAM group (P < 0.01). In contrast, the CSA of myofibers from the femorotibialis lateralis (FTL) muscle did not decrease in the BDL group. Type I fibers were large, round, and hypertrophic. Elongated type IIA and IIB fibers were also present. For IGF-1 immunostaining, the immunoreaction intensity was higher in the PCT in the BDL group than the SHAM group. Within the BDL group, type I fibers from FTL had a stronger immunoreaction intensity than the type II fibers. For IGF-1R immunostaining, the intensity of the immunoreactions was similar within the PCT in the BDL group compared with the SHAM group. For FTL, type I fibers had stronger reactions to IGF-1R than type II fibers in the BDL group. These results suggest that type I fibers express both IGF-1 and IGF-1R and become hypertrophic in chickens with hepatic fibrosis.

Deep learning reconstruction allows low-dose imaging while maintaining image quality: comparison of deep learning reconstruction and hybrid iterative reconstruction in contrast-enhanced abdominal CT

We aimed to compare the radiation dose and image quality of a low-dose abdominal computed tomography (CT) protocol reconstructed with deep learning reconstruction (DLR) with those of a routine-dose protocol reconstructed with hybrid-iterative reconstruction. This retrospective study enrolled 71 patients [61 men; average age, 71.9 years; mean body mass index (BMI), 24.3 kg/m2] who underwent both low-dose abdominal CT with DLR [advanced intelligent clear-IQ engine (AiCE)] and routine-dose abdominal CT with hybrid-iterative reconstruction [adaptive iterative dose reduction 3D (AIDR 3D)]. Radiation dose parameters included volume CT dose index (CTDIvol), effective dose (ED), and size-specific dose estimate (SSDE). Mean image noise and contrast-to-noise ratio (CNR) were calculated. Image noise was measured in the hepatic parenchyma and bilateral erector spinae muscles. Moreover, subjective assessment of perceived image quality and diagnostic acceptability was performed. The low-dose protocol helped reduce the CTDIvol by 44.3%, ED by 43.7%, and SSDE by 44.9%. Moreover, the noise was significantly lower and CNR significantly higher with the low-dose protocol than with the normal-dose protocol (P<0.001). In the subjective assessment of image quality, there was no significant difference between the protocols with regard to image noise. Overall, AiCE was superior to AIDR 3D in terms of diagnostic acceptability (P=0.001). The use of AiCE can reduce overall radiation dose by more than 40% without loss of image quality compared to routine-dose abdominal CT with AIDR 3D.

Pebbles and sand on asteroid (162173) Ryugu: In situ observation and particles returned to Earth

The Hayabusa2 spacecraft investigated the C-type (carbonaceous) asteroid (162173) Ryugu. The mission performed two landing operations to collect samples of surface and subsurface material, the latter exposed by an artificial impact. We present images of the second touchdown site, finding that ejecta from the impact crater was present at the sample location. Surface pebbles at both landing sites show morphological variations ranging from rugged to smooth, similar to Ryugu's boulders, and shapes from quasi-spherical to flattened. The samples were returned to Earth on 6 December 2020. We describe the morphology of >5 grams of returned pebbles and sand. Their diverse color, shape, and structure are consistent with the observed materials of Ryugu; we conclude that they are a representative sample of the asteroid.

A case of hepatic intraductal papillary neoplasm of the bile duct

In this report, we present a 57-year-old female with a history of mild alcoholic liver disease during a medical check-up. Abdominal computed tomography and magnetic resonance imaging showed a multicystic mass with a solid enhancing mural nodule in the right lobe of the liver. Subsequently, laparoscopic right liver lobectomy was performed and pathological findings revealed intraductal papillary neoplasm of the bile duct (IPNB) with an associated invasive carcinoma. IPNB is a relatively rare disease that should be considered in the differential diagnosis of hepatic cystic tumours. Our case report highlights the importance of capturing image findings of the IPNB as this disease has a high potential for malignancy.

Characterization of an under-development capacitor dosimeter equipped with a silicon x-ray diode

Herein, we evaluated a capacitor dosimeter under development by a manufacturer, which is designed to monitor the entrance dose in x-ray diagnosis and comprises a silicon x-ray diode (Si-XD), a 0.1 µF capacitor, and a dosimeter dock. The Si-XD is a high-sensitivity photodiode optimized for x-ray detection. The dosimeter was charged to 3.30 V using the dock before x-ray irradiation. The charging voltage was reduced by photocurrents flowing through the Si-XD during irradiation, and the discharging voltage was measured. For the fundamental characterization of this capacitor dosimeter, we investigated the x-ray tube-current and tube-voltage dependences of the measured dose using an industrial x-ray tube; the angular dependence was also investigated. A commercially available semiconductor dosimeter (RaySafe ThinX) was used for dose calibration. The doses were proportional to the tube current at a constant tube voltage of 100 kV and increased with increasing tube voltage at a constant tube current of 1.0 mA. The dose difference with respect to the commercially available semiconductor dosimeter was within 1.0% when the tube current was varied and it was within 3.0% when the tube voltage was varied. In the angular dependence measurement, a difference of up to 6.0% was observed as the angle varied from 0° to 355° in steps of 5°. The dose-calibration results indicated that the determination of the initial charging voltage was important for dose conversion using the capacitor dosimeter.

Superior objective and subjective image quality of deep learning reconstruction for low-dose abdominal CT imaging in comparison with model-based iterative reconstruction and filtered back projection

Objective:

This study aimed to conduct objective and subjective comparisons of image quality among abdominal computed tomography (CT) reconstructions with deep learning reconstruction (DLR) algorithms, model-based iterative reconstruction (MBIR), and filtered back projection (FBP).

Methods:

Datasets from consecutive patients who underwent low-dose liver CT were retrospectively identified. Images were reconstructed using DLR, MBIR, and FBP. Mean image noise and contrast-to-noise ratio (CNR) were calculated, and noise, artifacts, sharpness, and overall image quality were subjectively assessed. Dunnett’s test was used for statistical comparisons.

Results:

Ninety patients (67 ± 12.7 years; 63 males; mean body mass index [BMI], 25.5 kg/m²) were included. The mean noise in the abdominal aorta and hepatic parenchyma of DLR was lower than that in FBP and MBIR (p < .001). For FBP and MBIR, image noise was significantly higher for obese patients than for those with normal BMI. The CNR for the abdominal aorta and hepatic parenchyma was higher for DLR than for FBP and MBIR (p < .001). MBIR images were subjectively rated as superior to FBP images in terms of noise, artifacts, sharpness, and overall quality (p < .001). DLR images were rated as superior to MBIR images in terms of noise (p < .001) and overall quality (p = .03).

Conclusions:

Based on objective and subjective comparisons, the image quality of DLR was found to be superior to that of MBIR and FBP on low-dose abdominal CT. DLR was the only method for which image noise was not higher for obese patients than for those with a normal BMI.

Advances in knowledge:

This study provides previously unavailable information on the properties of DLR systems and their clinical utility.

Diagnostic Accuracy of Screening Arterial Spin-Labeling MRI Using Hadamard Encoding for the Detection of Reduced CBF in Adult Patients with Ischemic Moyamoya Disease

BACKGROUND AND PURPOSE

Adult patients with ischemic Moyamoya disease are advised to undergo selective revascularization surgery based on cerebral hemodynamics. The purpose of this study was to determine the diagnostic accuracy of arterial spin-labeling MR imaging using Hadamard-encoded multiple postlabeling delays for the detection of reduced CBF in such patients.

MATERIALS AND METHODS

Thirty-seven patients underwent brain perfusion SPECT and pseudocontinuous arterial spin-labeling MR imaging using standard postlabeling delay (1525 ms) and Hadamard-encoded multiple postlabeling delays. For Hadamard-encoded multiple postlabeling delays, based on data obtained from the 7 sub-boluses with combinations of different labeling durations and postlabeling delays, CBF corrected by the arterial transit time was calculated on a voxel-by-voxel basis. Using a 3D stereotaxic template, we automatically placed ROIs in the ipsilateral cerebellar hemisphere and 5 MCA territories in the symptomatic cerebral hemisphere; then, the ratio of the MCA to cerebellar ROI was calculated.

RESULTS

The area under the receiver operating characteristic curve for detecting reduced SPECT-CBF ratios (<0.686) was significantly greater for the Hadamard-encoded multiple postlabeling delays-CBF ratios (0.885) than for the standard postlabeling delay-CBF ratios (0.786) (P = .001). The sensitivity and negative predictive value for the Hadamard-encoded multiple postlabeling delays-CBF ratios were 100% (95% confidence interval, 100%-100%) and significantly higher than the sensitivity (95% CI, 44%-80%) and negative predictive value (95% CI, 88%-97%) for the standard postlabeling delay-CBF ratio, respectively.

CONCLUSIONS

ASL MR imaging using Hadamard-encoded multiple postlabeling delays may be applicable as a screening tool because it can detect reduced CBF on brain perfusion SPECT with 100% sensitivity and a 100% negative predictive value in adult patients with ischemic Moyamoya disease.

Prognostic value of noninvasive combined anatomic/functional assessment by cardiac CT in patients with suspected coronary artery disease - Comparison with invasive coronary angiography and nuclear myocardial perfusion imaging for the five-year-follow up of the CORE320 multicenter study

BACKGROUND

Few data exist on long-term outcome in patients undergoing combined coronary CT angiography (CTA) and myocardial CT perfusion imaging (CTP) as well as invasive coronary angiography (ICA) and single photon emission tomography (SPECT).

METHODS

At 16 centers, 381 patients were followed for major adverse cardiac events (MACE) for the CORE320 study. All patients underwent coronary CTA, CTP, and SPECT before ICA within 60 days. Prognostic performance according binary results (normal/abnormal) was assessed by 5-year major cardiovascular events (MACE) free survival and area under the receiver-operating-characteristic curve (AUC).

RESULTS

Follow up beyond 2-years was available in 323 patients. MACE-free survival rate was greater among patients with normal combined CTA-CTP findings compared to ICA-SPECT: 85 vs. 80% (95% confidence interval [CI] for difference 0.1, 11.3) though event-free survival time was similar (4.54 vs. 4.37 years, 95% CI for difference: -0.03, 0.36). Abnormal results by combined CTA-CTP was associated with 3.83 years event-free survival vs. 3.66 years after abnormal combined ICA-SPECT (95% CI for difference: -0.05, 0.39). Predicting MACE by AUC also was similar: 65 vs. 65 (difference 0.1; 95% CI -4.6, 4.9). When MACE was restricted to cardiovascular death, myocardial infarction, or stroke, AUC for CTA-CTP was 71 vs. 60 by ICA-SPECT (difference 11.2; 95% CI -1.0, 19.7).

CONCLUSIONS

Combined CTA-CTP evaluation yields at least equal 5-year prognostic information as combined ICA-SPECT assessment in patients presenting with suspected coronary artery disease. Noninvasive cardiac CT assessment may eliminate the need for diagnostic cardiac catheterization in many patients.

CLINICAL TRIAL REGISTRATION

NCT00934037.

Development of a dose-rate dosimeter for x-ray CT scanner using silicon x-ray diode

In an x-ray diagnosis, it is important to evaluate the entrance dose rate, as the dose rate of exposure becomes highest in that position. To investigate the effect of the entrance dose rate of x-ray CT scanners, a dose-rate dosimeter comprising a silicon x-ray diode (Si-XD), a CMOS dual operational amplifier, resistors, capacitors, and a mini-substrate measuring 20 × 17 mm² were developed. The Si-XD is desirable for measuring the changing entrance dose rate, as it enables the reduction of the response time, dimensions, and cost of the dosimeter. The dosimeter was connected to a microcomputer (mbed), and the output voltages from the dosimeter were measured using an analog-digital converter in the mbed. The output voltages were proportional to the tube currents at a constant tube voltage of 100 kV using an industrial x-ray tube, and the calibrated dose rates corresponded well to those obtained using a commercially available semiconductor dosimeter. However, owing to the energy dependence of the dosimeter, the calibrated dose rate was ∼10% higher than that of a commercially available semiconductor dosimeter at the lower tube voltage. In the angular dependence of the dosimeter, the flatness measured from 60° to 120° was ∼103% in this study. A fundamental study for measuring the dose-rate variations with rotation was performed. The results showed a different profile than the angular dependence due to the distance from the source and the complex factors of the scattered radiation.

Whole cancer-region enhancement using meglumine-gadopentetate-glucose solution and 7.0-T magnetic resonance imaging

To visualize whole cancerous region including hypoxic cancer without radiation exposure, we developed meglumine-gadopentetate-glucose solution for 7.0-T magnetic resonance imaging. The infusion solution consists of meglumine-gadopentetate and glucose solutions, and these solutions are mixed before the vein drip infusion. We used readily available solutions, and the concentrations of the meglumine-gadopentetate and glucose solutions were 37.14 and 5.0%, respectively. In the first and second experiments, vein infusions were conducted from a rabbit ear using meglumine-gadopentetate-saline and meglumine-gadopentetate-glucose solutions, and T1 weighted imaging was performed to visualize cancerous region. Using the meglumine-gadopentetate saline, it was not difficult to image cancer-growth regions with new blood vessels. Using the meglumine-gadopentetate-glucose solution, the signal intensity of whole cancerous region including hypoxic cancer substantially increased. The visualizing duration for the meglumine gadopentetate glucose was beyond 90 min, and the rabbit survived after the infusion. The signal intensity in the hypoxic cancer was increasing until 90 min using the meglumine-gadopentetate-glucose solution, since the meglumine-gadopentetate molecules were absorbed into almost the whole cancerous region along with glucose-molecule flows.

Reliability of respiratory-triggered two-dimensional cine k-adaptive-t-autocalibrating reconstruction for Cartesian sampling for the assessment of biventricular volume and function in patients with repaired tetralogy of Fallot

Objective:

To compare left ventricular (LV) and right ventricular (RV) volume, function, and image quality of a respiratory-triggered two-dimensional (2D)-cine k-adaptive-t-autocalibrating reconstruction for Cartesian sampling (2D kat-ARC) with those of the standard reference, namely, breath-hold 2D balanced steady-state free precession (2D SSFP), in patients with repaired tetralogy of Fallot (TOF).

Methods:

30 patients (14 males, mean age 32.2 ± 13.9 years) underwent cardiac magnetic resonance, and 2D kat-ARC and 2D SSFP images were acquired on short-axis view. Biventricular end-diastolic volume (EDV) and end-systolic volume (ESV), stroke volume (SV), ejection fraction (EF), and LV mass (LVM) were analysed.

Results:

The 2D kat-ARC had significantly shorter scan time (35.2 ± 9.1 s vs 80.4 ± 16.7 s; p < 0.0001). Despite an analysis of image quality showed significant impairment using 2D kat-ARC compared to 2D SSFP cine (p < 0.0001), the two sequences demonstrated no significant difference in terms of biventricular EDV, LVESV, LVSV, LVEF, and LVM. However, the RVESV was overestimated for 2D kat-ARC compared with that for 2D SSFP (73.8 ± 43.2 ml vs 70.3 ± 44.5 ml, p = 0.0002) and the RVSV and RVEF were underestimated (RVSV = 46.2±20.5 ml vs 49.4 ± 20.4 ml, p = 0.0024; RVEF = 40.2±12.7% vs. 43.5±14.0%, p = 0.0002).

Conclusion:

Respiratory-triggered 2D kat-ARC cine is a reliable technique that could be used in the evaluation of LV volumes and function.

Advances in knowledge:

2D cine kat-ARC is a reliable technique for the assessment LV volume and function in patients with repaired TOF.

Spatial and temporal variations of flip-angle distributions in the human brain using an eight-channel parallel transmission system at 7T: comparison of three radiofrequency excitation methods

We investigated the spatial and temporal variations of flip-angle (FA) distributions in the human brain from multiple scans, using an eight-channel parallel transmission (pTx) system at 7T. Nine healthy volunteers were scanned in five sessions using three radiofrequency excitation techniques each time: circular polarization (CP), static pTx, and dynamic pTx. We calculated the coefficients of variation of the FA values within the brain area to evaluate the variations, and the maximum intersession differences in the FA values (D_max), comparing them between the three methods. The coefficients of variation decreased in the following order: CP, static pTx, and dynamic pTx (median: 20.1%, 13.6%, and 5.7%, respectively; p < 0.001). The average D_max values were significantly higher for the static pTx (5.4°) than for the dynamic pTx (2.8°) and CP (1.7°) methods (p = 0.004 and 0.001, respectively). Compared to the CP method, the dynamic pTx method at 7T can efficiently minimize spatial variations in the FA distribution with a mild increase in temporal variations. The static pTx method exhibited a remarkably wide temporal variation.

Additive Value of CT to Age, Aortic Diameter, and Echocardiography in Diagnosis and Classification of Bicuspid Aortic Valve in Patients with Severe Aortic Stenosis

Purpose

To develop and validate a CT diagnostic algorithm for bicuspid aortic valve (BAV) classification.

Materials and Methods

This retrospective study included 212 consecutive patients with severe aortic stenosis who underwent CT followed by aortic valve replacement (mean age, 71 years [range, 27-93 years]; 125 women; 37% with a BAV) from 2012 to 2017. BAV diagnosis and BAV category were determined by using the CT diagnostic algorithm developed and were compared with those attained through surgical diagnosis. Reproducibility and agreement were assessed using the Cohen kappa (κ) coefficient. The value of adding CT to age, aortic diameter index, and transthoracic echocardiography (TTE) was evaluated by using the area under the receiver operating characteristic curve (AUC), net reclassification improvement (NRI), and decision-curve analysis.

Results

Intra- and interobserver reproducibility were good or excellent for all CT diagnoses (κ ≥ 0.6 for all). Agreement between CT and surgical diagnoses was excellent (κ = 0.90) for BAV detection and good (κ = 0.69) for BAV categorization. Sixteen percent (five of 31) of patients with functional BAV diagnosed by using CT received a diagnosis of congenital BAV at surgery. The addition of CT to age, aortic diameter, and TTE showed a higher AUC (with CT, 0.97 [95% CI: 0.91, 0.99] vs without CT, 0.91 [95% CI: 0.85, 0.95]; P = .003) and NRI (1.79 [95% CI: 1.65, 1.92], P < .001) and a higher net benefit among all BAV probabilities.

Conclusion

CT diagnosis was consistent with surgical diagnosis and had an additive value over traditional diagnostic methods; however, there was a risk of overlooking congenital BAV in patients with functional BAV diagnosed by using CT.Supplemental material is available for this article.© RSNA, 2021.

Intentional Stent Stenosis to Prevent Hyperperfusion Syndrome after Carotid Artery Stenting for Extremely High-Grade Stenosis

BACKGROUND AND PURPOSE

Intracranial hemorrhage due to hyperperfusion syndrome is a severe carotid artery stent placement complication of extremely high-grade stenosis, causing hemodynamic insufficiency. To prevent hyperperfusion syndrome, we attempted intentional residual stent stenosis and implemented "gentle" carotid artery stent placement, defined as carotid artery stent placement using a closed-cell stent coupled with slight balloon predilation, without balloon postdilation. Gradual stent expansion was expected. We investigated the incidence of hyperperfusion syndrome and long-term outcomes after gentle carotid artery stent placement.

MATERIALS AND METHODS

We included patients who underwent carotid artery stent placement for extremely high-grade stenosis from January 2015 to March 2019. We defined extremely high-grade stenosis as carotid stenosis with conventional angiographic "slow flow" and a reduced MCA signal intensity on MRA. A reduced MCA signal intensity was defined as MCA with a relative signal intensity of <0.9 in the ipsilateral compared with the contralateral MCA. We evaluated the stent diameter, CBF on SPECT, hyperperfusion syndrome, and intracranial hemorrhage. We defined hyperperfusion syndrome as a triad of ipsilateral headache, seizure, and hemiparesis.

RESULTS

Twenty-eight of the 191 patients met our inclusion criteria. After carotid artery stent placement, their median minimal stent diameter was 2.9 mm, which expanded to 3.9 mm at 4 months. Neither cerebral hyperperfusion syndrome nor intracranial hemorrhage occurred.

CONCLUSIONS

The gentle carotid artery stent placement strategy for intentional residual stent stenosis may prevent hyperperfusion syndrome in high-risk patients. Stents spontaneously dilated in 4 months.

Near-infrared-ray computed tomography with an 808 nm laser beam and high spatial resolutions

To increase the penetrating photons and to improve the spatial resolution in near-infrared-ray computed tomography (NIR-CT), we used an 808 nm laser module. The NIR photons are produced from the laser module, and an object is exposed to the laser beam. The laser power is controlled by the applied voltage, and the photodiode detects photons penetrating through the object. To reduce scattering photons from the object, a 1.0-mm-diameter graphite pinhole is set behind the object. The spatial resolutions were improved using a 1.0-mm-diameter 5.0-mm-length graphite collimator and were ∼1 × 1 mm². The NIR-CT was accomplished by repeating the object-reciprocating translations and rotations of the object using the turntable, and the ray-sampling-translation and rotation steps were 0.1 mm and 0.5°, respectively. The scanning time was 19.6 min at a total rotation angle of 180°. Triple-sensitivity CT was accomplished using amplifiers, and a graphite rod in the chicken fillet was visible when increasing amplification factor.

Prognostic value of noninvasive combined anatomic/functional assessment by cardiac ct in patients with suspected coronary heart disease

Background

Noninvasive evaluation of patients with stable angina is preferable over invasive testing if it leads to similar patient outcome. The combination of coronary angiography and vasodilator challenge myocardial perfusion imaging by computed tomography allows fast, comprehensive assessment of patients with suspected coronary heart disease.

Purpose

To compare the long-term prognostic value of combined computed tomography angiography (CTA) and myocardial CT perfusion imaging (CTP) with invasive coronary angiography (ICA) and single photon emission tomography (SPECT) in patients with suspected hemodynamically significant coronary heart disease.

Methods

At 16 centres, 381 patients were followed for major adverse cardiac events (MACE) for the CORE320 study. All patients underwent coronary CTA, CTP, and SPECT before ICA. Prognostic performance according binary results (normal/abnormal) was assessed by 5-year major cardiovascular events (MACE) free survival and area under the receiver-operating-characteristic curve (AUC).

Results

Follow up beyond 2-years was available in 323 patients. MACE-free survival rate was greater among patients with normal combined CTA/CTP findings compared to ICA/SPECT: 85 vs. 80% (95% confidence interval [CI] for difference 0.1, 11.3) though event-free survival time was similar (4.54 vs. 4.37 years, 95% CI for difference: 0.03, 0.36). Abnormal results by combined CTA/CTP was associated with 3.83 years event-free survival vs. 3.66 years after abnormal combined ICA/SPECT (95% CI for difference: 0.05, 0.39, CI −1.0, 11.1) (Figure). Predicting MACE by AUC also was similar: 65 vs. 65 (difference 0.1; 95% CI: −4.6, 4.9). When MACE was restricted to death, myocardial infarction, or stroke, AUC for CTA/CTP was 66 vs. 61 by ICA/SPECT (difference 5.1; 95% CI: −7.1, 12.9).

Conclusions

Combined CTA/CTP yield similar 5-year prognostic performance as joined ICA/SPECT assessment in patients presenting with suspected coronary heart disease and thus may represent a fast, non-invasive alternative to the traditional diagnostic approach.

Figure 1. 5-year event-free survival

Funding Acknowledgement

Type of funding source: Public Institution(s). Main funding source(s): National Institutes of Health

Basic mechanism of atrial and ventricular arrhythmia suppression by heavy ion irradiation in hypercholesterolemic elderly rabbits

Background

Recent development of electrophysiology-guided noninvasive cardiac radioablation therapy for ventricular tachycardia attracts a great deal of attention as a novel antiarrhythmic strategy (Robinson CG, Circulation 2019). As to underlying mechanisms, however, much remains to be clarified. We reported before that a single targeted heavy ion irradiation (THIR 15Gy) to rabbit hearts increased connexin43 (Cx43) expression, and a reduction of vulnerability to ventricular arrhythmias after myocardial infarction.

Purpose

We investigated the effects of THIR on in-vivo cardiac electrophysiology and vulnerability to atrial and ventricular tachyarrhythmias in aged rabbits with hypercholesterolemia.

Methods

Sixteen three-year old rabbits were fed with high fat/cholesterol chow (0.5% cholesterol and 10% coconut oil) for 14 weeks. A single THIR 15Gy was applied to 8 rabbits (HC+THIR) with a heavy ion medical accelerator. Eight rabbits without THIR were used as control (HC).

Results

Serum cholesterol levels in the HC and HC+THIR were 1545+386 and 1569+328 mg/dl (n=8, NS). Atrial (P-wave) late potential in signal-averaged ECG in HC+THIR showed a significantly larger root mean square voltage (RMS) than those in HC (12+0.5 vs. 2+0.5μV, n=4, p&lt;0.01). Ventricular late potentials in HC+THIR showed significantly less fQRS-D than HC (81+5 vs. 89+7 ms); less LAS40 (21+7 vs. 30+4 ms), and larger RMS (99+27 vs. 44+13μV) (n=4, p&lt;0.04). Atrial tachycardia or fibrillation (AT/AF) was induced spontaneously or by programmed/burst pacing of the left atria (LA) in 4 out of 4 HC, whereas in only 1 out of 4 HC+THIR. Ventricular tachycardia or fibrillation (VT/VF) was induced spontaneously or by programmed pacing or left stellate stimulation in 4 out of 4 HC rabbits, whereas in only 1 out of 4 HC+THIR. Immunolabeled Cx40 densities in LA and RA tissue from HC+THIR rabbits were significantly higher than those from HC rabbits by 44% and 60%, respectively (n=4, p&lt;0.01). Comparable upregulation of immunoreactive Cx43 was observed in LV and RV tissue from HC+THIR rabbits. Sympathetic nerve densities in LA, RA, LV and RV tissues, which was labeled with anti-neuronal growth-associated protein 43 (GAP43) antibody and tyrosine hydroxylase (TH) antibody were both significantly less in HC+THIR than those in HC.

Conclusion

These results suggest that THIR may improve cardiac conductivity of HC rabbits in favor of reduction of vulnerability to atrial and ventricular tachycardia/fibrillation, and that this antiarrhythmic effect is attributed to upregulation of gap junction protein (Cx40 and Cx43) and in part to prevention of sympathetic nerve sprouting.

Funding Acknowledgement

Type of funding source: Public grant(s) – National budget only. Main funding source(s): KAKENHI KIBAN (C) 53020

Sex-Related Differences in Cardiac Remodeling and Reverse Remodeling After Transcatheter Aortic Valve Implantation in Patients with Severe Aortic Stenosis in a Japanese Population

Left ventricular (LV) remodeling with aortic stenosis (AS) appears to differ according to sex, but reverse remodeling after transcatheter aortic valve implantation (TAVI) has not been elucidated in a Japanese population. This study aims to determine whether any sex-related differences in LV or reverse remodeling after TAVI exist in the context of severe AS.Of 208 patients who received TAVI for severe AS in our institution, 100 (men, 42; mean age, 83.0 ± 4.9 years) underwent transthoracic echocardiography before and 3 months after TAVI. Despite similar valvular gradients, women with severe AS had lower indexed LV mass (LVMi) than did men (152.3 ± 35.4 versus 173.2 ± 44.6 g/m², P = 0.005), with smaller indexed LV end-diastolic (LVEDVi) (50.2 ± 13.3 versus 61.4 ± 20.7 mL/m², P = 0.001) and end-systolic (LVESVi; 17.9 ± 8.7 versus 24.3 ± 13.8 mL/m², P = 0.006) volumes. After TAVI, women (-6.0% ± 14.4%) had higher reduction in the rate of change of relative wall thickness (RWT) than did men (4.4% ± 19.0%, P = 0.003). Men (-8.9% ± 3.9%) had higher reduction in the rate of change of LVEDVi than did women (1.5% ± 3.3%, P = 0.045). Incidence of LV reverse remodeling defined as a reduction in LVESV of >15% was significantly higher in men (50%) than in women (26%, P = 0.013).In addition to sex differences in the pattern of LV remodeling with AS, reverse LV remodeling after TAVI also differed between sexes.

Coagulopathy-related soft tissue hematoma: a comparison between computed tomography findings and clinical severity

Background

Despite increases in the incidence of coagulopathy-related soft-tissue hematoma (CRSH), the relationship between computed tomography (CT) features and clinical severity remains unclear.

Purpose

To retrospectively evaluate the correlation between CT findings and clinical outcomes in CRSH.

Material and Methods

We retrospectively reviewed data of patients diagnosed with CRSH between March 2011 and March 2018. CRSH was morphologically classified according to the presence or absence of the fluid level pattern and was also divided into groups with or without extravasation as per CT findings. These CT findings were compared with the patients' vital signs and laboratory investigation results.

Results

A total of 47 patients with CRSH were examined. Fluid level and non-fluid level patterns were observed in 28 (60%) and 19 (40%) patients, respectively. Anticoagulant therapy and extravasation were significantly correlated with the fluid level pattern. However, other clinicolaboratory outcomes, including shock index, hemoglobin, hematocrit, platelet count, and coagulation factors, showed no significant difference between the two patterns. In the comparison of hematomas with and without extravasation, none of the clinicolaboratory outcomes except for anticoagulant therapy showed significant differences.

Conclusion

CRSH with a fluid level pattern is significantly associated with extravasation. However, extravasation, which is generally suggestive of active bleeding, does not seem to be related to clinical severity in CRSH.

Embolization of medium-sized vessels with the penumbra occlusion device: evaluation of anchoring function

Background

The penumbra occlusion device (POD) is a recently developed metallic coil with a unique anchor segment. The purpose of this study was to investigate the anchoring function of the POD for embolization of medium-sized vessels in detail.

Materials and methods

We reviewed a series of cases of proximal embolization of medium-sized vessels in which the POD was used. Endovascular outcomes and complications were assessed. The distance between the distal end of the first-indwelled POD and the microcatheter tip was defined as the “landing distance,” and this was also evaluated via fluoroscopic analysis.

Results

POD deployment was successful in 17 of 18 patients. The median landing distance was 9.6 mm, and no distal POD migration was observed after the formation of anchor loops.

Conclusions

The specific anchoring function of the POD enables effective proximal occlusion of medium-sized vessels.

Japanese Survey of Radiation Dose Associated With Coronary Computed Tomography Angiography - 2013 Data From a Multicenter Registry in Daily Practice

BACKGROUND

Although coronary computed tomography angiography (CTA) is frequently used for identifying coronary artery disease, no studies have investigated the radiation dose in detail in Japan. The aim of this study was to estimate the radiation dose of coronary CTA in Japanese clinical practice and to identify the independent predictors associated with radiation dose.Methods and Results:A multicenter, retrospective, observational study (54 institutions) was conducted for estimating the radiation dose of coronary CTA in 2,469 patients between January and December 2013. Independent predictors associated with radiation dose were investigated on linear regression analysis. Median dose-length product (DLP) was 809.0 mGy·cm (IQR, 350.0-1,368.8 mGy·cm), corresponding to an estimated radiation dose of 11 mSv. The DLP per site significantly differed between institutions (median DLP per site, 92-2,131 mGy·cm; P<0.05). Independent predictors associated with radiation dose on multivariable linear regression were body weight, heart rate, non-stable sinus rhythm, scan length, tube voltage setting, electrocardiogram (ECG)-gated scanning protocol, and the image reconstruction technique (P<0.05 each).

CONCLUSIONS

The coronary CTA radiation dose was relatively high in 2013, and it varied significantly between institutions. Effective strategies for radiation dose reduction were low tube voltage ≤100 kVp, retrospective ECG-gated scanning with dose modulation technique, prospective ECG-gated scanning, and the iterative reconstruction technique.

Updates on Computed Tomography Imaging in Aortic Aneurysms and Dissection

Computed tomography (CT) is a primary imaging modality for the diagnosis of aortic diseases, because of its minimal invasiveness and agility.

Prompt and accurate diagnosis is crucial especially for acute aortic diseases, and the guidelines for acute aortic dissection recommend the use of CT for initial diagnosis. For the follow-up observation of longstanding aortic diseases, the strategy of imaging management by CT must be different from that for emergency and acute phases.

In this review, we document the differences in characteristics and clinical course between aortic aneurysm and aortic dissection and explain the use of recent CT techniques in diagnosing short- and longstanding aortic diseases.

An artificial impact on the asteroid (162173) Ryugu formed a crater in the gravity-dominated regime

The Hayabusa2 spacecraft investigated the small asteroid Ryugu, which has a rubble-pile structure. We describe an impact experiment on Ryugu using Hayabusa2's Small Carry-on Impactor. The impact produced an artificial crater with a diameter >10 meters, which has a semicircular shape, an elevated rim, and a central pit. Images of the impact and resulting ejecta were recorded by the Deployable CAMera 3 for >8 minutes, showing the growth of an ejecta curtain (the outer edge of the ejecta) and deposition of ejecta onto the surface. The ejecta curtain was asymmetric and heterogeneous and it never fully detached from the surface. The crater formed in the gravity-dominated regime; in other words, crater growth was limited by gravity not surface strength. We discuss implications for Ryugu's surface age.

Evaluating recanalization of relevant lenticulostriate arteries in acute ischemic stroke using high-resolution MRA at 7T

BACKGROUND

Occluded major intracranial arteries can spontaneously recanalize in patients with acute ischemic stroke mainly due to embolic mechanisms. However, it remains unknown whether recanalization can occur in perforating arteries, such as lenticulostriate arteries. Therefore, in the present study, we assessed changes suggesting recanalization of the lenticulostriate arteries in patients with acute ischemic stroke of the lenticulostriate artery territory using high-resolution magnetic resonance angiography (HR-MRA) at 7T.

METHODS

We prospectively examined 39 consecutive patients with acute infarcts confined within the lenticulostriate artery territory. Using a 7T scanner during the acute period and one month thereafter, we evaluated imaging findings indicating the recanalization of the relevant lenticulostriate arteries, following which we examined differences in other imaging findings and clinical characteristics between patients with/without recanalization.

RESULTS

HR-MRA findings suggestive of recanalization (i.e. patent lenticulostriate arteries within acute infarct lesions with/without hemorrhagic changes) were observed in 8 (25%) of 32 patients who were eligible for analyses. These findings were detected in three and five patients on the baseline and follow-up images, respectively. The lengths of relevant lenticulostriate arteries on the follow-up MRA were significantly larger in patients with recanalization than in those without (P = 0.01). However, there were no significant differences in the infarct volume or clinical outcomes between the recanalization and non-recanalization groups.

CONCLUSION

HR-MRA at 7T revealed that recanalization of the relevant lenticulostriate arteries can occur in patients with acute ischemic stroke confined to the lenticulostriate artery territory.

162 Detection of ovulation disorders and normal ovulation using wireless sensors of ventral tail surface temperature and neck acceleration data in Japanese Black cows

The present study aimed to clarify the possibility of detection of ovulation disorders and normal ovulation in Japanese Black cows using wearable wireless sensors based on continuous measurements of body surface temperature (ST) and neck acceleration data. For cows with normal ovulation (n=19, 8.5 years old, 476.2kg), controlled internal drug release (CIDR) and gonadotrophin-releasing hormone were administered on arbitrary days of the oestrous cycle (Day −10), and oestrus was induced by CIDR removal and prostaglandin F2α administration (Day −3). Ovulation (Day 0) was induced by gonadotrophin-releasing hormone administration on estimated oestrus day (Day −1) and was detected based on the disappearance of ≥8mm follicles using ultrasonography at 1- to 2-h intervals. For cows with spontaneous ovarian cysts (n=11, 8.6 years old, 471.2kg), oestrus and the next day were defined as Days −1 and 0, respectively. Plasma concentrations of progesterone (P4) and oestradiol-17β (E2) were measured on Days −9, −6, −2, −1, 0, 1, 5, and 8. The body ST sensor was attached to the ventral tail base (Day −16), and ST was measured every 10min for 24 days. For analysis of ST, after extracting hourly maximum ST values, the values were expressed as residual ST (RST; ST − mean ST for the same hour on the previous 3 days) for removal of circadian rhythm (Miura et al. 2017 Anim. Reprod. Sci. 180, 50-57; https://doi.org/10.1016/j.anireprosci.2017.03). The acceleration sensor (Farmnote Color, Farmnote Inc.) was attached to the neck (Day −16). Hourly oestrus level (amount of oestrus activity) was obtained from the amount of activity; the difference between the residual oestrus level (REL; same calculation as RST) and measured values of each day was used. To identify RST and REL of cows with normal ovulation and cows with ovarian cysts, the mean values and standard deviations for the same hours for 3-7 days before oestrus were calculated. Mean RST and REL for 3-7 days before oestrus were assumed according to the normal distribution. The 95% confidence range was determined using×1 standard deviation of all hours. Values over the 95% confidence range for ≥5h were considered to be different from the mean 4 days and the 5% level. For RST, no difference was found in both groups due to the large influence of environment, particularly low temperature. However, for REL, a difference was indicated for oestrus in all cows (P&lt;0.05). A large peak of REL appeared once on oestrus (&gt;14.4 REL for 20h) in normal cows, and three peaks occurred in &lt;21 days (&gt;16.2 REL for 21, 15, and 15h) in cows with ovulation disorders (P&lt;0.05). The REL rapidly increased following peaking E2 and decreasing P4 to oestrus (Day −1) in normal cows. In cows with an ovulation disorder, REL increased on oestrus; however, E2 and P4 remained high and low stable to oestrus, respectively. In conclusion, oestrus activity and the characteristics of normal cows and those with an ovulation disorder can be detected by the neck acceleration sensor using the correction value. This research was supported by The Research Project for the Future Agriculture Production Utilising Artificial Intelligence.

P295 Impact of Pre-existing Mitral Regurgitation on the Mid-Term Left Ventricular Mass Regression following Transcatheter Aortic Valve Implantation for Aortic Valve Stenosis

Background

Transcatheter aortic valve implantation (TAVI) results in an immediate and greater aortic pressure gradient improvement in patients with severe aortic valve stenosis (AS), and induces early left ventricular (LV) mass regression, which may be related to favorable effects on the mid to long term outcomes. However, the extent of LV mass regression after unloading of chronic pressure overload is varying, and its determinants are still unknown. Thus, the study aims to identify echocardiographic determinants of LV mass regression following TAVI.

Methods

We retrospectively screened all TAVI procedures in symptomatic AS from 2017 to 2019, and selected 74 successful TAVI cases that had serial echocardiographic studies both at the baseline and at the mid-term follow-up (4 to 6 months after the procedure). Through the digitalized medical records, clinical and echocardiographic data as well as angiographic grading (0-3) of post-procedure paravalvular leakage (PVL) were obtained. LV mass was calculated by using Cube formula. Thus, the extent of LV mass regression was defined as the differences of left ventricular mas index (LVMI) between at the baseline and at the follow-up (ΔLVMI). Quantification of the baseline mitral valve regurgitant volume was performed by stroke volume method with pulmonic site measurement on the assumption of no pre-existing intra/extra cardiac shunt. Cases with prior mitral valve replacement were excluded.

Results

At the post-procedure angiogram, only 3 cases had significant PVL (grade 2≤). At the mid-term follow–up, average LVMI decreased significantly from the baseline (165 ± 38 g/m2vs 140 ± 37 mg/ m2, P &lt; 0.0001) and 57 cases (70%) experienced the reduction of LVMI, although average relative wall thickness (2 × posterior wall thickness/left ventricular diastolic dimension) did not change (0.565 ± 0.135 vs 0.586 ± 0.168, P = 0.314). Among the baseline clinical and echocardiographic variables, the baseline peak A wave velocity, E/A ratio, mitral valve regurgitant volume and LVMI revealed simple correlation with ΔLVMI (γ=-0.298, p = 0.0188;γ=0.251, P = 0.0417;γ=0.354, p = 0.0041;γ=0.375, p &lt; 0.0010; respectively), whereas no correlation was observed in angiographic PVL grade. Stepwise multiple regression analysis demonstrated baseline mitral valve regurgitant volume and LVMI as the determinants of ΔLVMI (β=0.344, p = 0.032; β=0.335 P &lt; 0.0001; respectively).

Conclusions

Pre-existing mitral regurgitation has an impact on the mid–term left ventricular mass regression following TAVI. In severe AS, mitral regurgitation might be functioning as an afterload adjuster, and thus, produces protective effects on LV structure.

Feasibility of thin-slice abdominal CT in overweight patients using a vendor neutral image-based denoising algorithm: Assessment of image noise, contrast, and quality

The purpose of this study was to investigate whether the novel image-based noise reduction software (NRS) improves image quality, and to assess the feasibility of using this software in combination with hybrid iterative reconstruction (IR) in image quality on thin-slice abdominal CT. In this retrospective study, 54 patients who underwent dynamic liver CT between April and July 2017 and had a body mass index higher than 25 kg/m² were included. Three image sets of each patient were reconstructed as follows: hybrid IR images with 1-mm slice thickness (group A), hybrid IR images with 5-mm slice thickness (group B), and hybrid IR images with 1-mm slice thickness denoised using NRS (group C). The mean image noise and contrast-to-noise ratio relative to the muscle of the aorta and liver were assessed. Subjective image quality was evaluated by two radiologists for sharpness, noise, contrast, and overall quality using 5-point scales. The mean image noise was significantly lower in group C than in group A (p < 0.01), but no significant difference was observed between groups B and C. The contrast-to-noise ratio was significantly higher in group C than in group A (p < 0.01 and p = 0.01, respectively). Subjective image quality was also significantly higher in group C than in group A (p < 0.01), in terms of noise and overall quality, but not in terms of sharpness and contrast (p = 0.65 and 0.07, respectively). The contrast of images in group C was greater than that in group A, but this difference was not significant. Compared with hybrid IR alone, the novel NRS combined with a hybrid IR could result in significant noise reduction without sacrificing image quality on CT. This combined approach will likely be particularly useful for thin-slice abdominal CT examinations of overweight patients.