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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. [ABSTRACT FROM AUTHOR]

The pre-operative localisation of abnormal parathyroid glands (PG) in parathyroid scintigraphy is essential for suggesting treatment and assisting surgery. Human experts examine the scintigraphic image outputs. An assisting diagnostic framework for localisation reduces the workload of physicians and can serve educational purposes. Former studies from the authors suggested a successful deep learning model, but it produced many false positives. Between 2010 and 2020, 648 participants were enrolled in the Department of Nuclear Medicine of the University Hospital of Patras, Greece. An innovative modification of the well-known VGG19 network (ParaNet+) is proposed to classify scintigraphic images into normal and abnormal classes. The Grad-CAM++ algorithm is applied to localise the abnormal PGs. An external dataset of 100 patients imaged at the same department who underwent parathyroidectomy in 2021 and 2022 was used for evaluation. ParaNet+ agreed with the human readers, showing 0.9861 on a patient-level and 0.8831 on a PG-level basis under a 10-fold cross-validation on the training set of 648 participants. Regarding the external dataset, the experts identified 93 of 100 abnormal patient cases and 99 of 118 surgically excised abnormal PGs. The human-reader false-positive rate (FPR) was 10% on a PG basis. ParaNet+ identified 99/100 abnormal cases and 103/118 PGs, with an 11.2% FPR. The model achieved higher sensitivity on both patient and PG bases than the human reader (99.0% vs. 93% and 87.3% vs. 83.9%, respectively), with comparable FPRs. Deep learning can assist in detecting and localising abnormal PGs in scintigraphic scans of patients with primary hyperparathyroidism and can be adapted to the everyday routine. [ABSTRACT FROM AUTHOR]

The aim of this study was to examine [Gd.sub.2][O.sub.2]S:Eu (also known as GOS:Eu) powder scintillator under X-ray mammography imaging conditions. For this purpose, three scintillator screens with coating thicknesses of 33.1, 46.4 and 63.1 mg/[cm.sup.2] were prepared in our laboratory by sedimentation of [Gd.sub.2][O.sub.2]S:Eu powder. Light emission efficiency and optical emission spectra of the screens were measured under X-ray excitation using X-ray tube voltages (22-49 kVp) employed in mammography. Spectral compatibility with various optical photon detectors (photodiodes, photocathodes, charge coupled devices, films) and intrinsic conversion efficiency value (0.12) were determined by using emission spectrum data. In addition, parameters related to X-ray detection and energy absorption efficiency were calculated. [Gd.sub.2][O.sub.2]S:Eu showed peak emission in the wavelength range 620-630 nm. The 63.1 mg/[cm.sup.2] phosphor screen appeared with the maximum light emission efficiency. Due to its reddish emission spectrum, [Gd.sub.2][O.sub.2] S:Eu showed excellent compatibility with the sensitivity of many currently used photodetectors and could be considered for application in X-ray imaging especially in various digital detectors. Index Terms--[Gd.sub.2][O.sub.2] S:Eu, luminescence efficiency, matching factor powder phosphors.

This paper investigates the light emission efficiency of [Lu.sub.2]Si[O.sub.5]:Ce (LSO) powder scintillator under conditions employed in projection X-ray imaging. Although single-crystal LSO has been thoroughly studied in medical imaging energies, the efficiency of powder LSO has not been previously investigated experimentally under X-ray medical radiography conditions. For this purpose, three scintillating screens with a coating thickness of 63.4, 108.4, and 172.5 mg/[cm.sup.2] were prepared by sedimentation of LSO powder. Measurements of luminescence efficiency (emitted light energy flux over incident X-ray energy flux) were performed in the radiographic X-ray tube voltages range (40-140 kVp). Parameters related to X-ray detection, i.e., quantum detection efficiency, energy absorption efficiency and probability of K-fluorescence reabsorption were calculated. A theoretical model, describing radiation and light transfer, was employed to fit luminescence experimental data and to estimate values of the intrinsic conversion efficiency and of the light attenuation coefficients of the scintillating screens. The spectral compatibility of the LSO powder scintillator to various optical detectors used in digital radiography was also determined by performing light emission spectrum measurements and by taking into account the spectral sensitivity of electronic optical detectors. Maximum values of LSO luminescence efficiency were observed within the range from 40 to 60 kVp. The 172.5 mg/[cm.sup.2] thick screen was found more efficient than the two thinner screens examined in our experiments. The intrinsic conversion efficiency of LSO (0.10) was found close to that of currently employed phosphors. Spectral compatibility data of LSO screens indicates that LSO may be efficiently coupled to optical detectors used in digital radiography imaging systems. Index Terms--Inorganic scintillators, luminescence efficiency, LSO: Ce, powder phosphors.

LYSO:Ce and LuYAP:Ce are single crystal non-hygroscopic scintillators of high density, high light yield and short decay time, which have been successfully used in small animal PET imagers. In the present study, the luminescence emission properties of [([Lu.sub.0.9], [Y.sub.0.1]).sub.2] Si[O.sub.5]:Ce (LYSO:Ce) and ([Lu.sub.0.7], [Y.sub.0.3])Al[O.sub.3]:Ce (LuYAP:Ce) crystals were investigated for use in x-ray medical imaging. Both crystals had dimensions of 2 x 2 x 8 [mm.sup.3], with all surfaces polished. Evaluation was performed by determining the x-ray luminescence efficiency (XLE) (emitted light energy flux over incident x-ray energy flux) and the detector optical gain (DOG) (emitted light photons per incident x-ray photon) in a wide range of x-ray energies employed in mammography (22-49 kVp) and in general x-ray imaging (50-140 kVp). Measurements were performed using an experimental set-up based on a photomultiplier coupled to an integration sphere. The emission spectrum under x-ray excitation was measured using an optical grating monochromator to determine the spectral compatibility to various optical photon detectors incorporated in medical imaging detectors. Optical characteristics such as transmission and absorption spectra were investigated in addition to the scintillation properties. The light emission performance of the two scintillation materials studied was found adequately high for x-ray imaging. Index Terms--Detector optical gain, inorganic scintillators, luminescence eficiency, LuYAP:Ce, radiation detectors.

The luminescence of [(Lu, Y).sub.2]Si[O.sub.5]: Ce (LYSO:Ce) and [Gd.sub.2]Si[O.sub.5]: Ce (GSO:Ce) crystals was studied for use in tomographic medical x-ray imaging. LYSO:Ce and GSO:Ce are high density (7.1 g/[cm.sup.3] and 6.71 g/[cm.sup.3] respectively), high atomic number (71 for Lu and 64 for Gd), non-hydroscopic, and short decay time (40 ns and 60 ns respectively) scintillators. Evaluation was performed by determining: 1) the luminescence efficiency (LE) (emitted fight energy flux over incident x-ray energy flux) in x-ray energies employed in general x-ray imaging (40-140 kVp) and in mammographic x-ray imaging (22-49 kVp), 2) the fight emission spectrum, determined at various x-ray energies (22-140 kVp), and 3) the spectral compatibility to optical photon detectors, incorporated in medical imaging systems. Both scintillation materials exhibited adequately high LE in the x-ray diagnostic energy range, with LYSO:Ce's LE being distinctively higher. LYSO:Ce and GSO:Ce were found most compatible with the S-20 photocathode (0.9 for both materials) and adequately compatible to the amorphous silicon photodiode (0.74 for both materials), incorporated in many digital x-ray detectors. Index Terms--Inorganic scintillators, luminescence efficiency, LYSO:Ce, matching factor, radiation detectors.

[Gd.sub.2]Si[O.sub.5] :Ce (GSO:Ce) is a high-Z, nonhygroscopic fast emitting scintillator used in detectors of positron emission tomography (PET) systems. The purpose of this study was to evaluate the luminescence efficiency of GSO:Ce scintillator under irradiation conditions employed in X-ray medical imaging, since findings may be of value in novel applications such as computed tomography breast imaging or modern fast image producing X-ray computed tomography. To this aim the absolute luminescence efficiency (emitted light flux over X-ray exposure), the spectral matching factor (compatibility to optical detectors), and the effective efficiency (the product of absolute efficiency and spectral compatibility) were determined for X-ray tube voltages ranging from 20 to 140 kV. The efficiency of GSO:Ce was found to increase with increasing X-ray tube voltage, while the GSO:Ce spectrum, peaking at 440 and 490 nm, was found compatible to most optical detectors (photodiodes, photocathodes, and charge-coupled devices). Index Terms--Inorganic scintillators, luminescence efficiency, matching factor, radiation detectors.

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. [ABSTRACT FROM AUTHOR]

The purpose of the current study was to provide useful data, which may help neurosurgeons to manage the patient dose and image quality in spinal surgery procedures, utilising a phantom and a test object. The kerma area product, cumulative dose (CD) and entrance surface dose (ESD) rate on the phantom and image intensifier were measured, for selectable fields of view (FOVs), fluoroscopy modes, two geometric magnifications and various phantom thicknesses. The images were subjectively evaluated regarding low-contrast detectability and high-contrast resolution. Signal-to-noise ratio (SNR), contrast-to-noise ratio (CNR), high-contrast spatial resolution (HCSR) and figure of merit (FOM) values were also estimated. The ESD rates increased with increasing phantom thickness, when using electronic or geometric magnification, continuous or high-definition fluoroscopy (HDF). The observers' evaluation showed relatively slight changes in image quality when pulsed fluoroscopy was used. SNR, CNR and HCSR values decreased with increasing phantom thicknesses, while remained almost constant when using pulsed fluoroscopy. SNR and HCSR improved in HDF, while the CNR remained almost constant only for the FOVs 23 and 17 cm. By applying electronic magnification, this resulted in improved HCSR. FOM values decreased in HDF, with increasing phantom thickness and using electronic magnification. For the 'thinnest' patients, CD may overestimate skin dose by 25% than the actual values. Geometric magnification resulted in improved FOM, especially for low-dose fluoroscopy and FOV 23 cm. The knowledge of the increments in dose values, image quality and FOM indices concerning phantom thickness may help neurosurgeons to optimise spinal surgery procedures by selecting the appropriate operational parameters, which could contribute toward the establishment of a radiation protection culture. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]