Bladder trigone sparing radiotherapy in prostate cancer treatment.

INTRODUCTION: Evidence suggests the bladder trigone to be a potential organ at risk (OAR) in predicting acute and late genitourinary (GU) side effects when treating prostate cancer with radiotherapy. METHODS: A search of MEDLINE, Cinahl, EMBASE, PubMed, the Cochrane Database of Systematic Reviews and OpenGrey was conducted and no current or underway systematic reviews or scoping reviews on the topic were identified. A systematic literature review was carried out assessing the quality of this evidence. All evidence that prospectively or retrospectively reviewed radiotherapy or modelled radiotherapy dose to the bladder trigone were included. The search was conducted on the 8th July 2021 with 32 studies included in this review. This was repeated 10th June 2023 and two additional studies were identified. Any evidence published since this date have not been included and are a limitation of this review. RESULTS: MRI imaging is recommended to assist in delineating the trigone which has been shown to have a high amount of inter-observer variability and the use of specific training may reduce this. Across all radiotherapy treatment modalities, trigone dose contributed to GU acute and late toxicity symptoms. Trigone motion is relative to prostate motion but further research is required to confirm if the prostate can be used as a reliable surrogate for trigone position. The dose tolerance given for specific trigone related toxicities is debated within the literature, and on analysis the authors of this review suggest bladder trigone dose limits: Dmean < 45.8 Gy, V61.0Gy < 40%, V59.8Gy < 25%, V42.5Gy-V41.0Gy < 91% and V47.4Gy-V43.2Gy < 91% with α/ß of 3 Gy to reduce acute and late GU toxicities. CONCLUSION: There is evidence to support further research into bladder trigone sparing radiotherapy to improve patient outcomes. IMPLICATION FOR PRACTICE: Using the bladder trigone as an organ at risk is possible and the authors are currently seeking funding for a feasibility trial to further investigate this.

Using "iDose4" iterative reconstruction algorithm in adults' chest-abdomen-pelvis CT examinations: effect on image quality in relation to patient radiation exposure.

OBJECTIVE: The aim of this study is to examine the effect of iDose4 hybrid iterative reconstruction algorithm (Philips Healthcare, Cleveland, OH) on radiation dose and image quality in chest­abdomen­pelvis (CAP) CT scanning of adult patients. METHODS: CAP CT examinations were performed on 99 patients with the use of the "old standard" protocol performing filtered back projection reconstruction algorithm (FBP protocol) and on 84 patients with the use of iDose4 protocol on a 64-multidetector CT. Patients were subdivided into three weight groups (Group 1, 41­60kg; Group 2, 61­90kg; and Group 3, .90kg). Volume CT dose index and dose length product (DLP) were recorded, while effective dose was calculated from DLP measurements. Objective image noise, signal-to-noise ratio and contrast-to-noise ratio were calculated. Two radiologists reviewed images to evaluate image quality. RESULTS: Compared with the FBP protocol, there was an overall 46.5% significant decrease in effective dose with the use of iDose4 protocol. CONCLUSION: Objective image quality was higher in iDose4 images than in FBP images. Subjective image noise, sharpness, contrast and diagnostic confidence scores tended to be better for iDose4 protocol at the decreased radiation exposure level. Artefacts were minor for both protocols. ADVANCES IN KNOWLEDGE: Our results suggest that the iterative acquisition protocol provides great potential for reducing radiation exposure and maintaining or improving image quality in CAP CT examinations.