PurposeIn this paper, we report cases of two patients with vaginal tumor who underwent interstitial brachytherapy (ISBT), using three-dimensional (3D)-printed personalized templates designed inversely from computed tomography (CT) or magnetic resonance (MR) images.Material and methodsPatient 1 presenting with vaginal vault recurrence was planned to receive whole pelvis external beam radiotherapy (EBRT) followed by ISBT. The tumor invaded the paracolpium; thus, we planned to administer ISBT to include the tumor and vaginal membrane. A template was designed with holes for plastic needle applicator insertion considering the appropriate direction based on pre-treatment medical images. Patient 2 presenting with vaginal cancer was scheduled to receive EBRT and ISBT because of a paracolpium invasion. Before ISBT, MR imaging was performed with vaginal cylinder inserted in the patient’s vagina. By measuring the length of the tumor manually and projecting the tumor orthogonally to a plane parallel to the bottom surface of the cylinder applicator, a template was designed. Computer-aided design software was used for planning both templates. Polycarbonate/acrylonitrile-butadiene-styrene resin was selected as material of the templates.ResultsPatient 1 received 4-fraction ISBT one week apart. A mean of 10 applicators were inserted through the holes of the template in an average of 9 minutes (range, 5-15 minutes). All applicators were inserted toward the planned directions. Median minimum dose covering 90% (D90%) of the clinical target volume (CTV) was 634 cGy. Patient 2 underwent three-fraction irradiation twice daily at 6-hour interval. All applicators were inserted through the inside of the template. The median D90% of the CTV was 703 cGy. No grade 3 or higher toxicity were found in both series.Conclusions3D-printed templates designed using medical images are useful, especially for ISBT of vaginal tumors. Further verification of clinical indications, design of templates, and manufacturing process are needed.

The feasibility of estimating patient-specific dose verification results directly from linear accelerator (linac) log files has been investigated for prostate cancer patients who undergo volumetric modulated arc therapy (VMAT). Twenty-six patients who underwent VMAT in our facility were consecutively selected. VMAT plans were created using Monaco treatment planning system and were transferred to an Elekta linac. During the beam delivery, dynamic machine parameters such as positions of the multi-leaf collimator and the gantry were recorded in the log files; subsequently, root mean square (rms) values of control errors, speeds and accelerations of the above machine parameters were calculated for each delivery. Dose verification was performed for all the plans using a cylindrical phantom with diodes placed in a spiral array. The gamma index pass rates were evaluated under 3%/3 mm and 2%/2 mm criteria with a dose threshold of 10%. Subsequently, the correlation coefficients between the gamma index pass rates and each of the above rms values were calculated. Under the 2%/2 mm criteria, significant negative correlations were found between the gamma index pass rates and the rms gantry angle errors (r = 0.64, p < 0.001) as well as the pass rates and the rms gantry accelerations (r = 0.68, p < 0.001). On the other hand, the rms values of the other dynamic machine parameters did not significantly correlate with the gamma index pass rates. We suggest that the VMAT quality assurance (QA) results can be directly estimated from the log file thereby providing potential to simplify patient-specific prostate VMAT QA procedure.

ABSTRACT Our observational study aimed to verify the safety of our original titanium fiducial markers in gynecological cancer by using a simple insertion method. We prospectively evaluated the safety in patients with gynecological cancer who had undergone our insertion procedure of the titanium markers. The decision to implant a titanium marker was at the discretion of each radiation oncologist. The fiducial markers were manufactured by severing ligating clips for surgery into 3–6 mm pieces and were sterilized thereafter. We inserted an 18-gauge injection needle containing the marker before the marker was extruded by a 22-gauge Cattelan needle or shape memory alloy wire into the tumor or tissues close to the tumor. Severe complications within 3 months after implantation were scored according to the National Cancer Institute’s Common Terminology Criteria for Adverse Events version 4.0. Between August 2016 and December 2018, we enrolled 46 patients. Of 46, 44 underwent implantation. The median age was 58.5 years. The most common primary site was the cervix. Two patients experienced detachment of the markers after implantation. No Grade 3 or higher level of complications was observed. Our simple insertion technique for original titanium fiducial markers was well-tolerated.

The purpose of this study was to investigate the relationship between plan parameters verified with DICOM-RT and dosimetric results for volumetric modulated arc therapy (VMAT). We investigated three treatment locations: prostate cancer (ten cases), maxillary sinus cancer (four cases), and malignant pleura mesothelioma (four cases) with treatment plans generated by a Monaco TM treatment planning system (TPS), and delivered with an Elekta Synergy TM linear accelerator. We calculated plan parameters, including gantry and multileaf collimator (MLC) positions, Monitor Units (MU), and millimeters of MLC motion per degree of gantry rotation (mm/degree), and performed quality assurance (QA) with a DICOM-RT plan verification system. We measured the VMAT dose with a two-dimensional diode array detector. The average gamma passing rate with percent dose acceptance criteria and distance to agreement criteria of 2 mm and 2% (2 mm/2%) were 97.4%, 97.8% and 92.0% for prostate cancer, maxillary sinus cancer, and malignant pleural mesothelioma, respectively. The mean 95th percentile value for DICOM-calculated mm/degree was 4.0, 5.2, and 11.1 for prostate cancer, maxillary sinus cancer, and malignant pleural mesothelioma, respectively. The gamma passing rate showed a correlation with calculated mm/degree, with a coefficient of determination (R 2 ) of 0.60. Higher calculated mm/degree values led to increased dosimetric errors. We conclude that dose distribution calculated by a TPS is more reliable at smaller mm/degree.

Deformable image registration (DIR) has been an important component in adaptive radiotherapy (ART). Our goal was to examine the accuracy of ART using the dice similarity coefficient (DSC) and to determine the optimal timing of replanning. A total of 22 patients who underwent volume modulated arc therapy (VMAT) for head and neck (H&N) cancers were prospectively analyzed. The planning target volume (PTV) was to receive a total of 70 Gy in 33 fractions. A second planning CT scan (rescan) was performed at the 15th fraction. The DSC was calculated for each structure on both CT scans. The continuous variables to predict the need for replanning were assessed. The optimal cut-off value was determined using receiver operating characteristic (ROC) curve analysis. In the correlation between body weight loss and DSC of each structure, weight loss correlated negatively with DSC of the whole face (r s = −0.45) and the face surface (r s = −0.51). Patients who required replanning tended to have experienced rapid weight loss. The threshold DSC was 0.98 and 0.60 in the whole face and the face surface, respectively. Patients who showed low DSC in the whole face and the face surface required replanning at a significantly high rate (P < 0.05 and P < 0.01). Weight loss correlated with DSC in both the whole face and the face surface (P < 0.05 and P < 0.05). The DSC values in the face predicted the need for replanning. In addition, weight loss tended to correlate with DSC. DIR during ART was found to be a useful tool for replanning.