Solitary fibrous tumor (SFT) is an uncommon neoplasm located in the pelvis. Here, we report a case of hypervascular malignant SFT in the mesentery of the rectum that showed a significant response to preoperative radiotherapy. A 36-year-old man presented to our department with constipation and dysuria. Abdominal computed tomography confirmed a large round neoformation (155 mm in the longest diameter) with an evident contrastenhanced periphery and a central necrotic area in the pelvis. Considering the results of the examinations, a pelvic neoplasm was strongly suspected. Due to the difficulty of safe gross total removal, a diagnostic laparotomy was indicated. Histologically, hypercellularity with spindleshaped cells and high mitotic activity was observed. Immunohistochemically, the tumor was positive for CD34, CD99, and bcl-2. The diagnosis of hypervascular malignant SFT was made. After the appropriate information had been given, the patient chose the use of preoperative radiotherapy. After local irradiation, the tumor size regressed to 105 mm in the longest diameter. Laparotomy revealed a tumor originating from the mesentery of the rectum, and the tumor was successfully excised. This case strongly suggested the potential applicability of preoperative radiotherapy for the safe gross total removal of a large pelvic SFT.
Objective: The aim of this study was to investigate low-dose kilovoltage cone-beam CT (kV-CBCT) for image-guided radiotherapy, with a particular focus on the accuracy of image registration with low-dose protocols. Methods: Imaging doses were measured with a NOMEX semiconductor detector positioned at the front of head, thorax, and pelvis human body phantoms while kV-CBCT scans were acquired at different tube currents. Aspects of image quality (spatial resolution, noise, uniformity, contrast, geometric distortion, and Hounsfield unit sensitivity) and image registration accuracy using bone and soft tissue were evaluated. Results: With preset and the lowest tube currents, the imaging doses were 0.16 and 0.08 mGy, 5.29 and 2.80 mGy, and 18.23 and 2.69 mGy for head, thorax, and pelvis, respectively. Noise was the only quality aspect directly dependent on tube current, being increased by 1.5 times with a tube current half that of the preset in head and thorax, and by 2.2 times with a tube current 1/8 of the preset in the pelvis. Accurate auto-bone matching was performed within 1 mm at the lowest tube current. The auto-soft tissue matching could not be performed with the lowest tube current; however, manual-soft tissue matching could still be performed within 2 mm or less. Conclusion: Noise was the only image quality aspect dependent on the imaging dose. Auto-bone and manual-soft tissue matching could still be performed at the lowest imaging dose. Advances in knowledge: When optimizing kV-CBCT imaging dose, the impact on bone and soft tissue image registration accuracy should be evaluated.
Perforation of Meckel's diverticulum with enteroliths is a rare complication. Here, we report a case of perforation of Meckel's diverticulum with enteroliths, which could be accurately diagnosed by the preoperative computed tomography (CT). A 46-year-old man with acute onset of severe abdominal pain, and a localized muscle guarding in the right hypochondrium, had a solitary stone detected in the right abdomen by the radiography. The abdominal CT revealed a saclike outpouching of the small intestine, containing air/fluid levels and an enterolith, with surrounding free air and mesenteric inflammatory change in the right paraumbilical area. He was diagnosed as the perforation of Meckel's diverticulum with enterolith, and the emergency operation was indicated. The perforated Meckel's diverticulum was identified approximately 90 cm proximal to the ileocecal valve. The diverticulum was transected at the base, and removed. The patient's postoperative course was uneventful. This case strongly suggested the ability of CT enterography to accurately diagnose pathologies involving the small intestine, such as the perforation of Meckel's diverticulum, which open premises for its use in the diagnosis of acute abdomen preoperatively.
We have developed soft rubber (SR) bolus that can be shaped in real-time by heating flexibly and repeatedly. This study investigated whether the SR bolus could be used as an ideal bolus, such as not changing of the beam characteristics and homogeneity through the bolus and high plasticity to adhere a patient in addition to real-time shapeable and reusability, in electron radiotherapy. Percentage depth doses (PDDs) and lateral dose profiles (LDPs) were obtained for 4, 6, and 9 MeV electron beams and were compared between the SR and conventional gel boluses. For the LDP at depth of 90% dose, the penumbra as lateral distance between the 80% and 20% isodose lines (P 80−20) and the width of 90% dose level (r 90) were compared. To evaluate adhesion, the air gap volume between the boluses and nose of a head phantom was evaluated on CT image. The dose profiles along the center axis for the 6 MeV electron beam with SR, gel, and virtual boluses (thickness = 5 mm) on the head phantom were also calculated for the irradiation of 200 monitor unit with a treatment planning system and the depth of the maximum dose (d max) and maximum dose (D max) were compared. The PDDs, P 80−20, and r 90 between the SR and gel boluses corresponded well (within 2%, 0.4 mm, and 0.7 mm, respectively). The air gap volumes of the SR and gel boluses were 3.14 and 50.35 cm3, respectively. The d max with SR, gel and virtual boluses were 8.0, 6.0, and 7.0 mm (no bolus: 12.0 mm), and the D max values were 186.4, 170.6, and 186.8 cGy, respectively. The SR bolus had the equivalent electron beam characteristics and homogeneity to the gel bolus and achieved excellent adhesion to a body surface, which can be used in electron radiotherapy as an ideal bolus.
Purpose: Skin collimation provides a sharp penumbra for electron beams, while the effect of bremsstrahlung from shielding materials is a concern. This phantom study was conducted to evaluate the safety and efficacy of a real-time variable shape rubber containing-tungsten (STR) that can be placed on a patient's skin. Methods: Electron beam profiles were acquired with the STR placed on a waterequivalent phantom and low melting-point alloy (LMA) placed at the applicator according to commonly used procedures (field sizes: 20-and 40-mm diameters). Depth and lateral dose profiles for 6-and 12-MeV electron beams were obtained by Monte Carlo (MC) simulations and were benchmarked against film measurements. The width of the off-axis distance between 80% and 20% doses (P 80-20) and the maximum dose were obtained from the lateral dose profiles. Bremsstrahlung emission was analyzed by MC simulations at the depth of maximum dose (R 100). Results: The depth dose profiles calculated by the MC simulations were consistently within 2% of the measurements. The P 80-20 at R 100 for 20-and 40-mm diameters were 4.0 mm vs. 7.6 mm (STR vs. LMA) and 4.5 mm vs. 9.2 mm, respectively, for the 6-MeV electron beam with 7.0-mm-thick STR, and 2.7 mm vs. 5.6 mm and 4.5 mm vs. 7.1 mm, respectively, for the 12-MeV electron beam with 12.0-mm-thick STR. A hotspot was not observed on the lateral dose profiles obtained with the STR at R 100. The bremsstrahlung emission under the region shielded by the STR was comparable to that obtained with the LMA, even though the STR was placed on the surface of the phantom. Conclusions: Skin collimator with STR provided superior dosimetric characteristics and comparable bremsstrahlung emission to LMA collimator at the applicator. STR could be a new tool for the safe and efficient delivery of electron radiotherapy.
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