Temperature drift during environmental radiation monitoring and its unfolding

The aim of the presented paper is to examine the temperature drift and its unfolding for an environmental monitor equipped with a LaBr3(Ce) detector. It is known that temperature could influence energy, shape, and efficiency calibration. Consequently, when ambient temperature changes, the full energy absorption peak moves in the resulting spectrum. Research consists of experimental and analytical parts. During research in the climatic chamber, the dependence on temperature of energy, shape, and efficiency calibration was completed. The numerical method allows generating gamma spectra for theoretical so-called binary temperature variation.

Innovative advances in pediatric radiology: computed tomography reconstruction techniques, photon-counting detector computed tomography, and beyond

In pediatric radiology, balancing diagnostic accuracy with reduced radiation exposure is paramount due to the heightened vulnerability of younger patients to radiation. Technological advancements in computed tomography (CT) reconstruction techniques, especially model-based iterative reconstruction and deep learning image reconstruction, have enabled significant reductions in radiation doses without compromising image quality. Deep learning image reconstruction, powered by deep learning algorithms, has demonstrated superiority over traditional techniques like filtered back projection, providing enhanced image quality, especially in pediatric head and cardiac CT scans. Photon-counting detector CT has emerged as another groundbreaking technology, allowing for high-resolution images while substantially reducing radiation doses, proving highly beneficial for pediatric patients requiring frequent imaging. Furthermore, cloud-based dose tracking software focuses on monitoring radiation exposure, ensuring adherence to safety standards. However, the deployment of these technologies presents challenges, including the need for large datasets, computational demands, and potential data privacy issues. This article provides a comprehensive exploration of these technological advancements, their clinical implications, and the ongoing efforts to enhance pediatric radiology's safety and effectiveness.

[Radiation protection during fluoroscopic interventions]

Facts and figures about the frequencies of fluoroscopically guided interventions (FGI), typical patient exposures and occupational exposures are listed. Limits of radiation exposure do not exist for patients but only for occupationally exposed medical personnel. Measures for radiation protection of patients and personnel are explained. Nearly all technical radiation protection measures for patients also protect the personnel. To reduce the exposure of medical personnel, radiation protection equipment should be attached to the X‑ray modality and personal radiation protection equipment should be worn. The diagnostic reference values and the obligation to report incidents, including the reporting criteria, are explained. The radiation protection of patients and personnel for FGI in Germany is well regulated by diagnostic reference values, reporting criteria, prescribed or recommended protective measures, personal dosimetry and the obligation to involve medical physics experts.

On-line estimated peak skin dose during percutaneous coronary intervention for chronic total occlusion using new patient dose mapping technology

BACKGROUND

X-ray exposure during complex percutaneous coronary intervention is a very important issue.

AIM

To reduce patient peak skin dose during percutaneous coronary intervention procedures for chronic total occlusion using on-line estimated peak skin dose software (Dose Map).

METHODS

Throughout the procedure, Dose Map provided a map of local cumulative peak skin dose. This map was displayed in-room from 1Gy cumulative air kerma, and was updated every 0.5Gy. The operator's actions to minimize deterministic risks following map notification were collected. Skin reaction was evaluated 3 months after the procedure. A comparison with our historical X-ray exposure data (207 patients from January 2013 to July 2014) was performed.

RESULTS

From November 2015 to October 2016, 97 patients (Japanese chronic total occlusion score 2.1±1.1; 100 percutaneous coronary intervention procedures for chronic total occlusion) were prospectively enrolled. Fluoroscopy time was 40.8 (21.6-60.3) minutes, cumulative air kerma 1884 (1144-3231) mGy, estimated peak skin dose 962 (604-1474) mGy and kerma area product 115.8 (71.5-206.7) Gy.cm². Cumulative air kerma was>3Gy in 28% of cases, and>5Gy in 11% of cases. In 68% of cases, at least one action was taken by the operator after map notification to optimize skin dose distribution. Main changes included: gantry angulation (52%); field of view (25%); and collimation (13%). No skin injuries were observed at follow-up. In comparison with our chronic total occlusion historical radiation data, median cumulative air kerma and kerma area product were reduced by 31% and 33%, respectively (P<0.005.

CONCLUSION

Online skin dose mapping software allows the distribution of patient skin dose during complex percutaneous coronary intervention procedures, and may minimize X-ray exposure.

Monitoring Radiation Doses during Diagnostic and Therapeutic Neurointerventional Procedures: Multicenter Study for Establishment of Reference Levels

PURPOSE

To assess patient radiation doses during diagnostic and therapeutic neurointerventional procedures from multiple centers and propose dose reference level (RL).

MATERIALS AND METHODS

Consecutive neurointerventional procedures, performed in 22 hospitals from December 2020 to June 2021, were retrospectively studied. We collected data from a sample of 429 diagnostic and 731 therapeutic procedures. Parameters including dose-area product (DAP), cumulative air kerma (CAK), fluoroscopic time (FT), and total number of image frames (NI) were obtained. RL were calculated as the 3rd quartiles of the distribution.

RESULTS

Analysis of 1160 procedures from 22 hospitals confirmed the large variability in patient dose for similar procedures. RLs in terms of DAP, CAK, FT, and NI were 101.6 Gy·cm2, 711.3 mGy, 13.3 minutes, and 637 frames for cerebral angiography, 199.9 Gy·cm2, 3,458.7 mGy, 57.3 minutes, and 1,000 frames for aneurysm coiling, 225.1 Gy·cm2, 1,590 mGy, 44.7 minutes, and 800 frames for stroke thrombolysis, 412.3 Gy·cm2, 4,447.8 mGy, 99.3 minutes, and 1,621.3 frames for arteriovenous malformation (AVM) embolization, respectively. For all procedures, the results were comparable to most of those already published. Statistical analysis showed male and presence of procedural complications were significant factors in aneurysmal coiling. Male, number of passages, and procedural combined technique were significant factors in stroke thrombolysis. In AVM embolization, a significantly higher radiation dose was found in the definitive endovascular cure group.

CONCLUSION

Various RLs introduced in this study promote the optimization of patient doses in diagnostic and therapeutic interventional neuroradiology procedures. Proposed 3rd quartile DAP (Gy·cm2) values were 101.6 for diagnostic cerebral angiography, 199.9 for aneurysm coiling, 225.1 for stroke thrombolysis, and 412.3 for AVM embolization. Continual evolution of practices and technologies requires regular updates of RLs.

Dependence of photon registration efficiency on LaBr3(Ce) detector orientation for in situ radionuclide monitoring

Knowledge of a radiation detector's numerical characteristics allows its energy efficiency to be calibrated theoretically for any measurement geometry. Here, energy efficiency calibration is discussed for oriented LaBr₃(Ce) detectors used for in situ radiation monitoring. Vertical and horizontal detector orientations relative to the ground surface are compared using efficiency calibrations based on the detector's numerical characteristics and are equally effective. Quantitative assessment of the different measurement geometries was performed using a new analytical approach: integrated absolute full energy peak efficiency.

Ambient dose during intraoral radiography with current techniques: part 3: effect of tube voltage

OBJECTIVES

This study was conducted to assess the impact of tube voltage on ambient dose during intraoral radiography, specifically remnant-beam transmission and scattered radiation.

METHODS AND MATERIALS

Remnant-beam and scattered radiation doses were recorded using a phantom at tube voltages of 60, 63, 66 and 70 kV. Mathematical equations depicting their relations were then formulated, and reference values were calculated at the various voltages tested. Total ambient doses per exposure at 60 kV and at 70 kV were compared.

RESULTS

Both remnant-beam transmission and scattered radiation increased ~40% by increasing tube voltage from 60 kV to 70 kV, and the relation was linear. A remnant beam transmission reference value of 7.5% was established at 70 kV, as well as a conversion factor of 0.035 µSv/mAs at 1 m for scattered radiation at 60 kV. Given longer exposure times at 60 kV, total ambient dose proved higher at 60 kV than at 70 kV.

CONCLUSION

Higher tube voltage results in higher remnant-beam transmission and more scattered radiation per workload. The relation is linear in the range between 60kV and 70 kV. Remnant-beam transmission at 70 kV is safely assessed at 7.5%. A conversion factor at 60 kV of 0.035 µSv/mAs at 1 m for the scattered radiation dose can be proposed. Total ambient dose per exposure was higher at 60kV than at 70 kV.

[Comparison of radiation exposure in common hepatic interventions : A retrospective analysis of DeGIR registry data]

Hintergrund

Die transarterielle Chemoembolisation (TACE) oder auch Gallenganginterventionen stellen häufige Leberinterventionen dar.

Ziel der Arbeit

In dieser retrospektiven Studie soll die Strahlenexposition der Patienten mit einem hepatischen Eingriff in Abhängigkeit von Art und Feinziel der Intervention analysiert und verglichen werden.

Material und Methoden

Dies ist eine Analyse von 7003 DeGIR-Registerdatensätzen aus den Jahren 2016 bis 2018 für TACE und Gallenganginterventionen. Das Dosisflächenprodukt (DFP) und die Durchleuchtungszeit (DL) sowie die Interventionsart und das anatomisch definierte Feinziel der Interventionen wurden erfasst.

Ergebnisse

Insgesamt lagen Dosiswerte für 4985 durchgeführte TACE und 2018 Gallenganginterventionen vor. Bei Gallenganginterventionen lag der Median des DFP bei 2594 (Interquartilbereich [IQR] = 1174–5858) cGy*cm². Bei der TACE betrug der Median des DFP 11.632 [IQR = 5530–22.800] cGy*cm² und lag damit signifikant höher als bei Gallenganginterventionen (p < 0,0001). Gallengangeingriffe mit dem höchsten DFP sind Interventionen am Ductus hepaticus, während Eingriffe mit der längsten DL an der Hepatikusgabel stattfinden.

Diskussion

Die individuelle Strahlendosis für einen Patienten bei einer Leberintervention hängt weniger von der Komplexität des Eingriffs bzw. Durchleuchtungszeit ab, sondern von der Art des Eingriffs und vom Feinziel der Intervention. Die vorliegenden Dosisdaten können eine Hilfe sein, die Strahlenexposition bei einer Leberintervention bereits vor dem Eingriff grob abzuschätzen.

Advances in detection algorithms for radiation monitoring

This paper presents a review of up-to-date advancements in detection algorithms employed in radiation monitoring for generating radiation maps of ground contamination and tracking radioactive release into the atmosphere. Detection algorithms for true count processing, spectroscopy processing, and plume tracking are discussed in chronological order of development. Process steps of detection include height correction, solid-angle correction, background radioactivity correction, Compton continuum elimination, de-noising of gamma-radiation spectra, and recording of plume passage events.

Dental anomalies in people living in radionuclide-contaminated regions

The 1986 accident at the Chernobyl Nuclear Power Plant led to large-scale changes in the environmental situation. The purpose of our study was to conduct a comparative analysis of the morphological states of the dentition of individuals living in regions exposed to radiation to determine the groups at risk for the main classes of dental anomalies. We believe our results will support the development of a differentiated system for dental rehabilitation and follow-up of individuals exposed to radiation. The prevalence rate of dental anomalies was studied in 1,889 patients of both sexes divided by age in accordance with dentition formation stages and by regions of residence in accordance with the ¹³⁷Cs soil-contamination level. A statistically significant decrease was observed in the number of patients with normal dentition for their age among those who had been exposed to prenatal radiation. A sharp increase in combined dental anomalies was revealed in patients who lived in regions with a¹³⁷Cs soil-contamination level ranging from 555 to 1665 GBq/km²; concomitantly, multidirectional fluctuations were observed in the numbers of tooth and occlusion anomalies. Among the examined population, the most severe pathology of the oral organs was found in prenatally irradiated patients (born between April 26, 1986, and April 30, 1987). The prevalence of dental anomalies is interrelated not only with the level of radioactive contamination in the soil of the dwelling area, but also with the age of the surveyed individuals at the moment of the accident.

Review and performance of the Dose Profiler, a particle therapy treatments online monitor

Particle therapy (PT) can exploit heavy ions (such as He, C or O) to enhance the treatment efficacy, profiting from the increased Relative Biological Effectiveness and Oxygen Enhancement Ratio of these projectiles with respect to proton beams. To maximise the gain in tumor control probability a precise online monitoring of the dose release is needed, avoiding unnecessary large safety margins surroundings the tumor volume accounting for possible patient mispositioning or morphological changes with respect to the initial CT scan. The Dose Profiler (DP) detector, presented in this manuscript, is a scintillating fibres tracker of charged secondary particles (mainly protons) that will be operating during the treatment, allowing for an online range monitoring. Such monitoring technique is particularly promising in the context of heavy ions PT, in which the precision achievable by other techniques based on secondary photons detection is limited by the environmental background during the beam delivery. Developed and built at the SBAI department of "La Sapienza", within the INSIDE collaboration and as part of a Centro Fermi flagship project, the DP is a tracker detector specifically designed and planned for clinical applications inside a PT treatment room. The DP operation in clinical like conditions has been tested with the proton and carbon ions beams of Trento proton-therapy center and of the CNAO facility. In this contribution the detector performances are presented, in the context of the carbon ions monitoring clinical trial that is about to start at the CNAO centre.

[Analysis of individual dose monitoring results among radiation workers in a first-class hospital at Grade 3 from 2010 to 2017]

Objective: To understand the occupational external exposure dose among radiation workers in a first-class hospital at Grade 3 of Suzhou, and to provide reference for radiological protection. Methods: The individual dose of 1156 radiation workers in the hospital from 2010 to 2017 were detected, the annual collective effective dose and per capita annual effective dose were analyzed for different years, different occupations (diagnostic radiology, radiotherapy, nuclear medicine, interventional radiology) , gender, and age. Results: From 2010 to 2017, the total annual collective effective dose was 351.40 person·mSv, the per capita annual dose was 0.30 mSv/a, and radiation workers whose annual effective dose was less than 1 mSv accounted for 94.98%. There were 5 interventional radiology workers and 1 nuclear medicine worker with annual effective dose between 2 and 4 mSv. There was no worker with annual effective dose over 4 mSv. The per capita annual effective dose of nuclear medicine workers was the highest (0.40 mSv/a) . The per capita annual effective dose was not significantly different between radiation workers with different genders and ages (P>0.05) . Conclusion: Most of radiation workers have low individual dose level in the hospital. It is important to focus on nuclear medicine workers and interventional radiology workers.

An Environmental Scan of the National and Provincial Diagnostic Reference Levels in Canada for Common Adult Computed Tomography Scans

Several regulatory bodies have agreed that low-dose radiation used in medical imaging is a weak carcinogen that follows a linear, non-threshold model of cancer risk. While avoiding radiation is the best course of action to mitigate risk, computed tomography (CT) scans are often critical for diagnosis. In addition to the as low as reasonably achievable principle, a more concrete method of dose reduction for common CT imaging exams is the use of a diagnostic reference level (DRL). This paper examines Canada's national DRL values from the recent CT survey and compares it to published provincial DRLs as well as the DRLs in the United Kingdom and the United States of America for the 3 most common CT exams: head, chest, and abdomen/pelvis. Canada compares well on the international scale, but it should consider using more electronic dose monitoring solutions to create a culture of dose optimization.

Vendor free basics of radiation dose reduction techniques for CT

Although radiation dose in computed tomography (CT) decreased and CT became safer examinations than before, CT is the most significant source of the medical radiation exposure. Knowledge about available radiation dose reduction methods in CT is essential. Substantial improvement occurred regarding tube current selection (automatic exposure control) and image production method (iterative reconstruction). Optimizing the tube potential selection is expected to contribute to further CT radiation dose reduction. This review article summarizes the principles of radiation dose reduction in CT, principal methods of radiation dose reduction, auxiliary measures of radiation dose saving and recent issues of low dose CT.

Radiation exposure during CT-guided biopsies: recent CT machines provide markedly lower doses

OBJECTIVES

To examine radiation dose levels of CT-guided interventional procedures of chest, abdomen, spine and extremities on different CT-scanner generations at a large multicentre institute.

MATERIALS AND METHODS

1,219 CT-guided interventional biopsies of different organ regions ((A) abdomen (n=516), (B) chest (n=528), (C) spine (n=134) and (D) extremities (n=41)) on different CT-scanners ((I) SOMATOM-Definition-AS+, (II) Volume-Zoom, (III) Emotion6) were included from 2013-2016. Important CT-parameters and standard dose-descriptors were retrospectively examined. Additionally, effective dose and organ doses were calculated using Monte-Carlo simulation, following ICRP103.

RESULTS

Overall, radiation doses for CT interventions are highly dependent on CT-scanner generation: the newer the CT scanner, the lower the radiation dose imparted to patients. Mean effective doses for each of four procedures on available scanners are: (A) (I) 9.3mSv versus (II) 13.9mSv (B) (I) 7.3mSv versus (III) 11.4mSv (C) (I) 6.3mSv versus (II) 7.4mSv (D) (I) 4.3mSv versus (II) 10.8mSv. Standard dose descriptors [standard deviation (SD); CT dose index_vol (CTDI_vol); dose-length product (DLP_body); size-specific dose estimate (SSDE)] were also compared.

CONCLUSION

Effective dose, organ doses and SSDE for various CT-guided interventional biopsies on different CT-scanner generations following recommendations of the ICRP103 are provided. New CT-scanner generations involve markedly lower radiation doses versus older devices.

KEY POINTS

• Effective dose, organ dose and SSDE are provided for CT-guided interventional examinations. • These data allow identifying organs at risk of higher radiation dose. • Detailed knowledge of radiation dose may contribute to a better individual risk-stratification. • New CT-scanner generations involve markedly lower radiation doses compared to older devices.

Using two detectors concurrently to monitor ambient dose equivalent rates in vehicle surveys of radiocesium contaminated land

In response to the accident at Tokyo Electric Power Company's Fukushima Dai-ichi Nuclear Power Plant (FDNPP), vehicle-borne monitoring was used to map radiation levels for radiological protection of the public. By convention measurements from vehicle-borne surveys are converted to the ambient dose equivalent rate at 1 m height in the absence of the vehicle. This allows for comparison with results from other types of survey, including surveys with hand-held or airborne instruments. To improve the accuracy of the converted results from vehicle-borne surveys, we investigated combining measurements from two detectors mounted on the vehicle at different heights above the ground. A dual-detector setup was added to a JAEA monitoring car and compared against hand-held survey meter measurements in Fukushima Prefecture. The results obtained by combining measurements from two detectors were within ±20% of the hand-held reference measurements. The mean absolute percentage deviation from the reference measurements was 7.2%. The combined results from the two detectors were more accurate than those from either the roof-mounted detector, or the detector inside the vehicle, taken alone. One issue with vehicle-borne surveys is that ambient dose equivalent rates above roads are not necessarily representative of adjacent areas. This is because radiocesium is often deficient on asphalt surfaces, as it is easily scrubbed off by rain, wind and vehicle tires. To tackle this issue, we investigated mounting heights for vehicle-borne detectors using Monte Carlo gamma-ray simulations. When radiocesium is deficient on a road compared to the adjacent land, mounting detectors high on vehicles yields results closer to the values adjacent to the road. The ratio of ambient dose equivalent rates reported by detectors mounted at different heights in a dual-detector setup indicates whether radiocesium is deficient on the road compared to the adjacent land.

Benchmarking adult CT-dose levels to regional and national references using a dose-tracking software: a multicentre experience

Objectives

To benchmark CT-dose data for standard adult CT studies to regional and national reference levels using a dose-tracking system.

Methods

Data from five CT systems from three hospitals were collected over a 1- to 2.5-year period (2012–2014), using the same type of dose management system. Inclusion criteria were adult patients and standard CT-head, CT-abdomen-pelvis, CT-thorax, CT-lumbar spine, CT-pulmonary embolism, CT-cervical spine and CT-thorax-abdomen studies, with one helical scan. Volumetric CT-dose index (CTDI_vol), dose length product (DLP) and scan length from 31,709 scans were analysed statistically.

Results

After dose optimisation CTDI_vol and DLP values were below the national diagnostic reference levels (DRLs) for all CT studies and for all systems investigated. Mostly no significant differences were found between CTDI_vol and DLP levels (p values ≥ 0.01) of CT studies performed on different scanners within the same hospital. Significant dose differences (p values < 0.01) were instead observed among hospitals for comparable CT studies. Dose level range and scan length differences for similar CT studies were revealed.

Conclusions

Dose-tracking systems help to reduce CT-dose levels below national DRLs. However, dose and protocol data comparison between and within hospitals has the potential to further reduce variability in dose data of standard adult CT studies.

Key Points

• Retrospective three-centre study on dose levels of standard adult CT procedures.

• Dose-tracking systems help hospitals to stay below national dose reference levels.

• Dose-tracking systems help to align CT dose levels between scanners within hospitals.

• Benchmarking shows CT dose level variability for similar examinations in different hospitals.

• Differences in dose level range/scan length for similar CT studies are revealed.

Electronic supplementary material

The online version of this article (10.1007/s13244-017-0570-5) contains supplementary material, which is available to authorized users.

Personalized Feedback on Staff Dose in Fluoroscopy-Guided Interventions: A New Era in Radiation Dose Monitoring

PURPOSE

Radiation safety and protection are a key component of fluoroscopy-guided interventions. We hypothesize that providing weekly personal dose feedback will increase radiation awareness and ultimately will lead to optimized behavior. Therefore, we designed and implemented a personalized feedback of procedure and personal doses for medical staff involved in fluoroscopy-guided interventions.

MATERIALS AND METHODS

Medical staff (physicians and technicians, n = 27) involved in fluoroscopy-guided interventions were equipped with electronic personal dose meters (PDMs). Procedure dose data including the dose area product and effective doses from PDMs were prospectively monitored for each consecutive procedure over an 8-month period (n = 1082). A personalized feedback form was designed displaying for each staff individually the personal dose per procedure, as well as relative and cumulative doses. This study consisted of two phases: (1) 1-5th months: Staff did not receive feedback (n = 701) and (2) 6-8th months: Staff received weekly individual dose feedback (n = 381). An anonymous evaluation was performed on the feedback and occupational dose.

RESULTS

Personalized feedback was scored valuable by 76% of the staff and increased radiation dose awareness for 71%. 57 and 52% reported an increased feeling of occupational safety and changing their behavior because of personalized feedback, respectively. For technicians, the normalized dose was significantly lower in the feedback phase compared to the prefeedback phase: [median (IQR) normalized dose (phase 1) 0.12 (0.04-0.50) µSv/Gy cm² versus (phase 2) 0.08 (0.02-0.24) µSv/Gy cm², p = 0.002].

CONCLUSION

Personalized dose feedback increases radiation awareness and safety and can be provided to staff involved in fluoroscopy-guided interventions.

Real-Time Patient and Staff Radiation Dose Monitoring in IR Practice

PURPOSE

Knowledge of medical radiation exposure permits application of radiation protection principles. In our center, the first dedicated real-time, automated patient and staff dose monitoring system (DoseWise Portal, Philips Healthcare) was installed. Aim of this study was to obtain insight in the procedural and occupational doses.

MATERIALS AND METHODS

All interventional radiologists, vascular surgeons, and technicians wore personal dose meters (PDMs, DoseAware, Philips Healthcare). The dose monitoring system simultaneously registered for each procedure dose-related data as the dose area product (DAP) and effective staff dose (E) from PDMs. Use and type of shielding were recorded separately. All procedures were analyzed according to procedure type; these included among others cerebral interventions (n = 112), iliac and/or caval venous recanalization procedures (n = 68), endovascular aortic repair procedures (n = 63), biliary duct interventions (n = 58), and percutaneous gastrostomy procedure (n = 28).

RESULTS

Median (±IQR) DAP doses ranged from 2.0 (0.8-3.1) (percutaneous gastrostomy) to 84 (53-147) Gy cm² (aortic repair procedures). Median (±IQR) first operator doses ranged from 1.6 (1.1-5.0) μSv to 33.4 (12.1-125.0) for these procedures, respectively. The relative exposure, determined as first operator dose normalized to procedural DAP, ranged from 1.9 in biliary interventions to 0.1 μSv/Gy cm² in cerebral interventions, indicating large variation in staff dose per unit DAP among the procedure types.

CONCLUSION

Real-time dose monitoring was able to identify the types of interventions with either an absolute or relatively high staff dose, and may allow for specific optimization of radiation protection.

A dose monitoring system for dental radiography

Purpose

The current study investigates the feasibility of a platform for a nationwide dose monitoring system for dental radiography. The essential elements for an unerring system are also assessed.

Materials and Methods

An intraoral radiographic machine with 14 X-ray generators and five sensors, 45 panoramic radiographic machines, and 23 cone-beam computed tomography (CBCT) models used in Korean dental clinics were surveyed to investigate the type of dose report. A main server for storing the dose data from each radiographic machine was prepared. The dose report transfer pathways from the radiographic machine to the main sever were constructed. An effective dose calculation method was created based on the machine specifications and the exposure parameters of three intraoral radiographic machines, five panoramic radiographic machines, and four CBCTs. A viewing system was developed for both dentists and patients to view the calculated effective dose. Each procedure and the main server were integrated into one system.

Results

The dose data from each type of radiographic machine was successfully transferred to the main server and converted into an effective dose. The effective dose stored in the main server is automatically connected to a viewing program for dentist and patient access.

Conclusion

A patient radiation dose monitoring system is feasible for dental clinics. Future research in cooperation with clinicians, industry, and radiologists is needed to ensure format convertibility for an efficient dose monitoring system to monitor unexpected radiation dose.

Indication of the radioactive fallout in Riyadh, Saudi Arabia following the Fukushima nuclear accident

On March 2011, a severe damage has occurred to Fukushima Di-iachi nuclear reactor complex in Japan following the huge earthquake and the resulting Tsunami. Consequently, vast amounts of radioactive fallout were released into the atmosphere and contaminated the environment in Japan. Soon after the accident, traces of anthropogenic radionuclides were detected in environmental samples collected in many parts in the northern hemisphere even very far away from Japan creating a global concern. There is no information about radioactive contamination in the Arabian Peninsula caused by the Japanese Fukushima nuclear accident. The first evidence of Fukushima radioactive fallout in Riyadh (24° 43' N, 46° 38' E), Saudi Arabia has been confirmed in April 8, 2011. The airborne fission products (131)I, (134)Cs and (137)Cs were measured in air samples. The radionuclide concentrations were determined by identifying their characteristic gamma rays using a germanium detector. Their activity concentrations were studied as a function of time over a period of 20 days at the end of which they had mostly fallen below our limit of detection. The maximum activity concentration of (131)I, (134)Cs and (137)Cs in air of, respectively, 323.7 ± 18.5, 17.2 ± 1.0 and 26.0 ± 1.8 μBq m(-3) were observed on April 10-11, 2011. The (131)I/(137)Cs and (134)Cs/(137)Cs activity ratio values in air were presented and discussed. Finally, the effective doses to the public of Riyadh city from inhalation of (131)I, (134)Cs and (137)Cs due to contribution from Fukushima incident was found far below levels of concern.

Improvements in the method of radiation anomaly detection by spectral comparison ratios

We present a new procedure for configuring the Nuisance-rejection Spectral Comparison Ratio Anomaly Detection (N-SCRAD) method. The procedure minimizes detectable count rates of source spectra at a specified false positive rate using simulated annealing. We also present a new method for correcting the estimates of background variability used in N-SCRAD to current conditions of the total count rate. The correction lowers detection thresholds for a specified false positive rate, enabling greater sensitivity to targets.

Lightweight aerial vehicles for monitoring, assessment and mapping of radiation anomalies

The Fukushima Daiichi nuclear power plant (FDNPP) incident released a significant mass of radioactive material into the atmosphere. An estimated 22% of this material fell out over land following the incident. Immediately following the disaster, there was a severe lack of information not only pertaining to the identity of the radioactive material released, but also its distribution as fallout in the surrounding regions. Indeed, emergency aid groups including the UN did not have sufficient location specific radiation data to accurately assign exclusion and evacuation zones surrounding the plant in the days and weeks following the incident. A newly developed instrument to provide rapid and high spatial resolution assessment of radionuclide contamination in the environment is presented. The device consists of a low cost, lightweight, unmanned aerial platform with a microcontroller and integrated gamma spectrometer, GPS and LIDAR. We demonstrate that with this instrument it is possible to rapidly and remotely detect ground-based radiation anomalies with a high spatial resolution (<1 m). Critically, as the device is remotely operated, the user is removed from any unnecessary or unforeseen exposure to elevated levels of radiation.

A radiometric and petrographic interpretation of discrepancies on uranium content in samples collected at Alte Madonie Mounts region (Sicily, Italy)

The main goal of this work is to evaluate a correlation between anomalous Uranium (U) content and petrographic features of some soil and rock samples collected at Alte Madonie Mounts region (North-central Sicily, Italy). A total of 41 samples of selected soils and rocks were collected, powdered, dried and sealed in "Marinelli" beakers for 20 days before the measurement to ensure that radioactive equilibrium between (226)Ra and (214)Bi was reached. Gamma-ray spectrometric analysis was used to quantify radioactivity concentrations. Mineralogical and chemical features of the samples were determined by X-ray Fluorescence (XRF), X-ray Diffractometry (XRD), Attenuated Total Reflection-Fourier Transform Infrared (ATR-FTIR) and Scanning Electron Microscope - Energy Dispersive Spectrometry (SEM-EDS) analyses. The average values of concentrations of (226)Ra, (228)Ac and (40)K were respectively 30, 17 and 227 Bq kg(-1) while the greatest values were 134, 59 and 748 Bq kg(-1). Linear relationships were observed between (226)Ra, (228)Ac and (40)K concentrations: the activities of (226)Ra and (228)Ac were comparable, while those of (40)K were about 10 times greater. An exception was highlighted for a group of samples where (226)Ra activities were much higher than expectations. Chemical compositions and mineralogical features of the samples have made it possible to justify these anomalies.

Monitoring rainwater and seaweed reveals the presence of (131)I in southwest and central British Columbia, Canada following the Fukushima nuclear accident in Japan

Detailed analysis of (131)I levels in rainwater and in three species of seaweed (Fucus distichus Linnaeus, Macrocystis pyrifera, and Pyropia fallax) collected in southwest British Columbia and Bella Bella, B.C., Canada was performed using gamma-ray spectroscopy following the Fukushima nuclear power plant accident on March 11, 2011. Maximum (131)I activity was found to be 5.8(7) Bq/L in rainwater collected at the campus of Simon Fraser University in Burnaby, B.C. nine days after the accident. Concomitantly, maximum observed activity in the brown seaweed F. distichus Linnaeus was observed to be 130(7) Bq/kg dry weight in samples collected in North Vancouver 11 days following the accident and 67(6) Bq/kg dry weight in samples collected from the Bamfield Marine Sciences Centre on Vancouver Island 17 days following the accident. The (131)I activity in seaweed samples collected in southwest B.C. following the Fukushima accident was an order of magnitude less than what was observed following Chernobyl. Iodine-131 activity in F. distichus Linnaeus remained detectable for 60 days following the accident and was detectable in each seaweed species collected. The Germanium Detector for Elemental Analysis and Radioactivity Studies (GEARS) was modeled using the Geant4 software package and developed as an analytical tool by the Nuclear Science group in the Simon Fraser University Department of Chemistry for the purpose of these measurements.

Sci-Thur AM: Planning - 06: Planning target volume margin suitability in lung stereotactic body radiation therapy: A preliminary evaluation using cone-beam computed tomography

Stereotactic body radiation therapy (SBRT) requires precise delivery of radiation to the target; intra- and inter-fraction lung tumour motion may adversely impact local tumour control. The purpose of this study was to retrospectively evaluate the impact of planning target volume (PTV) margin size on the coverage of the internal target volume (ITV) as localized in pre- and post-treatment cone-beam computed tomography (CBCT) images. Data from two patients undergoing SBRT were evaluated. For planning, free-breathing and 4DCT scans were performed, and used to contour the ITV. A 5mm margin was added to create the PTV. During treatment, 14 CBCTs were collected pre- and post-beam delivery. A data set comprising the average 4DCT intensities where available and treatment planning CT intensities for voxels that were beyond the field of view of the 4DCT was constructed. Registration of the combined planning image to each CBCT was performed using a deformable image registration algorithm. The transformations aligning the combined planning image with the CBCTs were applied to the planning ITV to obtain the treatment ITVs. For each CBCT, the fraction of treatment ITV within the PTV was determined using Boolean logic. This was repeated for various PTV margins ranging from 0 to 10 mm at 1mm intervals. The 3 and 5 mm PTV margins covered 95.1 ± 5.9% and 99.0 ± 2.0% of the ITV, respectively. Analysis of additional patients will be performed to confirm these preliminary results, which reinforce the use of a 5mm PTV margin for lung SBRT.

SU-E-J-57: MRI-Linac (MRL) Guided Treatment for Esophageal Cancer

For radiotherapy, oesophageal cancer is located in a difficult area. Spatial control of the dose distribution is difficult to achieve with current CT-based radiation techniques, as on CT, soft-tissue contrast is too low. Furthermore, the oesophagus moves and organs at risk (e.g. lung, heart, liver, spinal cord) are in close proximity. An 1.5 T MRI-accelerator (MRL) has sufficient soft-tissue tumour visualization possibilities to allow for precise real-time, online, position verification and for dose escalation without organ at riskoverdose. Our research consists of the preparatory work for the first clinical study on the MRL for patients with oesophageal cancer. To improve image quality and reduce the motion artefacts, the benefit of cardiac triggering and breath holds is evaluated on fifteen oesophageal patients. Results show the superb image quality of these MRI sequences. The use of this high quality MRI gives the possibility for non-invasive real-time visualization andtracking of the tumour. We quantify oesophageal tumour motion on cineMRI. The tumour is tracked on sequential mixed T1/T2w images (acquisition time: 60s, temporal resolution: 0.5s, slice thickness: 7mm) of a single coronal and sagittal slice using a Minimum Output Sum of Squared Error (MOSSE) adaptive correlation filter. Tumour registration within the individual images can typically be done at a millisecond time scale. Motion of oesophageal tumours can well be tracked and is highly variable between patients. The greatest mobility is seen in cranio-caudal direction, with amaximum peak-to-peak amplitude of tumour movement of 24.5mm followed by the dorso-ventral and the medio-lateral direction. Movement seems greatest in tumours located in the lower part of the oesophagus. This study shows both the superb image quality for GTV localisation and the possibility for on-line and real time tumour tracking. The study opens thepossibility for tracked radiation delivery with a 1.5T MRI accelerator. Partial funding has been obtained by Elekta and Philips.

SU-E-T-251: Analysis of Irradiated Induced Lung Injury in Non-Small Cell Lung Cancer (NSCLC) Treated by Three-Dimensional Conformal Radiotherapy(3DCRT)

PURPOSE

The aim of this study was to analyze the affect factors with radiation induced lung injury of NSCLC treated by 3DCRT, in order to supply reference criteria for optimize the treatment planning, further to improve the local control rate and the quality of life of NSCLC patients.

METHODS

From August 2000 to December 2004, 107 NSCLC patients received 3DCRT were retrospectively enrolled in this study. All of patients received the prescription doses ranged from 60-68Gy with a median dose of 66Gy. Dosimetric parameters of dose-volume histograms from 3DCRT plans was recorded. The lung injury were assessed for each patient during the treatment and follow-up within 3 months after treatment completion. Acute radiation induced pneumonitis were graded by one radiation oncologist according to the RTOG/EORTC criteria. The correlation between dosimetric parameters with lung injury was evaluated by univariate and multivariate analysis using Logistic Regression Model of SPSS11.0 software.

RESULTS

In the 107 patients of NSCLC, the rate of irradiated induced lung injury was 62.6% and the rate of =2 grade radiation induced pneumonitis was 38.3%. Twenty-three cases were classified in grade 2, fourteen cases in grade 3, four cases in grade 4. Univariate analysis showed chronic obstructive pulmonary disease(COPD), number of beams field, lung mean dose, lung V5-V40 were important parameters on radiation induced lung injury. The rate of =2 grade lung injury was 56.3%(18/32) in patients accompany COPD, compared with 30.7%(23/75) of those without COPD. In the same way,the rate of =2 grade lung injury was 61.9%(26/42) in patients of lung mean dose=20Gy, which higher than 19.4%(12/62) of lung mean dose<20Gy. Further more, lung mean dose, lung V20 and COPD were likely to be the independent factors of radiation induced lung injury by Logistic Regression Model.

CONCLUSIONS

lung mean dose, lung V20 and COPD were the independent affect factors on irradiated induced lung injury. Our funding support received from National Natural Science Foundation of China (30870743).

SU-E-T-195: Experience in Implementing Intraoperative Radiation Therapy for Accelerated Partial Breast Irradiation Using Low-Energy X-Ray Source

PURPOSE

To present our preliminary experience and quality-assurance (QA) procedures in implementing intraoperative-radiation therapy (IORT) for accelerated-partial-breast irradiation (APBI) using the Axxent-system controller (Xoft Inc.) Methods: IORT was implemented in our institution utilizing a 50-keV x-ray source. APBI allows breast conserving in patients with early-stage-breast cancer by delivering radiation to the lumpectomy bed via an applicator balloon filled with water, to which a prescribed dose of 20 Gy was applied to its surface. In-situ anesthesiology, breast-surgery and radiation-oncology teams were required to achieve this procedure. Calibration of the source, including temperature and pressure corrections, was performed by the controller resulting in a calibration factor, which was manually introduced by a physicist into an in-house program providing the corrected dwell times. Evaluation of exposure measurements determined that personnel standing behind glass-rolling shields during irradiation were sufficient protection.

RESULTS

We have successfully treated four patients to date. Surgical times averaged about two hours, QA and setup of controller took about 30 minutes, while radiation-treatment times ranged 7.8-10.4 minutes. Exposure to personnel showed a negligible dose compared to background based on the in-vivo measurements. Our measurements have shown that placement of a shielding layer (FlexiShield) on top of the drape-protected breast reduced radiation exposure to in-room personnel. In one case, treatment was automatically stopped by the controller due to a sudden undetected cooling water flow; due to the pre-treatment training, treatment was successfully resumed within a minute after manual adjustment of the flow sensor.

CONCLUSIONS

Implementation of IORT to treat patients with APBI using low-energy x-ray source should follow the manufacturer's recommendations regarding to the acceptance and personnel training. Our experience indicates that two physicists are necessary at least at the implementation stage. Appropriate training to deal with potential problems is crucial before clinical treatment can be ready.

SU-D-217A-06: Impact of Anterior-Posterior (AP) and Posterior-Anterior (PA) Scout Scans on the CT Radiation Dose in the Whole Body PET/CT Scan

PURPOSE

CT can contribute over 50% of radiation dose in the whole body (WB) PET/CT scan. Tube current modulation (TCM) is a standard technique for reducing CT radiation dose to the patient by changing the tube current with the patient size, and is controlled by a very low-dose scoutscan, which assumes the patient is positioned at the center of the CT gantry opening. However, most patients are not positioned at the center due to practicality or to avoid claustrophobic or to reduce time of radiation exposure from the patient to the technologist. We study the impact of the AP and PA scout scans to the patient radiation exposure from CT.

METHODS

Ina retrospective study of 200 patients, each received two WB PET/CT scans: one with AP, and the other one with PA. The helical CT with TCM and PET acquisitions were identical in both scans. Separation of the two scans was about 10 months in average. The scans were performed on four GE PET/CT scanners: three 16- and one 64-slice with the same TCM settings. The 200patients were selected for the same scan coverage and similar body weight (difference = 3 kg). The tube current in each slice and average exposure tothe patient were recorded and compared.

RESULTS

The AP scout caused lower radiation dose on 94% of the patients. Both the tube current, and radiation exposure were reduced by 46±30 mA and 1.6±1.0 mGy, respectively. The effective radiation dose is reduced by 1.7±1.2 mSv. These results were statistically significant (p<0.00001).

CONCLUSIONS

The AP scout caused significantly less radiation dose than the PA scout in the CT scan of the whole-body PET/CT scan. Care should be taken to select theorientation of the scout scan to achieve appropriate radiation exposure to the patient when TCM is applied.

SU-E-T-490: Comparison of XVMC Monte Carlo Dose Calculations with Eclipse AAA Calculations for RapidArc Plans

PURPOSE

The consistency between the AAA and XVMC algorithm in the treatment planning for RapidArc is investigated. While the majority of the radiation field is blocked by the MLC system, multiple small dose islands with MLC opened only slightly can be observed in one control point. This raises questions on how accurate the clinically used AAA algorithm in Eclipse is able to calculate RapidArc dose distributions. The fast Monte Carlo Code XVMC was used as a benchmark to test the AAA algorithm.

METHODS

RadpidArc plans of 25 patients were calculated with AAA and XVMC. The patient cohort consisted of 4 different cancer sites (H&N, upper abdominal, lung, prostate). Dose distributions, PTV and OAR coverage were compared looking at the PTV mean dose Dmean, the volume V95% of the PTV receiving 95% of the prescribed dose, the dose D95% delivered to 95% of the PTV Volume, the percentage PTV mean dose with respect to the prescribed dose Dmean/prescr and OAR mean dose.

RESULTS

The recalculation of RapidArc plans yielded good agreement of both calculation algorithms for treatment plans of all four cancer sites. PTV mean dose differences of AAA and XVMC were found to be in between -0.11% and 4.89% of the prescribed dose. The mean dose difference found was 0.48±0.77 Gy. Local dose differences were found when comparing dose distributions in regions of big mass density differences and in high dose regions. One head and neck plan and one prostate plan revealed significant differences in PTV coverage (ΔDmean=3.25 Gy) and OAR mean dose (prostate mean dose -13.71 Gy) respectively.

CONCLUSIONS

The vast majority of treatment plans calculated with the AAA algorithm were found to agree within the expected and acceptable tolerances compared to XVMC results. Nevertheless in some cases dose differences were observed that could be of clinical significance. This work was funded by a Varian grant. Wolfram Laub is working in the physics group of CMS.

Poster - Thurs Eve-04: Mathematical modeling of liver metastases tumour growth and control with radiotherapy

Generating an optimized radiation treatment plan requires understanding the factors affecting tumour control. Mathematical models of tumour dynamics may help in future studies of factors predicting tumor sensitivity to radiotherapy. In this study, a time-dependent differential model, incorporating biological cancer markers, is presented to describe pre-treatment tumour growth, response to radiation, and recurrence. The model uses Gompertzian growth to model pre-treatment tumour growth. The effect of radiotherapy is handled by a realistic cell-kill term that includes a volume-dependent change in tumour sensitivity. Post-treatment, a Gompertzian, accelerated, delayed repopulation is employed. As proof-of-concept, we examined the fit of the model's prediction using various liver enzyme levels as markers of metastatic liver tumour growth in a liver cancer patient. Enzyme data were derived from repeated serum blood tests, and radiation treatment-related data were retrieved from the patient's chart. A tumour clonogen population model was formulated. Each enzyme was coupled to the same tumour population, and served as surrogates of the tumour. This dynamical model was solved numerically and compared to the measured enzyme levels. By minimizing the mean-squared error of the model enzyme predictions, we determined the following tumour model parameters: growth rate prior to treatment was 0.7% per day; the fractional radiation cell kill for the prescribed dose was 60% per day; and tumour repopulation rate was 3.5% per day. These preliminary results provided the basis to test the model in a larger series of patients, to apply biological markers for improving the efficacy of radiotherapy by determining the underlying tumour dynamics.