Evaluation of heterogeneity dose distributions for Stereotactic Radiotherapy (SRT): comparison of commercially available Monte Carlo dose calculation with other algorithms

<p>Abstract</p> <p>Background</p> <p>The purpose of this study was to compare dose distributions from three different algorithms with the x-ray Voxel Monte Carlo (XVMC) calculations, in actual computed tomography (CT) scans for use in stereotactic radiotherapy (SRT) of small lung cancers.</p> <p>Methods</p> <p>Slow CT scan of 20 patients was performed and the internal target volume (ITV) was delineated on Pinnacle³. All plans were first calculated with a scatter homogeneous mode (SHM) which is compatible with Clarkson algorithm using Pinnacle³treatment planning system (TPS). The planned dose was 48 Gy in 4 fractions. In a second step, the CT images, structures and beam data were exported to other treatment planning systems (TPSs). Collapsed cone convolution (CCC) from Pinnacle³, superposition (SP) from XiO, and XVMC from Monaco were used for recalculating. The dose distributions and the Dose Volume Histograms (DVHs) were compared with each other.</p> <p>Results</p> <p>The phantom test revealed that all algorithms could reproduce the measured data within 1% except for the SHM with inhomogeneous phantom. For the patient study, the SHM greatly overestimated the isocenter (IC) doses and the minimal dose received by 95% of the PTV (PTV95) compared to XVMC. The differences in mean doses were 2.96 Gy (6.17%) for IC and 5.02 Gy (11.18%) for PTV95. The DVH's and dose distributions with CCC and SP were in agreement with those obtained by XVMC. The average differences in IC doses between CCC and XVMC, and SP and XVMC were -1.14% (p = 0.17), and -2.67% (p = 0.0036), respectively.</p> <p>Conclusions</p> <p>Our work clearly confirms that the actual practice of relying solely on a Clarkson algorithm may be inappropriate for SRT planning. Meanwhile, CCC and SP were close to XVMC simulations and actual dose distributions obtained in lung SRT.</p

Impact of lifestyle and psychosocial factors on the onset of hypertension after the Great East Japan earthquake: a 7-year follow-up of the Fukushima Health Management Survey

Natural disasters force many evacuees to change several aspects of their lifestyles. This longitudinal study aimed to investigate whether factors such as living environment and lifestyle factors were related to new-onset hypertension in survivors of the Great East Japan Earthquake over a long-term follow-up of up to 7 years after the earthquake. The present study examined data collected from 29,025 Japanese participants aged 39-89 years, sourced from general health checkups and the Fukushima Mental Health and Lifestyle Survey, which was conducted in 13 communities between 2011 and 2018. A total of 10,861 participants received follow-up examinations. During a median follow-up of 4.3 years, 3744 participants (1588 men, 41.4%; 2,156 women, 30.7%) had newly developed hypertension. Heavy drinking (adjusted hazard ratio 1.38, 95% confidence interval 1.21-1.57, p < 0.001) and obesity (adjusted hazard ratio 1.27, 95% confidence interval 1.19-1.37, p < 0.001) were significantly associated with new-onset hypertension after the disaster in multivariate-adjusted analysis. Furthermore, experiencing evacuation after the disaster was also significantly associated with the risk of new-onset hypertension in men (adjusted hazard ratio 1.14, 95% confidence interval 1.02-1.27, p = 0.016). The present study indicated that lifestyle factors, such as drinking and obesity, and evacuation experience in men had significant effects on the risk of new-onset hypertension in the long term after the earthquake

Corticospinal tract-sparing intensity-modulated radiotherapy treatment planning

AimTo establish intensity-modulated radiotherapy (IMRT) planning procedures that spare the corticospinal tract by integrating diffusion tensor tractography into the treatment planning software.BackgroundOrgans at risk are generally contoured according to the outline of the organ as demonstrated by CT or MRI. But a part of the organ with specific function is difficult to protect, because such functional part of the organ cannot be delineated on CT or conventional sequence of MRI.MethodsDiagnostic and treatment planning images of glioblastoma patients who had been treated by conventional 3-dimensional conformal radiotherapy were used for re-planning of IMRT. Three-dimensional fiber maps of the corticospinal tracts were created from the diffusion tensors obtained from the patients before the surgery, and were blended with the anatomical MR images (i.e. gadolinium-enhanced T1-weighted images or T2-weighted images). DICOM-formatted blended images were transferred and fused to the planning CT images. Then, IMRT plans were attempted.ResultsThe corticospinal tracts could be contoured as organs at risk (OARs), because the blended images contained both anatomical information and fiber-tract maps. Other OARs were contoured in a way similar to that of ordinary IMRT planning. Gross tumor volumes, clinical target volumes, planning target volumes, and other OARs were contoured on the treatment planning software, and IMRT plans were made.ConclusionsIMRT plans with diminished doses to the corticospinal tract were attained. This technique enabled us to spare specific neuron fibers as OARs which were formerly “invisible” and to reduce the probability of late morbidities