Automatic Dose Research Articles

Radiation dose optimisation for conventional imaging in infants and newborns using automatic dose management software: an application of the new 2013/59 EURATOM directive.

Automatic dose management software (ADMS) was used to analyse 2678 studies of children from birth to 5 years of age, obtaining local diagnostic reference levels (DRLs) in terms of entrance surface air kerma. Given local DRL for infants and chest examinations exceeded the European Commission (EC) DRL, an optimisation was performed decreasing the kVp and applying the automatic control exposure. To assess the image quality, an analysis of high-contrast resolution (HCSR), signal-to-noise ratio (SNR) and figure of merit (FOM) was performed, as well as a blind test based on the generalised estimating equations method. For newborns and chest examinations, the local DRL exceeded the EC DRL by 113%. After the optimisation, a reduction of 54% was obtained. No significant differences were found in the image quality blindtest. A decrease in SNR (-37%) and HCSR (-68%), and an increase in FOM (42%), was observed. ADMS allows the fast calculation of local DRLs and the performance of optimisation procedures in babies without delay. However, physical and clinical analyses of image quality remain to be needed to ensure the diagnostic integrity after the optimisation process. Advances in knowledge: ADMS are useful to detect radiation protection problems and to perform optimisation procedures in paediatric conventional imaging without undue delay, as ED requires.

PO-0907: Fast, automatic and robust dose restoration for online IMPT adaptation

PO-0907: Fast, automatic and robust dose restoration for online IMPT adaptation

Feasibility of online IMPT adaptation using fast, automatic and robust dose restoration

Intensity-modulated proton therapy (IMPT) offers excellent dose conformity and healthy tissue sparing, but it can be substantially compromised in the presence of anatomical changes. A major dosimetric effect is caused by density changes, which alter the planned proton range in the patient. Three different methods, which automatically restore an IMPT plan dose on a daily CT image were implemented and compared: (1) simple dose restoration (DR) using optimization objectives of the initial plan, (2) voxel-wise dose restoration (vDR), and (3) isodose volume dose restoration (iDR). Dose restorations were calculated for three different clinical cases, selected to test different capabilities of the restoration methods: large range adaptation, complex dose distributions and robust re-optimization. All dose restorations were obtained in less than 5 min, without manual adjustments of the optimization settings. The evaluation of initial plans on repeated CTs showed large dose distortions, which were substantially reduced after restoration. In general, all dose restoration methods improved DVH-based scores in propagated target volumes and OARs. Analysis of local dose differences showed that, although all dose restorations performed similarly in high dose regions, iDR restored the initial dose with higher precision and accuracy in the whole patient anatomy. Median dose errors decreased from 13.55 Gy in distorted plan to 9.75 Gy (vDR), 6.2 Gy (DR) and 4.3 Gy (iDR). High quality dose restoration is essential to minimize or eventually by-pass the physician approval of the restored plan, as long as dose stability can be assumed. Motion (as well as setup and range uncertainties) can be taken into account by including robust optimization in the dose restoration. Restoring clinically-approved dose distribution on repeated CTs does not require new ROI segmentation and is compatible with an online adaptive workflow.

Quality assurance in CT: implementation of the updated national diagnostic reference levels using an automated CT dose monitoring system

To evaluate the implementation of the updated computed tomography (CT) diagnostic reference levels (DRLs) from the German Federal Office for Radiation Protection into clinical routine using an automatic CT dose monitoring system. CT radiation exposure was analysed before and after implementing the updated national DRLs into routine clinical work in 2016. After the implementation process, institutional CT protocols were mapped to the anatomical regions for which DRLs were provided. Systematically, protocols that exceeded the thresholds were optimised and analysed in detail. The CT radiation output parameters analysed were volumetric CT dose index (CTDIvol) and dose-length product (DLP). Three radiologists evaluated subjective image quality using a three-point Likert scale. The study included 94,258 CT series (from 27,103 CT examinations) in adult patients performed in 2016. When averaged over all body regions with available DRL, institutional CTDIvol/DLP values were always below the DRLs (65.2±32.9%/67.3±41.5% initially; 59.4±32%/60.5±39.9% after optimisation). Values exceeding the national DRLs were found for pelvis (n=268; CTDIvol 107.7±65.7%/DLP 106.3±79.3%), lumbar spine (n=91; 160.8±74.7%/175.2±104.1%), and facial bones (n=527; 108±39%/152.7±75.7%). After optimisation, CTDIvol and DLP were 87.9±73%/87.8±80.8% for the pelvis, 67.8±33.2%/74.5±50.6% for the lumbar spine and 95.1±45.8%/133.3±74.6% for the viscerocranium. An automatic CT dose monitoring system enabled not only comprehensive monitoring of a DRL implementation process but can also help to optimise radiation exposure.

Dose Rounding of Biologic and Cytotoxic Anticancer Agents: A Position Statement of the Hematology/Oncology Pharmacy Association.

To present a position statement from the Hematology/Oncology Pharmacy Association (HOPA) that pertains to dose rounding of biologic and cytotoxic anticancer agents. The HOPA Standards Committee organized a work group of oncology pharmacist specialists to examine the safety and value of dose rounding of biologic and cytotoxic anticancer agents. Primary literature that describes methods for dose rounding, with clinical or economic data, were analyzed. Relevant pharmacokinetic characteristics and aspects of product formulation were considered. Issues for institutional application were addressed. Rounding of biologic and cytotoxic agents within 10% of the ordered dose is designated as acceptable for routine clinical care. Dose changes ≤ 10% are not expected to reduce the safety or effectiveness of therapy. The rounding amount-10%-is rational in the context of standard dose adjustments for patient tolerance and tumor response (≥ 20%), clinical trial deficiency criteria (> 10%), and the influence of interpatient pharmacokinetic variability. HOPA supports the use of the same threshold for dose rounding of anticancer drugs as that used for palliative and curative therapy. Potential exceptions to dose rounding are discussed. Dose rounding reduces waste and health care costs. HOPA recommends that each institution develop its own dose-rounding policy that addresses biologic and cytotoxic agents. Institutional guidelines for dose rounding of anticancer agents, including criteria for automatic dose rounding, the allowable percentage, and institutional processes for operationalizing and documenting dose rounding, should be determined by collaborative stakeholder consensus. Exceptions to dose rounding should be determined a priori. Additional studies that evaluate the impact of dose rounding on patient outcome are warranted.

Adaptive Fractional Order Controller with Smith Predictor based Propofol Dosing in Intravenous Anaesthesia Automation

This paper is designed to propose a clinical simulation model for automatic propofol dose delivery. We suggest adaptive fractional order controller (AFCSP) with Smith predictor design based on Commande Robuste d'Ordre Non Entier (CRONE) principle to provide adequate hypnotic intravenous drug infusion regimen for propofol. The main aim of the proposed design is to avoid frequent adaption complexity and provide another approach of adaption based on sensitivity parameters in place of BIS signal. Proposed controller is designed from model-based analytical method with a two-time domain tuning parameters using explicit equations instead of complex nonlinear equations but yield the same results. AFCSP utilises the combination of bolus and continuous dose. Robustness test of AFCSP is carried out with patient variability, time delays, and surgical stimuli, compared with conventional methods. This scheme is advantageous in terms of improving speed of response, oscillations and overshoots in BIS, also examined on real dataset of 31 different patients.

Calvarial Deformities in Children: A Radiological Gamut, Studied at a Tertiary Hospital

Aims and Objectives: To present the application of a protocol of low dose optimized for multidetector TC of 64 slice developed in our institution and directed to the study of the cranial deformity in the pediatric population. • Compare the radiation doses obtained with this protocol with the standard reference levels recommended by ICRP (International council for Radiation Protection). • To evaluate the diagnostic quality of the images obtained with this protocol. Materials and Methods: We present this prospective study conducted in our institution between August 2015 and September 2017. A total of 87 studies were conducted in 81 patients (61 boys and 20 girls) with an age range of between 4 days and 6.5 years (median of 7 months). A single study was performed in 76 patients, two studies in 4 patients and three studies in 1 patient. All studies were carried out with a 64 slice MDCT (Multidetector CT) scanner with bone reconstruction (Philips Brilliance USA), equipped with an automatic dose modulation system on the Z axis (AutomA) and subsequent images in MIP (maximum intensity projection), MPR (Multiplanar Reconstruction) and 3D mode. Results: Of the total of 87 studies, 69 were initial CT for diagnosis, while 18 were follow-up studies. Of these 18 controls, 12 patients had one or more previous CT studies performed with our standard protocol. The studies were required, in descending order, by neurosurgeons, pediatricians and rehabilitators. The most frequent reason for the request was the study of cranial deformities, especially to differentiate between significant postural plagiocephaly and craniosynostosis; less frequently, they were requested for postsurgical control or for the evolutionary follow-up of fractures. Conclusion: This low dose protocol optimized for TCMD-64 and aimed at the study of cranial lesions, obtains images with good diagnostic quality using very low radiation doses. It may even obviate the need for simple radiography in clinically selected patients.

23. Development of a software based on an anthropomorphic image atlas for image quality optimization in 3D angiography mode dynamic collimation system improving target conformity of spot scanning proton therapy: Comparison of dose calculations for two nozzles

Introduction In order to improve patient dose management [1] , a software was developed to enable the visualization of the effect of 3D angiography (3DA) protocol optimization on Image Quality (IQ) and radiation dose in interventional radiology. Methods For the four most representative anatomic areas of our clinical practice (liver, pelvis, lung, spleen), five reference protocols were set-up in our interventional radiology system (Innova IGS 540, GE Healthcare, Buc, France) with different IQ/dose preferences from low dose to high Image Quality (IQ). These preferences were defined by adjusting the Automatic Dose Rate and Image Quality (ADRIQ) strategy, the detail level and the rotation speed for 3DA sequences. For these 20 protocols, 3D angiography images were acquired on an anthropomorphic phantom (PBU-60, Kyoto Kagaku). All acquired images were qualitatively validated by a senior radiologist. These images were implemented in a home-made software (ProtoEnhanceIR) in order to optimize protocols by displaying the anthropomorphic images and associated Peak Skin Dose (PSD). The radiologist has the ability to select the most suitable protocols in regard with his own clinical practice. Then, the operator has the possibility to import selected protocols in the system. The PSD delivered to the anthropomorphic phantom by our 3DA clinical routine protocol (PSDRoutine) was compared to the PSD for the 3DA optimized protocol chosen by the senior radiologist in ProtoEnhanceIR (PSDProtoEnhanceIR). Results Compared to our 3DA clinical routine protocol, the chosen 3DA optimized protocol proposed by ProtoEnhanceIR allowed an average dose reduction of 69% while keeping clinical IQ (for lung, liver, pelvis and spleen PSDProtoEnhanceIR was 0.98 ± 0.09; 2.95 ± 0.43; 3.07 ± 0.27; 3.11 ± 0.34 mGy while PSDRoutine was 2.79 ± 0.12; 10.02 ± 0.89; 10.94 ± 1.31; 11.20 ± 0.58 mGy respectively). Conclusions The proposed software allows improvement of the IQ/dose balance of IR protocols according to radiologists’ preferences. From our clinical experience, ProtoEnhanceIR offers significant dose reduction opportunities while maintaining validated clinical IQ.

Independent dose verification system with Monte Carlo simulations using TOPAS for passive scattering proton therapy at the National Cancer Center in Korea

For the independent validation of treatment plans, we developed a fully automated Monte Carlo (MC)-based patient dose calculation system with the tool for particle simulation (TOPAS) and proton therapy machine installed at the National Cancer Center in Korea to enable routine and automatic dose recalculation for each patient. The proton beam nozzle was modeled with TOPAS to simulate the therapeutic beam, and MC commissioning was performed by comparing percent depth dose with the measurement. The beam set-up based on the prescribed beam range and modulation width was automated by modifying the vendor-specific method. The CT phantom was modeled based on the DICOM CT files with TOPAS-built-in function, and an in-house-developed C++ code directly imports the CT files for positioning the CT phantom, RT-plan file for simulating the treatment plan, and RT-structure file for applying the Hounsfield unit (HU) assignment, respectively. The developed system was validated by comparing the dose distributions with those calculated by the treatment planning system (TPS) for a lung phantom and two patient cases of abdomen and internal mammary node. The results of the beam commissioning were in good agreement of up to 0.8 mm2 for B8 option in both of the beam range and the modulation width of the spread-out Bragg peaks. The beam set-up technique can predict the range and modulation width with an accuracy of 0.06% and 0.51%, respectively, with respect to the prescribed range and modulation in arbitrary points of B5 option (128.3, 132.0, and 141.2 mm2 of range). The dose distributions showed higher than 99% passing rate for the 3D gamma index (3 mm distance to agreement and 3% dose difference) between the MC simulations and the clinical TPS in the target volume. However, in the normal tissues, less favorable agreements were obtained for the radiation treatment planning with the lung phantom and internal mammary node cases. The discrepancies might come from the limitations of the clinical TPS, which is the inaccurate dose calculation algorithm for the scattering effect, in the range compensator and inhomogeneous material. Moreover, the steep slope of the compensator, conversion of the HU values to the human phantom, and the dose calculation algorithm for the HU assignment also could be reasons of the discrepancies. The current study could be used for the independent dose validation of treatment plans including high inhomogeneities, the steep compensator, and riskiness such as lung, head & neck cases. According to the treatment policy, the dose discrepancies predicted with MC could be used for the acceptance decision of the original treatment plan.

Evaluation of automatic dose rate control for flat panel imaging using a spatial frequency domain figure of merit

Current automatic dose rate controls (ADRCs) of dynamic x-ray imaging systems adjust their acquisition parameters in response to changes in patient thickness in order to achieve a constant signal level in the image receptor. This work compares a 3 parameter (3P) ADRC control to a more flexible 5-parameter (5P) method to meet this goal. A phantom composed of 15 composite poly(methyl) methacrylate (PMMA)/aluminium (Al) plates was imaged on a Siemens Artis Q dynamic system using standard 3P and 5P ADRC techniques. Phantom thickness covered a water equivalent thickness (WET) range of 2.5 cm to 37.5 cm. Acquisition parameter settings (tube potential, tube current, pulse length, copper filtration and focus size) and phantom entrance air kerma rate (EAKR) were recorded as the thickness changed. Signal difference to noise ratio (SDNR) was measured using a 0.3 mm iron insert centred in the PMMA stack, positioned at the system isocentre. SDNR was then multiplied by modulation transfer function (MTF) based correction factors for focal spot penumbral blurring and motion blurring, to give a spatial frequency dependent parameter, SDNR(u). These MTF correction factors were evaluated for an object motion of 25 mm s−1 and at a spatial frequency of 1.4 mm−1 in the object plane, typical for cardiac imaging. The figure of merit (FOM) was calculated as SDNR(u)²/EAKR for the two ADRC regimes. Using 5P versus 3P technique showed clear improvements over all thicknesses. Averaged over clinically relevant adult WET values (20 cm–37.5 cm), EAKR was reduced by 13% and 27% for fluoroscopy and acquisition modes, respectively, while the SDNR(u) based FOM increased by 16% and 34% for fluoroscopy and acquisition. In conclusion, the generalized FOM, taking into account the influence of focus size and object motion, showed benefit in terms of image quality and patient dose for the 5-parameter control over 3-parameter method for the ADRC programming of dynamic x-ray imaging systems.

Eye lens dose correlations with personal dose equivalent and patient exposure in paediatric interventional cardiology performed with a fluoroscopic biplane system

PurposeTo analyse the correlations between the eye lens dose estimates performed with dosimeters placed next to the eyes of paediatric interventional cardiologists working with a biplane system, the personal dose equivalent measured on the thorax and the patient dose. MethodsThe eye lens dose was estimated in terms of Hp(0.07) on a monthly basis, placing optically stimulated luminescence dosimeters (OSLDs) on goggles. The Hp(0.07) personal dose equivalent was measured over aprons with whole-body OSLDs. Data on patient dose as recorded by the kerma-area product (PKA) were collected using an automatic dose management system. The 2 paediatric cardiologists working in the facility were involved in the study, and 222 interventions in a 1-year period were evaluated. The ceiling-suspended screen was often disregarded during interventions. ResultsThe annual eye lens doses estimated on goggles were 4.13±0.93 and 4.98±1.28mSv. Over the aprons, the doses obtained were 10.83±0.99 and 11.97±1.44mSv. The correlation between the goggles and the apron dose was R2=0.89, with a ratio of 0.38. The correlation with the patient dose was R2=0.40, with a ratio of 1.79μSvGy−1cm−2. The dose per procedure obtained over the aprons was 102±16μSv, and on goggles 40±9μSv. The eye lens dose normalized to PKA was 2.21±0.58μSvGy−1cm−2. ConclusionsMeasurements of personal dose equivalent over the paediatric cardiologist’s apron are useful to estimate eye lens dose levels if no radiation protection devices are typically used.

Should the automatic exposure control system of CT be disabled when scanning patients with endoaortic stents or mechanical heart valves? A phantom study.

To estimate the impact of endoaortic stents/mechanical heart valves on the output of an automatic exposure control (AEC) system and CT radiation dose. In this phantom study, seven stents and two valves were scanned with varying tube voltage (80/100/120 kVp), AEC activation (enabled/disabled) and prosthesis (present/absent), for a total of 540 scans. For each prosthesis, the dose-length product (DLP) was compared between scans with the AEC enabled and disabled. Percentage confidence levels for differences due to the prosthesis were calculated. Differences between results with the AEC enabled and disabled were not statistically significant (p ≥ 0.059). In the comparison with and without the prosthesis, DLP was unchanged at 80 kVp and 100 kVp, while a slight increase was observed at 120 kVp. The radiation dose varied from 1.8mGy to 2.4mGy without the prosthesis and from 1.8mGy to 2.5mGy with the prosthesis (confidence level 37-100%). The effect of the prosthesis on the AEC system was negligible and not clinically relevant. Therefore, disabling the AEC system when scanning these patients is not likely to provide a benefit. • CT-AEC system is not impaired in patients with endoaortic prostheses/heart valves. • Negligible differences may be observed only at 120 kVp. • Disabling the AEC system in these patients is not recommended.

P1. Setting up the internal quality control of a F18 automatic sampler following the ordinance of 2008

Introduction The radiopharmaceutical laboratory of Avicenne Hospital has acquired in October 2015 automatic drug dose radiopharmaceutical labeled sampler Unidose® F18 at the Trasis brand. This system realises individual dose that will be injected into patients. It must therefore be controlled according to the order of 25 November 2008 laying down the procedures for quality control of nuclear medicine facilities. Methods The automatic sampler Unidose has two measurement areas: one for the tank that contains all received drug activity and an individual patient’s dose contained in a cartridge. Both systems were calibrated by CERCA LEA geometries measures used routinely. For each system, we will realize the internal control defined in item 5 of the ordinance of 2008, namely the fidelity of the measure, the reproducibility of the measurements, the volume of isosensibility and linearity. Results Part of quality control of Trasis system is partially automated (or set in the system), it is necessary first to define the constant sources in the software. For the first measurement area that is to say the tank, measure of accuracy, reproducibility and linearity show results conform to acceptability criteria. The volume of isosensibility is 3.5 cm between the vertical distance of 0.5 cm and 4 cm. For the second measurement system that determines the injected patient dose achieving quality controls following the ordinance of 2008 is more complex because the measurement system is not well ionisation chamber. The fidelity of measurement and reproducibility show results conform to acceptability. The evaluation of the system response linearity and determining the volume of isosensibility are ongoing. Conclusion Our feedback shows all the particularity of these fully automated systems and the limits of regulation. Indeed the use of a measuring system accessible with difficult and that is not an ionization chamber well confronts us with difficult steps following the ordinance of 2008.

Optimizing CT technique to reduce radiation dose: effect of changes in kVp, iterative reconstruction, and noise index on dose and noise in a human cadaver.

For assessment of the effect of varying the peak kilovoltage (kVp), the adaptive statistical iterative reconstruction technique (ASiR), and automatic dose modulation on radiation dose and image noise in a human cadaver, a cadaver torso underwent CT scanning at 80, 100, 120 and 140kVp, each at ASiR settings of 0, 30 and 50%, and noise indices (NIs) of 5.5, 11 and 22. The volume CT dose index (CTDIvol), image noise, and attenuation values of liver and fat were analyzed for 20 data sets. Size-specific dose estimates (SSDEs) and liver-to-fat contrast-to-noise ratios (CNRs) were calculated. Values for different combinations of kVp, ASiR, and NI were compared. The CTDIvol varied by a power of 2 with kVp values between 80 and 140 without ASiR. Increasing ASiR levels allowed a larger decrease in CTDIvol and SSDE at higher kVp than at lower kVp while image noise was held constant. In addition, CTDIvol and SSDE decreased with increasing NI at each kVp, but the decrease was greater at higher kVp than at lower kVp. Image noise increased with decreasing kVp despite a fixed NI; however, this noise could be offset with the use of ASiR. The CT number of the liver remained unchanged whereas that of fat decreased as the kVp decreased. Image noise and dose vary in a complicated manner when the kVp, ASiR, and NI are varied in a human cadaver. Optimization of CT protocols will require balancing of the effects of each of these parameters to maximize image quality while minimizing dose.

Variability in the amount of fluorine-18 fluorodeoxyglucose excreted in urine measured from oncology patients during PET/computed tomography imaging.

The objectives of this work were to estimate the amount of fluorine-18 fluorodeoxyglucose (F-FDG) excreted (AFE) in the patient urine during the uptake phase as percentage of the injected activity and to examine the effect of blood glucose levels (BGL) on the excreted amount and whether it varies among men and women using statistical analysis methods. Radiation dose rates were measured at 1 m from 50 patients, 24 men and 26 women, before and after the first void using a calibrated ionization chamber. The F-FDG was injected in the patients using a calibrated automatic dose injection system. Statistical analysis using hypothesis testing was carried out. Patients with BGL above 5 mmol/l had a higher AFE of 12.3% in comparison with 8.3% of the patients with BGL below 5 mmol/l. A statistically nonsignificant correlation (r=0.183, P<0.249) between AFE and BGL was found; a nonsignificant difference was found in the AFE measured among the male and female patients. The AFE measured was 12±6%, with a range of (2-30%). There was a wide variation in the first void time of 39±8 min, with a range of (17-68) min. A simple noninvasive measurement method is presented that enabled the estimation of the amount of F-FDG excreted from the patient during voiding. Statistical analysis concluded that the amount of F-FDG excreted does not depend on sex, but is perhaps influenced by BGL.

Reference levels in pediatric interventional cardiology: Preliminary results from the coccinelle study

Introduction The justification as well as the benefit–risk ratio of interventional cardiology procedures (ICP) is well established. However, the increasing use of ICP in pediatric population stresses the need of setting up reference levels and keeping doses to children as low as possible. Purpose The present study aims at evaluating radiation dose levels for the most frequent ICP performed in five French reference centers for complex congenital heart disease (CHD). Materials and methods For nearly 4,000 ICP performed among pediatric patients (age <16 years) over the period 2009–2013, the date of procedure, the age and weight of the patient were collected. Air kerma-area product (PKA) and fluoroscopy time (FT) were retrieved retrospectively from automatic dose recording. The median, first and third quartiles, minimum and maximum values of PKA and FT were calculated according to patients’ age and weight. Results The main ICP investigated were: Diagnostic, Patent Ductus Arterious closure, Atrial Septal Defects closure, Valvuloplasty and Angioplasty. Preliminary results will be presented and discussed in the light of methodological limits and in comparison of available reference levels for ICP. Conclusion This is the first study in France to focus on children undergoing ICP. In order to have a better evaluation of current practices in pediatric ICP at national level, this work will be extended to the whole French network for CHD. The present work is included in the framework of an epidemiological cohort study, named “Coccinelle” and specifically designed to evaluate long term cancer risks after ICP during childhood. Disclosure Nothing to disclose The justification as well as the benefit–risk ratio of interventional cardiology procedures (ICP) is well established. However, the increasing use of ICP in pediatric population stresses the need of setting up reference levels and keeping doses to children as low as possible. The present study aims at evaluating radiation dose levels for the most frequent ICP performed in five French reference centers for complex congenital heart disease (CHD). For nearly 4,000 ICP performed among pediatric patients (age <16 years) over the period 2009–2013, the date of procedure, the age and weight of the patient were collected. Air kerma-area product (PKA) and fluoroscopy time (FT) were retrieved retrospectively from automatic dose recording. The median, first and third quartiles, minimum and maximum values of PKA and FT were calculated according to patients’ age and weight. The main ICP investigated were: Diagnostic, Patent Ductus Arterious closure, Atrial Septal Defects closure, Valvuloplasty and Angioplasty. Preliminary results will be presented and discussed in the light of methodological limits and in comparison of available reference levels for ICP. This is the first study in France to focus on children undergoing ICP. In order to have a better evaluation of current practices in pediatric ICP at national level, this work will be extended to the whole French network for CHD. The present work is included in the framework of an epidemiological cohort study, named “Coccinelle” and specifically designed to evaluate long term cancer risks after ICP during childhood.

Assessing the feasibility of simulating different tube current limits in noise oriented ATCM systems

Introduction Automatic tube current modulation (ATCM) allows automatic dose tailoring in Computed Tomography (CT), according to patient size and anatomical region. In noise-oriented ATCM systems, it is advisable to set minimum and maximum values of tube current (Imin and Imax). Large-scale databases are changing the way medical physicists compare data. Therefore, it is important to understand how an incorrect value of Imin or Imax may be detected from large scale dose distributions. Purpose To characterize noise oriented ATCM systems from two different vendors, and assess the feasibility of simulating different values of Imin and Imax, for a patient population examined with optimized settings. Materials and methods A RS-330 Lung/Chest Phantom (RSD, USA) was imaged with different acquisition settings, using scanners GE Lightspeed and Toshiba Aquilion RXL. The tube current as a function of couch position, I(z), was extracted from DICOM headers. For each Imin and Imax, I(z) was compared with the full range curve thresholded to the desired values. Results The I(z) curves obtained suggest a series of equally-spaced modulation points. Between successive modulation points, I(z) varies almost linearly. The settings of Imin and Imax change the values of I attained at each modulation point, and therefore simulated and real I(z) curves are slightly different. This difference decreases when modulation points are closer together (finer sampling). The sampling depends on equipment and collimation settings. Conclusion With detailed sampling, differences between simulated and real I(z) curves are below 5%. This difference increases when sampling is less detailed, particularly for lower Imax. Disclosure The authors have no relevant financial or non-financial relationships to disclose.

Skin dose saving of the staff in 90Y/177Lu peptide receptor radionuclide therapy with the automatic dose dispenser.

When handling Y-labelled and Lu-labelled radiopharmaceuticals, skin exposure is mainly due to β-particles. This study aimed to investigate the equivalent dose saving of the staff when changing from an essentially manual radiolabelling procedure to an automatic dose dispenser (ADD). The chemist and physician were asked to wear thermoluminescence dosimeters on their fingertips to evaluate the quantity of Hp(0.07) on the skin. Data collected were divided into two groups: before introducing ADD (no ADD) and after introducing ADD. For the chemist, the mean values (95th percentile) of Hp(0.07) for no ADD and ADD are 0.030 (0.099) and 0.019 (0.076) mSv/GBq, respectively, for Y, and 0.022 (0.037) and 0.007 (0.023) mSv/GBq, respectively, for Lu. The reduction for ADD was significant (t-test with P<0.05) for both isotopes. The relative differences before and after ADD collected for every finger were treated using the Wilcoxon test, proving a significantly higher reduction in extremity dose to each fingertip for Lu than for Y (P<0.05). For the medical staff, the mean values of Hp(0.07) (95th percentile) for no ADD and ADD are 0.021 (0.0762) and 0.0143 (0.0565) mSv/GBq, respectively, for Y, and 0.0011 (0.00196) and 0.0009 (0.00263) mSv/GBq, respectively, for Lu. The t-test provided a P-value less than 0.05 for both isotopes, making the difference between ADD and no ADD significant. ADD positively affects the dose saving of the chemist in handling both isotopes. For the medical staff not directly involved with the introduction of the ADD system, the analysis shows a learning curve of the workers over a 5-year period. Specific devices and procedures allow staff skin dose to be limited.

SU‐D‐209‐05: Sensitivity of the Diagnostic Radiological Index of Protection (DRIP) to Procedural Factors in Fluoroscopy

Purpose:To evaluate the sensitivity of the Diagnostic Radiological Index of Protection (DRIP) to procedural factors in fluoroscopy in an effort to determine an appropriate set of scatter‐mimicking primary beams (SMPB) to be used in measuring the DRIP.Methods:A series of clinical and factorial Monte Carlo simulations were conducted to determine the shape of the scattered X‐ray spectra incident on the operator in different clinical fluoroscopy scenarios. Two clinical evaluations studied the sensitivity of the scattered spectrum to gantry angle and patient size while technical factors were varied according to measured automatic dose rate control (ADRC) data. Factorial evaluations studied the sensitivity of the scattered spectrum to gantry angle, field of view, patient size and beam quality for constant technical factors. Average energy was the figure of merit used to condense fluence in each energy bin to a single numerical index.Results:Beam quality had the strongest influence on the scattered spectrum in fluoroscopy. Many procedural factors affected the scattered spectrum indirectly through their effects on primary beam quality through ADRC, e.g., gantry angle and patient size. Lateral C‐arm rotation, common in interventional cardiology, increased the energy of the scattered spectrum, regardless of the direction of rotation. The effect of patient size on scattered radiation depended on ADRC characteristics, patient size, and procedure type.Conclusion:The scattered spectrum striking the operator in fluoroscopy, and therefore the DRIP, is most strongly influenced by primary beam quality, particularly kV. Use cases for protective garments should be classified by typical procedural primary beam qualities, which are governed by the ADRC according to the impacts of patient size, anatomical location, and gantry angle. These results will help determine an appropriate set of SMPB to be used for measuring the DRIP.

TH-C-BRC-02: A Review of Emerging Technologies in Robotic SRS/SBRT Delivery

The delivery techniques for SRS/SBRT have been under rapid developments in recent years, which pose new challenges to medical physicists ranging from planning and quality assurance to imaging and motion management. This educational course will provide a general overview of the latest delivery techniques in SRS/SBRT, and discuss the clinical processes to address the challenges of each technique with special emphasis on dedicated gamma-ray based device, robotic x-band linac-based system and conventional C-arm s-band linac-based SRS systems. (1). Gamma-ray based SRS/SRT: This is the gold standard of intracranial SRS. With the advent of precision imaging guidance and frameless patient positioning capabilities, novel stereoscopic CBCT and automatic dose adaption solution are introduced to the Gamma-ray based SRS for the first time. The first North American system has been approved by the US regulatory for patient treatments in the spring of 2016. (2). Robotic SRS/SBRT system: A number of technological milestones have been developed in the past few years, including variable aperture collimator, sequential optimization technique, and the time reduction technique. Recently, a new robotic model allows the option of a multi-leaf collimator. These technological advances have reduced the treatment time and improved dose conformity significantly and could potentially expand the application of radiosurgery for the treatment of targets not previously suitable for robotic SRS/SBRT or fractionated stereotactic radiotherapy. These technological advances have created new demanding mandates on hardware and patient quality assurance (QA) tasks, as well as the need for updating/educating the physicists in the community on these requirements. (3). Conventional Linac based treatments: Modulated arc therapy (MAT) has gained wide popularities in Linac-based treatments in recent years due to its high delivery efficiency and excellent dose conformities. Recently, MAT has been introduced to deliver highly conformal radiosurgery treatments to multiple targets simultaneously via a single isocenter to replace the conventional multi-iso multi-plan treatments. It becomes important to understand the advantages and limitations of this technique, and the pitfalls for implementing this technique in clinical practice. The planning process of single-iso multi-target MAT will be described, and its plan quality and delivery efficiency will be compared with multi-iso plans. The QA process for verifying such complex plans will be illustrated, and pitfalls in imaging and patient set up will be discussed. Overall, this session will focus on the following areas: 1) Update on the emerging technology in current SRS/SBRT delivery. 2) New developments in treatment planning and Quality Assurance program. 3) Imaging guidance and motion management. Learning Objectives: 1.To understand the SRS/SBRT principles and its clinical applications, and gain knowledge on the emerging technologies in SRS/SBRT. 2.To review planning concepts and useful tips in treatment planning. 3.To learn about the imaging guidance procedures and the quality assurance program in SRS/SBRT. National Institutes of Health, Varian Medical System; L. Ren, The presenter is funded by National Institutes of Health and Varian Medical System.