Usefulness of Diffusion-Weighted Imaging in Evaluating Acute Cellular Rejection and Monitoring Treatment Response in Liver Transplant Recipients.

Acute cellular rejection (ACR) is a significant immune issue among recipients following liver transplantation. Although diffusion-weighted magnetic resonance imaging (DWI) is widely used for diagnosing liver disease, it has not yet been utilized for monitoring ACR in patients after liver transplantation. Therefore, the aim of this study was to evaluate the efficacy of DWI in monitoring treatment response among recipients with ACR. This study enrolled 25 recipients with highly suspected ACR rejection, and all subjects underwent both biochemistry and DWI scans before and after treatment. A pathological biopsy was performed 4 to 24 h after the first MRI examination to confirm ACR and degree of rejection. All patients were followed up and underwent a repeated MRI scan when their liver function returned to the normal range. After data acquisition, the DWI data were post-processed to obtain the apparent diffusion coefficient (ADC) map on a voxel-by-voxel basis. Five regions of interest were identified on the liver parenchyma to measure the mean ADC values from each patient. Finally, the mean ADC values and biochemical markers were statistically compared between ACR and non-ACR groups. A receiver operating characteristic (ROC) curve was constructed to evaluate the performance of the ADC and biochemical data in detecting ACR, and correlation analysis was used to understand the relationship between the ADC values, biochemical markers, and the degree of rejection. The histopathologic results revealed that 20 recipients had ACR, including 10 mild, 9 moderate, and 1 severe rejection. The results demonstrated that the ACR patients had significantly lower hepatic ADC values than those in patients without ACR. After treatment, the hepatic ADC values in ACR patients significantly increased to levels similar to those in non-ACR patients with treatment. The ROC analysis showed that the sensitivity and specificity for detecting ACR were 80% and 95%, respectively. Furthermore, the correlation analysis revealed that the mean ADC value and alanine aminotransferase level had strong and moderate negative correlation with the degree of rejection, respectively (r = -0.72 and -0.47). The ADC values were useful for detecting hepatic ACR and monitoring treatment response after immunosuppressive therapy.

Use of blood oxygen level-dependent magnetic resonance imaging to detect acute cellular rejection post-liver transplantation.

OBJECTIVES: Acute cellular rejection (ACR) is a major immune occurrence post-liver transplant that can cause abnormal liver function. Blood oxygen level-dependent (BOLD) magnetic resonance imaging (MRI) can be used to evaluate liver disease, but it has not been utilized in the diagnosis of ACR post-liver transplant. Therefore, the purpose of this study is to evaluate the diagnostic performance of BOLD MRI and to monitor treatment response in recipients with ACR. METHODS: This prospective study was approved by the local institutional review board. Fifty-five recipients with highly suspected ACR were enrolled in this study. Each patient underwent hepatic BOLD MRI, blood biochemistry, and biopsy before treatment. Of 55 patients, 19 recipients with ACR received a follow-up MRI after treatment. After obtaining the R2* maps, five regions-of-interest were placed on liver parenchyma to estimate the mean R2* values for statistical analysis. Receiver operating characteristic curve (ROC) analysis was performed to assess the diagnostic performance of R2* values in detecting patients with ACR. RESULTS: The histopathologic results showed that 27 recipients had ACR (14 mild, 11 moderate, and 2 severe) and their hepatic R2* values were significantly lower than those of patients without ACR. ROC analysis revealed that the sensitivity and specificity of the R2* values for detection of ACR were 82.1% and 89.9%, respectively. Moreover, the R2* values and liver function in patients with ACR significantly increased after immunosuppressive treatment. CONCLUSION: The non-invasive BOLD MRI technique may be useful for assessment of hepatic ACR and monitoring of treatment response after immunosuppressive therapy. KEY POINTS: • Patients with acute cellular rejection post-liver transplant exhibited significantly decreased R2* values in liver parenchyma. • R2* values and liver function were significantly increased after immunosuppressive therapy. • R2* values were constructive indicators in detecting acute cellular rejection due to their high sensitivity and specificity.

Evaluation of scattered radiation dose received by medical staff during uterine artery embolization in the operating room.

BACKGROUND: The air kerma radiation doses have gained much attention since the operating room interventional radiology is a place where medical staff are exposed to a fluoroscopy environment and gain a cumulative dose during the uterine artery embolization procedure. OBJECTIVE: We aimed to evaluate the radiation dose received by medical staff by applying a flat X-ray machine in the surgical room during uterine artery embolization. METHODS: An ATOM humanoid model was laid on the operating table and simulated a patient. The scattered radiation dose received by the radiologist, anesthetist and radiologic technologist was evaluated. The scintillation detector was adopted. The measurement points were 50 cm, 100 cm and 150 cm above the floor, representing the limbs, abdomen and thyroid level, respectively. We compared the X-rays under different tube voltages of 70, 80, and 90, respectively and frames per second (FPS) of 30, 15, and 7.5, respectively. We configured the dose level per pulse of 40 nGy with a fixed detector. RESULTS: In Section 1, when the tube voltage was 70 kVp and 7.5 FPS, the average radiation doses of limbs, abdomen and thyroid level was 0.48, 1.3 and 1.9 µSv/min respectively. When the tube voltage was 80 kVp and the fluoroscopy decreases from 30 FPS to 7.5 FPS, 58% of the radiation dose was reduced. When the tube voltage was 90 kVp, the radiation dose in the lead garment increased 31-177% in comparison to when the tube voltage was 80 kVp. Sections 2 and 3 were far away from the central ray, so the highest radiation dose 100 cm above the floor were 0.05 and 0.02 µSv/min. CONCLUSIONS: Lead garment can effectively reduce medical staff from occupational doses with an average attenuation rate of 90%. 80 kVp was most commonly used. Fluoroscopy 7.5 FPS was used 100 cm above the floor in A section and the lowest radiation dose was 1.33 µSv/min. The operator should decrease the duration of X-rays or adopt suspended lead shielding to decrease the radiation dose received by the operator. When kVp increases, the penetration increases. Decreasing FPS cannot decrease occupational doses of medical staff.

Personal Exposure Prescription Method Reduces Dose in Radiography.

PURPOSE: To evaluate the effectiveness of an automatic, personalized exposure prescription method designed to reduce radiation dose during radiography examinations. METHODS: Using standard imaging parameters of average-sized patients, the authors measured individual body-part thicknesses or imaging regions of 116 patients (69 men, 47 women) and calculated each patient's exposure amount according to the thickness of the part or region. The data were used to develop each patient's personalized exposure prescription. Using the personalized exposure prescriptions, authors acquired chest images of the patients on a Carestream DRX-Revolution mobile digital radiography system. RESULTS: All images acquired using the personalized exposure prescription method were satisfactory for diagnosis; exposure indexes were above 1300, a figure deemed acceptable for diagnosis by the manufacturer. The personalized exposure method reduced the amount of radiation each patient received. DISCUSSION: Variation of tube voltage alone can control patients' exposure levels; however, using the personalized exposure prescription method eliminates the need to use automatic exposure controls. CONCLUSION: The personalized exposure prescription method is an effective tool for reducing radiation to patients during radiography as well as for eliminating dose creep.

Scattered radiation doses absorbed by technicians at different distances from X-ray exposure: Experiments on prosthesis.

UNLABELLED: This work aimed to investigate the spatial distribution of scattered radiation doses induced by exposure to the portable X-ray, the C-arm machine, and to simulate the radiologist without a shield of lead clothing, radiation doses absorbed by medical staff at 2 m from the central exposure point. MATERIAL AND METHOD: With the adoption of the Rando Phantom, several frequently X-rayed body parts were exposed to X-ray radiation, and the scattered radiation doses were measured by ionization chamber dosimeters at various angles from the patient. Assuming that the central point of the X-ray was located at the belly button, five detection points were distributed in the operation room at 1 m above the ground and 1-2 m from the central point horizontally. RESULTS: The radiation dose measured at point B was the lowest, and the scattered radiation dose absorbed by the prosthesis from the X-ray's vertical projection was 0.07 ±0.03 µGy, which was less than the background radiation levels. The Fluke biomedical model 660-5DE (400 cc) and 660-3DE (4 cc) ion chambers were used to detect air dose at a distance of approximately two meters from the central point. The AP projection radiation doses at point B was the lowest (0.07±0.03 µGy) and the radiation doses at point D was the highest (0.26±0.08 µGy) .Only taking the vertical projection into account, the radiation doses at point B was the lowest (0.52 µGy), and the radiation doses at point E was the highest (4 µGy).The PA projection radiation at point B was the lowest (0.36 µGy) and the radiation doses at point E was the highest(2.77 µGy), occupying 10-32% of the maximum doses. The maximum dose in five directions was nine times to the minimum dose. When the PX and the C-arm machine were used, the radiation doses at a distance of 2 m were attenuated to the background radiation level. The radiologist without a lead shield should stand at point B of patient's feet. Accordingly, teaching materials on radiation safety for radiological interns and clinical technicians were formulated.