A new-type linear accelerator (Linac) integrated with helical CT scanner was introduced into clinical application in 2019. In contrast with the design of CT-on-rails system, a diagnostic-quality 16slice CT scanner is compactly fixed behind the gantry of a C-arm Linac, and patient is sent through the scanner by moving the couch. The CT/Linac combination provides seamless workflow from simulation to treatment on one unit, and enables personalized adaptive radiotherapy. Recently, the CT-Linac was installed and put into clinical operation in our department. The aim of the present contribution was to report its technical characteristics and commissioning results as well as preliminary experience in clinical usage. Materials/Methods: The commissioning results of mechanical tests and imaging systems (MV CBCT and kV FBCT) tests were presented. IGRT accuracy was investigated through CBCT/FBCT image registration and couch correction. The machine performance over a period of three months, including stability of output, flatness and symmetry, were monitored and summarized. A series of end-to-end IMRT/ARC plans on different treatment sites were tested preclinically to estimate the overall accuracy for a treatment scheme. During the first stage of clinical usage, the results of pretreatment patient quality assurance (QA) for about 30 sIMRT plans on breast and rectum were reported. CBCT/FBCT image guidance were carried out in a treatment routine. Results of image registration and efficiency of the whole workflow were also evaluated. Results: The mechanical isocenter diameter was measured as less than 0.6 mm. The overall accuracy of CT-based IGRT was less than 0.5 mm considering couch precision from RT to CT position. Over the past three months, deviation of Linac output were 0.5AE0.3% from reference, and changes of flatness and symmetry were found less than 0.2%. Absolute point dose agreements for end-to-end tests and pretreatment QA plans between ion chamber measurements and TPS calculations were within 2% for all cases. The gamma passing rates of 3D dose distributions measured by Delta4 were better than 99% per plan and 95% per beam (3% DD, 2 mm DTA and 10% threshold), respectively. Concerning the IGRT workflow, it took about 2 min and 1.5 min from scanning to registration for CBCT and FBCT, respectively, both of which can provide accurate guidance for patient setup. Conclusion: The commissioning and pretreatment QA results show that the CT-Linac platform has a comparable machine performance as the Linac from other vendors. Other techniques like dIMRT and ARC deliveries will be clinically used in the next step. As the first clinical model type, its long-term reproducibility and stability are still under inspection. The integrated CT system, as a highlight, allows a diagnostic-quality visualization of internal patient anatomical structures for more accurate image guidance, and paves the way towards advanced and adaptive radiotherapy.
Dialysis access maintenance often requires a fistulogram or shuntogram of arteriovenous access. Assessment of the arterial inflow segment and arterial anastomosis is often a critical portion of the procedure. Retrograde occlusive angiography (ROA) is often used to properly assess the inflow. Manual compression using finger compression or a hemostat is often described in the literature. The Fogarty balloon occlusion technique using a 4-Fr Fogarty catheter balloon (Henry Shein) is a simple and cost-effective method that preserves image quality and decreases radiation exposure in retrograde occlusive angiography.
The aim of the study was to determine the impact of lung parenchymal-only failure on patient survival after stereotactic ablative body radiotherapy (SABR) for early stage non-small cell lung cancer (NSCLC) with the hypothesis that lung parenchymal-only failure does not adversely impact OS. Materials/Methods: The study population included 481 patients with early stage NSCLC who were treated with 3 to 5 fraction SABR between 2000 and 2016. Recurrences were determined by reviewing the patient's serial imaging (CT, PET/CT) and the clinical judgement of treating physicians. Sites of recurrences were defined as in-field, out-offield parenchymal-only lung failure (OLPF), nodal or distant. In-field failure was defined as failure within or abutting the PTV. OLPF included any failure that occurred within the treated lobe (but distant from the PTV), in a different ipsilateral lobe, or in the contralateral lung. Patients who failed in the nodes and/or distantly were considered to be metastatic. OS was calculated from the date of diagnosis until death or last follow-up and patients who were lost to follow up were censored at their last known follow-up. One to one propensity score matching using KPS, co-morbidity score, and smoking status (current, former, or never) was performed and OS of the matched cohorts was tested by the log-rank test (SAS). Survival curve was estimated using the Kaplan-Meier method. All statistical tests were two-sided, and p values <0.05 were deemed statistically significant. For pairwise comparisons p-value cutoff was adjusted for the number of comparisons to be made using the Bonferroni correction. Results: At a median follow-up of 6.2 years, the median OS was 3.0 years for all patients. Patients with (OLPF) did not have a significantly different OS compared to patients who never failed (p Z 0.0577, median OS 4.4 years with failure vs. 2.9 years never failure). Analysis in a 1:1 propensity score-matched cohort for KPS, co-morbidity score, and smoking status showed no differences in OS between patients that never failed and those with OLPF (p Z 0.9). In subgroup analyses exploring impact of time of failure on OS, patients with OLPF 6 months or more after diagnosis did not have significantly different OS compared to those who never failed, when accounting for immortal time bias (p Z 0.2, median OS 4.9 years vs 4 years never failure). Only seven patients in our dataset failed within 6 months of treatment, of which only four were confirmed to be true failures; therefore, limited data is available in our cohort on the impact of OLPF in 6 months on OS. Conclusion: OLPF after SABR for early stage NSCLC does not appear to adversely affect OS, especially if occurring at least 6 months after SABR. More studies are needed to understand if OLPF within 6 months of SABR is associated with adverse OS. These data are useful when discussing prognosis of lung parenchymal failures after initial SABR.
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