BackgroundTh e DASCOR device has recently been introduced as an innovative nucleus replacement alternative for the treatment of low-back pain caused by degenerative intervertebral disc disease. Th e purpose of this study was to characterize, through a series of preclinical mechanical bench and biomechanical tests, the eff ectiveness of this device. MethodsA number of samples were created using similar preparation methods in order to characterize the nucleus replacement device in multiple mechanical bench tests, using ASTM-guided protocols, where appropriate. Mechanical bench testing included static testing to characterize the device's compressive, shear properties, and fatigue testing to determine the device's compressive fatigue strength, wear, and durability. Biomechanical testing, using human cadaveric lumbar spines, was also conducted to determine the ability of the device to restore multidirectional segmental fl exibility and to determine its resulting endplate contact stress. ResultsTh e static compressive and shear moduli of the nucleus replacement device were determined to be between 4.2-5.6 MPa and 1.4-1.9 MPa, respectively. Similarly, the ultimate compressive and shear strength were 12,400 N and 6,993 N, respectively. Th e maximum axial compressive fatigue strength of the tested device that was able to withstand a runout without failure was determined to be approximately 3 MPa. Th e wear assessment determined that the device is durable and yielded minimal wear rates of 0.29mg/Mc. Finally, the biomechanical testing demonstrated that the device can restore the multidirectional segmental fl exibility to a level seen in the intact condition while concurrently producing a uniform endplate contact stress. ConclusionsTh e results of the present study provided a mechanical justifi cation supporting the clinical use of the nucleus replacement device and also help explain and support the positive clinical results obtained from two European studies and one US pilot study. Clinical RelevanceNucleus replacement devices are rapidly emerging to address specifi c conditions of degenerative disc disease. Preclinical testing of such devices is paramount in order to potentially ensure successful clinical outcomes post implantation

BackgroundThe DASCOR device has recently been introduced as an innovative nucleus replacement alternative for the treatment of low-back pain caused by degenerative intervertebral disc disease. The purpose of this study was to characterize, through a series of preclinical mechanical bench and biomechanical tests, the effectiveness of this device.MethodsA number of samples were created using similar preparation methods in order to characterize the nucleus replacement device in multiple mechanical bench tests, using ASTM-guided protocols, where appropriate. Mechanical bench testing included static testing to characterize the device's compressive, shear properties, and fatigue testing to determine the device's compressive fatigue strength, wear, and durability. Biomechanical testing, using human cadaveric lumbar spines, was also conducted to determine the ability of the device to restore multidirectional segmental flexibility and to determine its resulting endplate contact stress.ResultsThe static compressive and shear moduli of the nucleus replacement device were determined to be between 4.2–5.6 MPa and 1.4–1.9 MPa, respectively. Similarly, the ultimate compressive and shear strength were 12,400 N and 6,993 N, respectively. The maximum axial compressive fatigue strength of the tested device that was able to withstand a runout without failure was determined to be approximately 3 MPa. The wear assessment determined that the device is durable and yielded minimal wear rates of 0.29mg/Mc. Finally, the biomechanical testing demonstrated that the device can restore the multidirectional segmental flexibility to a level seen in the intact condition while concurrently producing a uniform endplate contact stress.ConclusionsThe results of the present study provided a mechanical justification supporting the clinical use of the nucleus replacement device and also help explain and support the positive clinical results obtained from two European studies and one US pilot study.Clinical RelevanceNucleus replacement devices are rapidly emerging to address specific conditions of degenerative disc disease. Preclinical testing of such devices is paramount in order to potentially ensure successful clinical outcomes post implantation

Purpose: The histogram analysis in radiation therapy (HART) software has been widely used for the research in intensity modulation radiation therapy (IMRT) treatments in cancer. The common application of HART is the precise and efficient dose volume histogram (DVH) analysis of structures in IMRT plans as presented earlier (Med Phys.35(6), p.2812 (2008)). The tool has been further developed with additional features, such as multi‐dimensional dose histogram (MDH) computational module, dose response modeling (DRM) and plan‐specific outcome analysis (POA) features. Methods and Materials: Matlab based codes were designed to read RTOG data formats exported from the Pinnacle3 treatment planning system (TPS; Philips Healthcare, Best, Netherlands), and to write into a simpler HART format. HART computes the MDH differential data utilizing the information on the raw dose values and the co‐ordinates of the primary dose grids for a given structure in the TPS. The DRM utilizes the polynomial models for cumulative DVH in order to simulate the optimal dose response models for structures. The POA feature can also be used for evaluations of IMRT plans using various biological modeling. DVH analysis results extracted by HART, can also be exported into customizable output formats. Results: HART offers MDH computational capability, DRM simulations, a simpler POA feature, and the DVH analysis module for IMRT plans. MDH computations and DRM simulations for an IMRT plan were accomplished relatively in 15–30 minutes with the clock speed of 1.8 GHz and 2 GB RAM support. The MDH and DVH analysis results were validated with the Pinnacle3 data. Conclusions: Several applications have been incorporated into a simpler, user‐friendly, and automated software package (HART). We have also implemented an open‐source mechanism for various users. We expect to develop HART for various applications in radiotherapy research, and its expansion to other TPSs. This work was partially supported by NIH/NIDCD grant.

There is significant loss of activity observed during radioembolization, which can have a major dosimetric impact. The total administered activity and the number of split injections during radioembolization are the main influencing factors. Further prospective studies as well as measures of clinical outcome are warranted.

Purpose: The purpose of this project was to develop dose‐volume histogram (DVH) analysis software that can be used for research with a large quantity of patient data in radiation therapy. Currently, the software converts RTOG output files from the Pinnacle treatment planning system (TPS) (Philips Healthcare, Best, Netherlands) into DVH analyzed data for all structures involved in the IMRT plans. Method and Materials: IMRT patient data to be analyzed were exported into RTOG format files from the TPS. RTOG files, with differential DVH information, were read and transformed into cumulative DVH data. Matlab (The Mathworks Inc, Natick, MA) based codes were developed to identify all the target and normal structure volumes, and treatment planning parameters in RTOG formats. The software utilized the CERR (Washington University at St. Louis) and standard DICOM image manipulation tools. The DVH analysis was based on a cosine interpolation numerical analysis technique; and the uncertainty in data interpolation was controlled by using piecewise polynomial fittings in DVH curves. The accuracy of DVH analysis was compared with TPS produced DVHs and evaluated with a 4‐mm resolution. Results: The execution time for fully automated DVH analysis of all organs in the IMRT plan was typically 10 minutes per patient data with the clock speed of 1.8 GHz and 1024 MB RAM. The normalized root mean square deviation (NRMSD) was less than 1% for all DVHs except in the high dose gradient slope regions (<2% NRMSD). Conclusion: A DVH analysis software system has been developed that can be efficiently used for research requiring the handling of a large number of structures or patient data. More user‐friendly features of dose and volume selections, expansion to other TPSs, and statistical indices are under development. The software will be available to the radiation oncology community in the future.