Feasibility of new patient dose management tool in digital radiography: Using clinical exposure index data of mobile chest radiography in a large university hospital.

The clinical anteroposterior (AP) chest images taken with a mobile radiography system were analyzed in this study to utilize the clinical exposure index (EI) as a patient dose-monitoring tool. The digital imaging and communications in medicine header of 6048 data points exposed under the 90 kVp and 2.5 mAs were extracted using Python for identifying the distribution of clinical EI. Even under the same exposure conditions, the clinical EI distribution was 137.82-4924.38. To determine the cause, the effect of a patient's body shape on EI was confirmed using actual clinical chest AP image data binarized into 0 and 255-pixel values using Python. As a result, the relationship between the direct X-ray area of the chest AP image, the higher the clinical EI, the larger the rate of the direct X-ray area. A conversion equation was also derived to infer entrance surface dose through clinical EI based on the patient thickness. This confirmed the possibility of directly monitoring patient dose through EI without a dosimeter in real-time. Therefore, to use the clinical EI of the mobile radiography system as a patient dose-monitoring tool, the derivation method of clinical EI considers several factors, such as the relationship between patient factors.

The significance of evaluating sphenoid sinus fluid by postmortem computed tomography in cases of drowning.

PURPOSE: In cases of drowning, the presence of sphenoid sinus fluid is a non-specific autopsy finding. However, studies have reported that fluid accumulation in the paranasal sinuses is more commonly observed in drowning victims. Furthermore, some laboratory tests, such as diatom and electrolyte analysis, can serve as supplementary diagnostic tools for diagnosing drowning. Therefore, accurate sphenoid sinus fluid sampling is an important aspect of an autopsy in suspected drowning cases. The aim of this study was to identify the significance of evaluating sphenoid sinus fluid by PMCT images in cases of drowning. METHODS: We retrospectively reviewed 54 drowning victims who underwent PMCT and forensic autopsy. Fluid volume in the sphenoid sinus was measured using a graduated syringe during autopsy and a three-dimensional (3D) workstation based on PMCT images was used for the purpose of comparison. The Mann-Whitney U test and Spearman's rank correlation coefficient was used to evaluate statistically significant differences and correlations. Additionally, a Bland-Altman plot was employed to assess the agreement between PMCT and autopsy. RESULTS: The median volume was 1.65 (range 0.00-12.4) ml and 1.55 (range 0.00-7.00) ml in the PMCT and autopsy, respectively, showing a statistically insignificant difference (p = 0.294) and a significant correlation (Rs = 0.896). In 35 cases, the PMCT overestimated the fluid volume more than the autopsy, whereas in 14 cases, the PMCT underestimated the fluid volume. No fluid was identified in seven cases during the autopsy, whereas in five patients, no fluid was found in both PMCT and autopsy. By analyzing the Bland-Altman plot, a bias of 0.73 ± 1.4 ml and limits of agreement ranging from -2.04 to 3.51 ml were observed for sphenoid sinus fluid volume measurements. CONCLUSIONS: Based on the limitations of traditional fluid volume measurement in the sphenoid sinus during autopsy, we propose the utilization of PMCT volumetric analysis prior to autopsy as a means to enhance the detection of sphenoid sinus fluid in cases of drowning.

Effect of anti-scatter grids on the image improvement factor in digital radiography for various phantom thicknesses and irradiation fields.

Digital radiography (DR) is used to acquire digital images with a consistent image brightness under different exposures and in the presence of various anti-scatter grids. This study effectively evaluates the image improvement factor and the conventional physical imaging properties, such as grid selectivity, contrast improvement ratio, and grid exposure factor. Various grids and acrylic phantoms of thicknesses 20 cm and 12 cm were used in this evaluation to simulate the pelvis and lumbar spine, and the cervical spine, respectively. Applied irradiation fields were adjusted according to the simulated body parts. Eight grids (four at 40 cm-1 strip frequency with grid ratios of 6:1, 8:1, 10:1, and 12:1, and four at 60 cm-1 strip frequency with grid ratios of 8:1, 10:1, 12:1, and 14:1) were used in this study. The grid selectivity, contrast improvement ratio, and grid exposure factor increased with higher grid ratios. At a constant grid ratio, these three parameters exhibited higher values at lower strip frequency (40 cm-1) than at higher strip frequency (60 cm-1). The change in the image improvement factor of the simulated cervical spine with respect to the grid was smaller than those of the simulated pelvis and lumbar spine. Our results suggested that the image improvement factor is a useful index for selecting grids according to object thickness at a constant exposure in DR systems.

Updated National Diagnostic Reference Levels and Achievable Doses for CT Protocols: A National Survey of Korean Hospitals.

Background: In 2021, the Korean government proposed a new CT diagnostic reference level. This study performed a nationwide survey and developed new DRLs and AD for 13 common CT examinations. We compared other countries' DRLs for CT examinations. Methods: This study investigated the CTDIvol and DLP of the 12 types of CT protocols for adults and brain CT protocol for pediatrics. A total of 7829 CT examinations were performed using 225 scanners. We defined the DRLs values in the distribution of radiation exposure levels to determine the nationwide patient dose and distribution status of the dose. Results: This study showed that the new Korean national CT DRLs are slightly higher or similar to those of previous surveys and are similar or lower than those of other countries. In some protocols, although the DLP value increased, the CTDIvol decreased; therefore, it can be concluded that the patient's dose in CT examinations was well managed. Conclusions: The new CT DRLs were slightly higher than or similar to that of the previous survey and were evaluated to be similar or lower than CT DRLs of other countries. These DRLs will be used for radiation optimization and effective dose calculation for an individual.

Potential for personal identification using the volume of the mastoid air cells extracted from postmortem computed tomographic images.

This study revealed the usefulness of volumetric analysis of mastoid air cells (MACs) extracted from postmortem computed tomography (PMCT) images in characterizing individuals. To characterize deceased persons, the MACs volumes of 61 Japanese PMCT images were measured after thresholding in Hounsfield units and based on the number of voxels on the right and left sides and the voxel size for each person. The volume differences between the right and left MACs and sex were examined. Although there were no obvious volume differences between males and females, the order of sizes on the two sides varied for each person. Moreover, deceased persons could be roughly classified using the total volume of MACs. Deceased persons with similar total volumes could be distinguished further by comparing the ratio of volumes in bilateral MACs. Although the identification process is dependent on samples and different sizes of bilateral MACs, our pilot study indicated that 81.9% (50/61) of deceased persons could be distinguished. In conclusion, volumetric analysis of MACs measured using PMCT imaging has the potential to identify individuals and reduce the number of candidates.

Monitoring clinical exposure index and deviation index for dose optimization based on national diagnostic reference level: Focusing on general radiography of extremities.

BACKGROUND: The International Electrotechnical Commission established the concept of the exposure index (EI), target exposure index (EIT) and deviation index (DI). Some studies have conducted to utilize the EI as a patient dose monitoring tool in the digital radiography (DR) system. OBJECTIVE: To establish the appropriate clinical EIT, this study aims to introduce the diagnostic reference level (DRL) for general radiography and confirm the usefulness of clinical EI and DI. METHODS: The relationship between entrance surface dose (ESD) and clinical EI is obtained by exposure under the national radiography conditions of Korea for 7 extremity examinations. The EI value when the ESD is the DRL is set as the clinical EIT, and the change of DI is then checked. RESULTS: The clinical EI has proportional relationship with ESD and is affected by the beam quality. When the clinical EIT is not adjusted according to the revision of DRLs, there is a difference of up to 2.03 in the DI value and may cause an evaluation error of up to 1.6 times for patient dose. CONCLUSIONS: If the clinical EIT is periodically managed according to the environment of medical institution, the appropriate patient dose and image exposure can be managed based on the clinical EI, EIT, and DI.

Evaluation of radiation dose to organs of neonatal patients during portable X-ray examination in incubators: A Monte Carlo simulation study.

BACKGROUND: Infants admitted to neonate intensive care units (NICUs) are placed in incubators to maintain body temperature and condition, which undergo normal radiographs and are exposed to radiation. Furthermore, different incubator structures in different hospitals exhibit varying object to image receptor distance (OID), source to image receptor distance (SID), presence of canopy, which results in variations in X-ray radiation conditions and doses absorbed by the neonatal patients. OBJECTIVE: To measure organ dose exposed to neonatal patient in different incubator settings. METHODS: A portable X-ray was performed on a neonatal patient placed in an incubator to identify disease progress, the injection path of the drug, and various factors. To minimize direct contact between neonatal patients and image receptor, radiologic technologists place the image receptor on a tray underneath the incubator and place the portable X-ray tube on top of the acrylic canopy of the incubators. SID and OID settings and value of organ dose exposed to the patient varied based on the incubator structure, and the organ absorbed dose was determined using Monte Carlo N-Particle (MCNP) simulation, PC-based Monte Carlo program (PCXMC) 2.0 simulation, and neonate phantoms. RESULTS: Evaluations of organ dose of neonatal patients in three hospitals with different incubator settings reveal that the average organ dose differs by 36% depending on change in OID and SID settings and reduces by 10% with an acrylic canopy. Therefore, owing to the presence of an acrylic canopy on the top of the incubator and the longer SID with the corresponding shorter OID, a lower dose was absorbed by organs of neonatal patient. CONCLUSION: Our results provide proof that proper incubator standard decreases organ dose to neonatal patient during continuously diagnostic X-ray procedure.

Effect of Exposure Angulation on the Occupational Radiation Exposure during Cardiac Angiography: Simulation Study.

Cardiac angiography to visualize the cardiac coronary artery for lesions causes a lot of radiation exposure dose to the interventional cardiologist. We evaluated the occupational radiation exposure to the interventional cardiologist based on changes to the angle of the X-ray tube used in cardiac angiography and calculated the conversion factor for effective dose in this study. To evaluate the occupational radiation exposure resulting from scattered radiation to interventional cardiologists, organ doses for eyeball, thyroid, and heart were calculated using Monte Carlo simulation with korean typical man(KTMAN) phantom at the left anterior oblique (LAO)30/cranial (CRAN)30, CRAN40, right anterior oblique (RAO)30/CRAN30, RAO30/caudal(CAUD)20, CAUD39, LAO40/CAUD35, and LAO40 positions in the femoral and the radial artery puncture. In this study, analysis of the different angles showed the highest radiation exposure on LAO30/CRAN30 and CRAN40 position, which were 150.65% and 135.3%, respectively, compared to AP angles. Therefore, to reduce occupational dose for interventional cardiologists, it is recommended that radiation protection, such as using radiation shield and personal protective equipment (PPE), be used at LAO30/CRAN30 and CRAN40 angulation, and the conversion factor for calculating the organ dose received by the interventional cardiologists based on patient dose can be applied for improved occupational dose management.

Proper Management of the Clinical Exposure Index Based on Body Thickness Using Dose Optimization Tools in Digital Chest Radiography: A Phantom Study.

In radiography, the exposure index (EI), as per the International Electrotechnical Commission standard, depends on the incident beam quality and exposure dose to the digital radiography system. Today automatic exposure control (AEC) systems are commonly employed to obtain the optimal image quality. An AEC system can maintain a constant incident exposure dose on the image receptor regardless of the patient thickness. In this study, we investigated the relationship between body thickness, entrance surface dose (ESD), EI, and the exposure indicator (S value) with the aim of using EI as the dose optimization tool in digital chest radiography (posterior-anterior and lateral projection). The exposure condition from the Korean national survey for determining diagnostic reference levels and two digital radiography systems (photostimulable phosphor plate and indirect flat panel detector) were used. As a result, ESD increased as the phantom became thicker with constant exposure indicator, which indicates similar settings to an AEC system, but the EI indicated comparatively constant values without following the tendency of ESD. Therefore, body thickness should be considered under the AEC system for introducing EI as the dose optimization tool in digital chest radiography.

USE OF CLINICAL EXPOSURE INDEX AND DEVIATION INDEX BASED ON NATIONAL DIAGNOSTIC REFERENCE LEVEL AS DOSE-OPTIMIZATION TOOLS FOR GENERAL RADIOGRAPHY IN KOREA.

The International Electrotechnical Commission introduced the concepts of exposure index (EI), target exposure index (EIT) and deviation index (DI) to manage and optimize patient dose in real time. In this study, we have proposed an appropriate method for setting the EIT based on the Korean national diagnostic reference levels (DRLs). Furthermore, we evaluated the use of clinical EI, EIT and DI as tools for patient dose optimization in clinical environments by observing the changes in DI with those in EIT. According to the Korean national exposure conditions, we conducted experiments on three representative radiographic examinations (chest posterior-anterior, lateral and abdomen anterior-posterior) of clinical environments. As the exposure conditions and DRLs varied, the clinical EI, EIT and DI also varied. These results reveal that the clinical EI, EIT and DI can be used as tools for optimizing the patient dose if EIT is periodically and properly updated.

Correction to: A simple method for the automatic classification of body parts and detection of implanted metal using postmortem computed tomography scout view.

In the original publication of the article, the authors affiliations were incorrectly published. The corrected affiliations are given in this correction.

Radiation exposure of interventional cardiologists during coronary angiography: evaluation by phantom measurement and computer simulation.

During interventional cardiological procedures, operators are exposed to patients' scatter radiation. Therefore, we measured the radiation exposure of the operator's eyeball, thyroid, and chest wall during angiography. We used the optically stimulated luminescence dosimeter in the anthropomorphic phantom and developed Monte Carlo simulations using the Korean human voxel phantom. At 15 frames/s, the radiation dose of the operator's right eyeball (RE), left eyeball (LE), thyroid (T), and chest wall (CW) at the femoral artery puncture position (FAPP) with protective equipment (PE) was 0.015, 0.16, 0.012, and 0.014 mGy, respectively. At 7.5 frames/sec, the radiation dose of the operator's RE, LE, T, and CW at FAPP with PE was 33.33%, 18.75%, 52.94%, and 45.00% lower than that of those at the radial artery puncture position (RAPP), respectively. At 15 frames/s, the radiation dose of the operator's RE, LE, T, and CW at RAPP without PE was 1.76 times, 2.23 times, 2.76 times, and 2.05 times higher than that of those with PE. Per the simulation results, the absorbed radiation dose of the eye ball, thyroid gland, and myocardium of the heart at FAPP with and without PE under 15 frame/s was 9.68%, 13.04%, 8.33% and 9.98%, 6.00%, 8.82% lower than at RAPP under similar conditions. Effective measures for occupational radiological protection are lower frame rate exposure, increased distance from the X-ray source, and PE use. Radiologist protection in interventional cardiology cannot be handled independently of patient protection, owing to several correlations; thus, reducing the patient dose will reduce the operator dose.

A simple method for the automatic classification of body parts and detection of implanted metal using postmortem computed tomography scout view.

Information on medical devices embedded in the body is important in the identification of an unidentified body. Computed tomography (CT) is a powerful imaging modality; however, metallic artifacts deteriorate the image quality because of the reconstruction method. On the contrary, CT scout view is less affected by metallic artifacts compared to CT. It is a simple method to classify the body into three rough parts for postmortem CT (PMCT) scout view, and an algorithm used to detect the location of the implanted metal has been developed for personal identification in forensic pathology. Of the test images, 97% were correctly classified into the three body parts. The true-positive rate for detection of the implanted metal in the scout view was 96.5%. Therefore, our simple methods are applicable in PMCT scout views and would be particularly useful for forensic pathology.

FEASIBILITY OF DISPLAYED EXPOSURE INDEX IN IEC STANDARD FRAMEWORK AS A DOSE OPTIMISATION TOOL FOR DIGITAL RADIOGRAPHY SYSTEMS.

International Electrotechnical Commission (IEC) established the framework for the use of exposure index (EI) for evaluating the exposure conditions with various digital systems. In this study, we investigated the feasibility of EI, as per the IEC, by comparing the EIs obtained through manual calculated and that displayed on the console of two computed radiography (CR) and digital radiography (DR) systems with radiation beam qualities of RQA3,5,7 and 9. As a result, both two systems indicated an uncertainty of less than 20% for both calculated and displayed EI with all beam qualities except displayed EI obtained by RQA3. However, the displayed EI values were different even under the same exposure conditions because of the characteristics of the imaging receptor materials, such as BaFI or CsI, of two systems. Therefore, when an operator attempts to introduce displayed EI for managing radiation dose, it is essential to understand the characteristics of the digital system.

Evaluation of the depiction ability of similar subtraction images using digital chest radiographs of different patients.

The temporal subtraction (TS) technique requires the same patient's chest radiographs (CXRs) acquired on different dates, whereas the similar subtraction (SS) technique can be used in patients who have no previous CXR, using similar CXRs from different patients. This study aimed to examine the depiction ability of SS images with simulated nodules in comparison with that of TS images with 2- and 7-year acquisition intervals. One hundred patients were randomly selected from our image database. The most recently acquired images of the patients were used as target images for subtraction. The simulated nodule was superimposed on each target image to examine the usefulness of the SS technique. The most (Top 1) and ten most (Top 10) similar images for each target image were identified in the 24,254-image database using a template-matching technique, and used for the SS technique. SS and TS images were obtained using a previously developed nonlinear image-warping technique. The depiction ability of SS and TS images was evaluated using the contrast-to-noise ratio (CNR). The proportion of Top 1 SS images showing higher CNR than that of the TS images with 2- and 7-year acquisition intervals was 28% (28/100) and 33% (33/100), respectively. Moreover, the proportion of cases that had any of the Top 10 SS images with higher CNRs than those of TS images with 2- and 7-year acquisition intervals was 56% (56/100) and 72% (72/100), respectively. Our study indicates that the SS technique can potentially be used to detect lung nodules on CXRs.

Improving image quality around subtle lung nodules by reducing artifacts in similar subtraction imaging.

Similar subtraction imaging is useful for the detection of lung nodules; however, some artifacts on similar subtraction images reduce their utility. The authors attempted to improve the image quality of similar subtraction images by reducing artifacts caused by differences in image contrast and sharpness between two images used for similar subtraction imaging. Image contrast was adjusted using the histogram specification technique. The differences in image sharpness were compensated for using a pixel matching technique. The improvement in image quality was evaluated objectively based on the degree of artifacts and the contrast-to-noise ratio (CNR) of the lung nodules. The artifacts in similar subtraction images were reduced in 94% (17/18) of cases, and CNR was improved in 83% (15/18) of cases. The results indicate that the combination of histogram specification and pixel matching techniques is potentially useful in improving image quality in similar subtraction imaging.

Real-Time Patient Radiation Dose Monitoring System Used in a Large University Hospital.

Radiation dose monitoring in medical imaging examination areas is mandatory for the reduction of patient radiation exposure. Recently, dose monitoring techniques that use digital imaging and communications in medicine (DICOM) dose structured reports (SR) have been introduced. The present paper discusses the setup of a radiation dose monitoring system based on DICOM data from university hospitals in Korea. This system utilizes the radiation dose data-archiving method of standard DICOM dose SR combined with a DICOM modality performed procedure step (MPPS). The analysis of dose data based on a method utilizing DICOM tag information is proposed herein. This method supports the display of dose data from non-dosimeter-attached X-ray equipment. This system tracks data from 62 pieces of equipment to analyze digital radiographic, mammographic, mobile radiographic, CT, PET-CT, angiographic, and fluorographic modalities.

Monte Carlo simulation-based feasibility study of novel indirect flat panel detector system for removing scatter radiation.

The purpose of this study is to investigate the feasibility of a novel indirect flat panel detector (FPD) system for removing scatter radiation. The substrate layer of our FPD system has a Pb net-like structure that matches the ineffective area and blocks the scatter radiation such that only primary X-rays reach the effective area on a thin-film transistor. To evaluate the performance of the proposed system, we used Monte Carlo simulations to derive the scatter fraction and contrast. The scatter fraction of the proposed system is lower than that of a parallel grid system, and the contrast is superior to that of a system without a grid. If the structure of the proposed FPD system is optimized with respect to the specifications of a specific detector, the purpose of the examination, and the energy range used, the FPD can be useful in diagnostic radiology.

Development of Diagnostic Reference Levels Using a Real-Time Radiation Dose Monitoring System at a Cardiovascular Center in Korea.

Digital cardiovascular angiography accounts for a major portion of the radiation dose among the examinations performed at cardiovascular centres. However, dose-related information is neither monitored nor recorded systemically. This report concerns the construction of a radiation dose monitoring system based on digital imaging and communications in medicine (DICOM) data and its use at the cardiovascular centre of the University Hospitals in Korea. The dose information was analysed according to DICOM standards for a series of procedures, and the formulation of diagnostic reference levels (DRLs) at our cardiovascular centre represents the first of its kind in Korea. We determined a dose area product (DAP) DRL for coronary angiography of 75.6 Gy cm(2) and a fluoroscopic time DRL of 318.0 s. The DAP DRL for percutaneous transluminal coronary intervention was 213.3 Gy cm(2), and the DRL for fluoroscopic time was 1207.5 s.

Monte Carlo simulation-based feasibility study of a dose-area product meter built into a collimator for diagnostic X-ray.

According to the International Electro-technical Commission, manufacturers of X-ray equipment should indicate the number of radiation doses to which a patient can be exposed. Dose-area product (DAP) meters are readily available devices that provide dose indices. Collimators are the most commonly employed radiation beam restrictors in X-ray equipment. DAP meters are attached to the lower surface of a collimator. A DAP meter consists of a chamber and electronics. This separation makes it difficult for operators to maintain the accuracy of a DAP meter. Developing a comprehensive system that has a DAP meter in place of a mirror in the collimator would be effective for measuring, recording the dose and maintaining the quality of the DAP meter. This study was conducted through experimental measurements and a simulation. A DAP meter built into a collimator was found to be feasible when its reading was multiplied by a correction factor.