Individual Organ Doses Research Articles

Patient radiation risk reduction by controlling the tube start angle in single and dual source spiral CT scans: A simulation study.

Organ doses in spiral CT scans depend on the tube startangle. To determine the effective dose in single source CT (SSCT) and dual source CT (DSCT) scans as a function of tube start angle and spiral pitch value to identify the dose reduction potential by selecting the optimal startangle. Using Monte Carlo simulations, dose values for different tube positions with an angular increment of and a longitudinal increment of were simulated over a range of with collimations of , , and . The simulations were performed for the thorax region of six adult patients based on clinical CT data. From the resulting dose distributions, organ doses and effective dose were determined as a function of tube angle and longitudinal position. Using these per-view dose data, the individual organ doses, as well as the total effective dose, were determined for spiral scans with and without tube current modulation (TCM) with pitch values ranging from 0.5 to 1.5 for SSCT and up to 3.0 for DSCT. The dose of the best and worst tube start angle in terms of dose was determined and compared to the mean dose over all tube startangles. With increasing pitch and collimation, the dose variations from the effective dose averaged over all start angles increase. While for a collimation of , the variations from the mean dose value stay below for SSCT, we find that for a spiral scan with a pitch of 3.0 for DSCT with TCM and collimation of , the dose for the best starting angle is on average lower than the mean value and lower than the maximumvalue. Variation of the tube start angle in spiral scans exhibits substantial differences in radiation dose especially for high pitch values and for high collimations. Therefore, we suggest to control the tube start angle to minimize patientrisk.

Artificial intelligence in diagnostic radiology for dose management : Advances and perspectives using the example of computed tomography

Imaging procedures employing ionizing radiation require compliance with European directives and national regulations in order to protect patients. Each exposure must be indicated, individually adapted, and documented. Unacceptable dose exceedances must be detected and reported. These tasks are time-consuming and require meticulous diligence. Computed tomography (CT) is the most important contributor to medical radiation exposure. Optimizing the patient's dose is therefore mandatory. Use of modern technology and reconstruction algorithms already reduces exposure. Checking the indication, planning, and performing the examination are further important process steps with regard to radiation protection. Patient exposure is usually monitored by dose management systems (DMS). In special cases, arisk assessment is required by calculating the organ doses. Artificial intelligence (AI)-assisted techniques are increasingly used in various steps of the process: they support examination planning, improve patient positioning, and enable automated scan length adjustments. They also provide real-time estimates of individual organ doses. The integration of AI into medical imaging is proving successful in terms of dose optimization in various areas of the radiological workflow, from reconstruction to examination planning and performing exams. However, the use of AI in conjunction with DMS has not yet been considered on alarge scale. AI processes offer promising tools to support dose management. However, their implementation in the clinical setting requires further research, extensive validation, and continuous monitoring.

2128: Individual organ dose calculations from CT imaging of Hodgkin lymphoma patients treated with protons

2128: Individual organ dose calculations from CT imaging of Hodgkin lymphoma patients treated with protons

Contribution of CT scan to patient's radiation exposure in parathyroid SPECT/CT scintigraphy

IntroductionDual phase technetium-99mTc-methoxy isobutyl isonitrile (MIBI) single-photon emission computed tomography with computed tomography (SPECT/CT) may be the most accurate conventional imaging approach for localization of enlarged parathyroid gland (EPG). The imaging is based on the radiopharmaceutical (RP) retention in EPG compared to washout from normal thyroid and normal parathyroid glands. This study aimed to estimate and optimize the contribution of computed tomography (CT) scan and scan range to effective dose (ED) in dual-phase MIBI SPECT/CT parathyroid scintigraphy. MethodsThe study included seventy-four patients; thirty-seven with reduced and thirty-seven with extended CT scan range. The ED caused by the CT scan was calculated using Dose Length Product (DLP) data and estimated using the Imaging Performance Assessment of CT scanners (ImPACT) calculator. ResultsFor all patients, the contribution of CT to the ED in a combined SPECT/CT examination was 2.62 ± 0.29 mSv (48%). The contribution of CT to the total ED was 1.8 ± 0.18 mSv (33%) when using reduced and 3.44 ± 0.23 mSv (64%) when using extended scan range. The DLP and ED were statistically significantly different between the reduced and extended CT scan range (p < 0.001) in the first and second phases. The individual organ dose was reduced from 8% to 94%. ConclusionThe hybrid SPECT/CT improves the interpretation of nuclear medicine images and also increases the radiation dose to the patient. An adequately defined CT scan range on SPECT/CT imaging, can significantly reduce a patient's ED. Implications for practiceThe research findings showed that knowledge of anatomy, pathology and technology can provide optimising diagnostic procedures and reduce patient ED after SPECT/CT scans.

Gridless adult cervical spine radiography and its' effect on image quality and radiation dose: A phantom study

IntroductionImaging of the cervical spine in general radiography is most frequently performed using an anti-scatter grid. The purpose of this study was to investigate the effects of a gridless setting on image quality and radiation dose during digital radiography of the anteroposterior (AP) and lateral (LAT) cervical spine. MethodsA phantom study was performed with a variety of tube voltages (63–75 kV) with and without an anti-scatter grid. The tube current time product (mAs) and dose area product (DAP) were recorded and used to calculate effective dose (ED) and individual organ dose using PCXMC 2.0 software, as well as entrance surface dose (ESD) and objective image quality: signal-to-noise ratio (SNR) and contrast-to-noise ratio (CNR). Subjective visual image quality grading characteristics (VGC) was performed by five qualified radiographers. ResultsIn a gridless setting, the AP and LAT positions showed significantly lower DAP (1.6 μGym2; 61.3 % and 1.6 μGym2; 51.2%), ESD (27.6 μGy; 57.3% and 77.2 μGy; 47.2%) and ED (4.2 μSv; 61.3% and 2.3 μSv; 48.9%). In a gridless setting in the AP position, there is a slight significant deterioration in image quality. In the lateral projection, on the other hand, the image quality without the use of grid was only significantly reduced in three of six criteria and there was no difference in the objective image quality between the two settings examined. ConclusionThe results of this study show that gridless setting significantly decreases radiation dose and image quality, but the quality in the lateral projection is still acceptable for diagnostic purpose. Implications for practiceThe protocol without the use of the anti-scatter grid in cervical spine radiography leads to a reduction in the radiation dose in both projections, but the image quality in the AP is significantly reduced for all criteria examined, with a slight deterioration in image quality in the lateral projection.

Biodistribution and radiation dosimetry of multiple tracers on total-body positron emission tomography/computed tomography.

[18F]F-FDG, [68Ga]Ga-PSMA-11, and [68Ga]Ga-FAPI-04 have achieved good results in multiple clinical trials and clinical practice, but the imaging of these tracers is limited to traditional short-axis positron emission tomography/computed tomography (PET/CT). Therefore, we aimed to use total-body PET/CT dynamic scanning to describe whole-body biodistribution of these three tracers and to calculate more precise radiation doses. Total-body PET/CT (uExplorer, United Imaging Healthcare) dynamic scanning was performed on 54 patients, including 30 patients with [18F]F-FDG, 10 patients with [68Ga]Ga-PSMA-11, and 14 patients with [68Ga]Ga-FAPI-04. A 60-minute dynamic scanning of whole body was performed simultaneously after bedside bolus injection of the corresponding tracers. The dynamic sequence of 92 frames was quantitatively analyzed by the Pmod4.0 software. Whole body biodistribution was calculated as time-activity curves (TACs) describing dynamic uptake patterns in the subject's major organs, followed by calculation of tracer kinetics and cumulative organ activity. Finally, combined with the OLINDA/EXM software, effective doses of the different tracers and individual organ doses were calculated. In a systematic TAC analysis of three tracers, we identified distinct biodistribution patterns in major organs. [68Ga]Ga-PSMA-11 showed a trend of rapid increasing and slow decreasing in liver, spleen, muscle, and bone. In the heart, stomach, brain, and lung, tracer decreased rapidly after rapid increasing. Similarly, tracer uptake in the kidney and urinary bladder increased gradually. [68Ga]Ga-FAPI-04 showed a rapid increasing and rapid decreasing trend in brain, lung, liver, spleen, bone, heart, kidney, and stomach. The mean effective dose of [68Ga]Ga-PSMA-11 was 1.47E-02 mSv/MBq, and the mean effective doses of [18F]F-FDG and [68Ga]Ga-FAPI-04 were comparable (2.52E-02 mSv/MBq and 2.23E-02 mSv/MBq). The mean effective dose of [18F]F-FDG was lower than that reported in the literature measured by previous short-axis PET, while both [68Ga]Ga-PSMA-11 and [68Ga]Ga-FAPI-04 had higher value than previously reported value. [18F]F-FDG, [68Ga]Ga-PSMA-11 and [68Ga]Ga-FAPI-04 have good biodistribution in human organs. Real-time high-sensitivity dynamic scanning with total-body PET/CT is a very effective way to accurately calculate biodistribution and effective dose of positron-labeled radiopharmaceuticals.

Investigating the adjacent patient radiation dose received during a simulated ward chest X-ray examination

Introduction: A patient having a chest X-ray will inevitably be exposed to radiation from the primary beam. Using a light beam diaphragm (LBD) on the X-ray tube reduces scattered radiation at the X-ray tube through longitudinal and horizontal collimation. But not scattered secondary radiation resulting from interactions of the primary beam. This study aimed to investigate whether lead protection on simulated hospital ward inpatients (opposite and adjacent to a simulated chest X-ray examination) would change the secondary scattered radiation dose received.&#x0D; Method: Two rando phantoms (simulated patients) were positioned at different distances from the simulated patient receiving the chest X-ray. The phantoms were positioned one metre adjacent (either side of the phantom being X-rayed) and two metres opposite. The scattered radiation dose to radiosensitive organs (thyroid, breast, and gonads) was recorded using Thermoluminescent Dosimeters (TLDs). Six exposures were conducted, three with lead protection and three without. The mean radiation dose and standard deviation were compared using a paired two-sample t-test for statistical significance (p&gt;0.05).&#x0D; Results: The lead protection reduced the radiation dose to the radiosensitive organs by 64%-100% (p=0.51-0.18) one metre adjacent and 65%-100% (p=0.65-0.18) two metres opposite. Noticeably the phantom two metres opposite had substantial individual organ dose reductions due to the distance from the primary beam.&#x0D; Conclusion: Lead aprons, thyroid collars, and distance reduced the radiation dose to the radiosensitive organs of the surrounding phantoms (simulated patients) from an adjacent chest X-ray examination and present opportunities for dose reduction techniques during ward chest X-ray examinations.

The effect of erect abdomen radiography on absorbed doses to internal organs and tissues: A clinical study

BackgroundAs low as reasonably achievable principles (ALARA) should be applied during all X-ray examinations. In some institutions, an acute abdomen series includes both erect and supine radiography. The purpose of the study was to evaluate the effect of an erect position on absorbed dose to internal abdominal organs when compared with the supine position. Material and MethodsA prospective study was undertaken where 81 patients were imaged in both supine and erect positions. The PCXMC Monte Carlo software was used to estimate individual organ doses using dose area product (DAP). Absorbed doses were calculated for the large intestines, active bone marrow, liver, lungs, small intestine, stomach, gallbladder, breasts, uterus, ovaries, urinary bladder, kidneys, testicles, and prostate. ResultsThe results showed a significant increase of absorbed dose by 1.4% when moving from a supine to an erect position. The testes were found to be the organs most affected by the erect position and then the urinary bladder. ConclusionsAccording to the study's findings, using the erect position during abdominal radiography increases the radiation dose for all of the selected organs compared to using a supine position. Therefore, it is advised that the use of erect abdomen radiography be restricted to certain circumstances.

Biodistribution and dosimetry in human healthy volunteers of the PET radioligands [11C]CHDI-00485180-R and [11C]CHDI-00485626, designed for quantification of cerebral aggregated mutant huntingtin.

Huntington's disease is caused by a trinucleotide expansion in the HTT gene, which leads to aggregation of mutant huntingtin (mHTT) protein in the brain and neurotoxicity. Direct in vivo measurement of mHTT aggregates in human brain parenchyma is not yet possible. In this first-in-human study, we investigated biodistribution and dosimetry in healthy volunteers of [11C]CHDI-00485180-R ([11C]CHDI-180R) and [11C]CHDI-00485626 ([11C]CHDI-626), two tracers designed for PET imaging of aggregated mHTT in the brain that have been validated in preclinical models. Biodistribution and radiation dosimetry studies were performed in 3 healthy volunteers (age 25.7 ± 0.5years; 2 F) for [11C]CHDI-180R and in 3 healthy volunteers (age 35.3 ± 6.8years; 2 F) for [11C]CHDI-626 using sequential whole-body PET-CT. Source organs were delineated in 3D using combined PET and CT data. Individual organ doses and effective doses were determined using OLINDA 2.1. There were no clinically relevant adverse events. The mean effective dose (ED) for [11C]CHDI-180R was 4.58 ± 0.65 μSv/MBq, with highest absorbed doses for liver (16.9μGy/MBq), heart wall (15.9μGy/MBq) and small intestine (15.8μGy/MBq). Mean ED for [11C]CHDI-626 was 5.09 ± 0.06 μSv/MBq with the highest absorbed doses for the gallbladder (26.5μGy/MBq), small intestine (20.4μGy/MBq) and liver (19.6μGy/MBq). Decay-corrected brain uptake curves showed promising kinetics for [11C]CHDI-180R, but for [11C]CHDI-626 an increasing signal over time was found, probably due to accumulation of a brain-penetrant metabolite. [11C]CHDI-180R and [11C]CHDI-626 are safe for in vivo PET imaging in humans. The estimated radiation burden is in line with most 11C-ligands. While [11C]CHDI-180R has promising kinetic properties in the brain, [11C]CHDI-626 is not suitable for human in vivo mHTT PET due to the possibility of a radiometabolite accumulating in brain parenchyma. EudraCT number 2020-002129-27. gov NCT05224115 (retrospectively registered).

Organ doses in preterm and full-term neonates and infants — a retrospective study on 1,064 chest radiographs

BackgroundChest radiography is the most frequent X-ray examination performed in the neonatal period. However, commonly used dosimetric entities do not describe the radiation risk sufficiently.ObjectiveThe aim of this study was to investigate selected organ doses and total body dose of chest radiographs in preterm and full-term neonates and infants.Materials and methodsIn this retrospective study, we evaluated 1,064 chest radiographs of 136 preterm and 305 full-term babies with respect to field size and centering. We calculated the entrance dose from the dose–area product. Upper and lower field borders referred to the corresponding vertebrae. We calculated individual organ doses of the thyroid, the breast, the liver and active bone marrow for each chest radiograph using the neonatal PCXMC program, a Monte Carlo program for calculating patient doses in medical X-ray examinations.ResultsThe median field size of chest radiographs ranged from 90 cm2 in preterm neonates at birth to 290 cm2 in full-term infants at the age of 6 months. Median values of entrance dose varied, depending on age, from 15 μGy to 25 μGy. The median organ doses ranged 1–20 μSv for the thyroid, 3–30 μSv for the breast, 2–20 μSv for the liver and 0.5–3.5 μSv for the bone marrow in preterm and full-term neonates and infants, respectively.ConclusionThe analysis of chest radiographs in preterm and full-term neonates and infants revealed high variability in field size. By contrast, the entrance dose varied to a minor extent. Organ dose calculations using the PCXMC program might be a valuable tool to calculate the individual radiation risk in neonates and infants.

Direct measurement of radiation exposure dose to individual organs during diagnostic computed tomography examination

Ionizing radiation from Computed tomography (CT) examinations and the associated health risks are growing concerns. The purpose of this study was to directly measure individual organ doses during routine clinical CT scanning protocols and to evaluate how these measurements vary with scanning conditions. Optically stimulated luminescence (OSL) dosimeters were surgically implanted into individual organs of fresh non-embalmed whole-body cadavers. Whole-body, head, chest, and abdomen CT scans were taken of 6 cadavers by simulating common clinical methods. The dosimeters were extracted and the radiation exposure doses for each organ were calculated. Average values were used for analysis. Measured individual organ doses for whole-body routine CT protocol were less than 20 mGy for all organs. The measured doses of surface/shallow organs were higher than those of deep organs under the same irradiation conditions. At the same tube voltage and tube current, all internal organ doses were significantly higher for whole-body scans compared with abdominal scans. This study could provide valuable information on individual organ doses and their trends under various scanning conditions. These data could be referenced and used when considering CT examination in daily clinical situations.

Ct Dosimetry for The Australian Cohort Data Linkage Study.

Children undergoing computed tomography (CT) scans have an increased risk of cancer in subsequent years, but it is unclear how much of the excess risk is due to reverse causation bias or confounding, rather than to causal effects of ionising radiation. An examination of the relationship between excess cancer risk and organ dose can help to resolve these uncertainties. Accordingly, we have estimated doses to 33 different organs arising from over 900000 CT scans between 1985 and 2005 in our previously described cohort of almost 12 million Australians aged 0-19years. We used a multi-tiered approach, starting with Medicare billing details for government-funded scans. We reconstructed technical parameters from national surveys, clinical protocols, regulator databases and peer-reviewed literature to estimate almost 28000000 individual organ doses. Doses were age-dependent and tended to decrease over time due to technological improvements and optimisation.

Use of CT simulation and 3-D radiation therapy treatment planning system to develop and validate a total-body irradiation technique for the New Zealand White rabbit

Purpose Well-controlled ionizing radiation injury animal models for testing medical countermeasure efficacy require robust radiation physics and dosimetry to ensure accuracy of dose-delivery and reproducibility of the radiation dose-response relationship. The objective of this study was to establish a simple, convenient, robust and accurate technique for validating total body irradiation (TBI) exposure of the New Zealand White rabbit. Methods We use radiotherapy techniques such as computed tomography simulation and a 3 D-conformal radiation therapy treatment planning system (TPS) on three animals to comprehensively design and preplan a TBI technique for rabbits. We evaluate the requirement for bolus, treatment geometry, bilateral vs anterior-posterior treatment delivery, the agreement between monitor units calculated using the TPS vs a traditional hand calculation to the mid-plane, and resulting individual organ doses. Results The optimal technique irradiates animals on the left-decubitus position using two isocentric bilateral parallel-opposed 6 MV x-ray beams. Placement of a 5 mm bolus and 8.5 mm beam spoiler was shown to increase the dose to within ≤5 mm of the surface, improving dose homogeneity throughout the body of the rabbit. A simple hand calculation formalism, dependent only on mid-abdominal separation, could be used to calculate the number of monitor units (MUs) required to accurately deliver the prescribed dose to the animal. For the representative animal, the total body volume receiving > 95% of the dose, V95% > 99%, V100% > 95%, and V107% < 20%. The area of the body receiving >107% of the prescribed dose was mainly within the limbs, head, and around the lungs of the animal, where the smaller animal width reduces the x-ray attenuation. Individual organs were contoured by an experienced dosimetrist, and each received doses within 95–107% of the intended dose, with mean values ∼104%. Only the bronchus showed a maximal dose >107% (113%) due to the decreased attenuation of the lungs. To validate the technique, twenty animals were irradiated with four optically-stimulated luminescence dosimeters (OSLDs) placed on the surface of each animal (two on each side in the center of the radiation beam). The average dose over all animals was within <0.1% from intended values, with no animal receiving an average dose more than ±3.1% from prescription. Conclusion The TBI technique developed in this pilot study was successfully used to establish the dose-response relationship for 45-day lethality across the dose-range to induce the hematopoietic-subsyndrome of the acute radiation syndrome (ARS).

What is the point of innovation in patient dose monitoring?

The Medical Futurist says that radiology is one of the fastest growing and developing areas of medicine, and therefore this might be the speciality in which we can expect to see the largest steps in development. So why do they think that, and does it apply to dose monitoring? The move from retrospective dose evaluation to a proactive dose management approach represents a serious area of research. Indeed, artificial intelligence and machine learning are consistently being integrated into best-in-class dose management software solutions. The development of clinical analytics and dashboards are already supporting operators in their decision-making, and these optimisations - if taken beyond a single machine, a single department, or a single health network - have the potential to drive real and lasting change. The question is for whom exactly are these innovations being developed? How can the patient know that their scan has been performed to the absolute best that the technology can deliver? Do they know or even care how much their lifetime risk for developing cancer has changed post examination? Do they want a personalised size-specific dose estimate or perhaps an individual organ dose assessment to share on Instagram? Let's get real about the clinical utility and regulatory application of dose monitoring, and shine a light on the shared responsibility in applying the technology and the associated innovations.

Abstract B60: Exposure assessment among an adult population on radiation therapy, chemotherapy, and other cancer therapies in childhood

Abstract Childhood cancer therapies are known risk factors for the development of second primary cancers. They are also suggested risk factors for late adverse health effects. Until now, there is no established questionnaire to retrospectively assess exposure to cancer therapies in childhood among adults. Therefore, we aim to validate a new self-administered questionnaire. The study population consists of 438 former childhood cancer patients of the KiKme study. Participants are asked whether they had received cancer therapies and how often and with which dose they were treated. Used medications and affected body regions are inquired. Questionnaire data are used to compute cytotoxic drugs dose of chemotherapy, taking patients’ weight and height into account, and to reconstruct individual organ doses. For validation, self-reports are compared to data of cancer therapies of 178 patients from hospitals and clinical studies. Quality assessment for binary variables are performed by measuring sensitivity and specificity. AUC and ROC curve are used for graphical comparison. The validity is analyzed by the positive (PPV) and negative predictive value (NPV). Cohen’s Kappa (κ) is used to measure the concordance between the two assessments. Continuous variables are tested for validity by the intraclass correlation coefficient. A Bland-Altman plot is used to consider the patterns of disagreement between the measurements. Influencing factors (e.g., number of neoplasms, sex, sociodemographic factors, comorbidities, time since cancer treatment) on the dichotomous outcome variable “degree of agreement” are analyzed using logistic regression. If the questionnaire is reliable, logistic regression and mixed models will be used to estimate possible risk associations with cancer therapies. A perfect agreement between questionnaire and therapy data was found on whether a chemotherapy was received (κ = 1.00). The agreement for exposure to radiotherapy was lower, but in the upper substantial area (κ = 0.77). For radiotherapy, sensitivity (94%) and PPV (96%) of the questionnaire were at a very high level. Specificity (85%) and NPV (80%) were less precise. The agreement for exposure to radiotherapy was higher in participants with one cancer (κ = 0.82) compared to participants with more than one diagnosis (κ = 0.62). The odds ratios for agreement were 0.5 (0.1; 1.8) for participants with two vs. one diagnosis, 1.3 (0.3; 4.9) for men vs. women, 10.9 (1.7; 71.9) for age over 36.4 years (median) vs. younger participants, 2.2 (0.6; 9.0) for high vs. low education, 0.3 (0.1; 1.4) for over 26.5 years of follow-up (median) vs. less, 2.4 (0.6; 9.5) for existing vs. nonexisting comorbidities. In conclusion, the new developed questionnaire seems to be reliable for the retrospective assessment of binary exposure to cancer therapies in childhood, especially for chemotherapy. However, for radiotherapy older participants showed a significant higher agreement. All other tested variables showed no significant influence. Citation Format: Lara Kim Brackmann, Caine Lucas Grandt, Heike Schwarz, Irene Schmidtmann, Thomas Hankeln, Danuta Galetzka, Sebastian Zahnreich, Peter Scholz-Kreisel, Maria Blettner, Heinz Schmidberger, Manuela Marron. Exposure assessment among an adult population on radiation therapy, chemotherapy, and other cancer therapies in childhood [abstract]. In: Proceedings of the AACR Special Conference on the Advances in Pediatric Cancer Research; 2019 Sep 17-20; Montreal, QC, Canada. Philadelphia (PA): AACR; Cancer Res 2020;80(14 Suppl):Abstract nr B60.

Biodistribution, dosimetry, and temporal signal-to-noise ratio analyses of normal and cancer uptake of [68Ga]Ga-P15-041, a gallium-68 labeled bisphosphonate, from first-in-human studies

Introduction[68Ga]Ga-P15-041 ([68Ga]Ga-HBED-CC-BP) is a novel bone-seeking PET radiotracer that can be generator-produced. We undertook a Phase 0/I clinical trial to assess its potential for imaging bone metastases in prostate cancer including assessment of radiotracer biodistribution and dosimetry. MethodsSubjects with prostate cancer and known or suspected osseous metastatic disease were enrolled into one of two arms: dosimetry or dynamic. Dosimetry was performed with 6 whole body PET acquisitions and urine collection spanning 3 h; normal organ dosimetry was calculated using OLINDA/EXM. Dynamic imaging included a 60 min acquisition over a site of known or suspected disease followed by two whole body scans. Bootstrapping and subsampling of the acquired list-mode data were conducted to recommend image acquisition parameters for future clinical trials. ResultsUp to 233 MBq (6.3 mCi) of [68Ga]Ga-P15-041 was injected into 12 enrolled volunteers, 8 in dosimetry and 4 in dynamic cohorts. Radiotracer accumulated in known bone lesions and cleared rapidly from blood and soft tissue. The highest individual organ dose was 0.135 mSv/MBq in the urinary bladder wall. The average effective dose was 0.0173 ± 0.0036 mSv/MBq. An average injected activity of 166.5 MBq (4.5 mCi) resulted in absorbed dose estimates of 22.5 mSv to the urinary bladder wall, 8.2 mSv to the kidneys, and an effective dose of 2.9 mSv. Lesion signal to noise ratios on images generated from subsampled data were significantly higher for injected activities above 74 MBq (2 mCi) and were also significantly higher for imaging at 90 min than at 180 min post-injection. ConclusionsDosimetry estimates are acceptable and [68Ga]Ga-P15-041 uptake characteristics in patients with confirmed bone metastases support its continued development. Advances in knowledge and implications for patient careUse of [68Ga]Ga-P15-041 would not require cyclotron infrastructure for manufacturing and distribution, allowing for improved patient access to a promising PET bone imaging agent.

Dental X-Rays and the Risk of Thyroid Cancer and Meningioma: A Systematic Review and Meta-Analysis of Current Epidemiological Evidence.

Background: Exposure to moderate-to-high doses of ionizing radiation is the only established environmental risk factor for thyroid cancer and brain and central nervous system tumors. Considering the high lifetime prevalence and frequency of exposure to dental X-rays, the most common source of diagnostic radiation exposure in the general population, even a small associated increase in cancer risk would be of considerable public health importance. With the objective to inform clinical practice and guidelines, we synthesized the current epidemiological evidence on the association between dental X-rays and the risk of thyroid cancer, meningioma, and other cancers of the head and neck region. Methods: The Medline, Embase, and Web of Science databases were searched to identify eligible studies. Summary odds ratio/relative risk estimates and confidence intervals were extracted, and pooled risk ratios (RRs) for each cancer were calculated using random effects meta-analysis. Results: The literature search identified 5537 publications; of these, 26 studies including 10,868 cancer patients were included in the synthesis. The random effects meta-analyses, based on seven studies of thyroid cancer (six case/control, one cohort) and eight studies of meningioma (all case/control), showed that multiple (or repeated) exposures to dental X-rays were significantly associated with an increased risk of thyroid cancer (pooled RR = 1.87 [95% confidence interval, CI 1.11-3.15]) and meningioma (pooled RR = 1.53 [CI 1.26-1.85]). There was no association with glioma, and there were too few studies of other cancers of the head and neck region to conduct a meaningful meta-analysis. Conclusions: Based on a meta-analysis of retrospective case/control studies, these findings provide some support to the hypothesis that multiple (or repeated) exposures to dental X-rays may be associated with an increased risk of thyroid cancer and meningioma. These studies did not include individual organ doses and ages at exposure, and are subject to recall bias and other limitations. Furthermore, the thyroid exposure has decreased dramatically over time from the use of thyroid shields and improved technology/equipment. Prospective studies, based on dental X-ray records and patient follow-up, are needed to test the hypothesis further and clarify the possible cancer risk associated with dental radiography, as although the risk at the individual level, particularly with improved technology/equipment, is likely to be very low, the proportion of the population exposed is high. Considering that about one-third of the general population in developed countries is routinely exposed to one or more dental X-rays per year, these findings manifest the need to reduce diagnostic radiation exposure as much as possible.

P034] Implementation of a dose data collection software system: Structure of data and CT preliminary results

Purpose CT protocols review and optimization require a considerable amount of time and dedicated staff especially to compare dose levels among multicentre institutions and with national and international average values. The purpose of this article is to describe the structure of data collection for a dose radiation tracking software used to analyse a large amount of CT dose data. This should be done in order to audit scanner protocols, improve staff and patient safety and optimize all the diagnostic workflow. Methods The software implementation team included a team leader, two radiology technologists, two medical physicists and the chief of radiology department. Very detailed data collection folders and diagnostic reference values (DRV) were created based on 25th percentile, as target value, and 75th percentile, as upper limit, values of CTDIvol and DLP extracted from Swiss CT DRV. Data were collected from seven different multislice CT scanners using the study description Dicom tag. Results Direct protocol comparison, for each institution/scanner, is presented. About 90% of CT exams applied a dose inferior to Swiss DRV. Conclusions DVRs represent a benchmark useful to optimize radiation dose. Multisite cross-analysis of CT protocols allows the adoption of the best dose-optimized protocols in each center. Outliers and dose reduction strategies are discussed periodically within a team meeting: analyses are performed using a Montecarlo simulation tool to optimize future exams by varying setup parameters and study length. On request, total effective and individual organ dose values, are available especially for pregnant patients immediately after diagnostic examinations.

Cancer risk from paediatric computed tomography scanning: implications for radiation protection in medicine.

The use of computed tomography (CT) imaging is clearly beneficial for millions of patients. However, the potential adverse health effects, particularly cancer, of ionising radiation exposure from CT early in life are an issue of growing concern in the radiological protection, medical, and public health communities. Although efforts to quantify these effects have been conducted, the precision and accuracy of reported risks needs confirmation. EPI-CT, a European collaborative epidemiological study, was set up to quantify risks from paediatric CT to optimise paediatric diagnostic protocol. The study, coordinated by the International Agency for Research on Cancer, was designed as a multi-national cohort study of children and young adults who underwent CT scanning for long-term follow-up. It combined data from existing and extended cohorts in France, the UK, and Germany, and from new cohorts assembled in Belgium, Denmark, the Netherlands, Norway, Spain, and Sweden using a common protocol. A flexible dose reconstruction approach that can accommodate collection of data from historical sources (prior to 2000) and automatically extract data from the Digital Imaging and Communications in Medicine headers of recorded images available in the Picture Archiving Communication System was developed. Individual organ dose estimates for each child were derived from Monte-Carlo-based radiation transport calculations using hybrid phantoms of different sexes and ages. To account for uncertainties due to missing input data, a simulation method that maintains correlations of doses for persons within subgroups with similar exposure attributes and simulates uncertain dose-model parameter values was used. Simulation studies to evaluate the potential impact of a range of potential confounders (e.g. underlying medical conditions, socio-economic status, missing medical procedures performed outside of participating hospitals) on risk estimates were conducted based on data from some EPI-CT countries and/or reasonable scenarios. In total, 1,170,186 patients (before censorship) were enrolled in the national cohorts. Most patients (75%) had only undergone one CT scan and 29% of all patients were aged <5 years at the time of their first CT examination. The median duration of follow-up was 8 years for the entire cohort, although this varied between countries. Overall, the follow-up accounted for nearly 10 million person-years. This study received partial funding from the European Commission 7th Framework Programme under Grant Agreement No. 269912.

Evaluation of the UF/NCI hybrid computational phantoms for use in organ dosimetry of pediatric patients undergoing fluoroscopically guided cardiac procedures**This work was supported by Advanced Laboratory for Radiation Dosimetry Studies, University of Florida, American Association of University Women, National Cancer Institute Grant 1F31 CA159464.

Epidemiologic data demonstrate that pediatric patients face a higher relative risk of radiation induced cancers than their adult counterparts at equivalent exposures. Infants and children with congenital heart defects are a critical patient population exposed to ionizing radiation during life-saving procedures. These patients will likely incur numerous procedures throughout their lifespan, each time increasing their cumulative radiation absorbed dose. As continued improvements in long-term prognosis of congenital heart defect patients is achieved, a better understanding of organ radiation dose following treatment becomes increasingly vital. Dosimetry of these patients can be accomplished using Monte Carlo radiation transport simulations, coupled with modern anatomical patient models. The aim of this study was to evaluate the performance of the University of Florida/National Cancer Institute (UF/NCI) pediatric hybrid computational phantom library for organ dose assessment of patients that have undergone fluoroscopically guided cardiac catheterizations. In this study, two types of simulations were modeled. A dose assessment was performed on 29 patient-specific voxel phantoms (taken as representing the patient’s true anatomy), height/weight-matched hybrid library phantoms, and age-matched reference phantoms. Two exposure studies were conducted for each phantom type. First, a parametric study was constructed by the attending pediatric interventional cardiologist at the University of Florida to model the range of parameters seen clinically. Second, four clinical cardiac procedures were simulated based upon internal logfiles captured by a Toshiba Infinix-i Cardiac Bi-Plane fluoroscopic unit. Performance of the phantom library was quantified by computing both the percent difference in individual organ doses, as well as the organ dose root mean square values for overall phantom assessment between the matched phantoms (UF/NCI library or reference) and the patient-specific phantoms. The UF/NCI hybrid phantoms performed at percent differences of between 15% and 30% for the parametric set of irradiation events. Among internal logfile reconstructed procedures, the UF/NCI hybrid phantoms performed with RMS organ dose values between 7% and 29%. Percent improvement in organ dosimetry via the use of hybrid library phantoms over the reference phantoms ranged from 6.6% to 93%. The use of a hybrid phantom library, Monte Carlo radiation transport methods, and clinical information on irradiation events provide a means for tracking organ dose in these radiosensitive patients undergoing fluoroscopically guided cardiac procedures.