Time Dependence of Intrafraction Patient Motion Assessed by Repeat Stereoscopic Imaging

The purpose of this study was to quantify the intrafraction motion of pediatric patients with brain tumors during radiation therapy and investigate any correlation between motion, use of general anesthesia, and daily treatment duration. 100 pediatric patients with a mean age of 8.5 years (range: 1.0 to 17.8) were included in this prospective study. Forty‐one patients required general anesthesia during treatment, mean age 4.8 years; 59 patients did not, mean age 11.2 years. Each patient had an intracranial tumor and was treated in the supine position with a thermoplastic facemask and headrest for immobilization. A pretreatment localization CBCT was acquired for each treatment fraction and a post‐treatment CBCT was acquired every other fraction. If the magnitude of the patient's position pre‐CBCT offset was ≥2 mm, the position was corrected. The difference between the patient's position based on the post‐CBCT and the assumed position at the start of treatment (either the pre‐CBCT offset if the magnitude was < 2 mm, or 0 offset due to correction) was determined and labeled intrafraction motion. Correlations between daily treatment duration and intrafraction motion were examined. There was an average of 14.2 post‐CBCTs acquired per patient. The magnitude of the mean intrafraction motion was 1.2±0.8 mm for patients requiring general anesthesia, and 1.5±1.2 mm for those without (p<0.001). The mean offset in each direction was less than 0.5 mm for both cohorts. There was no correlation between daily treatment duration and the magnitude of intrafraction motion. The intrafraction motion of pediatric patients undergoing external beam therapy for intracranial tumors is small, < 2 mm, and is independent of the daily treatment duration.PACS number: 87.53.Jw

Section: Discussioncontrasting

confidence: 87%

“…In the adult population, Hoogeman et al ( 2 ) found that intrafraction motion increases linearly with time for both intra‐ and extracranial patients. A concern that has not been addressed as of yet is whether or not treatment duration has an impact on intrafraction motion for pediatric patients.…”

Section: Introductionmentioning

confidence: 99%

Dependence of intrafraction motion on fraction duration for pediatric patients with brain tumors

Beltran

Merchant

2011

“…The 1‐minute time simulated the ability of a patient to hold still for imaging, and the 15‐minute time is a reasonable estimate of how long it takes to treat one isocenter with multiple arcs. In addition, a recent paper (15) indicated that rather significant systematic shift in patient position may occur in a 15‐minute period. For multiple‐isocenter treatments, patients are re‐imaged between isocenter changes.…”

Section: Resultsmentioning

confidence: 99%

“…The X‐ray imaging–based studies of intrafraction movement of the patient's head inside the immobilization mask was reported for both the Novalis (13) and CyberKnife (14) , (15) (Accuray, Sunnyvale, CA, U.S.A.) systems. These reports are based on relatively infrequent X‐ray snapshots taken by the localization system.…”

Section: Introductionmentioning

confidence: 99%

See 1 more Smart Citation

Simulation of intrafraction motion and overall geometric accuracy of a frameless intracranial radiosurgery process

Feygelman

Walker

Chinnaiyan

et al. 2008

We conducted a comprehensive evaluation of the clinical accuracy of an image‐guided frameless intracranial radiosurgery system. All links in the process chain were tested. Using healthy volunteers, we evaluated a novel method to prospectively quantify the range of target motion for optimal determination of the planning target volume (PTV) margin. The overall system isocentric accuracy was tested using a rigid anthropomorphic phantom containing a hidden target. Intrafraction motion was simulated in 5 healthy volunteers. Reinforced head‐and‐shoulders thermoplastic masks were used for immobilization. The subjects were placed in a treatment position for 15 minutes (the maximum expected time between repeated isocenter localizations) and the six‐degrees‐of‐freedom target displacements were recorded with high frequency by tracking infrared markers. The markers were placed on a customized piece of thermoplastic secured to the head independently of the immobilization mask. Additional data were collected with the subjects holding their breath, talking, and deliberately moving. As compared with fiducial matching, the automatic registration algorithm did not introduce clinically significant errors (<0.3 mm difference). The hidden target test confirmed overall system isocentric accuracy of ≤1 mm (total three‐dimensional displacement). The subjects exhibited various patterns and ranges of head motion during the mock treatment. The total displacement vector encompassing 95% of the positional points varied from 0.4 mm to 2.9 mm. Pre‐planning motion simulation with optical tracking was tested on volunteers and appears promising for determination of patient‐specific PTV margins. Further patient study is necessary and is planned. In the meantime, system accuracy is sufficient for confident clinical use with 3 mm PTV margins.PACS number: 87.53.Ly

Cost‐effective immobilization for whole brain radiation therapy

Rubinstein

Ingram

Anderson

et al. 2017

To investigate the inter‐ and intra‐fraction motion associated with the use of a low‐cost tape immobilization technique as an alternative to thermoplastic immobilization masks for whole‐brain treatments. The results of this study may be of interest to clinical staff with severely limited resources (e.g., in low‐income countries) and also when treating patients who cannot tolerate standard immobilization masks. Setup reproducibility of eight healthy volunteers was assessed for two different immobilization techniques. (a) One strip of tape was placed across the volunteer's forehead and attached to the sides of the treatment table. (b) A second strip was added to the first, under the chin, and secured to the table above the volunteer's head. After initial positioning, anterior and lateral photographs were acquired. Volunteers were positioned five times with each technique to allow calculation of inter‐fraction reproducibility measurements. To estimate intra‐fraction reproducibility, 5‐minute anterior and lateral videos were taken for each technique per volunteer. An in‐house software was used to analyze the photos and videos to assess setup reproducibility. The maximum intra‐fraction displacement for all volunteers was 2.8 mm. Intra‐fraction motion increased with time on table. The maximum inter‐fraction range of positions for all volunteers was 5.4 mm. The magnitude of inter‐fraction and intra‐fraction motion found using the “1‐strip” and “2‐strip” tape immobilization techniques was comparable to motion restrictions provided by a thermoplastic mask for whole‐brain radiotherapy. The results suggest that tape‐based immobilization techniques represent an economical and useful alternative to the thermoplastic mask.