[Effects of Changing the Source-to-image Receptor Distance Parameter of Scattered X-ray Correction after Exposure on Image Quality in Portable Chest Radiography].

PURPOSE: To validate the effects of changing the source-to-image receptor distance (SID) parameter of scattered X-ray correction after exposure on the image quality in portable chest radiography. METHODS: The actual SID and tube current-time product (mAs) were varied such that the direct X-ray dose to a flat panel detector (FPD) remained constant. We created two groups as follows: Group A (with the SID parameter unchanged) and Group B (with the SID parameter changed to the actual SID after a phantom chest exposure). The image contrast ratio and standard deviation (SD) were measured on the chest radiographs for physical assessment. Observer studies were performed by seven radiological technologists. Scheffé's (Ura) paired comparison methods were performed with image contrast, noise, and overall assessment as the assessment items. Receiver operating characteristic (ROC) analysis for lung nodules was performed. RESULTS: The image contrast ratio and SD in Group A changed, whereas the changes in Group B were less than those in Group A for both these properties. The observer study with Scheffé's methods showed a statistically significant difference (p<0.05) for all assessment items in Group A but not in Group B. The ROC analysis did not indicate any statistically significant differences in either group. CONCLUSION: Changing the SID parameter of scattered X-ray correction after exposure can possibly maintain image contrast and noise in portable chest radiography if the actual SID changes.

Intravascular Ultrasound Can Be Used to Locate Nerves, but not Confirm Ablation, During Renal Sympathetic Denervation.

BACKGROUND: No methods exist for confirming nerve ablation in catheter-based renal sympathetic denervation (RDN). METHODS: We investigated the feasibility of using intravascular ultrasound (IVUS) to locate nerves and observe nerve integrity changes during RDN in a pig. To confirm our observations, we used post-RDN histological sections matched anatomically to the IVUS images. RESULTS: IVUS revealed multiple hypoechoic structures along the renal artery, whose locations matched those of nerves in the histological sections. Nerves clustered near the junction between the renal artery and vein. Histology confirmed necrosis of nerve bundles at RDN ablation sites, but no changes in echogenicity were observed using IVUS. CONCLUSIONS: Although IVUS cannot currently be used to confirm ablation during RDN, it clearly reveals some clusters of renal sympathetic nerves. It remains to be demonstrated how IVUS can guide RDN devices and potentially improve ablation success.

A Patient with Bilateral Primary Aldosteronism Refractory to Oral Eplerenone Who Responded to Esaxerenone with Increased Renin Activity.

BACKGROUND When mineralocorticoid receptor antagonist therapy is initiated for primary aldosteronism, the response of plasma renin activity indicates the level of cardiovascular risk. The purpose of this article was to compare the effect of mineralocorticoid receptor blockers on plasma renin activity levels in a patient with primary aldosteronism. CASE REPORT The patient was a 45-year-old male with severe hypertension. Because his aldosterone/renin ratio was high and a saline infusion test was positive, primary aldosteronism was diagnosed. Computed tomography revealed a low-density mass measuring 10 mm in the left adrenal gland. Segmental adrenal vein sampling demonstrated bilateral primary aldosteronism, so pharmacotherapy was started. Before treatment, his plasma renin activity was 0.5 ng/mL/hour. Eplerenone was commenced and the dose was increased to 100 mg/day. However, his plasma renin activity was still 0.8 ng/mL/hour and the maximum dose of eplerenone did not elevate plasma renin activity above 1 ng/mL/hour. Since plasma renin activity remained below 1 ng/mL/hour with mineralocorticoid receptor antagonist therapy, this patient was considered to have a higher cardiovascular risk than patients with essential hypertension. Accordingly, eplerenone was switched to esaxerenone, a new generation mineralocorticoid receptor blocker that became available in May 2019. After switching to esaxerenone (5 mg/day), the patient's plasma renin activity increased to 1.8 ng/mL/hour and subsequently remained at 1 ng/mL/hour or higher. CONCLUSIONS This is the first case report to present interesting changes of plasma renin activity in a primary aldosteronism patient after switching from eplerenone to esaxerenone. Elevation of plasma renin activity by esaxerenone in our primary aldosteronism patient reflected a mineralocorticoid receptor antagonistic effect that may have alleviated excessive mineralocorticoid receptor activation and volume expansion.

Comparison of Arterial Spin-labeling Perfusion Images at Different Spatial Normalization Methods Based on Voxel-based Statistical Analysis.

PURPOSE: Spatial normalization is a significant image pre-processing operation in statistical parametric mapping (SPM) analysis. The purpose of this study was to clarify the optimal method of spatial normalization for improving diagnostic accuracy in SPM analysis of arterial spin-labeling (ASL) perfusion images. METHODS: We evaluated the SPM results of five spatial normalization methods obtained by comparing patients with Alzheimer's disease or normal pressure hydrocephalus complicated with dementia and cognitively healthy subjects. We used the following methods: 3DT1-conventional based on spatial normalization using anatomical images; 3DT1-DARTEL based on spatial normalization with DARTEL using anatomical images; 3DT1-conventional template and 3DT1-DARTEL template, created by averaging cognitively healthy subjects spatially normalized using the above methods; and ASL-DARTEL template created by averaging cognitively healthy subjects spatially normalized with DARTEL using ASL images only. RESULTS: Our results showed that ASL-DARTEL template was small compared with the other two templates. Our SPM results obtained with ASL-DARTEL template method were inaccurate. Also, there were no significant differences between 3DT1-conventional and 3DT1-DARTEL template methods. In contrast, the 3DT1-DARTEL method showed higher detection sensitivity, and precise anatomical location. CONCLUSIONS: Our SPM results suggest that we should perform spatial normalization with DARTEL using anatomical images.