Rectum Protection by Rectal Gel Injection in Cervical Cancer Brachytherapy: A Dosimetric Study via Deformable Surface Dose Accumulation and Machine-Learning-Based Discriminative Modeling

PurposeThis retrospective study aimed to evaluate the dosimetric effects of a rectal insertion of Kushen Ningjiao on rectal protection using deformable dose accumulation and machine learning–based discriminative modelling.Materials and MethodsSixty-two patients with cervical cancer enrolled in a clinical trial, who received a Kushen Ningjiao injection of 20 g into their rectum for rectal protection via high–dose rate brachytherapy (HDR-BT, 6 Gy/f), were studied. The cumulative equivalent 2-Gy fractional rectal surface dose was deformably summed using an in-house-developed topography-preserved point-matching deformable image registration method. The cumulative three-dimensional (3D) dose was flattened and mapped to a two-dimensional (2D) plane to obtain the rectal surface dose map (RSDM). For analysis, the rectal dose (RD) was further subdivided as follows: whole, anterior, and posterior 3D-RD and 2D-RSDM. The dose–volume parameters (DVPs) were extracted from the 3D-RD, while the dose geometric parameters (DGPs) and textures were extracted from the 2D-RSDM. These features were fed into 192 classification models (built with 8 classifiers and 24 feature selection methods) for discriminating the dose distributions between pre-Kushen Ningjiao and pro-Kushen Ningjiao.ResultsThe rectal insertion of Kushen Ningjiao dialated the rectum in the ambilateral direction, with the rectal column increased from pre-KN 15 cm3 to post-KN 18 cm3 (P < 0.001). The characteristics of DGPs accounted for the largest portions of the top-ranked features. The top-ranked dosimetric features extracted from the posterior rectum were more reliable indicators of the dosimetric effects/changes introduced by the rectal insertion of Kushen Ningjiao. A significant dosimetric impact was found on the dose–volume parameters D1.0cc–D2.5cc extracted on the posterior rectal wall.ConclusionsThe rectal insertion of Kushen Ningjiao incurs significant dosimetric changes on the posterior rectal wall. Whether this effect is eventually translated into clinical gains requires further long-term follow-up and more clinical data for confirmation.

Anorectal injury related to a personal watercraft: a case report and literature review

Background Douche injury is a rare consequence of water recreation activities. Generally, this type of trauma occurs when people fall into the water in a sitting position during high-speed activities such as using a personal watercraft (PWC). Here, we report a rare case of anorectal injury caused by water jets from a PWC during sudden acceleration from rest. Case presentation A 21-year-old male passenger on a PWC fell off backward from the rear seat when the craft suddenly accelerated. He fell into the water in a supine position with his legs open, and the water jets of the PWC struck his perineum directly. Thereafter, bleeding from the anus was seen, and he was transferred to our hospital. On physical examination, there was a deep laceration interrupting the external anal sphincter in the posterior rectal wall. Abdominal computed tomography revealed a full-layer perforation of the posterior rectal wall and leakage of feces into the extraperitoneal space, but intraperitoneal free air was not seen. Laparoscopic sigmoid loop colostomy and primary suturing of the sphincter and mucosa were performed. He did not have any complications and was discharged from our hospital 16 days after the surgery. His anal function was almost perfectly preserved, and his diverting colostomy was closed 4 months later. Conclusion Anorectal injuries related to PWCs can occur not only while traveling at high speeds, but also when suddenly accelerating from rest. A diverting colostomy should be performed for this type of trauma. In these trauma cases, clinicians must suspect complex and life-threatening anorectal injuries early.