Six dimensional analysis with daily stereoscopic x-ray imaging of intrafraction patient motion in head and neck treatments using five points fixation masks

The safety margins used to define the Planning Target Volume (PTV) should reflect the accuracy of the target localization during treatment that comprises both the reproducibility of the patient positioning and the positional uncertainty of the target, so both the inter- and intrafraction motion of the target. Our first aim in this study was to determine the intrafraction motion of patients immobilized with a five-point thermoplastic mask for head and neck treatments. The five-point masks have the advantage that the patient's shoulders as well as the cranial part of the patient's head is covered with the thermoplastic material that improves the overall immobilization of the head and neck region of the patient. Thirteen patients were consecutively assigned to use a five-point thermoplastic mask. The patients were positioned by tracking of infrared markers (IR) fixed to the immobilization device and stereoscopic x-ray images were used for daily on-line setup verification. Repositioning was carried out prior to treatment as needed; rotations were not corrected. Movements during treatment were monitored by real-time IR tracking. Intrafraction motion and rotation was supplementary assessed by a six-degree-of-freedom (6-D) fusion of x-ray images, taken before and after all 385 treatments, with DRR images generated from the planning CT data. The latter evaluates the movement of the patient within the thermoplastic mask independent from the mask movement, where IR tracking evaluates the movement of the mask caused by patient movement in the mask. These two movements are not necessarily equal to each other. The maximum intrafraction movement detected by IR tracking showed a shift [mean (SD; range)] of -0.1(0.7; 6.0), 0.1(0.6; 3.6), -0.2(0.8;5.5) mm in the vertical, longitudinal, and lateral direction, respectively, and rotations of 0.0(0.2; 1.6), 0.0(0.2; 1.7) and 0.2(0.2; 2.4) degrees about the vertical, longitudinal, and lateral axis, respectively. The standard deviations and ranges found with the 6-D fusion demonstrate intrafraction patient displacements of -0.5(1.2; 7.4), 0.3(0.7; 5.3), 0.0(0.7; 5.7) mm in the vertical, longitudinal, and lateral direction, respectively, and rotations of -0.1(0.6; 4.1), 0.1(0.7; 8.3) and -0.2(0.8; 8.2) degrees about the vertical, longitudinal, and lateral axis, respectively. The 6-D fusions are considerably larger (p < 0.05) than detected by IR tracking. This indicates that the external marker tracking underestimates the magnitude of the actual intrafraction motion and rotation of the patient. The intrafraction motion detected for the patients immobilized with a conventional thermoplastic mask was relatively large. The feasibility to reduce this intrafraction movement by the application of alternative five-point thermoplastic mask types was evaluated as a second aim of this study. The preliminary results showed a clear reduction in the range, being an indication for the random movements, of both the intrafraction shift and rotation for both alternative mask types. The 6-D fusion is found a useful tool for a fast evaluation of the actual patient's intrafraction shift and rotation and shows the latter is not negligible and needs to be taken into account additional to the initial setup accuracy when determining the PTV margin. © 2006 American Association of Physicists in Medicine.SCOPUS: ar.jFLWNAinfo:eu-repo/semantics/publishe

An assessment of the use of skin flashes in helical tomotherapy using phantom and in-vivo dosimetry

Background and purpose: In helical tomotherapy the nature of the optimizing and planning systems allows the delivery of dose on the skin using a build-up compensating technique (skin flash). However, positioning errors or changes in the patient's contour can influence the correct dosage in these regions. This work studies the behavior of skin-flash regions using phantom and in-vivo dosimetry. Materials and methods: The dosimetric accuracy of the tomotherapy planning system in skin-flash regions is checked using film and TLD on phantom. Positioning errors are induced and the effect on the skin dose is investigated. Further a volume decrease is simulated using bolus material and the results are compared. Results: Results show that the tomotherapy planning system calculates dose on skin regions within 2 SD using TLD measurements. Film measurements show drops of dose of 2.8% and 26% for, respectively, a 5 mm and 10 mm mispositioning of the phantom towards air and a dose increase of 9% for a 5 mm shift towards tissue. These measurements are confirmed by TLD measurements. A simulated volume reduction shows a similar behavior with a 2.6% and 19.4% drop in dose, measured with TLDs. Conclusion: The tomotherapy system allows adequate planning and delivery of dose using skin flashes. However, exact positioning is crucial to deliver the dose at the exact location. © 2007 Elsevier Ireland Ltd. All rights reserved.SCOPUS: ar.jinfo:eu-repo/semantics/publishe

Short time effects of radiotherapy on lymphatic vessels and restorative lymphatic pathways: Experimental approaches in a mouse model

Radiotherapy (RT) is an important component in the therapeutic approach to oncologic conditions. This study presents the investigative results on the impact of RT on lymphatic vessels and on the regenerative response of the lymphatic system in a mouse model. We first irradiated 3 groups of ten mice using brachytherapy in a single treatment of 20 Gy. We then performed morphological examination of the irradiated lymphatic vessels using an in vivo microscopic transillumination technique at 2, 4, and 6 weeks. Next we evaluated lymphatic flow using lymphoscintigraphy and in vivo microscopy at 6 to 11 weeks in: 10 additional mice following irradiation as above (IR), in 10 mice following incision of a lymphatic vessel (I), and in a non-treated control group of 10 mice (N). Intact lymphatic vessels were observed in all mice at 2, 4, and 8 weeks following the single dose of radiotherapy in the first group of mice and normal lymphatic flow was fully restored in the irradiated (IR) and incised (I) mice indicating that the reparative substitution lymphatic pathways are functioning normally. We found that following irradiation with one dose of 20 Gy, lymphatic vessels were not visibly damaged and also that lymphatic flow was consistently restored and substitutive lymphatic pathways formed.SCOPUS: ar.jinfo:eu-repo/semantics/publishe

Longitudinal assessment of parotid function in patients receiving tomotherapy for head-and-neck cancer

Background and Purpose: Conventional radiotherapy is associated with high doses to the salivary glands which causes xerostomia and adverse effects on quality of life. The study aims to investigate the potential of helical tomotherapy (Hi-Art Tomotherapy (R)) to preserve parotid function in head-and-neck cancer patients. Patients and Methods: Seven consecutive patients treated with helical tomotherapy at the UZ Brussel, Belgium, were included. During planning, priority was attributed to planning target volume (PTV) coverage: >= 95% of the dose must be delivered to >= 95% of the PTV. Elective nodal regions received 54 Gy (1.8 Gy/fraction). A dose of 70.5 Gy (2.35 Gy/fraction) was prescribed to the primary tumor and pathologic lymph nodes = simultaneous integrated boost scheme. If possible, the mean parotid dose was kept below 26 Gy. Salivary gland function was assessed by technetiurn scintigraphy. Results: There was a significant dose-response relationship between mean parotid dose and functional recuperation. If the mean dose was kept < 31 Gy, a recuperation of 75% can be expected at 12 months. The authors equally observed a significant correlation between salivary excretion (SE) and the percentage of parotid gland receiving a dose < 26 Gy (V-26%). In order to preserve 75% of SE, 46% of the parotid volume should receive a dose < 26 Gy. Conclusion: With the use of helical tomography the parotid gland function can largely be preserved since the mean dose to the entire gland as well as glandular volume receiving > 26 Gy can be reduced

Toxicity and outcome results of a class solution with moderately hypofractionated radiotherapy in inoperable Stage III non-small cell lung cancer using helical tomotherapy

PURPOSE: To prospectively assess the feasibility, toxicity, and local control of a class solution protocol of moderately hypofractionated tomotherapy in Stage III, inoperable, locally advanced non-small-cell lung cancer patients. METHODS AND MATERIALS: Eligible patients were treated according to a uniform class solution (70.5 Gy in 30 fractions) with fixed constraints and priorities using helical tomotherapy. Toxicity monitoring was performed using the Radiation Therapy Oncology Group criteria and the National Cancer Institute Common Terminology Criteria and Adverse Events (CTCAE) version 3.0. Pulmonary function tests were performed at the start and repeated at 3 months after treatment. RESULTS: Our class solution resulted in a deliverable plan in all 40 consecutive patients. Acute Grade 3 lung toxicity was seen in 10% of patients. Two patients died during acute follow-up with pulmonary toxicity. Correlations were found between changes in pulmonary function test results and mean lung dose or the lung volume receiving 20 Gy (V(20)). The correlation was strongest for lung diffusion capacity for carbon monoxide. A V(20) of >27% and >32% were predictive for Grades 2 and 3 acute lung toxicity respectively (p 18 Gy and a median lung dose of >5 Gy (p < 0.05). Median survival was 17 months, and the 1-year and 2-year local progression-free survivals were 66% and 50%, respectively. CONCLUSION: The current class solution using moderately hypofractionated helical tomotherapy in patients with locally advanced non-small-cell lung cancer is feasible. Toxicity was acceptable and in line with other reports on intensity-modulated radiotherapy. The local progression-free survival was encouraging considering the unselected population

Toxicity report of a phase 1/2 dose-escalation study in patients with inoperable, locally advanced nonsmall cell lung cancer with helical Tomotherapy and Concurrent Chemotherapy

BACKGROUND: The objective of the current study was to evaluate the feasibility and toxicity of radiation dose escalation with concurrent chemotherapy using helical tomotherapy (HT) in patients with inoperable, locally advanced, stage III nonsmall cell lung cancer (LANSCLC) (grading determined according to the American Joint Committee on Cancer 6th edition grading system). METHODS: This phase 1/2 study was designed to determine the maximum tolerated dose (MTD) of radiotherapy in patients with LANSCLC administered concurrently with docetaxel and cisplatin. Radiotherapy was delivered using HT. A dose per fraction escalation was applied starting at 2 grays (Gy), with an increase of 6% per dose cohort (DC). The Radiation Therapy Oncology Group acute radiation morbidity score was used to monitor pulmonary, esophageal, and cardiac toxicity. RESULTS: Dose escalation was performed in 34 patients over 5 DCs to a dose per fraction of 2.48 Gy. No differences were observed in acute toxicity between the different DCs. However, a significant increase in late lung toxicity in DC IV, which received a fraction size of 2.36 Gy, necessitated a halt in further dose escalation with the MTD defined as 2.24 Gy per fraction. The overall incidence of acute grade ≥3 esophageal and pulmonary toxicity was 24% and 3%, respectively (grading determined according to the Radiation Therapy Oncology Group-European Organisation for Research and Treatment of Cancer toxicity scoring system). The overall incidence of late lung toxicity was 21%, but the incidence was an acceptable 13% in DCs I, II, and III. The local response rate was 61% on computed tomography images. CONCLUSIONS: The use of HT to 67.2 Gy with concurrent cisplatin/docetaxel was feasible and resulted in acceptable toxicity. A full phase 2 study has been initiated to establish the true local response rate at the MTD of 2.24 Gy per fraction. © 2010 American Cancer Society.SCOPUS: ar.jFLWINinfo:eu-repo/semantics/publishe

International multi-institutional bench mark study on dosimetric and volumetric modulation using helical tomotherapy treatment planning for malignant pleural mesothelioma tumors

Determining the most desirable and achievable target dose and organ at risk (OAR) sparing using helical TomoTherapy planning system for mesothelioma treatment plans. A range of planning parameters was used. The reviewers’ ranking assessment (Ranking in Groups: 1 = Good, 2 = Above Average, 3 = Average, 4 = Poor).The overall rankings revealed that a plan with a balanced tradeoff among all planning objectives was preferred by most participants and reviewers. Other studies found low doses to the contralateral lung to be limiting. This was not the case in our study, with TomoTherapy we found the dose to contra lateral lung to be as low as V5Gy=0.87%. A pitch value of 0.287 or 0.43 would provide better result. A delivered modulation factor of above 1.7 and a treatment time around 500 sec will be beneficial consideration in planning