Surface imaging‐based analysis of intrafraction motion for breast radiotherapy patients

Abstract

Breast treatments are becoming increasingly complex as the use of modulated and partial breast therapies becomes more prevalent. These methods are predicated on accurate and precise positioning for treatment. However, the ability to quantify intrafraction motion has been limited by the excessive dose that would result from continuous X‐ray imaging throughout treatment. Recently, surface imaging has offered the opportunity to obtain 3D measurements of patient position throughout breast treatments without radiation exposure. Thirty free‐breathing breast patients were monitored with surface imaging for 831 monitoring sessions. Mean translations and rotations were calculated over each minute, each session, and over all sessions combined. The percentage of each session that the root mean squares (RMS) of the linear translations were outside of defined tolerances was determined for each patient. Correlations between mean translations per minute and time, and between standard deviation per minute and time, were evaluated using Pearson's r value. The mean RMS translation averaged over all patients was 2.39.15emmm±1.88.15emmm. The patients spent an average of 34%, 17%, 9%, and 5% of the monitoring time outside of 2 mm, 3 mm, 4 mm, and 5 mm RMS tolerances, respectively. The RMS values averaged over all patients were 2.71.15emmm±1.83.15emmm, 2.76±2.27, and 2.98.15emmm±2.30.15emmm over the 5th, 10th, and 15th minutes of monitoring, respectively. The RMS values (r=0.73,p=0) and standard deviations (r=0.88,p=0) over all patients showed strong significant correlations with time. We see that the majority of patients' treatment time is spent within 5 mm of the isocenter and that patient position drifts with increasing treatment time. Treatment length should be considered in the planning process. An 8 mm margin on a target volume would account for 2 SDs of motion for a treatment up to 15 minutes in length.PACS numbers: 87.53.Jw, 87.53.Kn, 87.56.Da, 87.63.L‐

Assessment of Iterative Closest Point Registration Accuracy for Different Phantom Surfaces Captured by an Optical 3D Sensor in Radiotherapy

“…Other works set the allowable tolerance a bit higher (e.g., [8] to 1 mm/1° and [11] to 3 mm/3°), but working with rigid phantoms without motion motivates our stricter limits.…”

“…Nowadays, image guided methods are increasingly used in radiotherapy [3–11]. The target regions of irradiation and the intended dose distributions are mostly defined on the basis of CT scans.…”

“…The investigated ICP algorithms do not treat shape variations which is a motivation for using solid phantoms instead of real cases. The influence of motion of real human bodies, caused by respiration for instance, is considered by other papers (e.g., [10, 11]).…”

“…It shows the estimated misalignment for translation and rotation in mm and °, respectively, by numbers with one-digit accuracy after the comma and by bars. At setup, the therapists attempt to minimize the shifts (by minimizing the length of the bars) [11]. The surface data is exported as object files and used for the registration by the other ICP algorithms.…”

Evaluation of setup and intrafraction motion for surface guided whole‐breast cancer radiotherapy

“…7,8 In this study we employ SGRT for positioning patients treated with whole breast irradiation in free breathing. 7,8 In this study we employ SGRT for positioning patients treated with whole breast irradiation in free breathing.…”