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• Surgeon eye lens dose measured in eight different interventional procedure types. • Dosemeters read by an iSO-17025 accredited service. • Median eye lens H p (3) range, with ceiling shield: 20–60 μSv per single procedure. • CT-guided lung biopsy median eye lens H p (3): 150μSv per single procedure. • H p (3)/KAP shows a statistically significant dependency on the surgeon's height. This study investigated the radiation dose to surgeon eye lens for single procedure and normalised to exposure parameters for eight selected neuroradiology, cardiovascular and radiology interventional procedures. The procedures investigated were diagnostic study, Arteriovenous Malformations treatment (AVM) and aneurysm embolization for neuroradiology procedures, Coronary Angiography and Percutaneous Transluminal Coronary Angioplasty (CA-PTCA), Pacemaker and Implantable Cardioverter-Defibrillator implantation (PM-ICD), Endovascular Aortic Repair (EVAR) and Fenestrated Endovascular Aortic Repair (FEVAR) for cardiovascular and electrophysiology procedures. CT-guided lung biopsy was also monitored. All procedures were performed with table-mounted and ceiling-suspended shields (0.5 mm lead equivalent thickness), except for FEVAR and PM-ICD where only a table mounted shield was present, and CT-guided lung biopsy where no shield was used. Dose assessment was performed using a dosemeter positioned close to the most exposed eye of the surgeon, outside the protective eyewear. The surgeon most exposed eye lens median H p (3) equivalent dose for a single procedure, without protective eyewear contribution, was 18 μSv for neuroradiology diagnostic study, 62 μSv for AVM, 38 μSv for aneurysm embolization, 33 μSv for CA-PTCA, 39 μSv for PM-ICD, 49 μSv for EVAR, 2500 μSv for FEVAR, 153 μSv for CT-guided lung biopsy. In interventional procedures, the 20 mSv/year dose limit for surgeon eye lens exposure might be exceeded if shields or protective eyewear are not used. Surgeon eye lens doses, normalised to single procedures and to exposure parameters, are a valuable tool for determining appropriate radiation protection measures and dedicated eye lens dosemeter assignment. [ABSTRACT FROM AUTHOR]

The purpose of this multicenter phantom study was to exploit an innovative approach, based on an extensive acquisition protocol and unsupervised clustering analysis, in order to assess any potential bias in apparent diffusion coefficient (ADC) estimation due to different scanner characteristics. Moreover, we aimed at assessing, for the first time, any effect of acquisition plan/phase encoding direction on ADC estimation. Water phantom acquisitions were carried out on 39 scanners. DWI acquisitions (b-value = 0–200-400–600-800–1000 s/mm2) with different acquisition plans (axial, coronal, sagittal) and phase encoding directions (anterior/posterior and right/left, for the axial acquisition plan), for 3 orthogonal diffusion weighting gradient directions, were performed. For each acquisition setup, ADC values were measured in-center and off-center (6 different positions), resulting in an entire dataset of 84 × 39 = 3276 ADC values. Spatial uniformity of ADC maps was assessed by means of the percentage difference between off-center and in-center ADC values (Δ). No significant dependence of in-center ADC values on acquisition plan/phase encoding direction was found. Ward unsupervised clustering analysis showed 3 distinct clusters of scanners and an association between Δ-values and manufacturer/model, whereas no association between Δ-values and maximum gradient strength, slew rate or static magnetic field strength was revealed. Several acquisition setups showed significant differences among groups, indicating the introduction of different biases in ADC estimation. Unsupervised clustering analysis of DWI data, obtained from several scanners using an extensive acquisition protocol, allows to reveal an association between measured ADC values and manufacturer/model of scanner, as well as to identify suboptimal DWI acquisition setups for accurate ADC estimation. [ABSTRACT FROM AUTHOR]

• Characterization of eye lens X-ray protection efficacy of different eyewear models. • Study of the influence of eyewear shape and ergonomics. • Combination of dosimetric measurements and geometrical modeling. • Introduction of the concept of Eye Protection Effectiveness, an "a priori" evaluation of the Dose Reduction Factor. Radioprotection of the eye lens of medical staff involved in Surgical procedures is a subject of international debates since ICRP recommended, on 2011, a lower equivalent dose limit for the lens of the eye. In this work we address the effectiveness of different models of X-ray protective eyewear by relating actual dosimetry measurements to an ad hoc developed mathematical model, in order to disentangle the contribution of geometrical factors and shield capabilities. Phantom irradiation was carried out in fixed exposure conditions in angiographic room: we found that measured Dose Reduction Factors (DRF) strongly depend on the ergonomics of the investigated eyewear. Actually a very poor DRF was observed in the case of a glass model in spite of its high nominal attenuation, whereas a protective tool with low shielding capabilities such a visor resulted much more effective as a consequence of is shape (i.e. extended geometric protection of the eye lens). Our work highlights the need of the introduction of a specific parameter to quantify the effectiveness of the protection tools and able to predict their DRF by taking into account the geometry of the clinical condition of exposure. Aiming at making steps forward the standardization of the guidelines concerning the features of eye protective tools, we developed a simple mathematical model describing the eye lens irradiation geometry which allows the introduction, for each eyewear, of a comprehensive parameter, the Eye Protection Effectiveness (EPE), that, for any defined clinical irradiation condition and glass shielding capabilities and shape, defines the overall effective X-ray protection of the eyewear. [ABSTRACT FROM AUTHOR]

• Cardiologists in catheterization procedures can receive high eye-lens equivalent doses. • Individual eye-lens dosimetry is recommended for highly exposed workers. • Accurate uncertainty assessment is needed in eye-lens dosimetry. To perform a multi-centre survey on the eye lens equivalent dose absorbed by primary interventionalist during catheterization procedures, using a personal dosimeter placed close to the eye lens. 15 different cardiologists working in 3 different centers, for a total of 5 operating rooms were enrolled. All of them were provided with a single thermoluminescent dosimeter positioned on the inner side of the temples of eyeglasses. The dose monitoring, performed on a two-months basis, started in 2016 and is still running. All dose measurements were performed by a ISO 17025 standard accredited dosimetry service thus providing certified uncertainties as well. Correlation of eye lens and wrist dose with KAP was also investigated. A total number of 101 eye lens measurements were performed. Annual eye lens dose estimation was obtained for all 15 surgeons (mean, mode, range, standard deviation: 10.8, 8, 4.9–27.3, 5.6 mSv, respectively). Uncertainties on annual eye lens dose estimations ranged between 10% and 20%. No significant correlation was found between eye lens dose and KAP. Cardiologists involved in catheterization procedures may receive annual eye lens doses close to the ICRP 118 dose limit and thus individual monitoring with a dedicated dosimeter should be carried out. Uncertainty assessment play a relevant role in eye lens equivalent dose estimation to ensure not to exceed dose limit. [ABSTRACT FROM AUTHOR]

Highlights • Radiation Protection in Ru-106 brachytherapy ophthalmic plaque surgery. • Ru-106 material shielding properties and build-up factors. • Ru-106 numerical simulation of bremsstrahlung X-ray radiation spectra. Abstract Pre and post-operative exposure levels of medical staff and people from public in intra-operative Ru-106 ophthalmic brachytherapy are reported, together with attenuation properties of selected shielding materials. In particular radiation exposure of workers during plaque transportation and during medical assistance of implanted plaque patient was measured. Taking into account dose rates and considering standard assistance procedure of hospitalized patients, the exposure of medical staff and people of the public were evaluated for a given workload. In order to provide tools to optimize radiation protection, considering social and economic aspects due to possible hospital discharge or hospital stay, the attenuation properties of common shielding materials (lead, concrete, red brick, PMMA and gypsum) were measured, considering both narrow and broad beam setups. The eye was simulated using a water equivalent phantom and plaque was fixed on it. All measurements were performed with calibrated survey meters. Results were compared with numerical simulation of bremsstrahlung X-ray radiation spectra emitted from patient eye. Exposure levels measured at 1 m distance in front of the implanted eye are 0.05 µSv/h/MBq, at 10 cm from patient head, 0.44 µSv/h/MBq (plaque side), 0.4 µSv/h/MBq (front), 0.25 µSv/h/MBq (lateral, opposed to plaque), 0.2 µSv/h/MBq (back). Average exposure levels, under conservative assumptions, for medical staff is 17 µSv/patient and less than 23 µSv/patient for careers and comforters. TVLs in lead and concrete are about 1.6 cm and 11.5 cm respectively. [ABSTRACT FROM AUTHOR]

Highlights • ADC inter-center assessments. • ADC spatial variation across different scanners. • ADC bias in LR an HF directions. • ADC quality assurance protocol. Abstract Purpose To propose an MRI quality assurance procedure that can be used for routine controls and multi-centre comparison of different MR-scanners for quantitative diffusion-weighted imaging (DWI). Materials and methods 44 MR-scanners with different field strengths (1 T, 1.5 T and 3 T) were included in the study. DWI acquisitions (b-value range 0–1000 s/mm2), with three different orthogonal diffusion gradient directions, were performed for each MR-scanner. All DWI acquisitions were performed by using a standard spherical plastic doped water phantom. Phantom solution ADC value and its dependence with temperature was measured using a DOSY sequence on a 600 MHz NMR spectrometer. Apparent diffusion coefficient (ADC) along each diffusion gradient direction and mean ADC were estimated, both at magnet isocentre and in six different position 50 mm away from isocentre, along positive and negative AP, RL and HF directions. Results A good agreement was found between the nominal and measured mean ADC at isocentre: more than 90% of mean ADC measurements were within 5% from the nominal value, and the highest deviation was 11.3%. Away from isocentre, the effect of the diffusion gradient direction on ADC estimation was larger than 5% in 47% of included scanners and a spatial non uniformity larger than 5% was reported in 13% of centres. Conclusion ADC accuracy and spatial uniformity can vary appreciably depending on MR scanner model, sequence implementation (i.e. gradient diffusion direction) and hardware characteristics. The DWI quality assurance protocol proposed in this study can be employed in order to assess the accuracy and spatial uniformity of estimated ADC values, in single- as well as multi-centre studies. [ABSTRACT FROM AUTHOR]

Highlight • Eighteen clinical scanners were enrolled in an MR-spectroscopy intercomparison study. • The feasibility of a quality control protocol for routine MR-spectroscopy was proved. • The water linewidth at isocenter was less than 0.03 ppm for 1.5 T and 3 T scanners. • The area under the water peak varied linearly with the acquisition voxel volume. • The coefficient of variation for repeated measurements of phantom T 2 was less than 9%. Abstract Purpose The aim of this study was to propose and validate across various clinical scanner systems a straightforward multiparametric quality assurance procedure for proton magnetic resonance spectroscopy (MRS). Methods Eighteen clinical 1.5 T and 3 T scanner systems for MRS, from 16 centres and 3 different manufacturers, were enrolled in the study. A standard spherical water phantom was employed by all centres. The acquisition protocol included 3 sets of single (isotropic) voxel (size 20 mm) PRESS acquisitions with unsuppressed water signal and acquisition voxel position at isocenter as well as off-center, repeated 4/5 times within approximately 2 months. Water peak linewidth (LW) and area under the water peak (AP) were estimated. Results LW values [mean (standard deviation)] were 1.4 (1.0) Hz and 0.8 (0.3) Hz for 3 T and 1.5 T scanners, respectively. The mean (standard deviation) (across all scanners) coefficient of variation of LW and AP for different spatial positions of acquisition voxel were 43% (20%) and 11% (11%), respectively. The mean (standard deviation) phantom T 2 values were 1145 (50) ms and 1010 (95) ms for 1.5 T and 3 T scanners, respectively. The mean (standard deviation) (across all scanners) coefficients of variation for repeated measurements of LW, AP and T 2 were 25% (20%), 10% (14%) and 5% (2%), respectively. Conclusions We proposed a straightforward multiparametric and not time consuming quality control protocol for MRS, which can be included in routine and periodic quality assurance procedures. The protocol has been validated and proven to be feasible in a multicentre comparison study of a fairly large number of clinical 1.5 T and 3 T scanner systems. [ABSTRACT FROM AUTHOR]

Purpose The use of unsealed sources (either in nuclear medicine or in radiochemical bio-laboratories) involves the risk of internal contamination for workers after partial evaporation of the unsealed source during its use. This issue was already addressed in [1] , the aim of this work is to extend that work towards a comprehensive model taking into account also the airborne contamination after radionuclide evaporation from the cumulated surface contamination of the working area. Methods The above mentioned model takes into account the manipulation time (t m , the manipulated activity (A), the frequency of manipulations, the total time the workers spend in the laboratory (on an yearly basis), the air exchange ratio (R) and the half-life of the manipulated radionuclides. According to the actual working conditions, the model evaluates firstly the radionuclide air concentration as a function of time and thereafter the committed effective dose depending on the time spent in the laboratory by the worker. Results During t m the radioisotope manipulation determines both air contamination (AC) and probabilistic surface contamination (SC). After t m AC decreases due to R, whereas surface contamination increases after each manipulation, decreasing only through physical decay, thus leading to an asymptotic SC in the long run. SC is more relevant for long-life radioisotopes. Conclusions Application of the model to an actual bio-laboratory case shows that contribution to inhaled activity from surface contamination may be relevant or even dominant especially for long-life radionuclide (i.e. 3H and 14C). Great care should be used in cleaning the working surfaces after each manipulation to avoid or at last reduce to a reasonable level surface contamination. Smear test looks the test of choice to accurately verify the effective contamination level. [ABSTRACT FROM AUTHOR]

Purpose MRI scanner performance temporal stability is fundamental aspect in several multi-parametric exams (like diffusion, functional and spectroscopy) effect of order of few percent may be clinically relevant. Revised version of Friedman protocol (JMRI, 23 -2006) was adopted to check stability of scanners over time on weekly basis. Linewidth of water peak in MR spectroscopy after optimization is considered as well. Results over a long period survey of several clinical scanners are reported. Methods The purpose of the procedure is to measure time stability of the scanners in conditions that are as similar as possible to the clinical settings. The head coil and scanning sequence used clinically were tested. A time series of 200 images of QA vendor phantom is collected. The automated analysis provides information about signal intensity, uniformity, magnitude spectrum, radius of decorrelation (RdC), short term reproducibility, SNR and signal fluctuation to noise ratio. RdC represents the size of ROI for which the main source of signal noise is systematic and not statistic. With same setup, linewidth after B 0 homogeneity optimisation is measured. Data were acquired on four 1.5 T MRI clinical scanners, on a 4 years time interval. Results Data fluctuations of considered parameters are of order of few percent (varying between 1% and 9%), significant variations have been observer after component change and software upgrade. Fourier analysis of short term signal doesn't show periodic noise. Short term reproducibility is below 1% for all considered scanners. RdC is 18 pixels for two scanners and 6 pixels for other. No significant variation have been observed during temporal series. Linewidth is stable within 6%. Conclusions Regular check of parameter stability provides strong feedback regarding scanner performances, and may allow to predict possible malfunctioning. Proposed protocol may be used as basic QA in advanced MRI technique. [ABSTRACT FROM AUTHOR]

Purpose Mammographic screening represents one of the most significant medical expose to radiation for women. The method proposed from European Reference Organisation for Quality Assured Breast Screening and Diagnostic Services (EUREF) evaluate average glandular dose (AGD) considering the breast glandularity (BG) a function of breast thickness (BT). VOLPARA software (Volpara Solutions Limited) compute BG from acquired images using a multi-parametric algorithm. The purpose of this study is to evaluate the difference between AGD computed in both method and to assess the applicability of automatic tools for patient dose optimisation and mammographic unit QCs. Methods Mammographic screening exams from last 10 years performed in our institution have been considered. More than 350'000 exams overall (total 1.5 M of expositions), from seven mammographic units (of three different vendors), were included in this study. Exams have been performed using automatic exposure control settings. Data was extracted from DICOM images and processed using VOLPARA software (Volpara Solutions Limited) and analysed with a custom Matlab software. For each exposition difference between Diff = AGD EUREF - AGD VOLPARA was determinated. Exposure data are retrieved to identify patient dose optimisation strategies and to track device performances. Results Average Diff is 0.07 ± 0.13 mGy (min/max −1.7/+1.8 mGy), mean breast thickness is 55 mm (SD 13 mm min/max 10/117 mm). In figure is reported percent distribution of Diff as function of BT. Large part of exams shows Diff > 0 (71% of total), the remains have Diff < 0. Breast thickness distribution of two considered classes are: (mean ± sd) 60 ± 10 mm, 53 ± 14 mm respectively for Diff < 0 and Diff > 0. These results are generally reproducible among seven mammographic units considered. Conclusions Presented results indicate EUREF approach overestimate AGD, the proposed method allow to assess personal dosimetry and could be implemented in order to monitor in live time AGD difference from EUREF evaluation. Use of automatic dose software allow to monitor possibly variation in exposition parameters. [ABSTRACT FROM AUTHOR]

Purpose The use of 106Ru plaque was introduced for choroidal melanomas therapy. The aim of this study is workers and public exposure evaluation, in pre and post-operative phase of the treated patient. In particular attenuation properties of selected shielding materials and exposure levels around patient head and transport/sterilisation safety containers are reported. Methods Exposure was measured around the head of five patients, in multiple positions at various distances from the skin. Dose rates around the transport/sterilisation container were also measured. Attenuation measurements were performed simulating the eye with a 25mm diameter plastic sphere, filled with water and the plaque attached on it. All measurements were performed with a calibrated instrumentations. Selected materials attenuation properties were measured in "narrow" beam mode (IEC 61331-1:2014). A custom code was developed to perform numerical simulation of BS spectrum. Results In Table HVLs and TVLs for selected materials and the average exposure levels (±SD) measured around patients are reported. Five positions around the head, at 10 cm distance from the skin were considered, plus two positions at 1m. Exposure levels around the transport container are nearly constant for any given direction; average values is 1.6 μSv/h/MBq at contact and 0.013 μSv/h/MBq at 1 m. Conclusions Considering typical activity of the implanted plaques, and conservative recovery and assistance times, up to 60 patients may be treated in a year, without exceeding 1mSv/y for post-operative activities. For the same number of patients, even considering a 8 hours/day standing at 1.5 m from the patient bed, the worker received dose is around 0.65 mSv/y. Attenuation properties for selected materials were measured and agree with simulated results. Main contribution to exposure comes from X- γ radiation, BS is almost negligible from radiation protection point of view. [ABSTRACT FROM AUTHOR]

Purpose The dependence of ADC (measured in isotropic phantom) on position and ADC phase encoding may be used to test MRI scanner performances and may play relevant effect on quantitative data accuracy in clinical imaging. Quantitative results of AIFM multicentre intercomparison are reported. Methods Twenty-six MR scanners (20/6 1.5 T/3.0 T magnetic field strength) were enrolled in this study. Custom spherical water phantom (14 cm diameter) specifically designed for DWI QA was provided to all participants. ADC value was certified as in [1]. Phantom was placed at isocentre of scanner. Using three DWI sequences (b-value varying form 0 s/mm2 to 1000 s/mm2), differing for the gradient diffusion direction (Gdd), 5 mm thick axial slices were acquired (5 mm gap). Acquisition was repeated exchanging frequency and phase encoding direction. ADC maps were generated for each Gdd. Seven 2 × 2 cm2 ROIs were considered: one at isocentre and six in periphery (left, right, superior, inferior, head and feet). For each acquisition, maximum relative difference between periphery and central ROIs ADC was calculated (δ ADC % x,y,z). Maximum δ ADC % x,y,z with respect to three acquisitions (δ M%) was also considered. As for phase/frequency encoding direction dependences, ADC x,y,z differences on central ROI were measured. Results Differences Absolute value of δ M is below 5% for 19 scanners, 18 scanners show δ M > 0. Spatial direction of maximal variation is "x" in 23 scanners, "y" in the other. Gdd associated to δ M is x/y/z for 9/12/5 scanners. Differences between −2% and +1% have been observed with respect to phase encoding direction. Conclusions A simple protocol for quantitative evaluation of ADC spatial and phase encoding dependence has been proposed. Difference in ADC between isocentre and periphery should be consider in precision ADC measurements. [ABSTRACT FROM AUTHOR]

Purpose The AIFM working group on MR intercomparison has proposed a quality assurance protocol for MRI diffusion weighted imaging (DWI). The aim of this study is to test the accuracy of apparent diffusion coefficient (ADC) evaluation at the isocentre of the scanner. Methods Seventeen centres and twenty-six MRI scanners (20/6; 1.5 T/3.0 T) were enrolled in this study. A custom spherical water phantom (14 cm diameter, filled with doped aqueous solution) specifically designed for DWI QA was provided to all participants. ADC value was certified as in [1]. Phantom was placed at isocentre of scanner. 5 mm thick axial slices at the isocentre were acquired, using three DWI sequences (b-value varying form 0 s/mm2 to 1000 s/mm2 at 200 s/mm2 steps), differing in gradient diffusion direction. For each diffusion direction, ADC image was generated with monoexponential fit and corrected for temperature. Analysis was performed with a custom Matlab software code. Average ADC was calculated for each diffusion direction ( ADC x , ADC y , ADC z) in a 2 × 2 cm2 ROI at the centre of the phantom. A chi-squared consistency test was performed on the three ADC values. The mean value ( ADC ref) was compared with the certified ADC C value. Results Differences within ADC x,y,z are less than 1.5%, for 21 scanners. For seven scanners ADC x,y,z were not consistent among themselves. ( ADC ref / ADC C - 1) vary from +10% to −7% (mean value −1%). Only in four scanners | (ADC ref / ADC C - 1) | is larger than 5%. Conclusions The proposed protocol and multipurpose phantom provide a simple ADC quality assurance procedure. The measured isocentre ADCs are within 1% with reference to wrt diffusion directions and consistent with certified value within 1%. [ABSTRACT FROM AUTHOR]

Purpose Quality assurance in advanced and quantitative magnetic resonance techniques is strongly recommended [1–3]. The aim of this study was to propose and validate across various clinical scanner systems a straightforward quality assurance procedure for proton Magnetic Resonance Spectroscopy (MRS). Methods Eighteen clinical 1.5 T and 3 T scanners for MRS were enrolled in the study. The protocol included 3 sets of single voxel PRESS acquisitions without water signal suppression, repeated 4/5 times within approximately 2 months and performed using a standard water phantom supplied to all centres. Water peak linewidth (LW), water peak area (AP) and phantom T2 were estimated. Results LW values ranged from 0.4 Hz to 1.6 Hz, with 3 T and 1.5 T scanner systems showing similar performances. Coefficient of variation (CV) of LW values for repeated measurements were lower than 35% (except for only 3 scanners). AP showed significant (p < 0.05) linear correlation with voxel volume (r > 0.99 and 0.95 for 1.5 T and 3 T scanner systems, respectively). CV of AP for different spatial positions was less than 25%, and no relevant difference was observed between 3 T and 1.5 T scanners. Mean phantom T2 value and CV for repeated measurements were 1147 ms and 4%, respectively, for 1.5 T scanners, and 1010 ms and 9%, respectively, for 3 T scanners. Conclusions We proposed a straightforward multiparametric and not time consuming quality control protocol for MRS, which can be included in routine quality assurance procedures. The protocol has been validated and proven to be feasible in a multicentre intercomparison study of 18 clinical 1.5 T and 3 T scanner systems. [ABSTRACT FROM AUTHOR]

Purpose The aim of this study is to propose a protocol for DWI QA being easy to implement while still providing quantitative information on relevant parameters for the scanner QC as well as for clinical applications. The measured quantity is the apparent diffusion coefficient (ADC) and its dependence from gradient diffusion direction (Gdd) and phase encoding direction (PED). Methods A spherical water phantom (14 cm diameter), designed to allow fast and easy measurement of solution temperature, is proposed. The phantom is filled with doped aqueous solution (ADC value certified) and placed at isocentre of scanner. The protocol consists of five set of acquisition of 19 slices, repeated for three orthogonal Gdd. First and second acquisitions are identical, the others differ for the PED and acquisition plane. Each slice (for each Gdd) is acquired with six different b-values varying from 0 s/mm 2 to 1000 s/mm 2. From each acquisition and Gdd, ADC map of the phantom is generated with monoexponential fit, corrected for temperature and ADC profile along three orthogonal direction is extracted. From first two acquisitions short term reproducibility and SNR are evaluated; second and third acquisitions are used to detect phase encoding direction effects, lasts three maps are used to detect acquisition plane effects on ADC (details in Table 1). Results A preliminary test of the protocol on 1.5T MRI scanner demonstrated its applicability to routine QA. Relative difference between on-centre and periphery ADC values varies from −5% and +3% and phase encoding effect is less than 0.5%. Gdd variations are around +1%. Acquisition plane differences are less than 1% at isocentre and of the order of 5% in periphery. SNR at isocenter is 550 and short term variation is 0.2%. Conclusions The proposed protocol provides a simple QA procedure for DWI application. Selected indexes provide quantitative information on many relevant acquisition parameters. [ABSTRACT FROM AUTHOR]

Purpose Diffusion tensor imaging is very sensitive to applied gradient diffusion. Because apparent diffusion coefficient (ADC) depends on the square of the amplitude of the diffusion sensitizing gradients, errors in the gradient calibration are exaggerated. The aim of this work is to propose a protocol to correct for these errors. Methods Custom spherical water phantom (14 cm diameter, filled with doped aqueous solution) was acquired. Phantom was placed at isocentre of scanner. 5 mm thick axial slices at the isocentre were acquired, using six DWI sequences (b-value 0 s/mm 2 and 1000 s/mm2), differing for the gradient diffusion direction (Gdd): ±x, ±y, ±z. For each Gdd, analysis on ADC maps was performed by a custom Matlab software code. A 2× 2 cm2 ROI was considered at phantom centre and average ADC was calculated for each Gdd. Six scaling factors (one for each Gdd) were calculated as square root of ratio between reference and fitted ADCs values. A second set of three acquisitions consisting of 12, 20 and 30 gradient diffusion directions sequences were acquired: ADC and fractional anisotropy (FA) were calculated. The present protocol was repeated weekly. Results Scaling factors are between −0.9% and 0.7% and are almost constant week by week. After a periodic maintenance a significant calibration variation have been reported. Significant differences between positive and negative directions have been reported (between −0.5% and 0.4%). FA and standard deviation on measurement of the ADC from a second series of acquisitions were calculated with the corrections of the gradients, which resulted in a reduction of a factor of about two. Conclusions It was found that the six gradient coils were calibrated differently, resulting an offset on FA. The proposed protocol allows correcting for this effect. Application of this protocol to anisotropic phantom will allow better quantifying the effect of proposed corrections. [ABSTRACT FROM AUTHOR]

Purpose The immediate consequence of the new equivalent dose limit for the lens of the eye was a change in the international basic safety standards (BSS) and in the European BSS and the adoption of new limit. For the Catheter Laboratory Procedure, available literature mentions a poor correlation between chest dose measurements and eye lens doses. Aim of the study is to evaluate, if there is any, the correlation between clinical and technical parameters and operator lens dose. Methods Operators, who have used ceiling suspended screen, were monitored throughout thermoluminescence dosimeters (TLDs). The accredited laboratory pass EURADOS intercomparison on Eye Lens in 2016, using TLD calibrated in Hp(0.07), therefore also Hp(0.07) dosimeters are suitable for this application. Chest TLD dosimeter were placed under the lead apron at chest level, hand TLD on the bracelet and the lens TLD was positioned under the shielded glasses. Patient dose values (kerma area product), clinical and technical parameters, as number and type of procedures, were recorded and analyzed. Results The lens dose for main operator in Catheterization Lab of the first 3 centres enrolled are reported. As expected, hands dose depends on the type of procedure performed. Despite this, it is possible to find a weak correlation between the hands dose and the total number of procedures performed by the operator. The chest dose seems to be a completely unrelated parameter with the lens dose. The lens dose does not correlate with the parameters analyzed. Conclusions Lens dose monitor is an extremely complex features. The position of the dosimeter, the type of procedure, the operator experience, and also clinical condition of the patient strongly affect that parameter. Chest and bracelet dosimeters appear not to be adequate for efficient lens dose monitoring. [ABSTRACT FROM AUTHOR]