Patient Dose Estimation in Computed Tomography-Guided Biopsy Procedures.

This study establishes typical Diagnostic Reference Levels (DRL) values and assesses patient doses in computed tomography (CT)-guided biopsy procedures. The Effective Dose (ED), Entrance Skin Dose (ESD), and Size-Specific Dose Estimate (SSDE) were calculated using the relevant literature-derived conversion factors. A retrospective analysis of 226 CT-guided biopsies across five categories (Iliac bone, liver, lung, mediastinum, and para-aortic lymph nodes) was conducted. Typical DRL values were computed as median distributions, following guidelines from the International Commission on Radiological Protection (ICRP) Publication 135. DRLs for helical mode CT acquisitions were set at 9.7 mGy for Iliac bone, 8.9 mGy for liver, 8.8 mGy for lung, 7.9 mGy for mediastinal mass, and 9 mGy for para-aortic lymph nodes biopsies. In contrast, DRLs for biopsy acquisitions were 7.3 mGy, 7.7 mGy, 5.6 mGy, 5.6 mGy, and 7.4 mGy, respectively. Median SSDE values varied from 7.6 mGy to 10 mGy for biopsy acquisitions and from 11.3 mGy to 12.6 mGy for helical scans. Median ED values ranged from 1.6 mSv to 5.7 mSv for biopsy scans and from 3.9 mSv to 9.3 mSv for helical scans. The study highlights the significance of using DRLs for optimizing CT-guided biopsy procedures, revealing notable variations in radiation exposure between helical scans covering entire anatomical regions and localized biopsy acquisitions.

A retrospective survey to establish institutional diagnostic reference levels for CT urography examinations based on clinical indications: preliminary results.

Objective. To establish institutional diagnostic reference levels (IDRLs) based on clinical indications (CIs) for three- and four-phase computed tomography urography (CTU).Methods. Volumetric computed tomography dose index (CTDIvol), dose-length product (DLP), patients' demographics, selected CIs like lithiasis, cancer, and other diseases, and protocols' parameters were retrospectively recorded for 198 CTUs conducted on a Toshiba Aquilion Prime 80 scanner. Patients were categorised based on CIs and number of phases. These groups' 75th percentiles of CTDIvoland DLP were proposed as IDRLs. The mean, median and IDRLs were compared with previously published values.Results. For the three-phase protocol, the CTDIvol(mGy) and DLP (mGy.cm) were 22.7/992 for the whole group, 23.4/992 for lithiasis, 22.8/1037 for cancer, and 21.2/981 for other diseases. The corresponding CTDIvol(mGy) and DLP (mGy.cm) values for the four-phase protocol were 28.6/1172, 30.6/1203, 27.3/1077, and 28.7/1252, respectively. A significant difference was found in CTDIvoland DLP between the two protocols, among the phases of three-phase (except cancer) and four-phase protocols (except DLP for other diseases), and in DLP between the second and third phases (except for cancer group). The results are comparable or lower than most studies published in the last decade.Conclusions. The CT technologist must be aware of the critical dose dependence on the scan length and the applied exposure parameters for each phase, according to the patient's clinical background and the corresponding imaging anatomy, which must have been properly targeted by the competent radiologist. When clinically feasible, restricting the number of phases to three instead of four could remarkably reduce the patient's radiation dose. CI-based IDRLs will serve as a baseline for comparison with CTU practice in other hospitals and could contribute to national DRL establishment. The awareness and knowledge of dose levels during CTU will prompt optimisation strategies in CT facilities.

Current Clinical Knowledge on GORE EXCLUDER Conformable Abdominal Aortic Aneurysm Repair Endoprosthesis: A Case Series and Literature Review.

The GORE EXCLUDER Conformable abdominal aortic aneurysm (AAA) Endoprosthesis (CEXC), is currently the newest stent-graft system for treating patients with AAA. CEXC is approved for patients with proximal aortic neck angles ≤90° with a ≥15 mm aortic neck length or proximal aortic neck angles ≤60° with ≥10 mm aortic neck length. The present study describes a clinical series of 5 males with AAA, one of whom had a ruptured infrarenal AAA and a 90° proximal aortic neck angle. All patients were treated with 100% technical success using the CEXC device. Dosimetric data were recorded regarding the total kerma-area product and total fluoroscopy time. During the 30-day follow-up, no device migration or failure was detected, whereas type Ib and II endoleaks were observed in two patients. The type Ib endoleak required re-intervention with limb extension placement, and the type II endoleak was treated with lumbar artery embolization. This clinical series showed that CEXC has no technical defects or AAA-related mortality. We also reviewed the current knowledge on CEXC's clinical outcomes, showing promising technical and clinical results in some studies, even outside the instructions for use. CEXC expands the vascular surgeons' armamentarium against hostile neck anatomy, as it is the only repositionable endovascular aneurysm repair device available. Multicenter, long-term outcome studies should confirm the promising preliminary results of our case series and the literature review.

BMI-Based organ doses in endovascular aneurysm repair interventions utilising Monte Carlo simulation.

In this study, the effect of body-mass-index (BMI) on organ doses (ODs) during infrarenal endovascular-aneurysm-repair (EVAR) procedures was evaluated. Patient- and intra-operative data from fifty-nine EVAR procedures were inserted into VirtualDose-IR software to calculate ODs. For overweight, obesity class-I and obesity class-II, ODs were up to 147%, 412% and 775% higher than those for normal weight-patients, respectively. A large variation was observed in ODs published in literature mainly due to the differences in the software and the technical parameters used for the calculations.

FACTORS INFLUENCING FLUOROSCOPY TIME IN ENDOVASCULAR TREATMENT OF ABDOMINAL ANEURYSMS: A RETROSPECTIVE STUDY.

Patients who undergo endovascular aortic aneurysm repair (EVAR) may require prolonged radiation exposure affected by several factors. The objectives of this study were to document fluoroscopy time (FT) during EVAR and identify possible factors that influence it. A retrospective analysis of a 180 patients' database with abdominal infrarenal aortic aneurysms submitted to EVAR during a 7-y period was performed. The FT is evaluated regarding risk factors and comorbidities, graft type and patient-related, clinical and technical parameters. FT's median (interquartile range) was 1011 (698-1500) s. Excluder and C3 Excluder were associated with significantly lower FT values when compared with other grafts. Hypertension, dyslipidemia, age ≥ 70 y, maximum aneurysm diameter ≥ 6 cm and procedure duration ≥2 h resulted in higher FT values. A significantly lower FT was found for the operations performed in the 7th y of the study's period compared with the previous 6 y, mainly because of the use of Excluder or C3 Excluder grafts. However, these grafts did not show any significant difference in FT values during the 7 y. A significant correlation between FT with age and procedure duration was found. Nevertheless, procedure duration is a poor FT predictor in linear and logistic regressions, although is significantly correlated with FT. Dyslipidemia, procedure duration and graft type are independent predictors of FT larger than the median, whereas only the procedure duration is a predictor for FT larger than the 75th percentile value. The identified factors regarding radiation protection issues should be considered when contemplating abdominal aortic aneurysm repair, however, without compromising the procedure's efficacy. Further work is necessary to identify more potential anatomical, clinical and technical factors affecting procedures' complexity and FT and patient radiation dose during EVAR interventions.

Non-dynamic and multiphase CT protocols for parathyroid glands imaging: a review of technical parameters, radiation dose and diagnostic accuracy.

INTRODUCTION: Our purpose was to review the scientific literature and collect information regarding clinical and technical parameters of different single- or multiphase CT protocols, their diagnostic performance and patient dose during parathyroid imaging. EVIDENCE ACQUISITION: PubMed and Scopus databases were searched for studies investigating the diagnostic performance of CT in detecting parathyroid lesions and the corresponding patients' dose. The following information was retrieved for each article: CT system, number, combination and time interval between phases, scanning length, sensitivity, specificity, accuracy, positive and negative predictive values, contrast enhancement in Hounsfield Units (HUs), technical and exposure parameters, and dose indices. Fifty studies published during the last sixteen years (2005-2021) were reviewed. EVIDENCE SYNTHESIS: A large discrepancy in the number and combination of phases, as well as clinical and technical parameters of the CT protocols was indicated. The variations in patients' doses are mainly due to scanners' technology, number and combination of phases, the extent of scanning length, technical parameters (tube voltage, tube current modulation, pitch, reconstruction algorithms), and patient-related parameters. Technical parameters are not always adjusted appropriately to the clinical question or patient size. These variations indicate a large potential to optimize dose during parathyroid imaging without compromising diagnostic performance. The potential is to decrease the number of phases or use low tube voltage protocols, tube current modulation, iterative reconstruction, and reduce the scanning length during some phases. CONCLUSIONS: The reporting results could inform researchers about the current status of CT parathyroid imaging and guide their future efforts to optimize both patients' dose and corresponding image quality.

Deep Learning Assessment for Mining Important Medical Image Features of Various Modalities.

Deep learning (DL) is a well-established pipeline for feature extraction in medical and nonmedical imaging tasks, such as object detection, segmentation, and classification. However, DL faces the issue of explainability, which prohibits reliable utilisation in everyday clinical practice. This study evaluates DL methods for their efficiency in revealing and suggesting potential image biomarkers. Eleven biomedical image datasets of various modalities are utilised, including SPECT, CT, photographs, microscopy, and X-ray. Seven state-of-the-art CNNs are employed and tuned to perform image classification in tasks. The main conclusion of the research is that DL reveals potential biomarkers in several cases, especially when the models are trained from scratch in domains where low-level features such as shapes and edges are not enough to make decisions. Furthermore, in some cases, device acquisition variations slightly affect the performance of DL models.

Organs' absorbed dose and comparison of different methods for effective dose calculation in computed tomography of parathyroid glands.

OBJECTIVE: To estimate organs' absorbed dose from the two-phase CT of parathyroid glands, effective dose (ED) based on three different methods, and compare the dose values with those reported by other published protocols. METHODS: Volumetric-computed-tomography-dose-index (CTDIvol), dose-length-product (DLP), and the corresponding scan length during each phase of a parathyroid protocol were recorded, for seventy-six patients. One k-factor, and two different k-factors for the neck and chest area were used to estimate the ED from DLP. A Monte Carlo software, VirtualDoseCT, was also used for the estimation of organs' absorbed dose and ED. RESULTS: Two-phase parathyroid CT resulted in a mean ED of 3.93 mSv, 4.29 mSv and 4.21 mSv according to the one k-factor, two k-factors, and VirtualDoseCT methods, respectively. The two k-factors method resulted in a slight overestimation of 1.9% in total ED compared to VirtualDoseCT. No statistically significant difference was found in ED values between these methods (Wilcoxon test, p > 0.05), except for female patients in the pre-contrast phase. The organs inside the scanning field of view (SFOV) received the following doses: thymus 23.3 mGy, lungs 11.5 mGy, oesophagus 9.2 mGy, thyroid 6.9 mGy, and breast 6.3 mGy. The ED and organs' dose (OD) values were significantly lower in the pre-contrast than in the arterial phase (Wilcoxon test, p < 0.001). A statistically significant difference was observed between male and female patients for the pre-contrast phase (Mann-Whitney test, p < 0.05), regarding the ED values obtained with the two k-factors method and VirtualDoseCT software. CONCLUSIONS: The two k-factors method could be applied for the ED estimation in clinical practice, if appropriate software is not available. An extensive range of ED values derived from the literature, mainly depending on the acquisition protocol parameters and the estimation method.

Applications of Generative Adversarial Networks (GANs) in Positron Emission Tomography (PET) imaging: A review.

PURPOSE: This paper reviews recent applications of Generative Adversarial Networks (GANs) in Positron Emission Tomography (PET) imaging. Recent advances in Deep Learning (DL) and GANs catalysed the research of their applications in medical imaging modalities. As a result, several unique GAN topologies have emerged and been assessed in an experimental environment over the last two years. METHODS: The present work extensively describes GAN architectures and their applications in PET imaging. The identification of relevant publications was performed via approved publication indexing websites and repositories. Web of Science, Scopus, and Google Scholar were the major sources of information. RESULTS: The research identified a hundred articles that address PET imaging applications such as attenuation correction, de-noising, scatter correction, removal of artefacts, image fusion, high-dose image estimation, super-resolution, segmentation, and cross-modality synthesis. These applications are presented and accompanied by the corresponding research works. CONCLUSION: GANs are rapidly employed in PET imaging tasks. However, specific limitations must be eliminated to reach their full potential and gain the medical community's trust in everyday clinical practice.

DOSIMETRIC EVALUATION OF THE TWO-PHASE COMPUTED TOMOGRAPHY IN PARATHYROID GLANDS IMAGING.

This study evaluates the patient radiation dose from the two-phase protocols of two different computed tomography (CT) systems and compares this with that delivered by the other similar protocols previously published. Two hundred and fourteen patients with primary hyperparathyroidism were included in the study with a two-phase CT scan between 2008 and 2020 by using a Toshiba Aquilion Prime 80 and a GE Light Speed 16. The standard 'neck' or a modified 'parathyroid' protocol was used. The patient dose was evaluated in terms of volumetric computed tomography dose index (CTDIvol), dose length product (DLP) and effective dose (ED) per acquisition protocol and CT system. CTDIvol and DLP were recorded retrospectively, while the ED was calculated based on DLP and an appropriate conversion coefficient. Comparisons of patient dose between the two protocols and two CT systems and the corresponding published values were established. A significantly lower patient dose (40.2-43.2%) than the GE system (p < 0.0001) resulted from the Toshiba system. The 'parathyroid' protocol resulted in a 6.5-9.6% lower patient dose than the standard 'neck' protocol. Compared with the literature, the lowest ED value (3.6 mSv) was observed since this protocol consists of a lowered tube voltage of 100 kVp, a reduced scan length for the pre-contrast phase and implementation of an iterative reconstruction algorithm.

KERMA-AREA PRODUCT, ENTRANCE SURFACE DOSE AND EFFECTIVE DOSE IN ABDOMINAL ENDOVASCULAR ANEURYSM REPAIR.

This study aims to evaluate patient radiation dose during fluoroscopically guided endovascular aneurysm repair (EVAR) procedures. Fluoroscopy time (FT) and kerma-area product (KAP) were recorded from 87 patients that underwent EVAR procedures with a mobile C-arm fluoroscopy system. Effective dose (ED) and organs' doses were calculated utilising appropriate conversion coefficients based on the recorded KAP values. Entrance surface dose (ESD) was calculated based on KAP values and technical parameters. The mean FT was 22.7 min (range 6.4-76.8 min), resulting in a mean KAP of 36.6 Gy cm2 (range 2.0-167.8 Gy cm2), a mean ED of 6.2 mSv (range 0.3-28.5 mSv) and a mean ESD of 458 mGy (range 26-2098 mGy). The corresponding median values were 17.4 min, 25.6 Gy cm2, 4.4 mSv and 320 mGy. The threshold of 2 Gy for skin erythema was exceeded in two procedures for a focus-to-skin distance (FSD) of 40 cm and six procedures when an FSD of 30 cm was considered. The highest doses absorbed by the adrenals, kidneys, spleen and pancreas and ranged between 3.7 and 313.3 mGy (average 66.8 mGy), 3.3 and 285.1 mGy (average 60.8 mGy), 1.3 and 111.1 mGy (average 23.7 mGy), 1.1 and 92.1 mGy (average 19.6 mGy), respectively. A wide range of patient doses was reported in the literature. The radiation dose received by the patients was comparative or lower than most of the previously reported values. However, higher doses can be revealed due to the X-ray system's non-optimum use and extended FTs, mainly affected by complex clinical conditions, patients' body habitus and vascular surgeon experience. The large variation of patient doses highlights the potential to optimise the EVAR procedure by considering the balance between the radiation dose and the required image quality. Additional studies need to be conducted in increasing the vascular surgeons' awareness regarding patient dose and radiation protection issues during EVAR procedures.

Automatic classification of solitary pulmonary nodules in PET/CT imaging employing transfer learning techniques.

Early and automatic diagnosis of Solitary Pulmonary Nodules (SPN) in Computed Tomography (CT) chest scans can provide early treatment for patients with lung cancer, as well as doctor liberation from time-consuming procedures. The purpose of this study is the automatic and reliable characterization of SPNs in CT scans extracted from Positron Emission Tomography and Computer Tomography (PET/CT) system. To achieve the aforementioned task, Deep Learning with Convolutional Neural Networks (CNN) is applied. The strategy of training specific CNN architectures from scratch and the strategy of transfer learning, by utilizing state-of-the-art pre-trained CNNs, are compared and evaluated. To enhance the training sets, data augmentation is performed. The publicly available database of CT scans, named as Lung Image Database Consortium and Image Database Resource Initiative (LIDC-IDRI), is also utilized to further expand the training set and is added to the PET/CT dataset. The results highlight the effectiveness of transfer learning and data augmentation for the classification task of small datasets. The best accuracy obtained on the PET/CT dataset reached 94%, utilizing a modification proposal of a state-of-the-art CNN, called VGG16, and enhancing the training set with LIDC-IDRI dataset. Besides, the proposed modification outperforms in terms of sensitivity several similar researches, which exploit the benefits of transfer learning. Overview of the experiment setup. The two datasets containing nodule representations are combined to evaluate the effectiveness of transfer learning over the traditional approach of training Convolutional Neural Networks from scratch.

Multi-input deep learning approach for Cardiovascular Disease diagnosis using Myocardial Perfusion Imaging and clinical data.

PURPOSE: Accurate detection and treatment of Coronary Artery Disease is mainly based on invasive Coronary Angiography, which could be avoided provided that a robust, non-invasive detection methodology emerged. Despite the progress of computational systems, this remains a challenging issue. The present research investigates Machine Learning and Deep Learning methods in competing with the medical experts' diagnostic yield. Although the highly accurate detection of Coronary Artery Disease, even from the experts, is presently implausible, developing Artificial Intelligence models to compete with the human eye and expertise is the first step towards a state-of-the-art Computer-Aided Diagnostic system. METHODS: A set of 566 patient samples is analysed. The dataset contains Polar Maps derived from scintigraphic Myocardial Perfusion Imaging studies, clinical data, and Coronary Angiography results. The latter is considered as reference standard. For the classification of the medical images, the InceptionV3 Convolutional Neural Network is employed, while, for the categorical and continuous features, Neural Networks and Random Forest classifier are proposed. RESULTS: The research suggests that an optimal strategy competing with the medical expert's accuracy involves a hybrid multi-input network composed of InceptionV3 and a Random Forest. This method matches the expert's accuracy, which is 79.15% in the particular dataset. CONCLUSION: Image classification using deep learning methods can cooperate with clinical data classification methods to enhance the robustness of the predicting model, aiming to compete with the medical expert's ability to identify Coronary Artery Disease subjects, from a large scale patient dataset.

Factors affecting radiation exposure in endovascular repair of abdominal aortic aneurysms: a pilot study.

BACKGROUND: Radiation exposure during endovascular repair (EVAR) of abdominal aortic aneurysms (AAAs) is a potential issue. Several studies have identified factors affecting radiation exposure, although they are limited. The aim of this study was to identify independent factors affecting radiation exposure in patients with AAA undergoing standard EVAR. METHODS: Forty-eight consecutive patients underwent elective EVAR for infrarenal AAA managed between April 2019 and April 2020. Fluoroscopy time (FT) and kerma area product (KAP) were the main outcome measures. RESULTS: Median (interquartile range) FT and KAP values were 1018 (653-1619) s and 2.68 (2.08-3.81) mGy·m2, respectively. C3 Excluder graft use and main body insertion site from the right femoral were associated with significantly lower FT. Coronary artery disease, endografts with two docking limbs, AAA diameter, neck angle and length, procedure duration, contrast amount, and hospitalization were associated with significantly higher FT. Neck angle was the single independent perioperative factor related to FT higher than the median value observed in the study (P=0.004, odds ratio: 1.073, 95% confidence interval: 1.023-1.126). The use of the C3 Excluder device was associated with lower KAP. AAA diameter, neck angle, procedure duration, contrast medium amount and postoperative hospitalization were associated with higher KAP. AAA diameter was the single independent factor related to KAP higher than the median value observed in the study (P=0.013, odds ratio: 3.73, 95% confidence interval: 1.32-10.56). CONCLUSIONS: This study has identified factors affecting radiation exposure during standard EVAR for infrarenal AAAs. These factors should be taken into account when contemplating AAA repair.

PATIENT SIZE INDICES AND DOSE IN FLUOROSCOPICALLY GUIDED LUMBAR DISCECTOMY AND FUSION: A PRELIMINARY STUDY.

Patient dose values varied significantly during interventional procedures, mainly due to the patient size, operators' choices and clinical complexity. In this study, the effect of applying a previously described and validated size-correction method to normalise kerma-area product (KAP) and average KAP rate values of the whole procedure (KAP rate) and isolate variations in dose due to the patient size and complexity, during lumbar discectomy and fusion (LDF) procedures, was investigated. Fluoroscopy time (FT), KAP, KAP rate and patient size data (weight, height and equivalent diameter) were recorded, for 96 patients who underwent single or multilevel LDF procedures by three senior neurosurgeons, defining three different patient groups (surgeon 1, surgeon 2, surgeon 3). Simple linear regression and coefficients of determination were used to investigate the relationship between uncorrected and corrected KAP and KAP rate values and patient size indices in these groups. The results showed that the size correction decreased the influence of patient size and could contribute to the isolation of the variations in patient dose due to the patient size. From this point of view, dose surveys during lumbar spine interventions may include dosimetric data from all patients independently of their body size and not only for standard-sized patients, providing the advantage of accessible data collection for the establishment of local dose reference levels and optimisation purposes, within the framework of the radiation protection program in the Neurosurgery Department.

LOW BMI PATIENT DOSE IN DIGITAL RADIOGRAPHY.

In this study, the radiation dose received by 364 low body mass index (BMI) adult patients undergoing chest, abdomen, lumbar spine, kidneys and urinary bladder (KUB) and pelvis X-ray examinations in an X-ray room with a digital radiography system was evaluated. The patients' kerma area product (KAP) values were recorded, and the entrance surface air kerma (ESAK) was calculated based on the X-ray tube output, exposure parameters and technical data. The 75th percentiles of the distribution of ESAK and KAP values were also estimated. The dose values were compared with the corresponding values for normal patients obtained from a previous survey in our hospital, as well as with the national and UK diagnostic reference levels (DRLs). The correlation of dose values with patient size metrics (mass, height, BMI) was also investigated. A statistically significant difference was found in KAP and the ESAK values between low BMI and normal patients (Mann-Whitney test, p < 0.05), for all examinations studied. The percentage difference for chest PA, chest LAT, abdomen PA, lumbar spine AP, lumbar spine LAT, pelvis AP and KUB AP examinations was 40, 36, 48, 68, 57, 46 and 67% for median KAP and 26, 43, 52, 48, 19, 44 and 51% for median ESAK, respectively. The corresponding 75th percentiles for low BMI patients were 0.065, 0.349, 0.683, 1.54, 3.92, 1.11, 0.67 mGy and 0.042, 0.218, 0.450, 0.280, 0.598, 0.597, 0.267 Gycm2 in terms of ESAK and KAP values, respectively. They were 74-90% lower compared to the national diagnostic reference levels (DRLs), 35-84% and 58-82% compared to the UK DRLs, for ESAK and KAP values, respectively. Regarding the gender of the patients, no statistically significant difference was found in the dose values between female and male patients (Mann-Whitney test, p > 0.05), for all examinations studied. A statistically significant correlation was found between ESAK and KAP values with BMI for KUB AP, pelvis AP, lumbar spine AP, lumbar spine LAT and chest PA, while for chest LAT examinations, only the ESAK were significantly correlated with BMI. They also significantly correlated with the mass for KUB AP, lumbar spine LAT, abdomen PA and chest PA examinations, while no significant correlation was found between the dose values and patients' height. It can be concluded that the low BMI patients received a significantly reduced radiation dose compared to normal patients. Additional studies need to be conducted for these patient groups, which could contribute to the further development of a radiation protection culture in diagnostic radiography.

DO THE BMI AND SURGEON INFLUENCE THE PATIENT DOSE IN FLUOROSCOPICALLY GUIDED LUMBAR DISCECTOMY AND FUSION?☆.

A survey was conducted to evaluate the role of the surgeon and the patients' body size, on patient radiation dose in fluoroscopically guided lumbar discectomy and fusion (LDF) procedures. Fluoroscopy time (FT), kerma area product (KAP), cumulative dose (CD), as well as anatomical and technical data were recorded for 100 patients, who underwent single or multi-level posterior LDF, which was carried out by three senior neurosurgeons utilising a C-arm fluoroscopy system. The patients were divided into three groups based on the body mass index (BMI) values (normal, overweight, obese) and the neurosurgeon that performed each procedure (surgeon 1, surgeon 2, surgeon 3). Entrance surface dose (ESD) was estimated based on KAP values and exposure data, while the effective dose (ED) was estimated utilising the KAP values and appropriate conversion coefficients. The mean FT, KAP, CD, ESD and ED values were 11.7 s, 0.65 Gy cm2, 2.96 mGy, 11.7 mGy and 0.08 mSv for normal patients, 22.1 s, 0.94 Gy cm2, 4.27 mGy, 21.4 mGy and 0.11 mSv for overweight patients and 67.7 s, 3.59 Gy cm2, 17.79 mGy, 107.2 mGy and 0.44 mSv for obese patients. The corresponding values were 21.5 s, 0.77 Gy cm2, 3.51 mGy, 17.5 mGy, 0.09 mSv for the first, 23.0 s, 1.44 Gy cm2, 6.52 mGy, 30.2 mGy, 0.18 mSv for the second and 14.2 s, 0.64 Gy cm2, 2.91 mGy, 17.0 mGy, 0.08 mSv for the third surgeon. Overweight patients received 83% and 38% higher ESD and ED, while obese patients 816% and 450%, compared to normal patients, respectively. The CD values should be implemented with caution, as a skin dose indicator, for all patient sizes. The weight-FT product could be useful in estimating KAP during LDF procedures. The third surgeon achieved the lowest dose values. Although the first surgeon had the same FT with the second surgeon, the corresponding dose values were decreased by 50%. The differences in FT, KAP, CD and ED values among the groups of patients studied were not statistically significant (Kruskal-Wallis test, p > 0.05), although the p-values were close to the threshold of statistical significance. The pairwise comparisons showed statistically significant differences for KAP, CD and ED values between obese and normal patients and between surgeon 1 and surgeon 3 (Mann-Whitney test, p < 0.05). The ESD values showed statistically significant differences among the BMI-based groups and among the surgeon-based groups studied (Kruskal-Wallis test, p < 0.05). This fact can be attributed to the better implementation of the fluoroscopy system technical parameters concerning the patients' size, clinical conditions and complexity of the procedures. Training and awareness of neurosurgeons on radiation protection issues are of critical importance; however, further studies should be performed towards optimisation procedures regarding patient dose.

Patient dose in brain perfusion imaging using an 80-slice CT system.

BACKGROUND AND PURPOSE: Brain CT Perfusion (CTP) is an X-ray imaging technique for the assessment of brain tissue perfusion, which can be used in several different entities. The aim of this study is the evaluation of the radiation dose to patients during a comprehensive brain CT prescription protocol (CPP) consisting of an unenhanced brain CT, a brain CT angiography and a CTP scan. MATERIALS AND METHODS: Eighteen patients were studied using an 80-slice CT system, with an iterative reconstruction algorithm. The volume Computed Tomography Dose Index (CTDIvol) and dose length product (DLP) were recorded from the dose report of the system. The calculation of effective dose (ED) was accomplished using the DLP values. RESULTS: For the CTP examinations, the CTDIvol ranged from 116.0 to 134.8mGy, with the mean value 119.5mGy. The DLP ranged from 463.9 to 539.2mGy·cm, with the mean value 478mGy·cm. For the CPP, the total ED ranged from 3.31 to 5.07mSv, with the mean value 4.37mSv. CONCLUSIONS: These values are lower than the values reported in corresponding studies, including studies utilizing CT systems with more slices.

PATIENT DOSE IN DIGITAL RADIOGRAPHY UTILISING BMI CLASSIFICATION.

Dose audit is important towards optimisation of patients' radiation protection in diagnostic radiography. In this study, the effect of the body mass index (BMI) on radiation dose received by 1869 adult patients undergoing chest, abdomen, lumbar spine, kidneys and urinary bladder (KUB) and pelvis radiography in an X-ray room with a digital radiography system was investigated. Patients were categorised into three groups (normal, overweight and obese) based on the BMI values. The patients' entrance surface air kerma (ESAK) and the effective dose (ED) were calculated based on the X-ray tube output, exposure parameters and technical data, as well as utilising appropriate conversion coefficients of the recorded kerma area product (KAP) values. The local diagnostic reference levels (LDRLs) were established at the 75th percentile of the distribution of ESAK and KAP values. Statistically, a significant increase was found in ESAK, KAP and ED values, for all examinations, both for overweight and obese patients compared to normal patients (Mann-Whitney test, p < 0.0001). Regarding the gender of the patients, a statistically significant increase was found in the dose values for male patients compared to female patients, except for the chest LAT examinations (Mann-Whitney test, p = 0.06). The percentage increase for chest PA, chest LAT, abdomen AP, lumbar spine AP, lumbar spine LAT, pelvis AP and KUB AP in overweight patients was 75%, 100%, 136%, 130%, 70%, 66% and 174% for median ESAK, 67%, 81%, 135%, 134%, 85%, 63% and 172% for median KAP, as well as 89%, 54%, 146%, 138%, 82%, 57% and 183% for median ED values, respectively. For obese patients, the corresponding increases were 200%, 186%, 459%, 345%, 203%, 150% and 785% for median ESAK, 200%, 185%, 423%, 357%, 227%, 142% and 597% for median KAP, as well as 222%, 156%, 446%, 363%, 218%, 136% and 625% for median ED. The corresponding LDRLs for overweight patients were 0.17 mGy, 1.21 mGy, 3.74 mGy, 7.70 mGy, 7.99 mGy, 4.07mGy, 5.03 mGy and 0.13 Gy cm2, 0.69 Gy cm2, 2.35 Gy cm2, 2.10 Gy cm2, 2.59 Gy cm2, 2.13 Gy cm2, 2.49 Gy cm2 in terms of ESAK and KAP values, respectively, while in the case of obese patients were 0.28 mGy, 1.82 mGy, 7.26 mGy, 15.10 mGy, 13.86 mGy, 6.89 mGy, 13.40 mGy and 0.21 Gy cm2, 1.10 Gy cm2, 4.68 Gy cm2, 4.01 Gy cm2, 4.80 Gy cm2, 3.27 Gy cm2, 6.02 Gy cm2, respectively. It can be concluded that overweight and obese patients received a significantly increased radiation dose. Careful adjustment of imaging protocols is needed for these patients to reduce patient dose, while keeping the image quality at an acceptable level. Additional studies need to be conducted for these patient groups, that could further contribute to the development of radiation protection culture in diagnostic radiography.

PATIENT DOSES IN COMMON DIAGNOSTIC X-RAY EXAMINATIONS.

A local survey was conducted, to evaluate the radiation dose to adult patients who underwent diagnostic X-ray examinations. Patient-related and technical data were recorded, in 1504 patients, for each of the 11 individual projections, of the 7 most common examinations performed in an X-ray room, with 1 digital radiography system. The patient entrance surface air kerma (ESAK) and the effective dose (ED) were calculated based on the X-ray tube output and the exposure parameters, as well as utilisation of suitable conversion coefficients, respectively. The 75th percentiles of the distribution of the ESAK and kerma area product (KAP) values were also established. The mean, median and 75th percentiles were compared with the national reference levels and the most common values reported at the European level through the DOSE DATAMED II project. The corresponding ED values were also compared with the average values reported for all European countries. The mean ESAK, KAP and ED values along with the uncertainty U values for chest PA, chest LAT, cranium AP, cranium LAT, cervical spine AP, cervical spine LAT, lumbar spine AP, lumbar spine LAT, pelvis AP, abdomen AP, kidneys and urinary bladder (KUB) AP were 0.12 (0.001) mGy, 0.66 (0.023) mGy, 1.01 (0.034) mGy, 0.69 (0.098) mGy, 0.72 (0.014) mGy, 0.63 (0.011) mGy, 4.12 (0.050) mGy, 5.74 (0.082) mGy, 2.57 (0.024) mGy, 1.94 (0.017) mGy, 2.47 (0.073) mGy, and 0.09 (0.001) Gy cm2, 0.38 (0.012) Gy cm2, 0.32 (0.009) Gy cm2, 0.27 (0.052) Gy cm2, 0.17 (0.004) Gy cm2, 0.21 (0.006) Gy cm2, 1.18 (0.018) Gy cm2, 1.86 (0.023) Gy cm2, 1.41 (0.012) Gy cm2, 1.27 (0.010) Gy cm2, 1.28 (0.038) Gy cm2, as well as 0.01 (0.0001) mSv, 0.05 (0.0016) mSv, 0.02 (0.0006) mSv, 0.01 (0.0012) mSv, 0.03 (0.0008) mSv, 0.03 (0.0006) mSv, 0.26 (0.0038) mSv, 0.17 (0.0022) mSv, 0.20 (0.0016) mSv, 0.23 (0.0018) mSv, 0.23 (0.0068) mSv, respectively. The 75th percentiles along with the uncertainty U values for chest PA, chest LAT, cranium AP, cranium LAT, cervical spine AP, cervical spine LAT, lumbar spine AP, lumbar spine LAT, pelvis AP, abdomen AP, kidneys and urinary bladder (KUB) AP were 0.14 (0.006) mGy, 0.88 (0.031) mGy, 1.22 (0.049) mGy, 0.94 (0.098) mGy, 0.93 (0.027) mGy, 0.78 (0.013) mGy, 5.16 (0.073) mGy, 7.24 (0.134) mGy, 2.96 (0.047) mGy, 2.59 (0.036) mGy, 3.07 (0.116) mGy, as well as 0.10 (0.0006) Gy cm2, 0.51 (0.017) Gy cm2, 0.37 (0.020) Gy cm2, 0.33 (0.040) Gy cm2, 0.23 (0.007) Gy cm2, 0.26 (0.011) Gy cm2, 1.50 (0.036) Gy cm2, 2.26 (0.035) Gy cm2, 1.61 (0.023) Gy cm2, 1.67 (0.017) Gy cm2, 1.56 (0.069) Gy cm2, in terms of ESAK and KAP values, respectively. The results were significantly lower compared with the national reference levels, the most common DRL values reported at the European level and other previously reported dose values. Patient dose surveys could contribute towards optimising radiation protection for patients, therefore, highlighting the necessity to increase the awareness and knowledge of the radiation dose in conjunction with the required image quality.