Benefits and limitations for the use of radiation dose management systems in medical imaging. practical experience in a university hospital

Objectives: Radiation dose management systems (DMS) are currently to help improve radiation protection in medical imaging and interventions. This study presents our experience using a homemade DMS called DOLQA (Dose On-Line for Quality Assurance). Methods: Our DMS is connected to 14 X-ray systems in a university hospital linked to the central data repository of a large network of 16 public hospitals in the Autonomous Community of Madrid, with 6.7 million inhabitants. The system allows us to manage individual patient dose data and groups of procedures with the same clinical indications, and compare them with diagnostic reference levels (DRLs). The system can also help to prioritize optimisation actions. Results: This study includes results of imaging examinations from 2020, with 3,7601 procedures and 28,6471 radiation events included in the radiation dose structured reports (RDSR), for computed tomography (CT), interventional procedures, positron emission tomography-CT (PET-CT) and mammography. Conclusions: The benefits of the system include: automatic registration and management of patient doses, creation of dose reports for patients, information on recurrent examinations, high dose alerts, and help to define optimisation actions. The system requires the support of medical physicists and implication of radiologists and radiographers. DMSs must undergo periodic quality controls and audit reports must be drawn up and submitted to the hospital’s quality committee. The drawbacks of DMSs include the need for continuous external support (medical physics experts, radiologists, radiographers, technical services of imaging equipment and hospital informatics services) and the need to include data on clinical indication for the imaging procedures. Advances in knowledge: DMS perform automatic management of radiation doses, produces patient dose reports, and registers high dose alerts to suggest optimisation actions. Benefits and limitations are derived from the practical experience in a large university hospital.

Dose Reduction and Low-Contrast Detectability Using Iterative CBCT Reconstruction Algorithm for Radiotherapy

Introduction: Several studies have reported the relation between the imaging dose and secondary cancer risk and have emphasized the need to minimize the additional imaging dose as low as reasonably achievable. The iterative cone-beam computed tomography (iCBCT) algorithm can improve the image quality by utilizing scatter correction and statistical reconstruction. We investigate the use of a novel iCBCT reconstruction algorithm to reduce the patient dose while maintaining low-contrast detectability and registration accuracy. Methods: Catphan and anthropomorphic phantoms were analyzed. All CBCT images were acquired with varying dose levels and reconstructed with a Feldkamp–Davis–Kress algorithm-based CBCT (FDK-CBCT) and iCBCT. The low-contrast detectability was subjectively assessed using a 9-point scale by 4 reviewers and objectively assessed using structure similarity index (SSIM). The soft tissue-based registration error was analyzed for each dose level and reconstruction technique. Results: The results of subjective low-contrast detectability found that the iCBCT acquired at two-thirds of a dose was superior to the FDK-CBCT acquired at a full dose (6.4 vs 5.4). Relative to FDK-CBCT acquired at full dose, SSIM was higher for iCBCT acquired at one-sixth dose in head and head and neck region while equivalent with iCBCT acquired at two-thirds dose in pelvis region. The soft tissue-based registration was 2.2 and 0.6 mm for FDK-CBCT and iCBCT, respectively. Conclusion: Use of iCBCT reconstruction algorithm can generally reduce the patient dose by approximately two-thirds compared to conventional reconstruction methods while maintaining low-contrast detectability and accuracy of registration.

Analysis and results from a UK national dose audit of paediatric CT examinations

Objectives: To present the results following a UK national patient dose audit of paediatric CT examinations, to propose updated UK national diagnostic reference levels (DRLs) and to analyse current practice to see if any recommendations can be made to assist with optimisation. Methods: A UK national dose audit was undertaken in 2019 focussing on paediatric CT examinations of the head, chest, abdomen/pelvis and cervical spine using the methods proposed by the International Commission on Radiological Protection. The audit pro-forma contained mandatory fields, of which the post-examination dosimetry (CTDIvol and DLP) and the patient weight (for body examinations) were the most important. Results: Analysis of the data submitted indicates that it is appropriate to propose national DRLs for CT head examinations in the 0- < 1, 1- < 5, 5- < 10 and 10- < 15 year age ranges. This extends the number of age categories of national DRLs from those at present and revises the existing values downwards. For CT chest examinations, it is appropriate to propose national DRLs for the first time in the UK for the 5- < 15, 15- < 30, 30- < 50 and 50- < 80 kg weight ranges. There were insufficient data received to propose national DRLs for abdomen/pelvis or cervical spine examinations. Recommendations towards optimisation focus on the use of tube current (mA) modulation, iterative reconstruction and the selection of examination tube voltage (kVp). Conclusions: Updated UK national DRLs are proposed for paediatric CT examinations of the head and chest. Advances in knowledge: A national patient dose audit of paediatric CT examinations has led to the proposal of updated national DRLs.

Patient dose monitoring using exposure index against body mass index level on chest X-ray examination

The image quality factor is not merely a matter of whether the image is repeated or not, but also has a wide range of information and also has to maintain the protection method for the patient is the reception of the dose due to radiographic action. So it is necessary to monitor the patient's dose using the EI value. The factors that determine the EI value are the exposure factor and the thickness of the object or BMI (Body Mass Index). Exposure factors (kV and mAs) are factors that have been commonly used as patient dose monitoring, where the tube voltage is a component that changes more often with a relatively constant tube current. The study used data on patients with Thoracic examination at the age of 20-65 years which were then categorized into BMI. The analysis was carried out on the EI value contained in the radiographic image. The results showed that BMI in the normal, Light Grade Fat (LGF), Heavy Grade Fat (HGF) categories, respectively, the EI values were 1562, 1679, and 1955 for the female sex, and 1266, 1600, and 1821 for the male gender. Significantly (P?0.05) the EI value showed difference between female and male sexes.

Correlation Between Anterior–Posterior and Lateral Dimensions with the Effective and Water-Equivalent Diameters in Axial Images From Head Computed Tomography Examinations

The study aims to correlate the effective diameter (Deff) and water-equivalent diameter (Dw) parameters with anterior–posterior (AP), lateral (LAT) and AP + LAT dimensions in order to estimate the patient dose in head CT examinations. Seventy-four patient datasets from head CT examinations were retrospectively collected. The patient’s sizes were calculated from the middle slice using a software of IndoseCT. Dw and Deff were plotted as functions of AP, LAT and AP + LAT dimensions. The best trendline fit for LAT and AP functions was a second order polynomial, which resulted in R2 of 0.89 for Deff vs LAT, 0.88 for Dw vs LAT, 0.92 for Deff vs AP and 0.91 for Dw vs AP. A linear correlation was found for Deff vs AP + LAT, Dw vs AP + LAT and Dw vs Deff with R2 of 0.97, 0.96 and 0.98, respectively.

Influence of Different Arm Positions in the Localizer Radiograph(s) on Patient Dose during Exposure-Controlled CT Examinations of the Neck to Pelvis

Our aim was to examine the impact of different arm positions during imaging of the localizer radiograph(s) on effective dose for exposure-controlled computed tomography (CT) (Siemens/Canon) scans of the neck to pelvis. An anthropomorphic whole-body phantom was scanned from the neck to pelvis with the arms positioned in three different ways during the acquisition of the localizer radiograph: (i) above the head, (ii) alongside the trunk, and (iii) along the trunk with the hands placed on the abdomen. In accordance with clinical routines, the arms were not included in the subsequent helical scans. Effective doses were computed to a standard-sized patient (male/female) using a dedicated system-specific Monte Carlo-based software. Effective doses for the Canon CT scanner for the different alternatives (male/female) were (a) 5.3/6.62 mSv, (b) 5.62/7.15 mSv and (c) 5.92/7.44 mSv. For the Siemens CT scanner, effective doses were (a) 4.47/5.59 mSv, (b) 5.4/6.69 mSv and (c) 5.7/6.99 mSv. Arms placed above the head during localizer radiograph imaging in the current CT procedures substantially reduced the total effective dose to the patient.

A comparison of two peak skin dose metrics calculated by patient dose management systems: implications for clinical management

Objective: The patient dose monitoring systems DoseWatch and DoseWise were compared to evaluate their reported patient Peak Skin Dose. Methods: 20 patients with the highest Peak Skin Dose on DoseWise were obtained; the values were converted to a Reference Point Air Kerma (RPAK) value and used for comparison. These patients were accessed in DoseWatch to obtain the recorded Worst Case RPAK. The co-ordinates for the position were obtained for each patient to find a primary and secondary angular position for the peak skin dose. The two positions produced by the two softwares were compared. Results: There is a mean deviation of over 0.5 Gy between the two software packages when comparing the calculated maximum skin air kerma Peak skin dose from DoseWise and the Worst Case RPAK from DoseWatch. Conclusion: We have shown mean deviations between these two systems. This difference is enough, for higher peak skin absorbed dose patients, to change the management of patients, so local services must understand their models to properly implement patient management. Advances in knowledge: Neither system is incorrect, but these differences show that a deeper understanding of the analysis limitations is required to properly inform post-procedural high-skin dose follow-up procedures.