Radiation therapy treatment verification imaging in Australia and New Zealand

Effect of patient size on image quality in radiotherapy kV planar verification imaging: a phantom study

INTRODUCTION

This study aimed to determine a maximal pelvic separation and waist circumference in pelvic patients to guide radiation therapists in acquiring kilovoltage (kV) planar images of acceptable quality for treatment verification.

METHODS

A pelvic anthropomorphic phantom modified with different bolus thicknesses was imaged at various default kV exposure settings. Radiation therapists rated image quality and acceptance/rejection of these images for treatment verification.

RESULTS

Sixteen radiation therapists participated in the study. Image quality was inversely proportional to phantom size. AP and lateral kV images were acceptable for treatment verification up to a waist circumference of 143 cm.

CONCLUSIONS

Exposure settings for kV image verification of large patients should be individualised to avoid unnecessary patient radiation dose through repeated imaging.

Radiation therapist perspectives on cone-beam computed tomography practices and response to information

Introduction

With recent technological advances in image-guided radiation therapy (IGRT), through cone-beam computed tomography (CBCT), more image-related clinical information is being collected, at more frequent intervals throughout the treatment course. As radiation therapy (RT) programmes further develop IGRT technology, the aim of this study is to assess whether the distribution and communication of professional responsibilities is evolving to ensure appropriate use of the technology.

Methods

Radiation therapists practicing at any of the 14 Ontario RT centres were sent an electronic survey (n = 400). Closed-ended quantitative items addressed perceptions regarding policies, comfort, and professional responsibility in addressing CBCT concerns. Focus was on gynaecological, lung, head and neck (H&N) disease sites. Options for qualitative comments and explanations were included where appropriate.

Results

Seventy-nine surveys were submitted. Respondents from 12/14 (85·7%) centres used CBCT for at least one of three disease sites, most commonly on a daily basis. Five of these centres (41·7%) did not require radiation oncologist CBCT review, with others requiring it Day 1 or weekly. Potential CBCT observations of concern were grouped as set-up issues, tumour changes, organ-at-risk (OAR) changes, contour changes and ancillary findings (especially lung and airway changes). Respondents believed they consulted another professional about a CBCT in 20·2% of H&N patients, 19·6% of lung patients and 9·7% of gynaecological patients. The level of comfort in doing so varied from 77·0% for H&N to 89·5% for lung. Respondents were most likely to believe themselves responsible for changes in OARs (92·2% believing themselves responsible), and least likely for ancillary findings (62·7%).

Conclusions

Through preliminary insight from Ontario therapists, a degree of inconsistency is apparent between perceptions, practices and assigned roles in the management of CBCT information. Clear definition of the scope and nature of therapists’ responsibility for interpreting and addressing changes on CBCT images should be developed within each centre.