An analysis of patient positioning during stereotactic lung radiotherapy performed without rigid external immobilization

doi:10.1016/j.radonc.2012.03.020

Radiotherapy and Oncology

Volume 104, Issue 1, July 2012, Pages 28-32

https://doi.org/10.1016/j.radonc.2012.03.020 Get rights and content

Abstract

Background and purpose

Intra-fraction patient motion is incompletely understood and the optimum amount of support or immobilization during stereotactic body radiotherapy (SBRT) is unclear. Rigid immobilization is often advocated, but motion still occurs. In contrast, we deliver the vast majority of SBRT using simple supporting devices, simultaneously emphasizing comfort, frequent position checks and progressive reduction in treatment times. We report spine stability during lung SBRT.

Materials and methods

Patients lie on a thin mattress with arms supported above their head and below-knee support. Stereoscopic spine X-rays before and after fraction delivery identified motion in three translational and three rotational directions.

Results

Images from 109 fractions in 30 patients resulted in 327 translational and 327 rotational pre- and post-fraction comparisons. Mean RapidArc® delivery time for variable fraction dose was 4.2 min (SD = 1.4). 92% and 97% of translational and rotational differences were ⩽1 mm and ⩽1° in any direction and 98% of translational differences were ⩽1.5 mm. Mean vertical, longitudinal and lateral motion was 0 mm (SD = 0.4), 0 mm (0.6) and 0 mm (0.6). 84% and 94% of the 109 fractions were delivered with ⩽1 and ⩽1.5 mm translation in all three directions and 93% with ⩽1° of rotation. Two patients accounted for 10/17 fractions with >1 mm translational motion.

Conclusions

Based on pre and post-fraction X-ray imaging during fast lung SBRT, simple support devices can result in spine stability that is comparable to that reported with rigid external immobilization.

Section snippets

Materials and methods

This manuscript reports anonymous clinical QA data that was acquired during the routine treatment of a cohort of patients with lung SBRT for the purpose of assuring the integrity of treatment delivery. These patients were treated according to our standard lung SBRT protocol that has been previously described [8]. Briefly, patients were imaged using free-breathing, non-coached 4-dimensional computed tomography (CT) performed on a 16 slice CT scanner (GE Healthcare, USA) fitted with the Real-time

Results

A total of 109 SBRT fractions from 30 patients were analyzed (median 4 fractions/patient, range 1–8). There were 23 male and 7 female patients, with median age 72 years (range 38–90). Dose fractionation schedules were 3 fractions of 18 Gy (n = 6), 5 fractions of 11 Gy (n = 8), 8 fractions of 7.5 Gy (n = 11), and 12 fractions of 5 Gy (n = 5). Data on fraction time was available for 108 fractions. The mean time from start of initial CBCT acquisition to first arc ‘beam-on’ was 6.2 min (range 4.0–27.6 min, SD = 2.7

Discussion

The main finding is that a routine strategy of not using rigid external immobilization results in satisfactory stability, as determined by the position of the spine before and after treatment delivery, for the majority of patients undergoing lung SBRT. Acknowledging differences in methodology and imaging systems (e.g. stereoscopic X-rays and cone-beam computed tomography), these data on intra-fraction stability of the spine are comparable with other published results, including those with or

Conflicts of interest statement

Department of Radiation Oncology, VU University medical center has research collaborations with Varian Medical Systems Inc., USA and Brainlab AG, Germany.

M.D. has received travel support from Varian Medical Systems Inc., and Brainlab AG and honoraria from Varian Medical Systems Inc.

W.V. has received travel support and honoraria from Varian Medical Systems Inc.

B.S. has received travel support and honoraria from Varian Medical Systems Inc., and Brainlab AG and has served as a consultant.

S.S. has

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SBRT of lung cancerAn analysis of patient positioning during stereotactic lung radiotherapy performed without rigid external immobilization

Abstract

Background and purpose

Materials and methods

Results

Conclusions

Section snippets

Materials and methods

Results

Discussion

Conflicts of interest statement

Int J Radiat Oncol Biol Phys

Med Dosim

Int J Radiat Oncol Biol Phys

Int J Radiat Oncol Biol Phys

Int J Radiat Oncol Biol Phys

Radiother Oncol

Radiother Oncol

Med Dosim

Radiother Oncol

Int J Radiat Oncol Biol Phys

SBRT of lung cancer
An analysis of patient positioning during stereotactic lung radiotherapy performed without rigid external immobilization