Real-time measurement of ICD lead motion during stereotactic body radiotherapy of ventricular tachycardia

Background: Here we aimed to evaluate the respiratory and cardiac-induced motion of a ICD lead used as surrogate in the heart during stereotactic body radiotherapy (SBRT) of ventricular tachycardia (VT). Data provides insight regarding motion and motion variations during treatment. Materials and methods: We analyzed the log files of surrogate motion during SBRT of ventricular tachycardia performed in 20 patients. Evaluated parameters included the ICD lead motion amplitudes; intrafraction amplitude variability; correlation error between the ICD lead and external markers; and margin expansion in the superior-inferior (SI), latero-lateral (LL), and anterior-posterior (AP) directions to cover 90% or 95% of all amplitudes. Results: In the SI, LL, and AP directions, respectively, the mean motion amplitudes were 5.0 +/- 2.6, 3.4. +/- 1.9, and 3.1 +/- 1.6 mm. The mean intrafraction amplitude variability was 2.6 +/- 0.9, 1.9 +/- 1.3, and 1.6 +/- 0.8 mm in the SI, LL, and AP directions, respectively. The margins required to cover 95% of ICD lead motion amplitudes were 9.5, 6.7, and 5.5 mm in the SI, LL, and AP directions, respectively. The mean correlation error was 2.2 +/- 0.9 mm. Conclusions: Data from online tracking indicated motion irregularities and correlation errors, necessitating an increased CTV-PTV margin of 3 mm. In 35% of cases, the motion variability exceeded 3 mm in one or more directions. We recommend verifying the correlation between CTV and surrogate individually for every patient, especially for targets with posterobasal localization where we observed the highest difference between the lead and CTV motion.Web of Science26113712

Analysis of moving targets in radiotherapy and evaluation of impact on accurate delivery of therapeutic doses via the robotic linear accelerator

Tématem disertační práce je analýza pohyblivých cílů v radioterapii a zhodnocení vlivu pohybů na přesné dodání terapeutické dávky robotickým ozařovačem v případech, kdy nemůžeme využít systémy online sledování ozařovaného cíle tzv. tracking. V těchto případech se přistupuje ke sledování polohy pacienta dle páteřních struktur a ozařuje se oblast pokrývající trajektorii ložiska bez přímého sledování této oblasti. Analýza pohyblivých cílů využívá data z léčby pacientů ve Fakultní nemocnici Ostrava a přináší nové poznatky o zákonitostech pohybů plicních ložisek. Tyto výsledky a reálné údaje o pohybech plicních nádorů během léčby byly využity pro vytvoření prediktivního modelu pro odhad intrafrakční variability a testování přesnosti dodání předepsané dávky do ozařovaného objemu pomocí filmové dozimetrie.The topic of thesis is the analysis of targets which move with respiration during radiotherapy and evaluation of the impact of movement on dose delivery accuracy in cases when online tracking cannot be used. In these cases the patient position is tracked according to position of spine structures and irradiated volume includes the whole area of target range of movements. Analysis of moving targets uses data of patients treated with online tracking at University hospital Ostrava and provides new findings about patterns of lung tumors motion. These findings and real tumor motion data from the treatment were used to create a predictive model for intafraction variability and to test the accuracy of prescribed dose delivery to the target using film dosimetry.450 - Katedra kybernetiky a biomedicínského inženýrstvívyhově

Influence of Bearing Movement in Therapeutic Doses Precision Delivery via the Robotic Feed

Import 11/07/2012Tématem diplomové práce je problematika dodání předepsané dávky do ozařovaného ložiska zejména v případech, kdy nemůžeme ozařované ložisko přímo sledovat. Celá práce je rozdělena do několika částí. Je rozebrána problematika radioterapie obecně, další část se již úzce zabývá přístrojem CyberKnife včetně jeho komponent. Následuje rozbor problematiky pohyblivých cílů, postup přípravy a provedení měření včetně implementace a rozboru výsledků. Pro ozařování plicních ložisek nabízí systém CyberKnife specifické metody pro sledování cíle. V případech, kdy nemůžeme využít žádnou z metod sledování pohyblivého cíle, přistupujeme k sledování polohy pacienta pomocí páteřních struktur a ozařovaný objem zahrnuje celou oblast rozsahů pohybů ložiska tzv. ITV. Je sledovaná jen poloha pacienta podle struktur páteře. Cílem práce je ověřit přesnost dodání předepsané dávky do ozařovaného objemu ITV za použití současných metod plánování.The topic of my thesis is the delivery of the prescribed dose to an irradiated target especially when the target itself cannot be tracked directly. The whole thesis is divided into several parts. General principles of radiation therapy are described; next part focuses on the robotic linear accelerator CyberKnife and its components. Analysis of the problems of moving targets, the process of preparation and implementation of measurements including the implementation and analysis of results follows. For lung cancer treatments CyberKnife system offers a specific methods for target tracking. In cases when we can’t use any tracking method for moving targets, we track the patient position using spine structures. The irradiated volume which includes the whole area of target range of movements is called ITV. The aim of the thesis is to verify the accuracy of prescribed dose delivery to the internal target volume (ITV) using current methods of treatment planning.450 - Katedra kybernetiky a biomedicínského inženýrstvívýborn

Analysis of lung tumor motion in a large sample: patterns and factors influencing precise delineation of internal target volume

Purpose/Objective To evaluate lung tumor motion during respiration and to describe factors affecting the range and variability of motion in patients treated with stereotactic ablative radiation therapy. Methods and Materials Log file analysis from online respiratory tumor tracking was performed in 145 patients. Geometric tumor location in the lungs, tumor volume and origin (primary or metastatic), sex, and tumor motion amplitudes in the superior-inferior (SI), latero-lateral (LL), and anterior-posterior (AP) directions were recorded. Tumor motion variability during treatment was described using intrafraction/interfraction amplitude variability and tumor motion baseline changes. Tumor movement dependent on the tumor volume, position and origin, and sex were evaluated using statistical regression and correlation analysis. Results After analysis of >500 hours of data, the highest rates of motion amplitudes, intrafraction/interfraction variation, and tumor baseline changes were in the SI direction (6.0 ± 2.2 mm, 2.2 ± 1.8 mm, 1.1 ± 0.9 mm, and −0.1 ± 2.6 mm). The mean motion amplitudes in the lower/upper geometric halves of the lungs were significantly different (P15 mm were observed only in the lower geometric quarter of the lungs. Higher tumor motion amplitudes generated higher intrafraction variations (R=.86, P3 mm indicated tumors contacting mediastinal structures or parietal pleura. On univariate analysis, neither sex nor tumor origin (primary vs metastatic) was an independent predictive factor of different movement patterns. Metastatic lesions in women, but not men, showed significantly higher mean amplitudes (P=.03) and variability (primary, 2.7 mm; metastatic, 4.9 mm; P=.002) than primary tumors. Conclusion Online tracking showed significant irregularities in lung tumor movement during respiration. Motion amplitude was significantly lower in upper lobe tumors; higher interfraction amplitude variability indicated tumors in contact with mediastinal structures, although adhesion to parietal pleura did not necessarily reduce tumor motion amplitudes. The most variable lung tumors were metastatic lesions in women.Web of Science96475875

A single reference measurement can predict liver tumor motion during respiration

Aim: To evaluate liver tumor motion and how well reference measurement predicts motion during treatment. Material and methods: This retrospective study included 20 patients with colorectal cancer that had metastasized to the liver who were treated with stereotactic ablative radiotherapy. An online respiratory tumor tracking system was used. Tumor motion amplitudes in the superior-inferior (SI), latero-lateral (LL), and anterior-posterior (AP) directions were collected to generate patient-specific margins. Reference margins were generated as the mean motion and 95th percentile of motion from measurements recorded for different lengths of time (1, 3, and 5 min). We analyzed the predictability of tumor motion in each axis, based on the reference measurement and intra-/interfraction motions. Results: About 96,000 amplitudes were analyzed. The mean tumor motions were 9.9 +/- 4.2 mm, 2.6 +/- 0.8 mm, and 4.5 +/- 1.8 mm in the SI, LL, and AP directions, respectively. The intrafraction variations were 3.5 +/- 1.8 mm, 0.63 +/- 0.35 mm, and 1.4 +/- 0.65 mm for the SI, LL, and AP directions, respectively. The interfraction motion variations were 1.32 +/- 0.79 mm, 0.31 +/- 0.23 mm, and 0.68 +/- 0.62 mm for the SI, LL, and AP directions, respectively. The Pear son's correlation coefficients for margins based on the reference measurement (mean motion or 95th percentile) and margins covering 95% of the motion during the whole treatment were 0.8-0.91, 0.57-0.7, and 0.77-0.82 in the SI, LL, and AP directions, respectively. Conclusion: Liver tumor motion in the SI direction can be adequately represented by the mean tumor motion amplitude generated from a single 1 min reference measurement. Longer reference measurements did not improve results for patients who were well-educated about the importance of regular breathing. Although the study was based on tumor tracking data, the results are useful for ITV delineation when tumor tracking is not available.Web of Science21328327

Accuracy analysis of the dose delivery process while using the Xsight (R) Spine Tracking technology

The Accuray CyberKnife (R) system provides radiotherapy for the treatment of moving lung tumors, thanks to the use of the Xsight (R) Lung Tracking technology for monitoring the motion of the target. However, there are situations in which this technology is not able to properly track the target. Thus, the aim of the proposed work is to study the accuracy of the dose delivery process while using the Xsight (R) Spine Tracking technology, which helps to overcome the aforementioned issue. The CIRS Dynamic Thorax Phantom was used to simulate the motion of a spherical target (diameter 2 cm), which moves along the craniocaudal direction (motion 3 cm). Monte Carlo algorithm calculated PTV and ITV treatment plans for isocentric and non-isocentric irradiation methods. Ionization Chamber and Film Dosimetry measurements were performed to study the accuracy of the dose delivery process to the center, and to the periphery of the tumor. Results obtained through the implementation of the PTV treatment plans were used as a baseline to analyze the accuracy of dose delivery for ITV plans. Although results indicated a decrease for the dose delivered compared to the planned one, the dose delivered was not lower than the prescribed one in any of the studied cases.Web of Science46art. no. Unsp 06503

HPV and RAD51 as Prognostic Factors for Survival in Inoperable Oral and Oropharyngeal Cancer in Patients Unfit for Chemotherapy Treated with Hyperfractionated Radiotherapy

Introduction: The incidence of advanced oral cavity and oropharyngeal cancers is generally high. Treatment outcomes for patients, especially those unfit for comprehensive cancer treatment, are unsatisfactory. Therefore, the search for factors to predict response to treatment and increase overall survival is underway. Objective: This study aimed to analyze the presence of 32 HPV genotypes in tumor samples of 34 patients and the effect of HPV status and RAD51 on overall survival. Method: Tumor samples of 34 patients with locally advanced oropharyngeal or oral cavity cancer treated with accelerated radiotherapy in monotherapy were analyzed using reverse hybridization and immunohistochemistry for the presence of HPV and RAD51. Its effect on overall survival was examined. Results: Only two types of HPV were identified—HPV 16 (dominant) and HPV 66 (two samples). The HPV positivity was associated with a borderline insignificant improvement in 2-year (p = 0.083), 5-year (p = 0.159), and overall survival (p = 0.083). Similarly, the RAD51 overexpression was associated with borderline insignificant improvement in 2-year (p = 0.083) and 5-year (p = 0.159) survival. Conclusion: We found no statistically significant differences but detected trends toward improvement in the survival of HPV-positive and RAD51 overexpressing patients unfit for surgical treatment or chemotherapy treated with hyperfractionated radiotherapy. The trends, however, indicate that in a larger group of patients, the effects of these two parameters would likely be statistically significant