How can the aetiological factors of rectal distension be managed to reduce interfraction prostate motion during a course of radiotherapy treatment

To degas or not to degas? The effectiveness of pharmaceuticals in reducing the impact of bowel volume variations during liver SBRT treatment

The indications for liver stereotactic body radiation therapy (SBRT) continue to expand in the management of liver cancer due to the improved rates of local control with acceptable normal tissue toxicity. Changes in internal anatomy, such as the bowel, may negatively impact the precision of treatment delivery of SBRT liver treatment by influencing daily image matching. Institutions have developed various approaches to promoting bowel volume consistency. One such strategy is the administration of pharmaceuticals. The administration of pharmaceuticals, such as Simethicone, has been adopted by the Princess Alexandra Hospital Radiation Oncology Department (ROPAIR) as a method to promote consistency in the amount of bowel gas observed in liver cancer patients. This case series examines a group of patients treated at ROPAIR with liver SBRT to determine whether current practices effectively reduce the impact of bowel volume variations for liver cancer patients. Initial observations from this hypothesis generating research suggest potential improved consistency of the small bowel's anatomical position for liver SBRT patients who were administered Simethicone (Bowel bag dice similarity coefficient - Simethicone group = 0.79-0.92, Standard group = 0.24-0.93). However, it appeared that this strategy alone may not be entirely effective achieving consistency in the amount of bowel gas present throughout the duration of treatment. Further investigation into the refinement of liver SBRT pre-treatment preparation is therefore recommended.

The Effect of Oral Laxatives on Rectal Distension and Image Quality in Magnetic Resonance Imaging of the Prostate

Introduction Increasing rectal size is associated with increased artefacts on magnetic resonance imaging (MRI) of the prostate and has the potential to degrade image quality. The objective of this study was to analyse the effect of oral laxative medication on rectal distension and image quality in prostate MRI. Methods Eighty patients prospectively received either 15 mg of oral senna (laxative group) or no medication (control group). Patients underwent prostate MRI according to standard local protocol and seven rectal dimensions on axial and sagittal images were measured. A subjective assessment of rectal distension was also made using a five-point Likert scale. Finally, artefacts on diffusion-weighted sequences were assessed using a four-point Likert scale. Results There was a small reduction in rectal diameter on sagittal images in the laxative group compared to the control group, with mean diameters of 27.1 mm and 30.0 mm respectively, p=0.02. There was no significant difference in rectal measurements of anteroposterior diameter, transverse diameter, or rectal circumference on axial imaging. Subjective scoring also demonstrated no significant difference in diffusion-weighted imaging quality between the laxative group and control group, p=0.82. Conclusion Bowel preparation with the oral laxative, senna, provided only a marginal decrease in rectal distension on one measure and no reduction in artefacts on diffusion-weighted sequences. The findings of this study do not support the routine use of this medication in patients undergoing prostate MRI.

Optimising prostate mpMRI: prepare for success

Multiparametric magnetic resonance imaging (MRI) now plays an essential role in prostate cancer diagnosis and management. The increasing use of MRI before biopsy makes obtaining images of the highest quality vital. The European Society of Urogenital Radiology (ESUR) 2012 guidelines and subsequent Prostate Imaging -Reporting Data System (PI-RADS) version 2 recommendations in 2015 address the technical considerations for optimising MRI acquisition; however, the quality of the multiparametric sequences employed depends not only on the hardware and software utilised and scanning parameters selected, but also on patient-related factors, for which current guidance is lacking. Patient preparation factors include bowel peristalsis, rectal distension, the presence of total hip replacement (THR), post-biopsy haemorrhage, and abstinence from ejaculation. New evidence has been accrued since the release of PI-RADS v2, and this review aims to explore the key issues of patient preparation and their potential to further optimise the image quality of mpMRI.

Evaluating the effect of rectal distension on prostate multiparametric MRI image quality

PURPOSE

To evaluate the effect of rectal distension on the quality of anatomical and functional prostate multiparametric (mp) MRI.

MATERIALS AND METHODS

Multiparametric (mp) 3T-MRI images of 173 patients were independently evaluated by two radiologists in this retrospective study. Planimetry rectal volumes were derived and a subjective assessment of rectal distension was made using a 5-point Likert scale (1=no stool/gas, 5=large amount of stool/gas). Image quality of diffusion-weighted imaging (DWI) was evaluated using a 5-point Likert scale. DWI was further scored for distortion and artefact. T2W images were evaluated for image sharpness and the presence of motion artefact. The stability of the dynamic contrast-enhancement acquisition was assessed by recording the number of corrupt data points during the wash-out phase.

RESULTS

There was a strong correlation between subjective scoring of rectal loading and objectively measured rectal volume (r=0.82), p<0.001. A significant correlation was shown between increased rectal distension and both reduced DW image quality (r=-0.628, p<0.001), and increased DW image distortion (r=0.814, p<0.001). There was also a significant trend for rectal distension to increase artefact at DWI (r=0.154, p=0.042). Increased rectal distension led to increased motion artefact on T2 (p=0.0096), but did not have a significant effect on T2-sharpness (p=0.0638). There was no relationship between rectal distension and DCE image quality (p=0.693). 63 patients underwent lesion-targeted biopsy post MRI, there was a trend to higher positive predictive values in patients with minor rectal distension (34/38, 89.5%) compared to those with moderate/marked distension (18/25, 72%), p=0.09.

CONCLUSION

Rectal distension has a significant negative effect on the quality of both T2W and DW images. Consideration should therefore be given to bowel preparation prior to prostate mpMRI to optimise image quality.