ResearchPad - Radiation https://www.researchpad.co Default RSS Feed en-us © 2020 Newgen KnowledgeWorks <![CDATA[LabBM Score and Extracranial Score As New Tools for Predicting Survival in Patients with Brain Metastases Treated with Focal Radiotherapy]]> https://www.researchpad.co/product?articleinfo=N4bb910af-261d-42ca-8a99-ebe0e7e39fff

Background

Two recently validated, untraditional prognostic scores include serum albumin and lactate dehydrogenase, among other parameters. The latter are hemoglobin, platelet counts, and C-reactive protein (three-tiered LabBM score), whereas the four-tiered extracranial score includes more than one extracranial site of metastatic involvement. Until now, head-to-head comparisons of these two scores in patients treated with focal radiotherapy for newly diagnosed brain metastases are not available.

Methods

This was a retrospective single-institution analysis of 51 patients, most of whom were managed with first-line stereotactic radiosurgery (SRS). Survival was stratified by the LabBM score and extracranial score.

Results

Both scores predicted survival, but the analyses were hampered by small subgroups. In particular, very few patients belonged to the unfavorable groups. Survival shorter than two months, which was recorded in 14%, was not well predicted by the LabBM score and extracranial score.

Conclusions

Very few patients treated with focal radiotherapy (largely SRS) had unfavorable prognostic features according to the two untraditional scores, which do not include the number of brain metastases and performance status. Additional research is needed to improve the tools that predict short survival because overtreatment during the terminal phase of metastatic disease continues to represent a relevant issue.

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<![CDATA[Dosimetric Limitations in Treating Breast Cancer with Accelerated Partial Breast Irradiation Using Strut Adjusted Volume Implant (SAVI)]]> https://www.researchpad.co/product?articleinfo=Nfbcfedd9-2f97-4fed-b16f-b36b4a42bd0b

We present one case of accelerated partial breast irradiation (APBI) using strut adjusted volume implant (SAVI) where there were limitations in delivering the dose as per the standard guidelines. The device was placed close to both the chest wall and the skin with little tissue surrounding the tip. Two plans were made in an attempt to achieve the standard therapeutic doses without over-treating the chest wall or the skin. Similar cases reported in the literature were reviewed. The dosimetry of the two plans was compared to the cases discussed in the literature.

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<![CDATA[Patient satisfaction with doctor-patient interaction in a radiotherapy centre during the severe acute respiratory syndrome outbreak]]> https://www.researchpad.co/product?articleinfo=N77fbb8ff-94f0-46dc-9228-7cae9ebc5bf1

Summary

An outpatient radiotherapy department assessed how precautions implemented during the severe acute respiratory syndrome (SARS) outbreak affected patient satisfaction with doctor–patient interaction and explored variables potentially influencing satisfaction. The information obtained would help prepare us for future infectious disease outbreaks. Outpatients seen during the outbreak completed a validated questionnaire assessing satisfaction with doctor–patient interaction. Additional items assessed included patients’ perception of SARS measures and patient demographics. Of 149 patients, 97% had heard of SARS, 92% believed SARS precautions necessary, and 54% believed contracting SARS was possible despite the precautions. Patients were satisfied with doctors wearing masks (97%), temperature checks (97%), and patients wearing masks (96%). Despite the high satisfaction levels with SARS precautions, 24% believed it had adversely affected doctor–patient interaction. With regards to doctor–patient interaction, 94% of patients were satisfied. Patients were most satisfied with the ‘information exchange’ domain (mean score 3.23 out of 4) compared to other domains (P < 0.0001, 100.00% confidence) and were less satisfied with the ‘empathy’ domain compared to other domains (P < 0.0001, 100.00% confidence). Patients were most satisfied with understanding their treatment plan (100%), doctor being honest (97%) and being understood (96%). Patients were least satisfied with information about caring for their illness (61%), that the visit could be better (59%), and the doctor showing more interest (58%). On multivariate analysis, patients who were less satisfied with SARS measures were significantly less satisfied with doctor–patient interaction (P = 0.0001). Dissatisfaction with SARS measures was associated with significant dissatisfaction for questions in all domains. Older age and non‐breast cancer patients were also less satisfied with doctor–patient interaction. Most (94%) of patients were satisfied with doctor–patient interaction, despite implementation of infectious disease prevention measures. However, patients who were dissatisfied with the SARS precautions had poorer satisfaction. In particular, physician empathy appeared to be most adversely affected. The results have relevance to any radiotherapy department preparing contingency plans in the event of infectious disease outbreaks.

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<![CDATA[Plasma Proteins as Biomarkers of Mortality After Total Body Irradiation in Mice]]> https://www.researchpad.co/product?articleinfo=N030eafab-bd4f-4230-9a64-dc5b3a0dce5a

During large-scale acute radiation exposure, rapidly distinguishing exposed individuals from nonexposed individuals is necessary. Identifying those exposed to high and potentially lethal radiation doses, and in need of immediate treatment, is especially important. To address this and find plasma biomarkers to assess ionizing radiation-induced mortality in the early stages, mice were administered a whole-body lethal dose of γ radiation, and radiation-induced damage was evaluated. Multiple blood biomarkers were screened using an antibody array, followed by validation using enzyme-linked immunoassay. The results revealed that irradiation (IR)-induced mortality in mice and caused body weight and blood platelet losses in deceased mice compared to surviving mice. The levels of certain proteins differed after IR between these 2 groups. Specific proteins in preirradiated mice were also found to potentiate radiosensitivity. Plasma levels of interleukin (IL)-22, urokinase, resistin, and IL-6 were associated with radiation-induced mortality in irradiated mice and may be useful as potential mortality predictors. Our results suggest that estimating the levels of certain plasma proteins is a promising alternative to conventional cytogenetic biodosimetry to accurately identify individuals exposed to high radiation doses and those at risk of death due to exposure. This strategy would facilitate the rapid triage of individuals requiring immediate and intensive medical treatment.

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<![CDATA[Screening of Long Noncoding RNAs Induced by Radiation Using Microarray]]> https://www.researchpad.co/product?articleinfo=Nb49b86ca-30c2-4975-81d2-b9504bc4a4af

DNA damage repair and G2/M arrest are the key factors regulating the survival of cancer cells exposed to radiation. Recent studies have shown that long noncoding RNAs (lncRNAs) play important roles in a variety of biological processes, including DNA repair, cell cycle regulation, differentiation, and epigenetic regulation. However, the knowledge about the genome scale of lncRNAs and their potential biological functions in tumor cells exposed to radiation are still unclear. In this study, we used LncRNA + mRNA Human Gene Expression Microarray V4.0 to profile lncRNA and messenger RNA (mRNA) from HeLa, MCF-7, and A549 cells after irradiation with 4 Gy of γ-radiation. We identified 230, 227, and 274 differentially expressed lncRNAs and 150, 214, and 274 differentially expressed mRNAs in HeLa, MCF-7, and A549 cells, respectively, among which there are 14 common differentially expressed lncRNAs and 22 common differentially expressed mRNAs in all of the 3 cell lines. Gene Ontology and Kyoto Encyclopedia of Genes and Genomes pathway analysis indicated that these differentially expressed mRNAs were mainly associated with cell cycle. Further, we also predicted the target genes and functions of these differentially expressed lncRNAs. Our study on lncRNAs has greatly expanded the field of gene research in the relationship of radiation, cell cycle, and DNA damage.

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<![CDATA[Risk of stomach cancer incidence in a cohort of Mayak PA workers occupationally exposed to ionizing radiation]]> https://www.researchpad.co/product?articleinfo=Nb5246167-3f67-43a4-8a84-93c6a22ed7ff

Stomach cancer is a widespread health condition associated with environmental and genetic factors. Contribution of ionizing radiation to stomach cancer etiology is not sufficiently studied. This study was aimed to assess an association of the stomach cancer incidence risk with doses from occupational radiation exposure in a cohort of workers hired at main Mayak production association facilities in 1948–1982 taking into account non-radiation factors including digestive disorders. The study cohort comprised 22,377 individuals and by 31.12.2013 343 stomach cancer diagnoses had been reported among the cohort members. Occupational stomach absorbed doses were provided by the Mayak Worker Dosimetry System– 2008 (MWDS–2008) for external gamma ray exposure and by the Mayak Worker Dosimetry System– 2013 (MWDS–2013) for internal exposure to plutonium. Excess relative risks (ERR) per Gy for stomach cancer were estimated using the Poisson’s regression. Analyses were run using the AMFIT module of the EPICURE software. The stomach cancer incidence risk in the study cohort was found to be significantly associated with the stomach absorbed dose of gamma rays: ERR/Gy = 0.19 (95% CI: 0.01, 0.44) with a 0 year lag, and ERR/Gy = 0.20 (95% CI: 0.01, 0.45) with a 5 year lag. To estimate the baseline risk, sex, attained age, smoking status and alcohol consumption, chronic diseases (peptic ulcer, gastritis and duodenitis) were taken into account. No modifications of the radiogenic risk by non-radiation factors were found in the study worker cohort. No association of the stomach cancer incidence risk with internal exposure to incorporated plutonium was observed.

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<![CDATA[Assessing the effects of intratendinous genipin injections: Mechanical augmentation and spatial distribution in an ex vivo degenerative tendon model]]> https://www.researchpad.co/product?articleinfo=N537496c4-2c39-41e6-9ca3-002a318b88b6

Background

Tendinopathy is a common musculoskeletal disorder and current treatment options show limited success. Genipin is an effective collagen crosslinker with low cytotoxicity and a promising therapeutic strategy for stabilizing an intratendinous lesion.

Purpose

This study examined the mechanical effect and delivery of intratendinous genipin injection in healthy and degenerated tendons.

Study design

Controlled laboratory study

Methods

Bovine superficial digital flexor tendons were randomized into four groups: Healthy control (N = 25), healthy genipin (N = 25), degenerated control (N = 45) and degenerated genipin (N = 45). Degeneration was induced by Collagenase D injection. After 24h, degenerated tendons were subsequently injected with either 0.2ml of 80mM genipin or buffer only. 24h post-treatment, samples were cyclically loaded for 500 cycles and then ramp loaded to failure. Fluorescence and absorption assays were performed to analyze genipin crosslink distribution and estimate tissue concentration after injection.

Results

Compared to controls, genipin treatment increased ultimate force by 19% in degenerated tendons (median control 530 N vs. 633 N; p = 0.0078). No significant differences in mechanical properties were observed in healthy tendons, while degenerated tendons showed a significant difference in ultimate stress (+23%, p = 0.049), stiffness (+27%, p = 0.037), work to failure (+42%, p = 0.009), and relative stress relaxation (-11%, p < 0.001) after genipin injection. Fluorescence and absorption were significantly higher in genipin treated tendons compared to control groups. A higher degree of crosslinking (+45%, p < 0.001) and a more localized distribution were observed in the treated healthy compared to degenerated tendons, with higher genipin tissue concentrations in healthy (7.9 mM) than in degenerated tissue (2.3 mM).

Conclusion

Using an ex-vivo tendinopathy model, intratendinous genipin injections recovered mechanical strength to the level of healthy tendons. Measured by genipin tissue distribution, injection is an effective method for local delivery.

Clinical relevance

This study provides a proof of concept for the use of intratendinous genipin injection in the treatment of tendinopathy. The results demonstrate that a degenerated tendon can be mechanically augmented by a clinically viable method of local genipin delivery. This warrants further in vivo studies towards the development of a clinically applicable treatment based on genipin.

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<![CDATA[Effect of internal surface structure of the north wall on Chinese solar greenhouse thermal microclimate based on computational fluid dynamics]]> https://www.researchpad.co/product?articleinfo=Nf5b70015-c0ce-4e08-9dc5-5525c2c91d69

Chinese solar greenhouses are unique facility agriculture buildings and widely used in northeastern China, providing a favorable requirement for crop growth. The north wall configurations play an essential role in heat storage and thermal insulation and directly affect the management of the internal environment. This research is devoted to further improve the thermal performance of the greenhouse and explore the potential of the north wall. A mathematical model was designed to investigate the concave-convex wall configurations based on computational fluid dynamics. Four passive heat-storage north walls were analyzed by using the same constituent materials, including a plane wall, a vertical wall, a horizontal wall and an alveolate wall. The numerical model was validated by experimental measurements. The temperature distributions of the north walls were examined and a comparative analysis of the heat storage-release capabilities was carried out. The results showed that the heat-storage capacity of the north wall is affected by the surface structure. Moreover, the critical factor influencing the air temperature is the sum of the heat load released by the wall and the energy increment of greenhouse air. The results suggested that the alveolate wall has preferable thermal accumulation capacity. The concave-convex wall configurations have a wider range of heat transfer performance along the thickness direction, while the plane wall has a superior thermal environment. This study provides a basic theoretical reference to rationally design the internal surface structures of the north wall.

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<![CDATA[Treatment for Recurrent Differentiated Thyroid Cancer: A Canadian Population Based Experience]]> https://www.researchpad.co/product?articleinfo=N15678ebf-6297-4a51-a41e-1a807c5b8844

Introduction: Management of recurrent differentiated thyroid cancer (DTC) may include surgery, radioactive iodine (RAI), and external beam radiotherapy (EBRT). Systemic therapy may also be offered for RAI-refractory DTC. The study objective was to review patterns of practice in British Columbia (BC) for treatment of recurrent DTC, assess rates of RAI-refractory disease, and evaluate outcomes.

Methods: BC Cancer provides cancer care to a population of 4.6 million. A retrospective review of all patients with DTC stage I-IVB disease referred to BC Cancer from 2009 to 2013 was conducted. Patient and DTC characteristics, locoregional and distant recurrence, surgical management, RAI, EBRT, and systemic therapy details were retrospectively collected. Relapse-free survival (RFS), overall survival (OS), and disease-specific survival (DSS) were calculated using the Kaplan-Meier method.

Results/Discussion: Some 1062 DTC patients were identified. Median follow-up was 4.1 years. Baseline characteristics: female 74%, median age 50, papillary/follicular/Hurthle cell 92%/6%/2%. Stage at presentation: I 60%, II 8%, III 22%, IVA/IVB 10%. Locoregional and/or distant recurrence occurred in 136 patients (13%). Locoregional recurrence (n=118) was treated with surgery +/- RAI or EBRT 48%, RAI +/- EBRT 40%, EBRT alone 1%, 11% were observed without treatment. Some 27 patients had a second cancer recurrence. Some 37 patients (3%) developed distant metastatic disease and common sites of distant metastases were: lung 76%, bone 30%, and liver 8%. Some 27 cases (2%) were deemed RAI-refractory. Some six patients (0.6%) received systemic therapy with a vascular endothelial growth factor tyrosine kinase inhibitor (VEGF TKI). Five-year RFS was calculated to be 82%, OS 95%, and DSS 98% for the study population.

Conclusions: In our population-based study cohort, 87% of patients were rendered disease-free by primary disease management. Multi-modality treatment of locoregional recurrence facilitated disease-free status in the majority of patients (67%). RAI-refractory disease developed in 2% of patients and despite a significant number of metastatic recurrences, only a small number of patients received systemic therapy.

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<![CDATA[The Effect of Radiation Emitted by Cell Phone on The Gelatinolytic Activity of Matrix Metalloproteinase-2 and -9 of Mouse Pre-Antral Follicles during In Vitro Culture]]> https://www.researchpad.co/product?articleinfo=Na598245b-3479-495e-879f-2104840c51ec

Objective

The unfavorable effects of electromagnetic radiation (EMR) emitted by the cell phone on reproduction health are controversial. Metalloproteinases play a vital role in ovarian follicle development. This study was designed to investigate the effects of exposure to the cell phone on the gelatinolytic activity of in vitro cultured mouse pre-antral follicle.

Materials and Methods

In this experimental study, pre-antral follicles were isolated from ovaries of immature mice (n=16) and cultured with or without exposure to the cell phone in talking mode for 60 minutes. The gelatinolytic activity was evaluated through the zymography method, as well as the gene expression of matrix metalloproteinases (MMPs) namely MMP-2 and -9 and tissue inhibitors of metalloproteinases (TIMPs) namely, TIMP-1 and -2 by the real-time polymerase chain reaction (PCR) method. Also, in parallel, the development of pre-antral follicles was assessed.

Results

The maturation parameters of the cell phone-exposed pre-antral follicles were significantly lower compared with the control group (P<0.05). The gelatinolytic activity was significantly decreased in the cell phone-exposed pre- antral follicles compared with the control group (P<0.05). The relative mRNA expression of the MMP-2 gene was significantly (P<0.05) increased in the cell phone-exposed pre-antral follicles whereas the expression rate of the MMP-9 gene was considerably (P<0.05) reduced when compared with the control group. Conversely, the relative expression of the TIMP-1 was markedly (P<0.05) increased in the cell phone-exposed pre-antral follicles while the expression of the TIMP-2 was (P<0.05) significantly diminished in comparison with the control group.

Conclusion

Exposure to the cell phone alters the growth and maturation rate of murine ovarian follicle through the changing in the expression of the MMP-2 and -9 genes, as well as the gelatinolytic activity.

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<![CDATA[Small Cell Carcinoma of the Prostate: A Case Report and Review of the Literature]]> https://www.researchpad.co/product?articleinfo=N658eb756-734a-4e4c-ac9a-ae7754cf31bf

Small cell carcinoma of the prostate (SCCP) is a rare malignancy that is considered a lethal entity of prostate cancer. Once it is diagnosed, patients characteristically experience an aggressive clinical course with poor overall survival rates, which unfortunately still holds even with modern treatments. In this report, we discuss the case of a 63-year-old African American male who initially presented to the hospital with an elevated prostate-specific antigen (PSA) level of 9.41 ng/mL and was found to have locally extensive SCCP. After one cycle of chemotherapy, the patient's symptoms worsened, and his disease continued to progress with an increased metastatic burden. In a matter of just a few months, the patient’s disease progressed from a locally advanced entity to a diffusely metastatic one, showcasing the true aggressive nature of this disease. Through an extensive literature review, this case report also sheds further light on SCCP's histological characteristics, its apparent differences from adenocarcinoma of the prostate, and its aggressive nature even through treatment.

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<![CDATA[Triple Head and Neck Carcinoma: Case Report and Literature Review]]> https://www.researchpad.co/product?articleinfo=N0aeae69f-d117-46dd-b556-8bf697d2d539

Synchronous cancers are multiple cancers that develop within six months of the initial diagnosis while metachronous cancers are those that develop more than six months after the initial diagnosis. A combination of three cancers is seen with several patients, which leads to a bad prognosis, and that of synchronous cancers is worse than that of metachronous cancers. Herein, we describe the case of a 62-year-old woman with multiple metachronous head and neck cancers.

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<![CDATA[Tumor Location and Treatment Modality are Associated with Overall Survival in Adult Medulloblastoma]]> https://www.researchpad.co/product?articleinfo=Nd8f9498b-81c7-4114-a5c4-a4d03f24ce88

Introduction

Medulloblastoma (MB) is an aggressive brain tumor most commonly found in children. Although prognostic factors are well studied in children, factors affecting survival in adults with medulloblastoma are unclear.

Methods

We queried the 1973-2015 United States Surveillance, Epidemiology, and End Results (SEER) registry to identify all adult cases of medulloblastoma, and performed multivariate survival analyses to assess the relationships amongst various clinical variables, including age, sex, race, tumor location, treatment modalities, and overall survival.

Results

A total of 857 patients, 20 years of age and older, with MB were identified in the SEER registry. Adult cases presented most frequently in the cerebellum (91.6%) compared to other less common regions (brain stem 3.2%, brain 2.2%, ventricle 1.8%). The overall median survival for adult MB is 60 months (SD = 94.3) and survival time is related to tumor location and course of treatment (P < 0.001). Multivariate Cox proportional hazard models showed that lesions found outside the cerebellum corresponded to worse median survival times (37 months) than those in the cerebellum (63 months) (hazard ratio 1.69, 95% CI 1.321-2.158, P = 0.001). Patients who were assigned chemotherapy had shorter survival (54 months) than those who were not (67 months) (HR 1.4515, 95% CI 1.26-1.671, P < 0.001), but receiving radiation therapy was associated with better overall survival (66 months) relative to not receiving radiation (25 months) (HR 0.581, 95% CI 0.48-0.70, P < 0.001).

Conclusions

Tumor location appears to be a significant prognostic factor for survival in adult MB. Recommended treatment regimes, likely reflective of the underlying aggressiveness of the tumor, also seem to impact survival.

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<![CDATA[Radiation Therapy as a Modality to Create Abscopal Effects: Current and Future Practices]]> https://www.researchpad.co/product?articleinfo=N5503d70a-9fd6-4a01-8bfd-8b915ba1012a

In our empathetic understanding of abscopal effect (AbE), research has shown that the immune system is stimulated by radiation, which results in the formation of an AbE. The AbE is referred to as a response from the irradiated volume. Despite the existence of key gaps in our understanding, there is an urgent need to explore what the underlying effect is. The aim of this article is to argue neurosurgeons and the healthcare practitioner's knowledge of the AbE. Our goal is to identify more gaps in our understanding of the AbE and seal other gaps as well. This study will review medical journals and bring together the most updated information related to AbEs.

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<![CDATA[Gamma Knife Surgery for Residual or Recurrent Craniopharyngioma After Surgical Resection: A Multi-institutional Retrospective Study in Japan]]> https://www.researchpad.co/product?articleinfo=Nb5de723c-c31d-4079-aa13-b1fc2c88d584

Objective

The optimal treatment for a craniopharyngioma has been controversial. Complete resection is ideal, but it has been difficult to obtain total resection in many cases because of intimate proximity to critical structures such as the optic pathway, hypothalamus, and pituitary gland. A growing number of studies have demonstrated the utility of radiosurgery in controlling residual or recurrent craniopharyngioma. However, most of them are small series. The aim of this multi-institutional study was to clarify the efficacy and safety of Gamma Knife (Elekta, Stockholm, Sweden) surgery for patients with a craniopharyngioma.

Methods

This was a multi-institutional retrospective study by 16 medical centers of the Japan Leksell Gamma Knife Society. Data on patients with craniopharyngiomas treated with Gamma Knife Surgery (GKS) between 1991 and 2013 were obtained from individual institutional review board-approved databases at each center. A total of 242 patients with craniopharyngioma were included in this study. The mean age of the patients was 41 (range, 3 to 86) years. The median follow-up time was 61.4 months (range, 3 to 180 months). The mean radiosurgery target volume was 3.1 ml (range, 0.03-22.3 ml), and the mean marginal dose was 11.4 Gy (range, 8-20.4 Gy).

Results

Two-hundred twenty patients were alive at the time of the last follow-up visit. The three-, five-, and 10-year overall survival rates after GKS were 95.4%, 92.5%, and 82.0%, respectively. The three-, five-, and 10-year progression-free survival rates after GKS were 73.1%, 62.2%, and 42.6% respectively. The rate of radiation-induced complications was 6.2%.

Conclusion

GKS is effective for controlling the tumor growth of craniopharyngiomas with an acceptable complication rate.

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<![CDATA[A phantom based evaluation of the dose prediction and effects in treatment plans, when calculating on a direct density CT reconstruction]]> https://www.researchpad.co/product?articleinfo=N87b6df23-1b4c-42cd-9fd7-5e65042ea6c9

Abstract

In radiation therapy, a Computed Tomography (CT) image is needed for an accurate dose calculation. To allow such a calculation, the CT image values have to be converted into relative electron densities. Thus, standard procedure is to calibrate the CT numbers to relative electron density (RED) by using a phantom with known composition inserts. This calibration curve is energy and CT dependent, therefore most radiotherapy CT acquisitions are obtained with 120 kVp, as each tube voltage needs an additional calibration curve. The commercially available DirectDensityTM (DD) reconstruction algorithm presents a reconstruction implementation without any dependence on the tube voltage. In comparison, it allows a calibration curve that is directly proportional to the RED, reducing the need of more than one calibration curve. This could potentially optimize CT acquisitions and reducing the dose given to the patient. Three different phantoms were used to evaluate the DirectDensityTM algorithm in simple and anthropomorphic geometries, as well as setups with metal implants. Scans with the DD algorithm were performed for 80, 100, 120, and 140 kVp. As reference a scan with the standard 120 kVp scan was used. Radiotherapy photon plans were optimized and calculated on the reference image and then transferred to the DD images, where they were recalculated. The dose distributions obtained this way were compared to the reference dose. Differences were found mainly in pure air and high density materials such as bones. The difference of the mean dose was below 0.7%, in most cases below 0.4%. No indication was found that the algorithm is corrupted by metal inserts, enabling the application for all clinical cases. This algorithm offers more variability in CT parameters for radiation therapy and thus a more personalized image acquisition with a high image quality and a lower dose exposure at a robust clinical workflow.

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<![CDATA[Evaluation of the dosimetric impact of manufacturing variations for the INTRABEAM x‐ray source]]> https://www.researchpad.co/product?articleinfo=Nbaea2992-f9ad-4189-9980-fc477cf7f7ec

Abstract

Introduction

INTRABEAM x‐ray sources (XRSs) have distinct output characteristics due to subtle variations between the ideal and manufactured products. The objective of this study is to intercompare 15 XRSs and to dosimetrically quantify the impact of manufacturing variations on the delivered dose.

Methods and Materials

The normality of the XRS datasets was evaluated with the Shapiro–Wilk test, the accuracy of the calibrated depth–dose curves (DDCs) was validated with ionization chamber measurements, and the shape of each DDC was evaluated using depth–dose ratios (DDRs). For 20 Gy prescribed to the spherical applicator surface, the dose was computed at 5‐mm and 10‐mm depths from the spherical applicator surface for all XRSs.

Results

At 5‐, 10‐, 20‐, and 30‐mm depths from the source, the coefficient of variation (CV) of the XRS output for 40 kVp was 4.4%, 2.8%, 2.0%, and 3.1% and for 50 kVp was 4.2%, 3.8%, 3.8%, and 3.4%, respectively. At a 20‐mm depth from the source, the 40‐kVp energy had a mean output in Gy/Minute = 0.36, standard deviation (SD) = 0.0072, minimum output = 0.34, and maximum output = 0.37 and a 50‐kVp energy had a mean output = 0.56, SD = 0.021, minimum output = 0.52, and maximum output = 0.60. We noted the maximum DRR values of 2.8% and 2.5% for 40 kVp and 50 kVp, respectively. For all XRSs, the maximum dosimetric effect of these variations within a 10‐mm depth of the applicator surface is ≤ 2.5%. The CV increased as depth increased and as applicator size decreased.

Conclusion

The American Association of Physicist in Medicine Task Group‐167 requires that the impurities in radionuclides used for brachytherapy produce ≤ 5.0% dosimetric variations. Because of differences in an XRS output and DDC, we have demonstrated the dosimetric variations within a 10‐mm depth of the applicator surface to be ≤ 2.5%.

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<![CDATA[Independent review of 4DCT scans used for SABR treatment planning]]> https://www.researchpad.co/product?articleinfo=Na586a5c0-c586-4a7b-b083-53a98861dbac

Abstract

Four‐dimensional computerized tomography (4DCT) is required for stereotactic ablative body radiotherapy (SABR) of mobile targets to account for tumor motion during treatment planning and delivery. In this study, we report on the impact of an image review quality assurance process performed prior to treatment planning by medical physicists for 4DCT scans used for SABR treatment. Reviews were performed of 211 4DCT scans (193 patients) over a 3‐yr period (October 2014 to October 2017). Treatment sites included lung (n = 168), kidney/adrenal/adrenal gland (n = 12), rib (n = 4), mediastinum (n = 10), liver (n = 2), T‐spine (n = 1), and other abdominal sites (n = 14). It was found that in 23% (n = 49) of cases patient management was altered due to the review process. The most frequent intervention involved patient‐specific contouring advice (n = 35 cases, 17%) including adjustment of internal target volume (ITV) margins. In 13 cases (6%) a rescan was requested due to extensive motion artifact rendering the scan inadequate for SABR treatment planning. 4DCT review by medical physicists was found to be an effective method to improve plan quality for SABR.

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<![CDATA[Dosimetric characterization of a body‐conforming radiochromic sheet]]> https://www.researchpad.co/product?articleinfo=N6e2b0172-b647-4652-abf9-081693d36373

Abstract

Purpose

A novel radiochromic PRESAGE sheet (Heuris Inc.) with 3 mm thickness has been developed as a measurement tool for 2D dosimetry. Its inherent ability to conform to irregular surfaces makes this dosimeter advantageous for patient surface dosimetry. This study is a comprehensive investigation into the PRESAGE sheet’s dosimetric characteristic, accuracy and its potential use as a dosimeter for clinical applications.

Methods

The characterization of the dosimeter included evaluation of the temporal stability of the dose linearity, reproducibility, measurement uncertainties, dose rate, energy, temperature and angular dependence, lateral response artifacts, percent depth dose curve, and 2D dose measurement. Dose distribution measurements were acquired for regular square fields on a flat and irregular surface and an irregular modulated field on the smooth surface. All measurements were performed using an Epson 11000XL high‐resolution scanner.

Results

The examined dosimeters exhibit stable linear response, standard error of repeated measurements within 2%, negligible dose rate, energy, and angular dependence. The same linear dose response was measured while the dosimeter was in contact with a heated water surface. Gamma test and histogram analysis of the dose difference between PRESAGE and EBT3 film, PRESAGE and the treatment planning system (TPS) were used to evaluate the measured dose distributions. The PRESAGE sheet dose distributions showed good agreement with EBT3 film and TPS. A discrepancy smaller than the statistical error of the two dosimeters was reported.

Conclusions

This study established a full dosimetric characterization of the PRESAGE sheets with the purpose of laying the foundation for future clinical uses. The results presented here for the comparison of this novel dosimeter with those currently in use reinforce the possibility of using this dosimeter as an alternative for irregular surface dose measurements.

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<![CDATA[Incorporating biological modeling into patient‐specific plan verification]]> https://www.researchpad.co/product?articleinfo=N2ad61a93-8453-44a5-96ef-6edb772fe984

Abstract

Purpose

Dose–volume histogram (DVH) measurements have been integrated into commercially available quality assurance systems to provide a metric for evaluating accuracy of delivery in addition to gamma analysis. We hypothesize that tumor control probability and normal tissue complication probability calculations can provide additional insight beyond conventional dose delivery verification methods.

Methods

A commercial quality assurance system was used to generate DVHs of treatment plan using the planning CT images and patient‐specific QA measurements on a phantom. Biological modeling was performed on the DVHs produced by both the treatment planning system and the quality assurance system.

Results

The complication‐free tumor control probability, P +, has been calculated for previously treated intensity modulated radiotherapy (IMRT) patients with diseases in the following sites: brain (−3.9% ± 5.8%), head‐neck (+4.8% ± 8.5%), lung (+7.8% ± 1.3%), pelvis (+7.1% ± 12.1%), and prostate (+0.5% ± 3.6%).

Conclusion

Dose measurements on a phantom can be used for pretreatment estimation of tumor control and normal tissue complication probabilities. Results in this study show how biological modeling can be used to provide additional insight about accuracy of delivery during pretreatment verification.

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