Retracted: Chest digital dynamic radiography to detect changes in human pulmonary perfusion in response to alveolar hypoxia.

INTRODUCTION: Hypoxic pulmonary vasoconstriction optimises oxygenation in the lung by matching the local-blood perfusion to local-ventilation ratio upon exposure to alveolar hypoxia. It plays an important role in various pulmonary diseases, but few imaging evaluations of this phenomenon in humans. This study aimed to determine whether chest digital dynamic radiography could detect hypoxic pulmonary vasoconstriction as changes in pulmonary blood flow in healthy individuals. METHODS: Five Asian men underwent chest digital dynamic radiography before and after 60 sec breath-holding at the maximal inspiratory level in upright and supine positions. Alveolar partial pressure of oxygen and atmospheric pressure were calculated using the blood gas test and digital dynamic radiography imaging, respectively. To evaluate the blood flow, the correlation rate of temporal change in each pixel value between the lung fields and left cardiac ventricles was analysed. RESULTS: Sixty seconds of breath-holding caused a mean reduction of 26.7 ± 6.4 mmHg in alveolar partial pressure of oxygen. The mean correlation rate of blood flow in the whole lung was significantly lower after than before breath-holding (before, upright 51.5%, supine 52.2%; after, upright 45.5%, supine 46.1%; both P < 0.05). The correlation rate significantly differed before and after breath-holding in the lower lung fields (upright, 11.8% difference; supine, 10.7% difference; both P < 0.05). The mean radiation exposure of each scan was 0.98 ± 0.09 mGy. No complications occurred. CONCLUSIONS: Chest digital dynamic radiography could detect the rapid decrease in pulmonary perfusion in response to alveolar hypoxia. It may suggest hypoxic pulmonary vasoconstriction in healthy individuals.

First experience of efficacy and radiation exposure in 320-detector row CT fluoroscopy-guided interventions.

OBJECTIVE: We investigated the efficacy and exposure to radiation in 320-detector row computed tomography fluoroscopy-guided (CTF-guided) interventions. METHODS: We analysed 231 320-detector row CTF-guided interventions (207 patients over 2 years and 6 months) in terms of technical success rates, clinical success rates, complications, scanner settings, overall radiation doses (dose-length product, mGy*cm), patient doses of peri-interventional CT series, and interventional CT (including CTF), as a retrospective cohort study. The relationships between patient radiation dose and interventional factors were assessed using multivariate analysis. RESULTS: Overall technical success rate was 98.7% (228/231). The technical success rates of biopsies, drainages, and aspirations were 98.7% (154/156), 98.5% (66/67), and 100% (8/8), respectively. The clinical success rate of biopsies was 93.5% (146/156). All three major complications occurred in chest biopsies. The median total radiation dose was 522.4 (393.4-819.8) mGy*cm. Of the total radiation dose, 87% was applied during the pre- and post-interventional CT series. Post-interventional CT accounted for 24.4% of the total radiation dose. Only 11.4% of the dose was applied by CTF-guided intervention. Multilinear regression demonstrated that male sex, body mass index, drainage, intervention time, and helical scan as post-interventional CT were significantly associated with higher dose. CONCLUSION: The 320-detector row CTF interventions achieved a high success rate. Dose reduction in post-interventional CT provides patient dose reduction without decreasing the technical success rates. ADVANCES IN KNOWLEDGE: This is the first study on the relationship between various interventional outcomes and patient exposure to radiation in 320-detector row CTF-guided interventions, suggesting a new perspective on dose reduction.

Low psoas muscle index is a poor prognostic factor for lower gastrointestinal perforation: a single-center retrospective cohort study.

BACKGROUND: Various body composition indices have been reported as prognostic factors for different cancers. However, whether body composition affects prognosis after lower gastrointestinal tract perforation requiring emergency surgery and multidisciplinary treatment has not been clarified. This study examined whether body composition evaluations that can be measured easily and quickly from computed tomography (CT) are useful for predicting prognosis. METHODS: Subjects comprised 64 patients diagnosed with perforation at final diagnosis after emergency surgery for a preoperative diagnosis of lower gastrointestinal tract perforation and penetration. They were divided into a survival group and a non-survival (in-hospital mortality) group and compared. Body composition indices (psoas muscle index (PMI); psoas muscle attenuation (PMA); subcutaneous adipose tissue index (SATI); visceral adipose tissue index (VATI); visceral-to-subcutaneous fat area ratio (VSR)) were measured from preoperative CT. Cross-sectional psoas muscle area at the level of the 3rd lumbar vertebra was quantified. Optimal cut-off values were calculated using receiver operating characteristic curve analysis. Poor prognostic factors were investigated from multivariate logistic regression analyses that included patient factors, perioperative factors, intraoperative factors, and body composition indices as explanatory variables. RESULTS: The cause of perforation was malignant disease in 12 cases (18.7%), and benign disease in 52 cases (81.2%). The most common cause was diverticulum of the large intestine. Emergency surgery for the 64 patients led to survival in 52 patients and death in 12 patients. On multivariate logistic regression analysis, independent predictors of poor prognosis were Sequential Organ Failure Assessment score (odds ratio 1.908; 95% confidence interval (CI) 1.235-3.681; P = 0.0020) and PMI (odds ratio 13.478; 95%CI 1.342-332.690; P = 0.0252). The cut-off PMI was 4.75 cm2/m2 for males and 2.89 cm2/m2 for females. Among survivors, duration of hospitalization was significantly longer in the low PMI group (29 days) than in the high PMI group (22 days, p = 0.0257). CONCLUSIONS: PMI is easily determined from CT and allows rapid evaluation of prognosis following lower gastrointestinal perforation.

Dose calculation with a cone beam CT image in image-guided radiation therapy.

A kilo-voltage cone-beam CT (CBCT) attached to a linear accelerator can verify a target position in each radiation therapy. If CBCT images can be used in dose calculation, we can verify an actual dose distribution on every treatment day. However, the CBCT images are degraded by several factors, and so we cannot use the CBCT images directly in place of conventional multi-slice CT (MSCT) images that are used in the initial dose planning. In this paper, we proposed a new method for using CBCT and MSCT images in the calculation of a dose distribution. Our proposed method segments the CBCT and MSCT images into regions of three major organs (lungs, bones and soft tissues) by use of histogram analysis. We also calculated a value such as the median of the MSCT numbers in each region of the MSCT images, and we set three representative values to the corresponding regions of the CBCT images. In the calculation of a dose distribution, we used these modified CBCT images. The validity of our method was confirmed with experiments in which we used images of a heterogeneous phantom and patients' lungs in comparison with conventional methods. The results showed that the dose distribution determined by our method was similar to that of the initial dose plan, and our method was superior to the conventional methods in terms of pass rates of a distance-to-agreement analysis and γ analysis. The results of a dose-volume-histogram analysis also showed the accuracy of our proposed method.