Investigation of the Relationship between Body Parameters and mAs Using Non-Contact Two-Dimensional Thickness Measurement in Chest Digital Radiography.

The current study aimed to investigate the relationship between body parameters and the current-time product (mAs) in chest digital radiography using a non-contact infrared thickness-measurement sensor. An anthropomorphic chest phantom was first used to understand variations in mAs over multiple positionings during chest radiography when using the automatic exposure control (AEC) technique. In a human study, 929 consecutive male subjects who underwent regular chest examinations were enrolled, and their height (H), weight (W), and body mass index (BMI) were recorded. In addition, their chest thickness (T) was measured at exhalation using a non-contact infrared sensor, and chest radiography was then performed using the AEC technique. Finally, the relationship between four body parameters (T, BMI, T*BMI, and W/H) and mAs was investigated by fitting the body parameters to mAs using three curve models. The phantom study showed that the maximum mAs was 1.76 times higher than the lowest mAs during multiple positionings in chest radiography. In the human study, all chest radiographs passed the routine quality control procedure and had an exposure index between 100 and 212. In curve fitting, the comparisons showed that W/H had a closer relationship with mAs than the other body parameters, while the first-order power model with W/H fitted to mAs performed the best and had an R-square of 0.9971. We concluded that the relationship between W/H and mAs in the first-order power model may be helpful in predicting the optimal mAs and reducing the radiation dose for chest radiography when using the AEC technique.

Repeated stereotactic ablative radiotherapy using CyberKnife for patients with hepatocellular carcinoma.

BACKGROUND AND AIM: This study aimed to evaluate the outcomes and toxicities of repeated stereotactic ablative radiotherapy (SABR) in hepatocellular carcinoma (HCC). METHODS: Fourteen HCC patients with local recurrence (18 lesions) after liver SABR received repeated radiotherapy with SABR using CyberKnife. No patients experienced radiation-induced liver disease after the first SABR course. The median first SABR dose was 41 Gy (range, 34-60 Gy); the median second SABR dose, 40 Gy (range, 25-50 Gy); and the median interval, 12.9 months. Local recurrence was divided into in-field recurrence and out-field recurrence. RESULTS: Objective responses were observed in 11 tumors (61.1%), including five tumors (27.8%) with complete responses. Intrahepatic out-field failure was the main cause of treatment failure (7 of 14 patients). In-field failure had developed in 1 of 18 tumors (5.6%), resulting in a 2-year in-field failure-free rate of 88.2%. The median time to progression was 14.0 months, with 1- and 2-year progression-free survival rates of 68.6% and 42.9%, respectively. One- and two-year overall survival rates were 76% and 59.1%, respectively. Of the 14 patients, one developed radiation-induced liver disease and three showed progression of the Child-Turcotte-Pugh class after the second SABR course. Other toxicities were generally mild and tolerable. CONCLUSION: Repeated SABR in selected HCC patients is feasible with acceptable toxicity.

Stereotactic ablative radiotherapy for unresectable hepatocellular carcinoma patients who failed or were unsuitable for transarterial chemoembolization.

BACKGROUND: The role of stereotactic ablative radiotherapy (SABR) in patients with hepatocellular carcinoma (HCC) who are refractory to or unsuitable for transarterial chemoembolization remains unclear. We examined the efficacy and safety of Cyberknife SABR and its effect on survival in this group of HCC patients. MATERIALS AND METHODS: From June 2008 to June 2011, 53 patients with 68 tumors of unresectable HCC were treated using Cyberknife SABR. The tumors measured 1.1-13 cm (median, 4.3 cm). The median prescribed dose was 40 Gy in four to five fractions over 4-5 consecutive working days. RESULTS: The median follow-up period was 13.1 months for all patients and 18.1 months for the living patients. Objective responses were observed in 48 of 67 tumors (71.6%), including 22 tumors (32.8%) with complete responses. The 1- and 2-year in-field failure-free rate was 73.3 and 66.8%, respectively. Out-field intrahepatic recurrence was the main cause of treatment failure (28/52 patients). The median survival time was 20.0 months, and the 1- and 2-year overall survival rate was 70.1 and 45.4%, respectively. Multivariable analysis showed that Eastern Cooperative Oncology Group performance status (≤1 vs. >1) and tumor response (responder vs. nonresponder) were independent prognostic factors for overall survival. Radiation-induced liver disease, including classic and nonclassic types, developed in five patients (9.4%). Other acute toxicities were generally mild and tolerable. CONCLUSION: Our findings supported the feasibility of SABR as a salvage treatment for HCC when transarterial chemoembolization was ineffective or technically unsuitable. Additional efforts to improve the response rate and reduce out-field recurrence are required.