A. Dubey

A feasibility study to investigate the use of thin-plate splines to account for prostate deformation

Image registration is an important step in the radiotherapy treatment planning process. It provides a method of fusing different types of diagnostic imaging information. One such application is to combine magnetic resonance spectroscopic images (MRSI) of the prostate with anatomical MRI and/or computed tomography images that are routinely used in the radiation treatment planning of prostate cancer. MRSI provides in vivo information related to the underlying metabolic activity of tissues, and can be related to the presence of cancer. However, the inflated endorectal coil required during MRS imaging poses a potential problem by deforming the prostate when it is filled with approximately 100 cm3 of air during image acquisition. This pushes the prostate superiorly/anteriorly, deforming the prostate and consequently the spectroscopic imaging data in a nonlinear manner. In this application, the coil-deformed MRS images are warped back to a non-deformed state, using a single data set. A nonlinear warping algorithm is presented to achieve this. Results indicate that the algorithm attains an accuracy of 97% (4 cm3 difference) when reproducing the total prostate volume compared to a Radiation Oncologist defined prostate volume. This difference is slightly smaller than the measured intra-operator variance of +/-1.5 cm3 (deflated coil) and the measured algorithm variance of +/-1.0 cm3. Additionally, intraprostatic nodules were used to assess the accuracy of the warping algorithm in regions inside the prostate. While choosing anatomical tie points along the external prostate surface, analysis of the nodules revealed the algorithm accuracy reduced to 63-93%.

Low-cost optical scanner and 3-dimensional printing technology to create lead shielding for radiation therapy of facial skin cancer: First clinical case series

Purpose Three-dimensional printing has been implemented at our institution to create customized treatment accessories, including lead shields used during radiation therapy for facial skin cancer. To effectively use 3-dimensional printing, the topography of the patient must first be acquired. We evaluated a low-cost, structured-light, 3-dimensional, optical scanner to assess the clinical viability of this technology. Methods and materials For ease of use, the scanner was mounted to a simple gantry that guided its motion and maintained an optimum distance between the scanner and the object. To characterize the spatial accuracy of the scanner, we used a geometric phantom and an anthropomorphic head phantom. The geometric phantom was machined from plastic and included hemispherical and tetrahedral protrusions that were roughly the dimensions of an average forehead and nose, respectively. Polygon meshes acquired by the optical scanner were compared with meshes generated from high-resolution computed tomography images. Most optical scans contained minor artifacts. Using an algorithm that calculated the distances between the 2 meshes, we found that most of the optical scanner measurements agreed with those from the computed tomography scanner within approximately 1 mm for the geometric phantom and approximately 2 mm for the head phantom. We used this optical scanner along with 3-dimensional printer technology to create custom lead shields for 10 patients receiving orthovoltage treatments of nonmelanoma skin cancers of the face. Patient, tumor, and treatment data were documented. Results Lead shields created using this approach were accurate, fitting the contours of each patients face. This process added to patient convenience and addressed potential claustrophobia and medical inability to lie supine. Conclusions The scanner was found to be clinically acceptable, and we suggest that the use of an optical scanner and 3-dimensional printer technology become the new standard of care to generate lead shielding for orthovoltage radiation therapy of nonmelanoma facial skin cancer.

Comparison of 7th and 8th editions of the UICC/AJCC TNM staging for non-small cell lung cancer in a non-metastatic North American cohort undergoing primary radiation treatment

BACKGROUND We compared the performance of 7th and 8th edition of the Union for International Cancer Control (UICC) / American Joint Committee on Cancer (AJCC) TNM staging for non-small cell lung cancer (NSCLC) in non-metastatic (stage I-III) North American cohort undergoing primary radiation treatment. METHODS Newly diagnosed NSCLC between (Jan 2011 - Dec 2014) were screened through a Canadian Provincial Cancer Registry. Clinico-radiologically and pathologically confirmed non-metastatic NSCLC undergoing primary radiation treatment were included. Kaplan-Meier methods, Cox proportional hazard regression and Akaike information criterion (AIC) were applied to evaluate discriminatory ability and prognostic performance of 7th and 8th edition of staging systems. RESULTS In this cohort of 295 patients, 8th edition stages IA3, IB, IIA, IIB, IIIA, IIIB, and IIIC showed progressive increase in the hazard ratio compared to best stage IA2 (8th edition IA3 vs IA2: HR 1.72; IB vs IA2: HR 2.04; IIA vs IA2: HR 2.66; IIB vs IA2: HR 2.91; IIIA vs IA2: HR 3.38; IIIB vs IA2: HR 3.62 and IIIC vs IA2: HR 8.22). In a multivariate model, 8th edition stage grouping had smaller AIC of 2342.08 compared to 7th edition 2349.55, confirming better performance. International Association for the Study of Lung Cancer (IASLC) map based nodal categorization N1, N2 and N3, showed good survival and hazard discrimination over stage N0 (1.39, 1.48 and 2.16 respectively). CONCLUSION In an independent cohort of non-metastatic NSCLC undergoing primary radiation treatment, improved performance of 8th edition UICC/AJCC staging system over 7th edition was observed.

Analysis of First Case Series in the World of Skin Cancer Patients Where Lead Shielding for Radiation Therapy of Facial Skin Cancer was Designed Utilizing Optical Scanner and 3D Printer Technology

Purpose Radiation is one of the modalities used to treat non-melanoma skin cancers. For facial lesions; ortho-voltage radiotherapy (RT) can require the creation of lead shielding to protect vulnerable organs at risk (OAR). Creating a lead shield is often difficult due to the complex contours of the face. The traditional method involves creating a plaster mould of a patients face to use as a template for creating a shield. This requires another patient visit, and for patients who are claustrophobic or medically unable to lie flat, this strategy is not ideal. We address this by utilizing optical scanner and 3D printer technology to create lead shields and report the first case series in the English literature here.

Po-Thur Eve General-26: Tracking intraprostatic volumes for determining non-linear warping algorithm variability

Magnetic resonance spectroscopy imaging(MRSI) is becoming routinely used for diagnosis and treatment planning of prostate cancer.MRSI provides physicians and physicists with information related to metabolic activity of tissues within the prostate. During the MRSIdata acquisition, an endorectal radio frequency coil is utilized to boost signal strength in the localized volume, and brings about a ∼10 fold increase in the signal to noise ratio. A challenge exist is using the MRSI data collected using the endorectal coil technique. The endorectal coil, while crucially important to data acquisition, is filled with approximately with ∼100ccs of air. This pushes the prostate superiorly/anteriorly, deforming the prostate and consequently the spectroscopic imaging data in a non‐linear manner. In this application, the coil‐deformed MRS images are warped back to a non‐deformed state, using a single data set. A non‐linear warping algorithm is presented to achieve this. For this case study, physicians were able to contour both the total prostate volume, and intraprostatic nodules. While choosing anatomical tie points along the external prostate surface (needed for the non‐linear warping algorithm), analysis of the nodules revealed the algorithm accuracy ranges from 63–93%. While the algorithm accuracy itself, when reproducing the total prostate volume, achieved an accuracy of 97%.