Organ Doses Research Articles

Dose response analysis of protracted absorbed organ dose and site-specific cancer incidence in Sweden after the Chernobyl accident

Dose response analysis of protracted absorbed organ dose and site-specific cancer incidence in Sweden after the Chernobyl accident

Individualized dose calculation for internal exposure on radionuclide intake: GPU acceleration approach

Objective. The rapid and accurate assessment of internal exposure dose is a crucial safeguard for personnel health and safety. This study aims to investigate a precise and efficient GPU Monte Carlo simulation approach for internal exposure dose calculation. It directly calculates doses from common radioactive nuclides intake, like 60Co for occupational exposure, allowing personalized assessments. Approach. This study developed a GPU-accelerated Monte Carlo program for internal exposure on radionuclide intake, successfully realizing photoelectronic coupled transport, nuclide simulation, and optimized acceleration. The generation of internal irradiation sources and sampling methods were achieved, along with the establishment of a personalized phantom construction process. Three irradiation scenarios were simulated to assess computational accuracy and efficiency, and to investigate the influence of posture variations on internal dose estimations. Main results. Using the International Commission on Radiological Protection (ICRP) voxel-type phantom, the internal dose of radionuclides in individual organs was calculated, exhibiting relative deviation of less than 3% in comparison to organ dose results interpolated by Specific Absorbed Fractions in ICRP Publication 133. Employing the Chinese reference phantom for calculating internal irradiation dose from the intake of various radionuclides, the use of GPU Monte Carlo program significantly shortened the simulation time compared to using CPU programs, by a factor of 150–500. Internal dose estimation utilizing a seated Chinese phantom revealed up to a 75% maximum difference in organ dose compared to the same phantom in a standing posture. Significance. This study presents a rapid GPU-based simulation method for internal irradiation doses, capable of directly simulating dose outcomes from nuclide intake and accommodating individualized phantoms for more realistic and expeditious calculations tailored to specific internal irradiation scenarios. It provides an effective and feasible tool for precisely calculating internal irradiation doses in real-world scenarios.

Impact of contrast agents on organ dosimetry in pediatric diagnostic fluoroscopy: the voiding cystourethrogram.

ICRP Task Group 113 is developing reference values of organ and effective dose coefficients for radiography, fluoroscopy, and computed tomography imaging exams. In support of these efforts, our focus is on pediatric diagnostic fluoroscopy. Contrast agents used during clinical examinations are an important consideration of the work undertaken by the Task Group. This work demonstrates the importance of including organ contrast volume concentrations for the calculation of reference organ dose coefficients in the voiding cystourethrogram (VCUG). The ICRP newborn and 15-year female reference phantoms were utilized within the Particle and Heavy Ion Transport code System (PHITS) for the calculation of organ dose coefficients. A pediatric radiologist with over 30 years of clinical experience defined the imaging fields for a VCUG examination consistent with clinical practice. Of these, four imaging fields were selected for investigation. The transport simulations modeled an iodinated contrast solution similar to Bracco Group's 18% weight per volume, cystografin diatrizoate meglumine and typical bladder content was supplemented to make up the remainder volume. Iodinated contrast volumes of 0, 25, 50, 75, and 100 percent concentration by volume were modeled and associated dose coefficients for in-field organs were computed. Organ dose coefficients were calculated for the urinary bladder wall, colon wall, ovaries, and uterus for both female phantoms under irradiation geometries representative of a VCUG examination. Some organ dose coefficients increased with iodine volume in the bladder and other organ dose coefficients decreased as the iodine contrast volume completely filled the bladder (100%). The study results demonstrate for the newborn phantom percent differences in organ dose coefficients varied between 0-10% for the organs of interest, while they varied between 0-22% in the 15-year phantom suggesting the importance of including contrast media in Monte Carlo radiation transport simulations of the VCUG examination.&#xD.

Impact of Posttreatment SPECT/CT on Patient Management During 177Lu-PSMA-617 Radiopharmaceutical Therapy.

177Lu can be imaged after administration using SPECT/CT. Most work to date has focused on using posttreatment imaging to measure normal organ and tumor dose. We aimed to assess the impact of posttreatment SPECT/CT on the management of patients undergoing 177Lu-prostate-specific membrane antigen (PSMA) radiopharmaceutical therapy (RPT). Methods: In this retrospective study, 122 patients underwent PSMA RPT with subsequent SPECT/CT 24 h after treatment. We determined a qualitative response at each cycle and reviewed patient charts to assess the impact that posttreatment SPECT/CT had on patient management. Changes in patient management were classified as changes on the basis of progression and response, and specific cycles when they occurred were noted. Miscellaneous changes in patient management were also evaluated. Results: Among the 122 consecutive patients examined, 42%-56% exhibited stable disease, whereas 19%-39% of patients exhibited response on visual assessment across treatment cycles. In total, 49% (n = 60) of patients experienced changes in management, of which 57% (n = 34) were due to progression, 40% (n = 24) were due to response, and 3% (n = 2) were due to miscellaneous changes. Changes due to disease progression were observed mostly after cycles 2 and 4. Changes due to response to RPT occurred mostly after cycles 3 and 4. Conclusion: At our center, 49% of patients experienced changes in management based on posttreatment SPECT/CT, and most of these changes occurred at cycles 2 and 4. Integrating posttreatment SPECT/CT into routine PSMA RPT protocols can aid in patient management.

A framework for in-field and out-of-field patient specific secondary cancer risk estimates from treatment plans using the TOPAS Monte Carlo system

Objective. To allow the estimation of secondary cancer risks from radiation therapy treatment plans in a comprehensive and user-friendly Monte Carlo (MC) framework. Method. Patient planning computed tomography scans were extended superior-inferior using the International Commission on Radiological Protection’s Publication 145 computational mesh phantoms and skeletal matching. Dose distributions were calculated with the TOPAS MC system using novel mesh capabilities and the digital imaging and communications in medicine radiotherapy extension interface. Finally, in-field and out-of-field cancer risk was calculated using both sarcoma and carcinoma risk models with two alternative parameter sets. Result. The TOPAS MC framework was extended to facilitate epidemiological studies on radiation-induced cancer risk. The framework is efficient and allows automated analysis of large datasets. Out-of-field organ dose was small compared to in-field dose, but the risk estimates indicate a non-negligible contribution to the total radiation induced cancer risk. Significance. This work equips the TOPAS MC system with anatomical extension, mesh geometry, and cancer risk model capabilities that make state-of-the-art out-of-field dose calculation and risk estimation accessible to a large pool of users. Furthermore, these capabilities will facilitate further refinement of risk models and sensitivity analysis of patient specific treatment options.

Biodistribution and Radiation Dosimetry for 68 Ga-DOTA-CCK-66, a Novel CCK 2 R-Targeting Compound for Imaging of Medullary Thyroid Cancer.

Cholecystokinin 2 receptor (CCK 2 R) is a promising target for imaging and treatment of medullary thyroid cancer due to its overexpression in over 90% of tumor cells. 68 Ga-DOTA-CCK-66 is a recently introduced PET tracer selective for CCK 2 R, which has shown favorable pharmacokinetics in vivo in preclinical experiments. In order to further investigate safety and suitability of this tracer in the human setting, whole-body distribution and radiation dosimetry were evaluated. Six patients with a history of medullary thyroid cancer were injected intravenously with 169 ± 19 MBq of 68 Ga-DOTA-CCK-66. Whole-body PET/CT scans were acquired at 10 minutes, 1 hour, 2 hours, and 4 hours after tracer injection. Time-activity curves per organ were determined, and mean organ-absorbed doses and effective doses were calculated using OLINDA/EXM. Injection of a standard activity of 150 MBq of 68 Ga-DOTA-CCK-66 results in an effective dose of 4.5 ± 0.9 mSv. The highest absorbed organ doses were observed in the urinary bladder wall (40 mGy) and the stomach (15 mGy), followed by the kidneys (6 mGy), as well as the liver and the spleen (3 mGy each). CCK 2 R-expressing tumor manifestations could be detected in 2 of the 6 patients, including lymph node, bone, and liver metastases. 68 Ga-DOTA-CCK-66 exhibits a favorable dosimetry. Beyond physiologic receptor expression of the stomach, no other relevant tracer accumulation could be observed, rendering this organ at risk in case of subsequent radioligand therapy using 177 Lu-DOTA-CCK-66.

A methodology for computationally generating phase space files for Monte Carlo simulations applied to treatment plans for medical linear accelerators

The application of Monte Carlo (MC) simulation in the context of Medical Linear Accelerator (LinAc) treatment planning has increased in recent decades owing to its accuracy in dose calculations. The Multileaf Collimator (MLC), a component of the LinAc heads, plays an essential role by allowing the precise customization of the treatment beam's shape, effectively targeting the tumor area while minimizing radiation exposure to surrounding healthy structures. During a jaws static treatment, this MLC configuration varies for each angular position of the accelerator gantry, while the rest of the LinAc geometry remains static. To address the operation of the accelerator during the treatment planning avoiding the need of computationally intensive and repetitive simulations, phase-space files (PSF) are widely employed in LinAc MC calculations. This study aims to introduce and validate a methodology for the computational generation of PSFs specifically defined just below the MLC. These PSFs will assume the appropriate shape corresponding to the angle at which the accelerator gantry is positioned during treatment. The core of this methodology involves the creation of a comprehensive database containing precalculated probability functions derived from MC. In order to validate the methodology, simulated dose values of a LinAc emitting a 6 MV photon beam have been employed. The results have been tested against experimental data, and compared with the results from complete simulations, yielding PSFs of varying shapes. Finally, this study reveals that the results obtained by comparing organ dose values computed from the generated PSFs to those from the reference PSF are statistically compatible. This innovative method not only offers a valuable tool for optimizing LinAc treatment planning but also underscores the importance of accurate dose calculations in the field of radiation therapy.

A Multicentric study on a dosimetric comparison of extended SSD technique, VMAT-Based and helical tomotherapy (HT) for total body irradiation (TBI)

PurposeIn study, it was aimed to evaluate the dose volume histograms (DVH) of extended SSD technique, VMAT-based, and helical tomotherapy plans dosimetrically in a multi-institutional context to achieve higher plan quality and to harmonize total body irradiation plans. MethodsFour different clinical centers participated in the study. The CT images of ten patients were used in this study. During the first phase, ten patients enrolled for TBI were planned by multiple centers according to a common protocol. During the second phase, all centers shared their plans’ DVHs. Treatment plans were evaluated according to the critical organ dose limits. Statistical analysis was performed in the SPSS (version 22.0) program (p < 0.05). ResultsIn study, the results indicated that there was a statistically significant and considerable difference in the dose coverage of PTV, beam delivery time and MU, lens doses, and kidney doses between the four techniques (p < 0.001). The mean lung doses of the four centers were below 10 Gy. No significant difference in maximum liver doses between plans was obtained. ConclusionIn conclusion, although four treatment techniques were suitable for TBI treatment, more homogeneous dose distribution, and lower critical organ doses were obtained with the tomotherapy technique. However, treatment time, MU, and dose rate for lung were disadvantages of the tomotherapy technique. When it comes to deciding on the TBI treatment method, it need to be reviewed some important points. It is needed to sufficient data on long-term results to be able to standardize TBI techniques between centers.

Evaluation of direct point dose estimation based on the distribution of the size-specific dose estimate.

The aim of this study was to evaluate the point doses using a distribution of the size-specific dose estimate (SSDE) from axial CT images of in-house phantoms having diameters from 8 to 40cm. In-house phantoms made of polyester-resin (PESR) mixed with methyl ethyl ketone peroxide (MEKP) were used. The phantoms were built with different diameter sizes of 8, 16, 24, 32, and 40cm. The phantoms were scanned by Siemens a SOMATOM Perspective-128 slice CT scanner with constant input parameters. The point doses were interpolated from the central SSDE (SSDEc) and the peripheral SSDE (SSDEp). The SSDEc and SSDEp were calculated from the SSDE with h- and k-factors. The point doses were compared to the direct measurements using the nanoDot™ optically-stimulated luminescence dosimeter (OSLD) in dedicated holes on the phantoms. It was found that the point dose decreases as the phantom diameter increased. The doses obtained using two approaches differed by 11% on average. The highest difference was 40% and the lowest difference was < 1%. It was found that dose based on the SSDE concept tended to be higher compared to the measured dose by OSLD. Point dose estimation using the concept of SSDE distribution can be considered an alternative for accurate and simple estimation. This approach still requires improvements to increase its accuracy and its application to estimate the organ dose needs further investigation.

Comparison of the tolerability of 161Tb- and 177Lu-labeled somatostatin analogues in the preclinical setting.

[177Lu]Lu-DOTATATE is an established somatostatin receptor (SSTR) agonist for the treatment of metastasized neuroendocrine neoplasms, while the SSTR antagonist [177Lu]Lu-DOTA-LM3 has only scarcely been employed in clinics. Impressive preclinical data obtained with [161Tb]Tb-DOTA-LM3 in tumor-bearing mice indicated the potential of terbium-161 as an alternative to lutetium-177. The aim of the present study was to compare the tolerability of 161Tb- and 177Lu-based DOTA-LM3 and DOTATATE in immunocompetent mice. Dosimetry calculations were performed based on biodistribution data of the radiopeptides in immunocompetent mice. Treatment-related effects on blood cell counts were assessed on Days 10, 28 and 56 after application of [161Tb]Tb-DOTA-LM3 or [161Tb]Tb-DOTATATE at 20 MBq per mouse. These radiopeptides were also applied at 100 MBq per mouse and the effects compared to those observed after application of the 177Lu-labeled counterparts. Bone marrow smears, blood plasma parameters and organ histology were assessed at the end of the study. The absorbed organ dose was commonly higher for the SSTR antagonist than for the SSTR agonist and for terbium-161 over lutetium-177. Application of a therapeutic activity level of 20 MBq [161Tb]Tb-DOTA-LM3 or [161Tb]Tb-DOTATATE was well tolerated without major hematological changes. The injection of 100 MBq of the 161Tb- and 177Lu-based somatostatin analogues affected the blood cell counts, however. The lymphocytes were 40-50% lower in treated mice compared to the untreated controls on Day 10 irrespective of the radionuclide employed. At the same timepoint, thrombocyte and erythrocyte counts were 30-50% and 6-12% lower, respectively, after administration of the SSTR antagonist (p < 0.05) while changes were less pronounced in mice injected with the SSTR agonist. All blood cell counts were in the normal range on Day 56. Histological analyses revealed minimal abnormalities in the kidneys, liver and spleen of treated mice. No correlation was observed between the organ dose and frequency of the occurrence of abnormalities. Hematologic changes were more pronounced in mice treated with the SSTR antagonist than in those treated with the SSTR agonist. Despite the increased absorbed dose delivered by terbium-161 over lutetium-177, [161Tb]Tb-DOTA-LM3 and [161Tb]Tb-DOTATATE should be safe at activity levels that are recommended for their respective 177Lu-based analogues.

Comparative post-therapeutic dosimetry between 2D planar-based and hybrid-based methods for personalized Lu-177 treatment.

This study aims to compare the calculated absorbed dose in target organs and tumors obtained using the different imaging protocols and the calculation methodologies implemented by HERMES HybridViewer dosimetry software for 177Lu-PSMA I&T and 177Lu-DOTATATE therapy. Multiple time-point whole-body planar images and one SPECT/CT image were acquired from 18 patients including 177Lu-PSMA I&T (13 patients) and 177Lu-DOTATATE treatment (5 patients) after administration of 3.80-8.58GBq injected activity. The regions of interest were drawn in the whole body, kidneys, liver, urinary bladder, salivary glands, and tumors to determine the time-integrated activity (TIA) in source organs. Absorbed doses in target organs were calculated according to the Medical Internal Radiation Dose (MIRD) scheme using the HERMES HybridViewer dosimetry integrated with OLINDA/EXM V.2.1 that utilizes the non-uniform rational B-splines (NURBS) for computational digital phantom. The planar-based dosimetry showed a higher dose per injected activity compared to the hybrid-based dosimetry, primarily due to organ overlap. The highest difference in absorbed dose between the imaging scenarios was observed in the spleen with a variation of up to 51.6%, while the difference for other target organs and tumors was less than 40%. The dosimetry calculation derived from the 2D planar-based method consistently demonstrates a significantly higher absorbed dose in organs and tumors compared with the hybrid-based method. However, the hybrid method outperforms the planar method in terms of tumor visualization and overlap-free organ delineation.

Comparison of the dosimetry of scandium-43 and scandium-44 patient organ doses in relation to commonly used gallium-68 for imaging neuroendocrine tumours

BackgroundSeveral research groups have explored the potential of scandium radionuclides for theragnostic applications due to their longer half-lives and equal or similar coordination chemistry between their diagnostic and therapeutic counterparts, as well as lutetium-177 and terbium-161, respectively. Unlike the gallium-68/lutetium-177 pair, which may show different in-vivo uptake patterns, the use of scandium radioisotopes promises consistent behaviour between diagnostic and therapeutic radiopeptides. An advantage of scandium’s longer half-life over gallium-68 is the ability to study radiopeptide uptake over extended periods and its suitability for centralized production and distribution. However, concerns arise from scandium-44’s decay characteristics and scandium-43’s high production costs. This study aimed to evaluate the dosimetric implications of using scandium radioisotopes with somatostatin analogues against gallium-68 for PET imaging of neuroendocrine tumours.MethodsAbsorbed dose per injected activity (AD/IA) from the generated time-integrated activity curve (TIAC) were estimated using the radiopeptides [43/44/44mSc]Sc- and [68Ga]Ga-DOTATATE. The kidneys, liver, spleen, and red bone marrow (RBM) were selected for dose estimation studies. The EGSnrc and MCNP6.1 Monte Carlo (MC) codes were used with female (AF) and male (AM) ICRP phantoms. The results were compared to Olinda/EXM software, and the effective dose concentrations assessed, varying composition between the scandium radioisotopes.ResultsOur findings showed good agreement between the MC codes, with − 3 ± 8% mean difference. Kidneys, liver, and spleen showed differences between the MC codes (min and max) in a range of − 4% to 8%. This was observed for both phantoms for all radiopeptides used in the study. Compared to Olinda/EXM the largest observed difference was for the RBM, of 21% for the AF and 16% for the AM for scandium- and gallium-based radiopeptides. Despite the differences, our findings showed a higher absorbed dose on [43/44Sc]Sc-DOTATATE compared to its 68Ga-based counterpart.ConclusionThis study found that [43/44Sc]Sc-DOTATATE delivers a higher absorbed dose to organs at risk compared to [68Ga]Ga-DOTATATE, assuming equal distribution. This is due to the longer half-life of scandium radioisotopes compared to gallium-68. However, calculated doses are within acceptable ranges, making scandium radioisotopes a feasible replacement for gallium-68 in PET imaging, potentially offering enhanced diagnostic potential with later timepoint imaging.

Radiogenic cancer risk from contrast enhanced computed tomography during pediatric abdomen and pelvis examinations in Saudi Arabia

The sensitivity to ionizing radiation is increasing by age of development for some malignant tumors. Therefore, children have higher risk to radiation induced tumors due the high cellular rate of proliferation and long lifespan probability. The risk is also increase with increase the effective and organ doses. Computed tomography (CT) exposed pediatric patients to higher radiation dose during multiphase image acquisition, repeated exams, for follow-up procedures. This research intended to estimate the radiogenic risks and effective radiation doses resulted from CT enhanced contrast for abdomen and pelvis. 126 (66 (62.3%) males, 60 (47.7%) females) pediatric patients underwent CT enhanced abdominal examination at Medical Imaging Department at King Khalid Hospital and Prince Sultan Center for Health Services, Alkharj, Saudi Arabia. The average and range of pediatric age (years) is 11.6 ± 5.0 (0.1–17). The mean, standard deviation, and range of the volume CT air kerma index (CVOL (mGy) and the air kerma length product (PKL, mGy.cm) were 9.8 ± 9.4 (2.1–45.8) and 1795 (221–3150) per abdominopelvic procedure, respectively. The mean and range of the effective dose (mSv) per procedure are 26.9 (2.4–59.1). The effective dose is higher compared to the most previously published studies. The effective dose per pediatric abdomen and pelvis with contrast procedure suggest that the patient dose is not optimized yet. Because the chest and pelvis region contain sensitive organs that are irradiated repeatedly, dose optimization is crucial.

Secondary cancer risk in six anatomical sites when using PAT, IMPT, and VMAT/IMRT radiotherapy

Background and purposeCompared to intensity modulated proton therapy (IMPT), proton arc therapy (PAT) is expected to improve dose conformality, delivery efficiency, and provide a more favorable LET distribution. Alternatively, the low-dose bath is potentially spread over larger volumes, which could impact the likelihood of developing a radiation-induced, secondary cancer (SC). The goal of this study was to evaluate this risk in several anatomical sites using newly developed commercial tools. Materials and methodsTreatment plans encompassing six anatomical sites, five patients per site, and three techniques per patient were created using RayStation. Techniques included PAT and IMPT for protons, and either volumetrically modulated radiotherapy (VMAT) or intensity modulated radiotherapy (IMRT) for photons. Risk estimates were based on the organ-equivalent dose (OED) concept using both Schneider’s mechanistic dose–response model for carcinoma induction and a linear dose–response model. ResultsWith few exceptions, mean and integral dose were lowest with PAT. For protons, the factor OEDIMPT/OEDPAT ranged from 0.7 to 1.8 with both the mechanistic and linear model, while for photons OEDphoton/OEDPAT ranged from 1.5 to 10 using the mechanistic model and 1.3 to using the linear model. A strong correlation was found between mean dose and OED for organs with significant repopulation/repair (high R value) and less cell death from single hit interactions (low α value). ConclusionBased on results from both mechanistic and linear risk models, the transition from IMPT to PAT should not substantially affect SC risk in patients treated with proton therapy. Additionally, when using Schneider’s model, the shapes of the dose–response curves can be used as a good predictor of how SC risk will respond to shifts from intermediate dose to low dose as anticipated when moving from IMPT to PAT.

Organ dose equivalents of albedo protons and neutrons under exposure to large solar particle events during lunar human landing missions

Astronauts participating in lunar landing missions will encounter exposure to albedo particles emitted from the lunar surface as well as primary high-energy particles in the spectra of galactic cosmic rays (GCRs) and solar particle events (SPEs). While existing studies have examined particle energy spectra and absorbed doses in limited radiation exposure scenarios on and near the Moon, comprehensive research encompassing various shielding amounts and large SPEs on the lunar surface remains lacking. Additionally, detailed organ dose equivalents of albedo particles in a human model on the lunar surface have yet to be investigated. This work assesses the organ dose equivalents of albedo neutrons and albedo protons during historically large SPEs in August 1972 and September 1989 utilizing realistic computational anthropomorphic human phantom for the first time. Dosimetric quantities within human organs have been evaluated based on the PHITS Monte Carlo simulation results and quality factors of the state-of-the-art NASA Space Cancer Risk (NSCR) model, as well as ICRP publications. The results with the NSCR model indicate that the albedo contribution to organ dose equivalent is less than 3 % for 1 g/cm2 aluminum shielding, while it increases to more than 30 % in some organs for 50 g/cm2 aluminum shielding during exposure to low-energy-proton-rich SPEs.

Empirical model for a three-dimensional dose verification system and its application in volumetric-modulated arc therapy for heterogeneous and long-target tumors

PurposeTo perform commissioning of the VMAT dose verification system 3DVH from a unique perspective and investigating its clinical applications in unreported cases with heterogeneous organs or long-target tumors. MethodsInitially, the standard ArcCheck calibration process was conducted. Then, the impact of absolute dose calibration values and ArcCheck CT density settings on the accuracy of the 3DVH reconstruction model was assessed. Subsequently, ten lung cancer cases with heterogeneous organ-encased targets and ten cervical cancer cases with large target volumes were selected to receive VMAT treatment with a TrueBeam Linac. Finally, the performance of the 3DVH method in such radiotherapy validations was assessed. ResultsVarious calibration files had distinct impacts on ArcCheck 2D surface dosimetry and 3DVH dose reconstruction, thus requiring separate optimal calibrations files for these two purposes. The 3DVH dose reconstruction mode exhibited the highest accuracy when using the optimal ArcCheck density value of 1.1787 g/cm³ and an absolute dose calibration value of 249.96 cGy. In all test cases, deviations for target Dmean and D95% were within ±4.2% compared to the planned dose, with notable variations in critical organ doses. In structure-based 3D gamma evaluation, differences were observed compared to existing reports. ConclusionsIt's crucial to account for the ArcCheck array calibration and the interplay between CT density settings and absolute dose calibration values to identify the best combination for an optimal 3DVH dose reconstruction model. The performance of 3DVH in verifying VMAT doses for tumors in heterogeneous or longer target areas may exhibit slight variations compared to other regions.

HDR brachytherapy versus robotic-based and linac-based stereotactic ablative body radiotherapy in the treatment of liver metastases – A dosimetric comparison study of three radioablative techniques

PurposeThe aim of our study was to compare dosimetric aspects of three radioablation modalities – direct high-dose-rate brachytherapy (HDR-BT) and virtually planned stereotactic body radiation therapy performed on CyberKnife (SBRTck) and Elekta Versa HD LINAC (SBRTe) applied in patients with liver metastases. Material and methodsWe selected 30 patients with liver metastases, who received liver interstitial HDR-BT and virtually prepared plans for SBRTck and SBRTe. In all the cases, the prescribed dose was a single fraction of 25 Gy. Treatment delivery time, doses delivered to PTV and organs at risk, as well as conformity indices, were calculated and compared. ResultsThe longest median treatment delivery time was observed in SBRTck in contrast to HDR-BT and SBRTe which were significantly shorter and comparable. HDR-BT plans achieved better coverage of PTV (except for D98%) in contrast to SBRT modalities. Between both SBRT modalities, SBRTck plans resulted in better dose coverage in Dmean, D50%, and D90% values compared to SBRTe without difference in D98%. The SBRTe was the most advantageous considering the PCI and R100%. SBRTck plans achieved the best HI, while R50% value was comparable between SBRTe and SBRTck. The lowest median doses delivered to uninvolved liver volume (V5Gy, V9.1Gy) were achieved with HDR-BT, while the difference between SBRT modalities was insignificant. SBRT plans were better regarding more favourable dose distribution in the duodenum and right kidney, while HDR-BT achieved lower doses in the stomach, heart, great vessels, ribs, skin and spinal cord. There were no significant differences in bowel and biliary tract dose distribution between all selected modalities. ConclusionsHDR-BT resulted in more favourable dose distribution within PTVs and lower doses in organs at risk, which suggests that this treatment modality could be regarded as an alternative to other local ablative therapies in carefully selected patients’ with liver malignancies. Future studies should further address the issue of comparing treatment modalities in different liver locations and clinical scenarios.

Pediatrics organ dose and lifetime attributable cancer risk estimates in routine computed tomography

ObjectivesEvaluating organ doses received by pediatric patients and estimating lifetime attributable risk (LAR) in Riyadh, Saudi Arabia from chest and abdominal pelvic Computed Tomography (CT) scans. MethodsA total of 155 patients under the age of 15 were divided into four age groups: under 1, 1–5, 5–10, and 10–15. The organ dose was determined using the National Cancer Institute dosimetry system for (NCICT) software, and the LAR if cancer incident was measured according to the BEIR VII report. The 1st, 2nd, and 3rd quartiles were calculated for organs received primary X-ray beams. ResultsThe highest and lowest median doses were for the kidney in the 10-15-year-old group 4.84 mGy (Cl95%, 0.15–9.54) and the prostate in the >1-year-old group 0.02 mGy (Cl95%, −0.01 – 0.05), respectively. Furthermore, there was a correlation between age and breast doses in chest scans, as median doses increased from 0.08 mGy to 3.70 mGy. Breast cancer in females had a highest LAR from chest CT and colon cancer in abdomen-pelvic CT. The group 1–5 years old had the highest risk of breast cancer, followed by chest CT (LAR = 25.94). However, colon cancer (LAR = 10.39), followed by an abdomen-pelvic CT, had the highest risk in the same group in both genders. Colon and breast cancers had the highest LAR among males and females in all groups. ConclusionThe study found that older patients received higher median organ doses for the same examination than younger patients. Females have greater organ doses in the thorax compared to males, resulting in a higher mean LAR. While CT scans are useful tools for diagnosis, it's essential to consider the patient's dose, particularly in pediatric cases.

Study of urologic exposure dose in selective organ's cell & behavior of Wistar rats

BackgroundRadiologic fluoroscopy procedures have been imposing considerable exposure dose to staff with serious consequences relative to dose quantity which is still continuing as challenge of studies, hence the aims were to assess the animal behavior, quantify blood components and red blood cells morphology after exposure to x-ray urologic fluoroscopy doses (0.3, 0.8, 1.8 and 2.5 mSv). Methodsurologic exposure doses measured by TLDs chips and TLD reader Model 5500 from selected hospitals. These doses used to expose Wister male rats weighted (275 ± 2.0 g). The collected data were animal behavior, quantity of blood components and cellular changes in RBCs, kidneys, liver & testicles then analyzed by SPSS- 20 (SPSS Inc., Chicago, IL, USA) Resultsshowed that a dose of 2.5 mSv decreased significantly (p value = 0.00) the motor activity of rats. and the blood components decreased as follows: WBC (30.2%), Lymphocytes (40%.0), Neutrophils (35.7%), RBC (37.9%), MCV (32.2%) and RCDW (31.5%). At exposure dose of 0.3 mSv a mild morphological changes as circular shape deformity and loss of bi-concavity of RBCs. At 0.8 mSv RBCs diameter increment (10 ± 0.4 μm) and formation of spikes. At 1.8 mSv RBC underwent anisocytosis and poikilocytosis. While at 2.5 mSv the RBC showed intensive spikes, clustering and some underwent hemolysis. Morphological changes were induced also, at 2.5 mSv for the followings: The renal cortex showed bleeding & congestion at 2.5 mSv. The Renal medulla showed bleeding at 2.5 mSv. The liver texture showed bleeding and congestion with two nuclei- Kupffer cells hyperplasia, ballooning of hepatocytes with Acidophilic bodies at 2.5 mSv. the testicles tissues developed congestion and bleeding. Conclusionfluoroscopic urologic exposure dose can induce significant behavioral, RBCs changes and reduction in blood components.

Dosimetric Study and Robustness Analysis of Base Note Intensive Locked Field Radiotherapy for Left Breast Cancer.

The locked vision plan can make the left breast cancer heart and lung organs dose. The aim of the present study was to compare the dosimetric differences between field-locked and field-split plans in intensity-modulated radiotherapy for left-sided breast cancer, to explore the effect of field-locking on the low-dose region, and to evaluate its robustness to the radiotherapy target, in order to provide a reference for the selection of clinical radiotherapy protocols. A total of 30 patients were selected after radical left breast cancer surgery, and 7-field locked-field and split-field plans were developed to compare the dose difference (∆D) between the target area and each organ at risk, and to introduce offsets of 3, 5 and 7 mm in six directions and recalculate the perturbed dose distributions, and to compare the ∆D between the original and the perturbed plans according to the robustness of the plans. The results revealed that the D98%, D95% and Dmean values of the planning target volume (PTV) of the two plans differed little and were not statistically different. The locked field plan provided better protection for the left lung, right lung, heart, right breast and left anterior descending coronary artery. For PTV∆D98%, PTV∆D95%, PTV∆Dmean, the ∆D was higher for the Locked Fields plan, and for LungL∆5, LungL∆20 and Heart∆mean, the ∆D was higher for the original plan. It was concluded that the field-locking plan could reduce the low-dose area of the affected lung and provide improved protection to the remaining critical organs, and the field-locking plan was more robust in protecting critical organs. Meanwhile, the field-locking plan showed higher sensitivity to positional deviation for target PTV.