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Clinical Radiology Sep 2019To evaluate the effect of modification of dose mode and frame rate on patient radiation dose during modified barium swallow (MBS) examinations.
AIM
To evaluate the effect of modification of dose mode and frame rate on patient radiation dose during modified barium swallow (MBS) examinations.
MATERIALS AND METHODS
A retrospective review was undertaken of consecutive MBS examinations performed over 6 months in the inpatient setting. Patients were divided into two cohorts: pre-implementation of the MBS Impairment Profile (MBSImP; low rate, normal dose) and post-implementation (high rate, low dose). Prior to implementation, pulse rate and dose testing were performed on multiple phantoms.
RESULTS
Four hundred and forty-nine patients were included in the pre-implementation cohort and 378 in the post-implementation cohort. Phantom dose testing demonstrated no significant difference in dose on either phantom between low rate/normal dose and high rate/low dose modes. Prior to MBS standardisation, the mean radiation dose was 5.86 (±4.35) mGy. Following standardisation, the mean radiation dose was 4.72 (±3.77) mGy (p<0.0001). The mean fluoroscopy time for MBS prior to standardisation was 83.8 (±44.4) seconds and the mean fluoroscopy time for MBS after standardisation was 82.3 (±39.8) seconds (p=0.62). The dose rate for MBS prior to standardisation was 4.35 (±2.42) and the dose rate for MBS after standardisation was 3.55 (±2.41) mGy/s (p<0.0001).
CONCLUSION
Adjustments made to lower the dose mode and the increase in fluoroscopy frame rate decreased the patient radiation dose and did not increase fluoroscopy time.
Topics: Administration, Oral; Adult; Barium Sulfate; Contrast Media; Deglutition Disorders; Female; Fluoroscopy; Heart Rate; Humans; Male; Phantoms, Imaging; Radiation Dosage; Retrospective Studies; Time Factors
PubMed: 31256907
DOI: 10.1016/j.crad.2019.05.030 -
Current Oncology Reports Jan 2017Radiation therapy is an integral component in the multimodality management of many gastrointestinal (GI) cancers at all stages of clinical presentation. With recent... (Review)
Review
Radiation therapy is an integral component in the multimodality management of many gastrointestinal (GI) cancers at all stages of clinical presentation. With recent advances in technology and radiation delivery, external beam radiation therapy (EBRT) can be delivered with reduced toxicity. However, despite these advances, EBRT doses are still limited by the presence of radiosensitive serial structures near clinical targets in the GI tract. Relative to EBRT techniques, brachytherapy techniques have a lower integral dose and more rapid fall-off, allowing for high-dose delivery with little normal tissue exposure. Given the unique characteristics of brachytherapy, it is an attractive strategy to treat GI malignancies. This review addresses the application of both high-dose rate brachytherapy (HDRBT) and low-dose rate brachytherapy (LDRBT) to multiple GI malignancies for both definitive and palliative management.
Topics: Brachytherapy; Combined Modality Therapy; Gastrointestinal Neoplasms; Gastrointestinal Tract; Humans; Radiation Injuries; Radiotherapy Dosage
PubMed: 28110462
DOI: 10.1007/s11912-017-0561-1 -
Cancer Radiotherapie : Journal de La... Oct 2019Literature review reporting results of salvage brachytherapy and stereotactic body radiotherapy for prostate recurrence only after radiotherapy for prostate cancer. (Review)
Review
PURPOSE
Literature review reporting results of salvage brachytherapy and stereotactic body radiotherapy for prostate recurrence only after radiotherapy for prostate cancer.
MATERIALS AND METHODS
A total of 38 studies (including at least 15 patients per study) were analysed: 19 using low-dose-rate brachytherapy, nine high-dose-rate brachytherapy and ten stereotactic body radiotherapy. Only five studies were prospective. The median numbers of patients were 30 for low-dose-rate brachytherapy, 34 for high-dose-rate brachytherapy, and 30 for stereotactic body radiotherapy. The median follow-up were 47months for low-dose-rate brachytherapy, 36months for high-dose-rate brachytherapy and 21months for stereotactic body radiotherapy.
RESULTS
Late genitourinary toxicity rates ranged, for grade 2: from 4 to 42% for low-dose-rate brachytherapy, from 7 to 54% for high-dose-rate brachytherapy and from 3 to 20% for stereotactic body radiotherapy, and for grade 3 or above: from 0 to 24% for low-dose-rate brachytherapy, from 0 to 13% for high-dose-rate brachytherapy and from 0 to 3% for grade 3 or above (except 12% in one study) for stereotactic body radiotherapy. Late gastrointestinal toxicity rates ranged, for grade 2: from 0 to 6% for low-dose-rate brachytherapy, from 0 to 14% for high-dose-rate brachytherapy and from 0 to 11% for stereotactic body radiotherapy, and for grade 3 or above: from 0 to 6% for low-dose-rate brachytherapy, and from 0 to 1% for high-dose-rate brachytherapy and stereotactic body radiotherapy. The 5-year biochemical disease-free survival rates ranged from 20 to 77% for low-dose-rate brachytherapy and from 51 to 68% for high-dose-rate brachytherapy. The 2- and 3-year disease-free survival rates ranged from 40 to 82% for stereotactic body radiotherapy. Prognostic factors of biochemical recurrence have been identified.
CONCLUSION
Despite a lack of prospective data, salvage reirradiation for prostate cancer recurrence can be proposed to highly selected patients and tumours. Prospective comparative studies are needed.
Topics: Brachytherapy; Humans; Male; Neoplasm Recurrence, Local; Prostatic Neoplasms; Radiosurgery; Re-Irradiation; Salvage Therapy
PubMed: 31421999
DOI: 10.1016/j.canrad.2019.07.125 -
Journal of Applied Clinical Medical... Oct 2021A signal dependence on dose rate was reported for the ArcCHECK array due to recombination processes within the diodes. The purpose of our work was to quantify the...
PURPOSE
A signal dependence on dose rate was reported for the ArcCHECK array due to recombination processes within the diodes. The purpose of our work was to quantify the necessary correction and apply them to quality assurance measurements.
METHODS
Static 10 × 10 cm 6-MV fields delivered by a linear accelerator were applied to the detector array while decreasing the average dose rate, that is, the pulse frequency, from 500 to 30 MU/min. An ion chamber was placed inside the ArcCHECK cavity as a reference. Furthermore, the instantaneous dose rate dependence (DRD) was studied. The position of the detector was adjusted to change the dose-per-pulse, varying the distance between the focus and the diode closest to the focus between 69.6 and 359.6 cm. Reference measurements were performed with an ion chamber placed inside a PMMA slab phantom at the same source-to-detector distances ( . Exponential saturation functions were fitted to the data, with different parameters to account for two generations of ArcCHECK detectors (types 2 and 3) and both DRDs. Corrections were applied to 12 volumetric modulated arc therapy plans.
RESULTS
The sensitivity decreased by up to 2.8% with a decrease in average dose rate and by 9% with a decrease in instantaneous dose rate. Correcting the average DRD, the mean gamma pass rates (2%/2-mm criterion) of the treatment plans were improved by 5 percentage points (PP) for diode type 3 and 0.4 PP for type 2. Correcting the instantaneous DRD, the improvement was 8.4 PP for type 3 and 0.9 PP for type 2.
CONCLUSIONS
The instantaneous DRD was identified as the prevailing effect on the diode sensitivity. We developed and validated a method to correct this behavior. The number of falsely not passed treatment plans could be considerably reduced.
Topics: Humans; Particle Accelerators; Quality Assurance, Health Care; Radiometry; Radiotherapy Dosage; Radiotherapy Planning, Computer-Assisted; Radiotherapy, Intensity-Modulated; Silicon
PubMed: 34519437
DOI: 10.1002/acm2.13409 -
Physics in Medicine and Biology Apr 2021FLASH irradiation has been shown to reduce significantly normal tissue toxicity compared to conventional irradiation, while maintaining tumor control probability at...
FLASH irradiation has been shown to reduce significantly normal tissue toxicity compared to conventional irradiation, while maintaining tumor control probability at similar level. Clinical translation of FLASH irradiation necessitates comprehensive laboratory studies to elucidate biological effects as well as pertinent technological and physical requirements. At present, FLASH research employs complex accelerator technologies of limited accessibilities. Here, we study the feasibility of a novel self-shielded x-ray irradiation cabinet system, as an enabling technology to enhance the preclinical research capabilities. The proposed system employs two commercially available high capacity 150 kVp fluoroscopy x-ray sources with rotating anode technology in a parallel-opposed arrangement. Simulation was performed with the GEANT4 Monte-Carlo platform. Simulated dosimetric properties of the x-ray beam for both FLASH and conventional dose-rate irradiations were characterized. Dose and dose rate from a single kV x-ray fluoroscopy source in solid water phantom were verified with measurements using Gafchromic films. The parallel-opposed x-ray sources can deliver over 50 Gy doses to a 20 mm thick water equivalent medium at ultrahigh dose-rates of 40-240 Gy s. A uniform depth-dose rate (±5%) is achieved over 8-12 mm in the central region of the phantom. Mirrored beams minimize heel effect of the source and achieve reasonable cross-beam uniformity (±3%). Conventional dose-rate irradiation (≤0.1 Gy s) can also be achieved by reducing the tube current and increasing the distance between the phantom and tubes. The rotating anode x-ray source can be used to deliver both FLASH and conventional dose-rate irradiations with the field dimensions well suitable for small animal and cell-culture irradiations. For FLASH irradiation using parallel-opposed sources, entrance and exit doses can be higher by 30% than the dose at the phantom center. Beam angling can be employed to minimize the high surface doses. Our proposed system is amendable to self-shielding and enhance research in regular laboratory setting.
Topics: Animals; Monte Carlo Method; Radiometry; Radiotherapy Dosage; Research; X-Rays
PubMed: 33780922
DOI: 10.1088/1361-6560/abf2fa -
Journal of Radiation Research Nov 2017Laser-generated electron beams are distinguished from conventional accelerated particles by ultrashort beam pulses in the femtoseconds to picoseconds duration range, and...
Laser-generated electron beams are distinguished from conventional accelerated particles by ultrashort beam pulses in the femtoseconds to picoseconds duration range, and their application may elucidate primary radiobiological effects. The aim of the present study was to determine the dose-rate effect of laser-generated ultrashort pulses of 4 MeV electron beam radiation on DNA damage and repair in human cells. The dose rate was increased via changing the pulse repetition frequency, without increasing the electron energy. The human chronic myeloid leukemia K-562 cell line was used to estimate the DNA damage and repair after irradiation, via the comet assay. A distribution analysis of the DNA damage was performed. The same mean level of initial DNA damages was observed at low (3.6 Gy/min) and high (36 Gy/min) dose-rate irradiation. In the case of low-dose-rate irradiation, the detected DNA damages were completely repairable, whereas the high-dose-rate irradiation demonstrated a lower level of reparability. The distribution analysis of initial DNA damages after high-dose-rate irradiation revealed a shift towards higher amounts of damage and a broadening in distribution. Thus, increasing the dose rate via changing the pulse frequency of ultrafast electrons leads to an increase in the complexity of DNA damages, with a consequent decrease in their reparability. Since the application of an ultrashort pulsed electron beam permits us to describe the primary radiobiological effects, it can be assumed that the observed dose-rate effect on DNA damage/repair is mainly caused by primary lesions appearing at the moment of irradiation.
Topics: Comet Assay; DNA Damage; DNA Repair; Dose-Response Relationship, Radiation; Electrons; Humans; K562 Cells; Probability
PubMed: 28992052
DOI: 10.1093/jrr/rrx035 -
Environmental Science and Pollution... Oct 2023Radiation is present everywhere in the earth, and human beings are continuously exposed to gamma radiation. The health consequences of environmental radiation exposure...
Radiation is present everywhere in the earth, and human beings are continuously exposed to gamma radiation. The health consequences of environmental radiation exposure are a serious societal issue. The purpose of this study was to analyse outdoor radiation in four districts of Gujarat, India: Anand, Bharuch, Narmada, and Vadodara during summer and winter seasons. This study illustrated the influence of lithology of areas on gamma radiation dose values. Summer and winter seasons are the primary factors that alter the causes directly or indirectly; therefore, the influence of season fluctuation on radiation dose rate was investigated. The annual dose rate and mean gamma radiation dose rate values from four districts were found to be greater than the global population weight average value. The mean value of gamma radiation dose rate from 439 locations in the summer and winter seasons was 136.23 nSv/h and 141.58 nSv/h, respectively. According to a paired differences sample study, the significance value between outdoor gamma dose rate in summer and winter seasons was 0.05 indicating that seasons have a significant impact on gamma radiation dose rate. The impact of various types of lithology on gamma radiation dose was studied in all 439 places, and the statistical analysis revealed that there was no significant association between lithology and gamma radiation dose rate in the summer season, but a relationship between lithology and gamma dose rate was observed in the winter season.
Topics: Humans; Gamma Rays; Environmental Exposure; Environmental Pollution; India; Radiation Exposure; Seasons
PubMed: 36807856
DOI: 10.1007/s11356-023-25711-4 -
BMC Ophthalmology Jun 2022To compare the recurrence rate of retinopathy of prematurity (ROP) after treatment with 0.3 mg vs. 0.25 mg ranibizumab.
OBJECTIVE
To compare the recurrence rate of retinopathy of prematurity (ROP) after treatment with 0.3 mg vs. 0.25 mg ranibizumab.
SUBJECTS
All patients with ROP who underwent intravitreal injection of ranibizumab in Hainan General Hospital between January 2014 and May 2020 were included in this retrospective study.
METHODS
Eighty-two cases (146 eyes) who received intravitreal injection of 0.25 mg ranibizumab were included in the conventional-dose group, and 59 cases (108 eyes) who received intravitreal injection of 0.3 mg ranibizumab were included in the high-dose group. The two groups were further divided into the 25-28-week, 29-31-week, 32-34-week, and 35-36-week GA subgroups. The differences between the conventional-dose group and the high-dose group in gestational age (GA), birth weight (BW), age at initial injection (weeks), incidence of systemic diseases, the recurrence rate of ROP, and age at retinal vascularization completed (weeks) were analyzed.
RESULTS
GA, BW, age at initial injection, and the incidence of systemic diseases were not significantly different between the conventional-dose group and the high-dose group (p > 0.05). The recurrence rates of ROP were significantly lower in the 25-28-week, 29-31-week, and 32-34-week subgroups of the high-dose group than in the same subgroups of the conventional-dose group (p < 0.05). Within the conventional-dose group, the recurrence rate of ROP was significantly lower in the 32-34-week and 35-36-week subgroups than in the 25-28-week and 29-31-week subgroups (p < 0.05). Within the high-dose group, the recurrence rate of ROP was not significantly different between the four subgroups (p > 0.05). Retinal vascularization was completed at a later age in the 32-34-week subgroup of the high-dose group than in the 32-34-week subgroup of the conventional-dose group (p < 0.05) but was not significantly different between the two groups at any other GA range (p > 0.05). No severe ocular or systemic complications occurred in any patient.
CONCLUSION
Treatment with 0.3 mg ranibizumab can reduce the recurrence rate of ROP without prolonging retinal vascularization or causing serious systemic complications. Therefore, this dose may be an appropriate therapeutic dose for ROP.
Topics: Angiogenesis Inhibitors; Bevacizumab; Gestational Age; Humans; Infant, Newborn; Intravitreal Injections; Ranibizumab; Retinal Neovascularization; Retinopathy of Prematurity; Retrospective Studies; Treatment Outcome
PubMed: 35729540
DOI: 10.1186/s12886-022-02489-6 -
Journal of Radiation Research Dec 2022The polymer gel dosimeter has been proposed for use as a 3D dosimeter for complex dose distribution measurement of high dose-rate (HDR) brachytherapy. However, various...
The polymer gel dosimeter has been proposed for use as a 3D dosimeter for complex dose distribution measurement of high dose-rate (HDR) brachytherapy. However, various shapes of catheter/applicator for sealed radioactive source transport used in clinical cases must be placed in the gel sample. The absorbed dose readout for the magnetic resonance (MR)-based polymer gel dosimeters requires calibration data for the dose-transverse relaxation rate (R2) response. In this study, we evaluated in detail the dose uncertainty and dose resolution of three calibration methods, the multi-sample and distance methods using the Ir-192 source and the linear accelerator (linac) method using 6MV X-rays. The use of Ir-192 sources increases dose uncertainty with steep dose gradients. We clarified that the uniformly irradiated gel sample improved the signal-to-noise ratio (SNR) due to the large slice thickness of MR images and could acquire an accurate calibration curve using the linac method. The curved tandem and ovoid applicator used for intracavitary irradiation of HDR brachytherapy for cervical cancer were reproduced with a glass tube to verify the dose distribution. The results of comparison with the treatment planning system (TPS) calculation by gamma analysis on the 3%/2 mm criterion were in good agreement with a gamma pass rate of 90%. In addition, the prescription dose could be evaluated accurately. We conclude that it is easy to place catheter/applicator in the polymer gel dosimeters, making them a useful tool for verifying the 3D dose distribution of HDR brachytherapy with accurate calibration methods.
Topics: Female; Humans; Uterine Cervical Neoplasms; Polymers; Nerve Tissue Proteins
PubMed: 36109319
DOI: 10.1093/jrr/rrac053