Koyo Kikuchi

Three-dimensional summation of rectal doses in brachytherapy combined with external beam radiotherapy for prostate cancer

BACKGROUND AND PURPOSE To determine the dose constraints for rectal bleeding in brachytherapy (BRT) combined with external beam radiotherapy (EBRT). MATERIALS AND METHODS Post-BRT, pelvic computed tomography images were used for subsequent EBRT planning and BRT postplans in 37 patients. The physical doses for each plan were converted to biologically effective doses, and corresponding voxel doses were integrated to plot the summed dose-volume histogram (sum-DVH). Between 5 patients with (bled-pts) and 32 without (spared-pts) grade 2 or 3 rectal bleeding, the differences in the mean minimal dose (rDn) covering the rectal volume of 0.5-10.0 cc and the rectal volume (rVn) receiving the calculated dose of 20-150Gy were compared. RESULTS The differences in the summed-rDn were determined by BRT exposure, while those of the summed-rVn were determined in the low-dose range and superimposed in the high-dose range by EBRT exposure. Of the 13 patients with rV150 of >1.2 cc, 4 were bled-pts (30.8%). Of the 24 patients with rV150 of ≤ 1.2cc, 1 was a bled-pts (4.2%) (p=0.024; odds ratio, 10.2; CI (95%), 1.0-104.3). CONCLUSIONS The mono-scale DVH analysis is a promising method for exploring the threshold for rectal bleeding in combined radiotherapy.

Narrow safety range of intraoperative rectal irradiation exposure volume for avoiding bleeding after seed implant brachytherapy

Background & PurposeRectal toxicity is less common after 125I seed implant brachytherapy for prostate cancer, and intraoperative rectal dose-volume constraints (the constraint) is still undetermined in pioneering studies. As our constraint failed to prevent grade 2 or 3 rectal bleeding (bled-pts) in 5.1% of patients, we retrospectively explored another constraint for the prevention of rectal bleeding.Materials and methodsThe study population consisted of 197 patients treated with the brachytherapy as monotherapy using real-time intraoperative transrectal ultrasound (US)-guided treatment at a prescribed dose of 145 Gy. Post-implant dosimetry was performed on Day 1 and Day 30 after implantation using computed tomography (CT) imaging. Rectal bleeding toxicity was classified by CTC-AE ver. 3.0 during a mean 29-month (range, 12-48 months) period after implantation. The differences in rV100s were compared among intraoperative, Day 1 and Day 30 dosimetry, and between that of patients with grade 2 or 3 rectal bleeding (the bled-pts) and of the others (the spared-pts). All patients were divided into groups based on provisional rV100s that were increased stepwise in 0.1-cc increments from 0 to 1.0 cc. The difference in the ratios of the bled-pts to the spared-pts was tested by chi-square tests, and their odds ratios were calculated (bled-OR). All statistical analyses were performed by t-tests.ResultsThe mean values of rV100us, rV100CT_1, and rV100CT_30 were 0.31 ± 0.43, 0.22 ± 0.36, and 0.59 ± 0.68 cc, respectively. These values temporarily decreased (p = 0.020) on Day 1 and increased (p = 0.000) on Day 30. There was no significant difference in rV100s between the bled-pts and spared-pts at any time of dosimetry. The maximum bled-OR was identified among patients with an rV100us value above 0.1 cc (p = 0.025; OR = 7.8; 95% CI, 1.4-145.8); an rV100CT_1 value above 0.3 cc (p = 0.014; OR = 16.2; 95% CI, 3.9-110.7), and an rV100CT_30 value above 0.5 cc (p = 0.019; OR = 6.3; 95% CI, 1.5-42.3).ConclusionBy retrospective analysis exploring rV100 as intraoperative rectal dose-volume thresholds in 125I seed implant brachytherapy for prostate cancer, it is proved that rV100 should be less than 0.1 cc for preventing rectal bleeding.

Spontaneous temporomandibular joint herniation into the external auditory canal through a persistent foramen tympanicum (Huschke): radiographic features.

Persistent foramen tympanicum (Huschke) is an anatomical variation located in the anteroinferior portion of the external auditory canal. We present a case of symptomatic temporomandibular joint (TMJ) herniation into the external auditory canal though an enlarged osseous defect. The herniated retrodiscal TMJ tissue moved backward when the patients mouth was closed, and forward, when opened. Magnetic resonance imaging findings were useful for differentiating TMJ herniation from salivary fistula caused by an ectopic salivary gland.

Partial Bladder Boost Using Lipiodol Marking During Image-guided Radiotherapy for Bladder Cancer

Background/Aim: Secure dose escalation is required to compensate avoidance of concurrent chemotherapy in radiotherapy for increasing elderly bladder cancer. We aimed to evaluate the efficacy of lipiodol submucosally injected as a fiducial marker during image-guided radiotherapy (Lip-IGRT) for muscle invasive bladder cancer (BC). Patients and Methods: Twenty-three patients with T2a-4aN0-1M0 BC underwent whole-bladder irradiation of 46 Gy and Lip-IGRT of 20 Gy, conventionally. The bladder volume exposed to 19 Gy (bV19:%) on Lip-IGRT was referred as an index predicting cystitis. Results: Lipiodol consistently highlighted the boundaries of 20 tumors (88%) on planning and portal verification images. Three of 4 patients under oral anticoagulant agents usage were complicated with grade ≥2 hematuria for 3 days (a patient with a bV19 of >50%) or more than a year (2 patients with bV19 of <50%) after the injection. The 3-year overall survival and disease-free survival rates were 70.4% and 71.1%, respectively. Conclusion: Lipiodol marking is an effective way of demarcating BC. However, it is necessary to address the comorbidities of elderly patients.

Case report of a mental nerve neurilemmoma

We present a case of a mental neurilemmoma with characteristic findings on cone-beam computed tomography (CBCT) and magnetic resonance imaging (MRI). A 62-year-old man was referred to our hospital for a painless swelling in the right cheek. CBCT imaging demonstrated dilatation of the mental foramen. On MRI, a layered pattern on T2-weighted images and enhancement with gadolinium were observed within a low-signal pseudo-capsule. On the basis of these findings, a neurilemmoma was considered likely, and this diagnosis was confirmed histologically.