Toward Large-Scale Process Control to Enable Consistent CT Radiation Dose Optimization

A Vision for Global CT Radiation Dose Optimization

The topic of CT radiation dose management is receiving renewed attention since the recent approval by CMS for new CT dose measures. Widespread variation in CT dose persists in practices across the world, suggesting that current dose optimization techniques are lacking. The author outlines a proposed strategy for facilitating global CT radiation dose optimization. CT radiation dose optimization can be defined as the routine use of CT scan parameters that consistently produce images just above the minimum threshold of acceptable image quality for a given clinical indication, accounting for relevant patient characteristics, using the most dose-efficient techniques available on the scanner. To accomplish this, an image quality-based target dose must be established for every protocol; for nonhead CT applications, these target dose values must be expressed as a function of patient size. As variation in outcomes is reduced, the dose targets can be decreased to more closely approximate the minimum image quality threshold. Maintaining CT radiation dose optimization requires a process control program, including measurement, evaluation, feedback, and control. This is best accomplished by local teams made up of radiologists, medical physicists, and technologists, supported with protected time and needed tools, including analytics and protocol management applications. Other stakeholders critical to facilitating CT radiation dose management include researchers, funding agencies, industry, regulators, accreditors, payers, and the ACR. Analogous coordinated approaches have transformed quality in other industries and can be the mechanism for achieving the universal goal of CT radiation dose optimization.

Implementation of a computed tomography dose management program across a multinational healthcare organization

OBJECTIVES

Radiation dose index monitoring (RDIM) systems may help identify CT dose reduction opportunities, but variability and complexity of imaging procedures make consistent dose optimization and standardization a challenge. This study aimed to investigate the feasibility to standardize and optimize CT protocols through the implementation of a Dose Excellence Program within a European healthcare network.

METHODS

The Dose Excellence Program consisted of a multidisciplinary team that developed standardized organizational adult CT protocols and thresholds for relevant radiation dose indices (RDIs). Baseline data were collected retrospectively from the RDIM (Phase I, 2015). Organization's protocols were implemented and monitored from the RDIM for deviations (Phase II, 2016). Following standardization, radiation dose optimization was initiated (Phase III, 2017). Data from the three most used protocols were retrospectively extracted and grouped by country for all phases. The mean number of series (RS) and RDIs were compared between phases and with organizational reference levels. A Mann-Whitney test was conducted; p < .05 was considered as significant.

RESULTS

Data from 9588, 12638, and 6093 examinations were analyzed from General Chest, General Head, and Thorax/Abdomen/Pelvis (TAP) multiphase respectively. Overall, after Phase III, mean RS and CTDI_vol p⁷⁵ were below the organizational reference levels in all countries for the three protocols. The CTDI_vol decreased by 45% in Switzerland (p < .00001), 32% in Turkey (p < .00001), and 28% in Switzerland (p = .0027) for General Chest, General Head, and TAP multiphase respectively.

CONCLUSIONS

The implementation of a Dose Excellence Program within a large-scale healthcare organization allowed unifying protocols and optimizing radiation dose across countries.

KEY POINTS

• Engaging a multidisciplinary team can enhance the use of an RDIM system for CT dose management in a multinational healthcare environment. • Deep dive of baseline data and standardization of CT practices by defining organizational clinical indication CT protocols with RPIDs is an essential step before optimization of radiation dose. • Following the implementation of the program, the mean RS and CTDIvol were below or equal to the organizational reference levels in all countries.

Variability in image quality and radiation dose within and across 97 medical facilities

Purpose: To characterize variability in image quality and radiation dose across a large cohort of computed tomography (CT) examinations and identify the scan factors with the highest influence on the observed variabilities. Approach: This retrospective institutional-review-board-exempt investigation was performed on 87,629 chest and abdomen-pelvis CT scans acquired for 97 facilities from 2018 to 2019. Images were assessed in terms of noise, resolution, and dose metrics (global noise, frequency in which modulation transfer function is at 0.50, and volumetric CT dose index, respectively). The results were fit to linear mixed-effects models to quantify the variabilities as affected by scan parameters and settings and patient characteristics. A list of factors, ranked by t -value with p < 0.05 , was ascertained for each of the six mixed effects models. A type III p -value test was used to assess the influence of facility. Results: Across different facilities, image quality and dose were significantly different ( p < 0.05 ), with little correlation between their mean magnitudes and consistency (Pearson's correlation coefficient < 0.34 ). Scanner model, slice thickness, recon field-of-view and kernel, mAs, kVp, patient size, and centering were the most influential factors. The two body regions exhibited similar rankings of these factors for noise (Spearman's correlation coefficient = 0.76 ) and dose (Spearman's correlation coefficient = 0.86 ) but not for resolution (Spearman's correlation coefficient = 0.52 ). Conclusions: Clinical CT scans can vary in image quality and dose with broad implications for diagnostic utility and radiation burden. Average scan quality was not correlated with interpatient scan-quality consistency. For a given facility, this variability can be quite large, with magnitude differences across facilities. The knowledge of the most influential factors per body region may be used to better manage these variabilities within and across facilities.

Customer Service in Radiology: Satisfying Your Patients and Referrers

Radiology has long been a service-oriented specialty. Although physicians in other specialties have direct interactions with patients, radiologists' interactions with patients are often indirect, most often occurring as a direct result of another provider's order. As such, radiology practices have had to focus on two distinct groups, patients and ordering providers, to grow their businesses and retain their patients. One could argue that during the past 2 decades, many of the most visible customer service initiatives in radiology practices have been directed toward the ordering provider. These initiatives have included implementing picture archiving and communication systems to improve image distribution and availability, voice dictation systems to decrease report turnaround time, computerized order entry to ease the ordering process, and structured reporting to improve the readability of the radiology report. As the practice of radiology is evolving to become more patient oriented, it is clear that the specialty needs to pivot and implement more initiatives that directly benefit patients. In this article, the concepts of customer service and a radiology department's primary customer are defined and discussed, and the concept of service quality is introduced. In addition, the author highlights the five dimensions of service quality: reliability, assurance, tangibles, empathy, and responsiveness. Each dimension is described in detail, first by using an archetypal business example and then by using an example of a project that has been successfully implemented in the author's radiology department. ^©RSNA, 2018.

Practical dose reduction tips for abdominal interventional procedures using CT-guidance

Reducing the radiation dose should be an endeavor not only for diagnostic CT exams but also for interventional procedures using CT-guidance. Given that interventional procedures vary in scope and complexity, there is greater variability in radiation doses delivered during CT procedures. The goal in an interventional procedure is simply to advance the interventional instruments into the target lesions, and as such diagnostic level doses are not required and only narrow scan range scans need to be acquired. Adherence to the principles outlined in this article will allow such procedures to be performed with reduced radiation doses.

Patient Vertical Centering and Correlation with Radiation Output in Adult Abdominopelvic CT

The purpose of this study was to determine if there is a significant effect, independent of patient size, of patient vertical centering on the current-modulated CT scanner radiation output in adult abdominopelvic CT. A phantom was used to evaluate calculation of vertical positioning and effective diameter at five different table heights. In addition, 656 consecutive contrast-enhanced abdominopelvic scans using the same protocol and automatic tube current modulation settings on a Philips Brilliance 64 MDCT scanner were retrospectively evaluated. The vertical position of the patient center of mass and the average effective diameter of the scanned patient were computed using the reconstructed images. The average volume CT dose index (CTDIvol) for each scan was recorded. The mean patient center of mass y coordinate ranged from -3.7 to 6.7 cm (mean ± SD, 2.8 ± 1.2 cm), indicating that patients were on average positioned slightly below the scanner isocenter. There was a slight tendency for smaller patients to be mis-centered lower than larger patients. Average CTDIvol closely fit a quadratic regression curve with respect to mean effective diameter. However, the value of the regression coefficient relating CTDIvol to the patient's vertical position was nearly zero, indicating only a very slight increase in CTDIvol with patient mis-centering for the scanner used in this study. The techniques used here may be useful both for automated evaluation of proper patient positioning in CT and for estimating the radiation dose effects of patient mis-centering for any CT scanner.