Biomechanical analysis of the effect of ‘intermediate screws’ in short segment posterior fixation of unstable burst fractures of thoracolumbar spine in calf spine model

Background: Efforts in preserving motion levels in unstable thoracolumbar burst fractures steered to short segment fixation. However, short segment spanning fixation in clinical scenario reported high failure rates.  Augmentation of spanning fixation by inserting intermediate screws into the fracture level is proposed to enhance stability. An experimental comparative study was performed to assess the biomechanical role of the ‘intermediate screws.’ Methods: Five calf spine specimens were freshly prepared to record the biomechanical characteristics, range of motion (ROM), and stiffness. CT scan confirmed an unstable burst fracture in each specimen. Each specimen was instrumented with short-segment posterior fixation with an intermediate screw. The same test protocols were repeated with and without intermediate screws. Results: Intermediate screws contribute to 20.2%, 16.5%, 14.5% and 23% decrease in ROM and 15.4%, 25.6%, 48.3%, and 160.2% increase in construct stiffness. Conclusions: Intermediate screws significantly increase the construct stiffness and decrease the ROM. 

Effects of metal implants and validation of four treatment planning methods used for radiotherapy dose calculation

Background: The radiotherapy treatment planning process involves target delineation and dose calculation, both of which directly depend on image quality and Hounsfield unit (HU) accuracy of computed tomography (CT) images. CT images of patients having metal implants undergo image quality deterioration and show inaccurate HU values due to various artifacts. Metal artifact reduction (MAR) is used to improve the image quality. In this study, four treatment planning methods with and without MAR, in combination with actual and assigned HU values, were analyzed for dose calculation accuracy. The aim was to study the effects of metal implants on planning CT and to evaluate the dose calculation accuracy of four treatment planning methods for radiotherapy. Materials and methods: Two phantoms with six different metal inserts were scanned in the extended HU mode, with and without MAR. Geometry verification and HU analysis of the metals and the surrounding region were carried out. Water equivalent distance (WED) measurements and dose calculation for each metal insert were done in the treatment planning system (TPS) using the anisotropic analytical algorithm (AAA). Point dose and two-dimensional dose distribution were studied. Percentage variation analysis between calculated and measured doses and gamma evaluation were conducted to determine the most suitable method for treatment planning. Conclusion: This study concludes that an MARCT image with an assigned HU similar to that of the metal implant is better for contouring and high dose calculation accuracy. If MAR is not available, the actual HU value from the extended HU CT for the metal should be used for dose calculation

The “Skipped Segment Screw” Construct: An Alternative to Conventional Lateral Mass Fixation–Biomechanical Analysis in a Porcine Cervical Spine Model

Study DesignCadaveric biomechanical study.PurposeWe compared the “skipped segment screw” (SSS) construct with the conventional “all segment screw” (ASS) construct for cervical spine fixation in six degrees of freedom in terms of the range of motion (ROM).Overview of LiteratureCurrently, no clear guidelines are available in the literature for the configuration of lateral mass (LM) screwrod fixation for cervical spine stabilization. Most surgeons tend to insert screws bilaterally at all segments from C3 to C6 with the assumption that implants at every level will provide maximum stability.MethodsSix porcine cervical spine specimens were harvested from fresh 6–9-month-old pigs. Each specimen was sequentially tested in the following order: intact uninstrumented (UIS), SSS (LM screws in C3, C5, and C7 bilaterally), and ASS (LM screws in C3–C7 bilaterally). Biomechanical testing was performed with a force of 2 Nm in six degrees of freedom and 3D motion tracking was performed.ResultsThe two-tailed paired t-test was used for statistical analysis. There was a significant decrease in ROM in instrumented specimens compared with that in UIS specimens in all six degrees of motion (p<0.05), whereas there was no significant difference in ROM between the different types of constructs (SSS and ASS).ConclusionsBecause both configurations provide comparable stability under physiological loading, we provide a biomechanical basis for the use of SSS configuration owing to its potential clinical advantages, such as relatively less bulk of implants within a small operative field, relative ease of manipulating the rod into position, shorter surgical time, less blood loss, lower risk of screw-related complications, less implant-related costs, and most importantly, no compromise in the required stability needed until fusion

Analyzing the characteristics of 6 MV photon beam at low monitor unit settings

Analyzing the characteristics of a low monitor unit (MU) setting is essential, particularly for intensity-modulated techniques. Intensity modulation can be achieved through intensity-modulated radiotherapy (IMRT) or volumetric-modulated arc therapy (VMAT). There is possibility for low MUs in the segments of IMRT and VMAT plans. The minimum MU/segment must be set by the physicist in the treatment planning system at the time of commissioning. In this study, the characteristics such as dose linearity, stability, flatness, and symmetry of 6 MV photon beam of a Synergy linear accelerator at low MU settings were investigated for different dose rates. The measurements were performed for Synergy linear accelerator using a slab phantom with a FC65-G chamber and Profiler 2. The MU linearity was studied for 1–100 MU using a field size of 10 cm ×10 cm. The linearity error for 1 MU was 4.2%. Flatness of the beam was deteriorated in 1 MU condition. The beam stability and symmetry was well within the specification. Using this study, we conclude that the treatment delivered with <3 MU may result in uncertainty in dose delivery. To ensure the correct dose delivery with less uncertainty, it is recommended to use ≥3 MU as the minimum MU per segment in IMRT and VMAT plans

National conference on Nanomaterials for Environmental [NCNER-2015] Preparation and characterization of Kidney stone phantom with its flexural strength studies

Abstract : Kidney stone phantoms were prepared using commercially available material called Begostone. Prepared stone types were characterized using X-Ray Diffraction( XRD) and Fourier Transform Infrared Spectroscopy (FTIR). Characterization results provides the structural properties and particular functional groups.Flexural strength analysis were done in an Universal Testing Machine (UTM). This study will help in optimizing the treatment parameters of shockwave lithotripsy and other similar non-invasive techniques

Comparative analysis of volumetric-modulated arc therapy and intensity-modulated radiotherapy for base of tongue cancer

The aim of this study was to compare the various dosimetric parameters of dynamic multileaf collimator (MLC) intensity modulated radiation therapy (IMRT) plans with volumetric modulated arc therapy (VMAT) plans for base of tongue cases. All plans were done in Monaco planning system for Elekta synergy linear accelerator with 80 MLC. IMRT plans were planned with nine stationary beams, and VMAT plans were done for 360° arc with single arc or dual arc. The dose to the planning target volumes (PTV) for 70, 63, and 56 Gy was compared. The dose to 95, 98, and 50% volume of PTV were analyzed. The homogeneity index (HI) and the conformity index (CI) of the PTV 70 were also analyzed. IMRT and VMAT plan showed similar dose coverage, HI, and CI. Maximum dose and dose to 1-cc volume of spinal cord, planning risk volume (PRV) cord, and brain stem were compared. IMRT plan and VMAT plan showed similar results except for the 1 cc of PRV cord that received slightly higher dose in VMAT plan. Mean dose and dose to 50% volume of right and left parotid glands were analyzed. VMAT plan gave better sparing of parotid glands than IMRT. In normal tissue dose analyses VMAT was better than IMRT. The number of monitor units (MU) required for delivering the good quality of the plan and the time required to deliver the plan for IMRT and VMAT were compared. The number of MUs for VMAT was higher than that of IMRT plans. However, the delivery time was reduced by a factor of two for VMAT compared with IMRT. VMAT plans yielded good quality of the plan compared with IMRT, resulting in reduced treatment time and improved efficiency for base of tongue cases

Influence of increment of gantry angle and number of arcs on esophageal volumetric modulated arc therapy planning in Monaco planning system: A planning study

The objective of this study was to analyze the influence of the increment of gantry angle and the number of arcs on esophageal volumetric modulated arc therapy plan. All plans were done in Monaco planning system for Elekta Synergy linear accelerator with 80 multileaf collimator (MLC). Volumetric modulated arc therapy (VMAT) plans were done with different increment of gantry angle like 15 o , 20 o , 30 o and 40 o . The remaining parameters were similar for all the plans. The results were compared. To compare the plan quality with number of arcs, VMAT plans were done with single and dual arc with increment of gantry angle of 20 o . The dose to gross tumor volume (GTV) for 60 Gy and planning target volume (PTV) for 48 Gy was compared. The dosimetric parameters D 98% , D 95% , D 50% and D max of GTV were analyzed. The homogeneity index (HI) and conformity index (CI) of GTV were studied and the dose to 98% and 95% of PTV was analyzed. Maximum dose to spinal cord and planning risk volume of cord (PRV cord) was compared. The Volume of lung receiving 10 Gy, 20 Gy and mean dose was analyzed. The volume of heart receiving 30 Gy and 45 Gy was compared. The volume of normal tissue receiving greater than 2 Gy and 5 Gy was compared. The number of monitor units (MU) required to deliver the plans were compared. The plan with larger increment of gantry angle proved to be superior to smaller increment of gantry angle plans in terms of dose coverage, HI, CI and normal tissue sparing. The number of arcs did not make any difference in the quality of the plan

In vitro and In vivo study on the effect of Scoparia Dulcis in inhibiting the growth of urinary crystals.

Urolithiasis is a very common and highly recurring painful disease both in developing and developed nations due to the change in lifestyle and food habits. Scoparia Dulcis is herbal plant which has been used as a traditional medicine for dissolving urinary stones by the tribal group of people in Western Ghats, India. This experimental study gives a scientific awareness about the effect of Scoparia Dulcis in dissolving the urinary crystals and will confirm the drug’s effect on the organs like kidney and liver. The invitro testing was done by developing urinary crystals using single diffusion gel growth technique and the water extract of the drug is incorporated to monitor the growth of the crystal. The statistical analysis was done for the in vitro study and has proved 2ml dosage shows the highest significance in variation. In invivo testing, the urinary crystals were induced in Wistar Rats and the drug was fed to monitor its effect on the growth of crystals as well as on nearby organs.  The urine and serum samples were tested for all the group of rats and parameters analysis proved the significance of the drug. The histopathology analysis gives the sectional view and report of diseased and treated groups. In both the invitro as well as invivo testing, the drug showed a significant effect in inhibiting the growth of urinary crystals

Verification of dosimetric commissioning accuracy of intensity modulated radiation therapy and volumetric modulated arc therapy delivery using task Group-119 guidelines

Aim: The purpose of this study is to verify the accuracy of the commissioning of intensity-modulated radiation therapy (IMRT) and volumetric-modulated arc therapy (VMAT) based on the recommendation of the American Association of Physicists in Medicine Task Group 119 (TG-119). Materials and Methods: TG-119 proposes a set of clinical test cases to verify the accuracy of IMRT planning and delivery system. For these test cases, we generated two sets of treatment plans, the first plan using 7–9 IMRT fields and a second plan utilizing two-arc VMAT technique for both 6 MV and 15 MV photon beams. The template plans of TG-119 were optimized and calculated by Varian Eclipse Treatment Planning System (version 13.5). Dose prescription and planning objectives were set according to the TG-119 goals. The point dose (mean dose to the contoured chamber volume) at the specified positions/locations was measured using compact (CC-13) ion chamber. The composite planar dose was measured with IMatriXX Evaluation 2D array with OmniPro IMRT Software (version 1.7b). The per-field relative gamma was measured using electronic portal imaging device in a way similar to the routine pretreatment patient-specific quality assurance. Results: Our planning results are compared with the TG-119 data. Point dose and fluence comparison data where within the acceptable confident limit. Conclusion: From the obtained data in this study, we conclude that the commissioning of IMRT and VMAT delivery were found within the limits of TG-119