A survey on table tolerances and couch overrides in radiotherapy

Abstract

The purpose of this study was to survey current departmental policies on treatment couch overrides and the values of table tolerances used clinically. A 25-question electronic survey on couch overrides and tolerances was sent to full members of the American Association of Physicists in Medicine (AAPM). The first part of the survey asked participants if table overrides were allowed at their institution, who was allowed to perform these overrides, and if imaging was required with overrides. The second part of the survey asked individuals to provide table tolerance data for the following treatment sites: brain/head and neck (H&N), lung, breast, abdo-men/pelvis and prostate. Each site was further divided into IMRT/VMAT and 3D conformal techniques. Spaces for free-text were provided, allowing respondents to enter any table tolerance data they were unable to specify under the treatment sites listed. A total of 361 individuals responded, of which approximately half partici-pated in the couch tolerances portion of the survey. Overall, 86% of respondents' institutions allow couch tolerance overrides at treatment. Therapists were the most common staff members permitted to perform overrides, followed by physicists, dosimetrists, and physicians, respectively. Of the institutions allowing overrides, 34% reported overriding daily. More than half of the centers document the over-ride and/or require a setup image to radiographically verify the treatment site. With respect to table tolerances, SRS/SBRT table tolerances were the tightest, while clinical setup table tolerances were the largest. There were minimal statistically significant differences between IMRT/VMAT and 3D conformal table tolerances. Our results demonstrated that table overrides are relatively common in radiotherapy despite being a potential safety concern. Institutions should review their override policy and table tolerance values in light of the practices of other institutions. Careful attention to these matters is crucial in ensuring the safe and accurate delivery of radiotherapy.

Figure 1

Number of responses vs. individual table tolerance value for (a) IMRT/VMAT and (b) 3D conformal brain/H&N treatments. $\text{Vrt}=\text{vertical couch tolerance},\text{Lng}=\text{longitudinal couch tolerance},\text{Lat}=\text{lateral couch tolerance}$.

Figure 2

Number of responses vs. individual table tolerance value for (a) IMRT/VMAT and (b) 3D conformal breast treatments. $\text{Vrt}=\text{vertical couch tolerance},\text{Lng}=\text{longitudinal couch tolerance},\text{Lat}=\text{lateral couch tolerance}$.

Figure 3

Number of responses vs. individual table tolerance value for (a) IMRT/VMAT and (b) 3D conformal lung treatments. $\text{Vrt}=\text{vertical couch tolerance},\text{Lng}=\text{longitudinal couch tolerance},\text{Lat}=\text{lateral couch tolerance}$.

Figure 4

Number of responses vs. individual table tolerance value for (a) IMRT/VMAT and (b) 3D conformal abdomen/ pelvis treatments. $\text{Vrt}=\text{vertical couch tolerance},\text{Lng}=\text{longitudinal couch tolerance},\text{Lat}=\text{lateral couch tolerance}$.

Figure 5

Number of responses vs. individual table tolerance value for (a) IMRT/VMAT and (b) 3D conformal prostate treatments. $\text{Vrt}=\text{vertical couch tolerance},\text{Lng}=\text{longitudinal couch tolerance},\text{Lat}=\text{lateral couch tolerance}$.

Figure 6

Number of responses vs. individual table tolerance value for (a) SRS/SBRT treatments and (b) 3D conformal clinical setup treatments. $\text{Vrt}=\text{vertical couch tolerance},\text{Lng}=\text{longitudinal couch tolerance},\text{Lat}=\text{lateral couch tolerance}$.