M Gopalakrishnan

A computational tool for the efficient analysis of dose-volume histograms from radiation therapy treatment plans

A Histogram Analysis in Radiation Therapy (HART) program was primarily developed to increase the efficiency and accuracy of dose–volume histogram (DVH) analysis of large quantities of patient data in radiation therapy research. The program was written in MATLAB to analyze patient plans exported from the treatment planning system (Pinnacle3) in the American Association of Physicists in Medicine/Radiation Therapy Oncology Group (AAPM/RTOG) format. HART‐computed DVH data was validated against manually extracted data from the planning system for five head and neck cancer patients treated with the intensity‐modulated radiation therapy (IMRT) technique. HART calculated over 4000 parameters from the differential DVH (dDVH) curves for each patient in approximately 10–15 minutes. Manual extraction of this amount of data required 5 to 6 hours. The normalized root mean square deviation (NRMSD) for the HART–extracted DVH outcomes was less than 1%, or within 0.5% distance‐to‐agreement (DTA). This tool is supported with various user‐friendly options and graphical displays. Additional features include optimal polynomial modeling of DVH curves for organs, treatment plan indices (TPI) evaluation, plan‐specific outcome analysis (POA), and spatial DVH (zDVH) and dose surface histogram (DSH) analyses, respectively. HART is freely available to the radiation oncology community. PACS numbers: 87.53.‐j; 87.53.Tf; 87.53.Xd.

Cardiac-Sparing Whole Lung IMRT in Children With Lung Metastasis

PURPOSE To demonstrate the dosimetric advantages of cardiac-sparing (CS) intensity modulated radiation therapy (IMRT) in children undergoing whole lung irradiation (WLI). METHODS AND MATERIALS Chest CT scans of 22 children who underwent simulation with 3-dimensional (n=10) or 4-dimensional (n=12) techniques were used for this study. Treatment planning was performed using standard anteroposterior-posteroanterior (S-RT) technique and CS-IMRT. Left and right flank fields were added to WLI fields to determine whether CS-IMRT offered any added protection to normal tissues at the junction between these fields. The radiation dose to the lung PTV, cardiac structures, liver, and thyroid were analyzed and compared. RESULTS CS-IMRT had 4 significant advantages over S-RT: (1) superior cardiac protection (2) superior 4-dimensional lung planning target volume coverage, (3) superior dose uniformity in the lungs with fewer hot spots, and (4) significantly lower dose to the heart when flank RT is administered after WLI. CONCLUSIONS The use of CS-IMRT and 4-dimensional treatment planning has the potential to improve tumor control rates and reduce cardiac toxicity in children receiving WLI.

Advantages of Whole-liver Intensity Modulated Radiation Therapy in Children With Wilms Tumor and Liver Metastasis

PURPOSE To demonstrate the dosimetric advantages of intensity modulated radiation therapy (IMRT) in children with Wilms tumor (WT) undergoing whole-liver (WL) RT. METHODS AND MATERIALS Computed tomography simulation scans of 10 children, either 3 (3D) or 4-dimensional (4D), were used for this study. The WL PTV was determined by the 3D or 4D liver volumes, with a margin of 1 cm. A total of 40 WL RT plans were performed: 10 each for left- and right-sided WT with IMRT and anteroposterior-posteroanterior (AP-PA) techniques. The radiation dose-volume coverage of the WL planning target volume (PTV), remaining kidney, and other organs were analyzed and compared. RESULTS The 95% dose coverage to WL PTV for left and right WT were as follows: 97% ± 4% (IMRT), 83% ± 8% (AP-PA) (P<.01) and 99% ± 1% (IMRT), 94% ± 5% (AP-PA) (P<.01), respectively. When 3D WL PTV was used for RT planning, the AP-PA technique delivered 95% of dose to only 78% ± 13% and 88% ± 8% of 4D liver volume. For left WT, the right kidney V15 and V10 for IMRT were 29% ± 7% and 55% ± 8%, compared with 61% ± 29% (P<.01) and 78% ± 25% (P<.01) with AP-PA. For right WT, the left kidney V15 and V10 were 0 ± 0 and 2% ± 3% for IMRT, compared with 25% ± 19% (P<.01) and 40% ± 31% (P<.01) for AP-PA. CONCLUSIONS The use of IMRT and 4D treatment planning resulted in the delivery of a higher RT dose to the liver compared with the standard AP-PA technique. Whole-liver IMRT also delivered a significantly lower dose to the remaining kidney.

Dosimetric impact of cylinder size in high-dose rate vaginal cuff brachytherapy (VCBT) for primary endometrial cancer

The purpose of this study was to evaluate the dosimetric impact of cylinder size in high‐dose‐rate (HDR) vaginal cuff brachytherapy (VCBT). Sample plans of HDR VCBT in a list of cylinders ranging from 2.5 to 4 cm in diameter at 0.5 cm increment were created and analyzed. The doses were prescribed either at the 0.5 cm depth with 5.5 Gy for 4 fractions or at the cylinder surface with 8.8 Gy for 4 fractions, in various treatment lengths. A 0.5 cm shell volume called PTV_Eval was contoured for each plan and served as the target volume for dosimetric evaluation. The cumulative and differential dose volume histograms (c‐DVH and d‐DVH), mean doses (D‐mean) and the doses covering 90% (D90), 10% (D10), and 5% (D5) of PTV_Eval were calculated. In the 0.5 cm depth regimen, the DVH curves were found to have shifted toward the lower dose zone when a larger cylinder was used, but in the surface regimen the DVH curves shifted toward the higher dose zone as the cylinder size increased. The D‐means of the both regimens were between 6.9 and 7.8 Gy and dependent on the cylinder size but independent of the treatment length. A 0.5 cm variation of diameter could result in a 4% change of D‐mean. Average D90s were 5.7 (ranging from 5.6 to 5.8 Gy) and 6.1 Gy (from 5.7 to 6.4 Gy), respectively, for the 0.5 cm and surface regimens. Average D10 and D5 were 9.2 and 11 Gy, respectively, for the 0.5 cm depth regimen, and 8.9 and 9.7 Gy, respectively, for the surface regimen. D‐mean, D90, D10, and D5 for other prescription doses could be calculated from the lookup tables of this study. Results indicated that the cylinder size has moderate dosimetric impact, and that both regimens are comparable in dosimetric quality. PACS number(s): 87.61.‐c, 87.53.Jw, 87.19.xjThe purpose of this study was to evaluate the dosimetric impact of cylinder size in high-dose-rate (HDR) vaginal cuff brachytherapy (VCBT). Sample plans of HDR VCBT in a list of cylinders ranging from 2.5 to 4 cm in diameter at 0.5 cm increment were created and analyzed. The doses were prescribed either at the 0.5 cm depth with 5.5 Gy for 4 fractions or at the cylinder surface with 8.8 Gy for 4 fractions, in various treatment lengths. A 0.5 cm shell volume called PTV_Eval was contoured for each plan and served as the target volume for dosimetric evaluation. The cumulative and differential dose volume histograms (c-DVH and d-DVH), mean doses (D-mean) and the doses covering 90% (D90), 10% (D10), and 5% (D5) of PTV_Eval were calculated. In the 0.5 cm depth regimen, the DVH curves were found to have shifted toward the lower dose zone when a larger cylinder was used, but in the surface regimen the DVH curves shifted toward the higher dose zone as the cylinder size increased. The D-means of the both regimens were between 6.9 and 7.8 Gy and dependent on the cylinder size but independent of the treatment length. A 0.5 cm variation of diameter could result in a 4% change of D-mean. Average D90s were 5.7 (ranging from 5.6 to 5.8 Gy) and 6.1 Gy (from 5.7 to 6.4 Gy), respectively, for the 0.5 cm and surface regimens. Average D10 and D5 were 9.2 and 11 Gy, respectively, for the 0.5 cm depth regimen, and 8.9 and 9.7 Gy, respectively, for the surface regimen. D-mean, D90, D10, and D5 for other prescription doses could be calculated from the lookup tables of this study. Results indicated that the cylinder size has moderate dosimetric impact, and that both regimens are comparable in dosimetric quality. PACS number(s): 87.61.-c, 87.53.Jw, 87.19.xj.

Cardiac-Sparing Whole Lung Intensity Modulated Radiation Therapy in Children with Wilms Tumor: Final Report on Technique and Abdominal Field Matching to Maximize Normal Tissue Protection

PURPOSE Cardiac-sparing whole lung intensity modulated radiation therapy (WL IMRT) has been shown to improve cardiac protection and lung volume dose coverage compared with standard anteroposterior techniques. This dosimetry study had 2 aims: To determine the dosimetric advantages of a modified WL IMRT (M-WL IMRT) technique, designed to reduce radiation exposure to the thyroid gland and breast tissues, compared with standard WL IMRT (S-WL IMRT) and to determine the dosimetric advantages of M-WL IMRT and dosimetrically matched abdomen and flank radiation therapy (RT) fields designed to reduce normal tissue exposure compared with standard field matching techniques. METHODS AND MATERIALS Computed tomography scans of the chest and abdomen that were obtained during computed tomography simulation of 10 female children were used. For Aim 1, for S-WL IMRT, the planning target volume (PTV) was obtained with a 1-cm expansion of the 4-dimensional lung volume (internal target volume). For M-WL IMRT, the PTV was reduced around the breast and thyroid gland to facilitate thyroid and breast sparing. For Aim 2, standard matching techniques for 3-dimensional anterior/posterior-posterior/anteriorwhole lung and abdominal RT fields were compared with a new dosimetric matching technique for WL IMRT and abdomen and flank fields. For both aims, the dose coverage of the lungs and radiation exposure to normal tissues (heart, thyroid, breasts) were statistically compared. RESULTS Compared with S-WL IMRT, the M-WL IMRT technique provided similar lung PTV dose coverage and a significantly superior reduction in mean breast and thyroid doses, without compromising cardiac protection. The M-WL IMRT technique combined with a dosimetrically matched abdomen and flank fields showed significantly superior normal tissue protection compared with standard matched anterior/posterior-posterior/anteriorlung and abdomen and flank RT fields. CONCLUSIONS This study has shown that the M-WL IMRT technique can reduce radiation exposure to the thyroid gland and breast tissue without compromising cardiac protection and 4-dimensional lung volume dose coverage. This report also describes a new dosimetric matching technique between WL IMRT and abdomen and flank fields that will improve normal tissue sparing compared with standard techniques.

Feasibility and accuracy of UF/NCI phantoms and Monte Carlo retrospective dosimetry in children treated on National Wilms Tumor Study protocols

This pilot study was done to determine the feasibility and accuracy of University of Florida/National Cancer Institute (UF/NCI) phantoms and Monte Carlo (MC) retrospective dosimetry and had two aims: (1) to determine the anatomic accuracy of UF/NCI phantoms by comparing 3D organ doses in National Wilms Tumor Study (NWTS) patient‐matched UF/NCI phantoms to organ doses in corresponding patient‐matched CT scans and (2) to compare infield and out‐of‐field organ dosimetry using two dosimetry methods—standard radiation therapy (RT) treatment planning systems (TPS) and MC dosimetry in these two anatomic models.

DVH Analytics: A DVH database for clinicians and researchers

Abstract In this study, we build a vendor‐agnostic software application capable of importing and analyzing non‐image‐based DICOM files for various radiation treatment modalities (i.e., DICOM RT Dose, RT Structure, and RT Plan files). Dose‐volume histogram (DVH) and planning data are imported into a SQL database, and methods are provided to manage, edit, view, and download data. Furthermore, the software provides various analytical tools for plan evaluations, plan comparisons, benchmarking, and plan outcome predictions. DVH Analytics is developed using Python, including libraries such as pydicom, dicompyler, psycopg2, SciPy, Statsmodels, and Bokeh for parsing DICOM files, computing DVHs, communicating with a PostgreSQL database, performing statistical analyses, and creating a web‐based user interface. This software is open‐source and compatible with Windows, Mac OS, and Linux. For proof‐of‐concept, a database with over 3,000 DVHs from a single physicians head & neck practice was built. From these data, differences in means, correlations, and temporal trends in dose to multiple organs‐at‐risk (OARs) were observed. Furthermore, an example of the predictive regression tool is reported, where a model was constructed to predict maximum dose to brainstem based on minimum distance from planning target volume (PTV) and treatment beam source‐to‐skin distance (SSD). With DVH Analytics, we have developed a free, open‐source software program to parse, organize, and analyze non‐image‐based DICOM data for use in a radiation oncology setting. Furthermore, this software can be used to generate statistical models for the purposes of quality control or outcome predictions and correlations.

Advanced small cell carcinoma of the cervix – Successful treatment with concurrent etoposide and cisplatin chemotherapy and extended field radiation: A case report and discussion

The purpose of this article is to present a case of successful treatment of a patient with stage IVB small cell carcinoma of the cervix (SCCC) who was treated with concurrent chemoradiotherapy (CCRT) consisting of etoposide/cisplatin (EP) chemotherapy, external beam radiation therapy (EBRT), and brachytherapy. The patient has since remained without evidence of disease for nearly six years. This report reviews and summarizes the existing case literature on SCCC.

Dejerine-Roussy syndrome from thalamic metastasis treated with stereotactic radiosurgery

Dejerine-Roussy syndrome (central thalamic pain) is associated with damage to the ventral posterior sensory nuclei of the thalamus. We report a patient with breast cancer who developed contralateral hemibody paresthesias and dysesthesias. MR imaging revealed limited volume intracranial metastatic disease including a right posterior thalamic lesion. Stereotactic radiosurgery was utilized to selectively treat the lesion while preserving the remaining thalamus. Two months following treatment, the patient reported vastly improved to complete resolution of her sensory symptoms. This is the first reported case of thalamic tumor directed radiosurgical treatment leading to resolution of central neuropathic pain.

SU-F-T-117: A Pilot Study of Organ Dose Reconstruction for Wilms Tumor Patients Treated with Radiation Therapy

PURPOSE To reconstruct major organ doses for the Wilms tumor pediatric patients treated with radiation therapy using pediatric computational phantoms, treatment planning system (TPS), and Monte Carlo (MC) dose calculation methods. METHODS A total of ten female and male pediatric patients (15-88 months old) were selected from the National Wilms Tumor Study cohort and ten pediatric computational phantoms corresponding to the patients height and weight were selected for the organ dose reconstruction. Treatment plans were reconstructed on the computational phantoms in a Pinnacle TPS (v9.10) referring to treatment records and exported into DICOM-RT files, which were then used to generate the input files for XVMC MC code. The mean doses to major organs and the dose received by 50% of the heart were calculated and compared between TPS and MC calculations. The same calculations were conducted by replacing the computational human phantoms with a series of diagnostic patient CT images selected by matching the height and weight of the patients to validate the anatomical accuracy of the computational phantoms. RESULTS Dose to organs located within the treatment fields from the computational phantoms and the diagnostic patient CT images agreed within 2% for all cases for both TPS and MC calculations. The maximum difference of organ doses was 55.9 % (thyroid), but the absolute dose difference in this case was 0.33 Gy which was 0.96% of the prescription dose. The doses to ovaries and testes from MC in out-of-field provided more discrepancy (the maximum difference of 13.2% and 50.8%, respectively). The maximum difference of the 50% heart volume dose between the phantoms and the patient CT images was 40.0%. CONCLUSION This study showed the pediatric computational phantoms are applicable to organ doses reconstruction for the radiotherapy patients whose three-dimensional radiological images are not available.