Trends of CT Utilization in North America Over the Last Decade

Adult national diagnostic reference levels for common computed tomography examinations in Zambia: A preliminary study with findings from public hospitals

INTRODUCTION

While many European and American countries have established national diagnostic reference levels (NDRLs), few African countries have. Therefore, this study aimed to propose adult NDRLs for common computed tomography (CT) examinations in Zambia.

METHODS

1360 CT patient data for the brain, chest, abdomen and pelvis were collected from 10 public CT facilities. The CT images were assessed for acceptable image quality and patient anthropometry was done, with patients' anteroposterior diameter used as the patient parameter. NDRLs were set at the 75th percentile of the distribution of volume-based CT dose index (CTDIvol) and dose length product (DLP) and were compared to countries' NDRLs.

RESULTS

NDRLs for CTDIvol in mGy were calculated as follows; non-contrast brain 70.5, contrast brain 56.74, non-contrast chest 20.24, contrast chest 20, non-contrast abdomen/pelvis, 21.3, contrast abdomen/pelvic 21.3, non-contrast chest/abdomen/pelvis 20 and contrast chest/abdomen/pelvis 19.1. The corresponding NDRLs for DLP in mGy.cm are 1455, 1206, 745.8, DLP 666.7, 1103, 1103, 1237 and 1141. Variations in DLP values between facilities were statistically significant (p < 0.0001). NDRLs for the brain and chest were higher than those from other countries but lower for the abdomen/pelvis and chest/abdomen/pelvis. Correlations between the CT scanner's number of detector rows and CTDIvol were (r = 0.08285, p < 0.0.0022) and (r = 0.5038, p < 0.0001) between patients' AP diameter and CTDIvol. CONCLUSION: The proposed NDRLs confirmed the need to optimise CT scan parameters and protocols in Zambia. Therefore, extensive training of all CT radiographers in optimising CT image acquisition parameters and regular dose audits is recommended.

IMPLICATION OF PRACTICE

NDRLs will likely provide a benchmarking mechanism for dose optimisation practices among CT radiographers in Zambia and beyond.

Trends in computed tomography utilization among emergency department patients with foot and ankle trauma

The aim of this study was to assess the number of foot/ankle computed tomography (CT) exams ordered per encounter for patients presenting to the emergency department (ED) with foot and ankle trauma over a 5-year period. Secondary aims included evaluating the positivity rate of foot/ankle CT exams and identifying factors associated with receiving a CT foot/ankle. This retrospective study analyzed data from a large urban Level-1 trauma center between 2016 and 2021. Patients were identified by charted chief complaints related to foot and ankle trauma. The primary outcome was the number of CT foot/ankle exams ordered per patient in a given period. A univariate chi-square analysis was conducted to evaluate differences in patient presentations and imaging rates across the study period. Over the 5-year span, there were 9,845 patient encounters, with a significant increase in CT foot/ankle orders from 2.4 % to 6.6 % (p < 0.001). The CT positivity rate, defined as CTs with positive findings, declined from 95.2 % in 2016 to 84.1 % in 2021 (p < 0.001). Black patients had lower odds of receiving CT scans compared to White patients, as did Medicare recipients compared to Medicaid recipients (p < 0.001). Factors such as age (OR: 1.02 per year), year of visit (OR: 2.66 for 2021), time of day (OR: 1.62 for evening arrivals), and arrival by EMS (OR: 5.60) were significantly associated with higher CT order rates. This study highlights a marked increase in CT utilization for foot and ankle trauma with a corresponding decline in the rate of positive findings. Further research is necessary to explore the reasons behind this trend and to identify potential workflow or protocol adjustments to improve imaging efficacy.

Assessing and coping with the financial burden of computed tomography utilization in Limbe, Cameroon: a sequential explanatory mixed-methods study

BACKGROUND

There has been a significant increase in computed tomography (CT) utilization over the past two decades with the major challenges being a high exposure to ionizing radiation and rising cost. In this study we assess the risk of financial hardship after CT utilization and elaborate on how users adapt and cope in a sub-Saharan context with user fee for services and no national health insurance policy.

METHODS

We carried out a sequential explanatory mixed methods study with a quantitative hospital-based survey of CT users followed by in-depth interviews of some purposively selected participants who reported risk of financial hardship after CT utilization. Data was summarized using frequencies, percentages and 95% confidence intervals. Logistic regression was used in multivariable analysis to determine predictors of risk of financial hardship. Identified themes from in-depth interviews were categorized. Quantitative and qualitative findings were integrated.

RESULTS

A total of 372 participants were surveyed with a male to female sex ratio of 1:1.2. The mean age (standard deviation) was 52(17) years. CT scans of the head and facial bones accounted for 63% (95%CI: 59-68%) and the top three indications were suspected stroke (27% [95%CI: 22-32%]), trauma (14% [95%CI: 10-18%]) and persistent headaches (14% [95%CI: 10-18%]). Seventy-two percent (95%CI: 67-76%) of the respondents reported being at risk of financial hardship after CT utilization and predictors in the multivariable analysis were a low socioeconomic status (aOR: 0.19 [95%CI: 0.10-0.38]; p < 0.001), being unemployed or retired (aOR: 11.75 [95%CI: 2.59-53.18]; p = 0.001) and not having any form of health insurance (aOR: 3.59 [95%CI: 1.31-9.85]; p = 0.013). Coping strategies included getting financial support from family and friends, borrowing money and obtaining discounts from the hospital administration and staff.

CONCLUSION

No health insurance ownership, being unemployed or retired and a low socioeconomic status are associated with financial hardship after CT utilization. Diverse coping strategies are utilized to lessen the financial burden, some with negative consequences. Minimizing out-of-pocket payments and/or the direct cost of CT can reduce this financial burden and improve CT access.

Individualization of computed tomography protocols for suspected pulmonary embolism: a national investigation of routines

Objective

Given the extensive use of computed tomography (CT) in radiation-sensitive patients such as pregnant and pediatric patients, and considering the importance of tailoring CT protocols to patient characteristics for both the radiation dose and image quality, this study was performed to investigate the extent to which individualization of CT protocols is practiced across Norway.

Methods

This cross-sectional study involved collection of CT protocols and administration of a mini-questionnaire to obtain additional information about how CT examinations are individualized. All public hospitals performing CT to detect pulmonary embolism were invited, and 41% participated.

Results

Tailoring a standard protocol to different patient groups was more common than using dedicated protocols. Most of the available radiation dose-reduction approaches were used. However, implementation of these strategies was not systematic. Children and pregnant patients were examined without using dedicated CT protocols or by using protocol adjustments focusing on radiation dose reduction in 30% and 39% of the hospitals, respectively.

Conclusion

Practice optimization is needed, especially the development of dedicated CT protocols or guidelines that tailor the existing protocol to pediatric and pregnant patients. Practice might benefit from a more systematic approach to individualization of CT examinations, such as inserting tailoring instructions into CT protocols.

Impact of Referring Hospital Imaging on Mortality at a Level I Trauma Center

BACKGROUND

Computed tomography (CT) has become a standard adjunct in the evaluation of patients with trauma. However, utility of imaging at the referring hospital remains controversial. We study the effect of CT scans at referring hospitals on in-hospital mortality at a receiving trauma center.

MATERIALS AND METHODS

A retrospective cohort study was performed with adult patients with severe trauma transferred to a level I trauma center from regional nontrauma hospitals between 2012 and 2017. Baseline characteristics were compared with Student's t-test and Pearson's chi-squared testing. The primary endpoint was in-hospital mortality. Cox regression, controlling for transfer time, was used to evaluate the effect of imaging on mortality.

RESULTS

Three thousand four hundred and fifteen adult patients with trauma were included: 1135 (33.2%) received a pretransfer CT scan, whereas 2280 (66.8%) did not. Patients who received a pretransfer CT scan were more likely to be older, female, white, have a higher Charlson Comorbidity Index, less severely injured, have a blunt mechanism, and be transferred by ground. There was no difference in distance (58.3 miles versus 57.0 miles, P = 0.34), but transfer times were significantly increased for those who received pretransfer scans (288 versus 213 min, P < 0.005). The adjusted model controlling for multiple variables has a hazard ratio of 0.533 (95% confidence interval 0.42-0.68, P < 0.005).

CONCLUSIONS

There is a survival advantage for patients who receive pretransfer CT scans despite having significantly longer transport times. We suggest that this decreased mortality associated with pretransfer imaging may reflect improving trends in referring physician transfer decisions.

Chest CT Scan at Radiation Dose of a Posteroanterior and Lateral Chest Radiograph Series: A Proof of Principle in Lymphangioleiomyomatosis

BACKGROUND

Given the rising utilization of medical imaging and the risks of radiation, there is increased interest in reducing radiation exposure. The objective of this study was to evaluate, as a proof of principle, CT scans performed at radiation doses equivalent to that of a posteroanterior and lateral chest radiograph series in the cystic lung disease lymphangioleiomyomatosis (LAM).

METHODS

From November 2016 to May 2018, 105 consecutive subjects with LAM received chest CT scans at standard and ultra-low radiation doses. Standard and ultra-low-dose images, respectively, were reconstructed with routine iterative and newer model-based iterative reconstruction. LAM severity can be quantified as cyst score (percentage of lung occupied by cysts), an ideal benchmark for validating CT scans performed at a reduced dose compared with a standard dose. Cyst scores were quantified using semi-automated software and evaluated by linear correlation and Bland-Altman analysis.

RESULTS

Overall, ultra-low-dose CT scans represented a 96% dose reduction, with a median dose equivalent to 1 vs 22 posteroanterior and lateral chest radiograph series (0.14 mSv; 5th-95th percentile, 0.10-0.20 vs standard dose 3.4 mSv; 5th-95th percentile, 1.5-7.4; P < .0001). The mean difference in cyst scores between ultra-low- and standard-dose CT scans was 1.1% ± 2.0%, with a relative difference in cyst score of 11%. Linear correlation coefficient was excellent at 0.97 (P < .0001).

CONCLUSIONS

In LAM chest CT scan at substantial radiation reduction to doses equivalent to that of a posteroanterior and lateral chest radiograph series provides cyst score quantification similar to that of standard-dose CT scan.

TRIAL REGISTRY

ClinicalTrials.gov; Nos.: NCT00001465 and NCT00001532; URL: www.clinicaltrials.gov.

Maximizing Benefit and Minimizing Risk in Medical Imaging Use: An Educational Primer for Health Care Professions Students

"I am not young enough to know everything."Oscar Wilde.

BACKGROUND

There is insufficient knowledge among providers and patients/caregivers of ionizing radiation exposure from medical imaging examinations. This study used a brief, interactive educational intervention targeting the topics of best imaging practices and radiation safety early in health professions students' training. The authors hypothesized that public health, medical, and physician assistant students who receive early education for imaging appropriateness and radiation safety will undergo a change in attitude and have increased awareness and knowledge of these topics.

MATERIALS AND METHODS

The authors conducted a 1.5-hour interactive educational intervention focusing on medical imaging utilization and radiation safety. Students were presented with a pre/postquestionnaire and data were analyzed using t tests and multivariate analysis of variance.

RESULTS

A total of 301 students were enrolled in the study. There was 58% (P < .01) and 85% (P < .01) improvement in attitude and knowledge regarding appropriateness of imaging, respectively. The authors also found an 8% increase (P < .01) in students who thought informed consent should be obtained prior to pediatric computed tomographic imaging. Physical assistant students were more likely than medical students to prefer obtaining informed consent at baseline (P = .03).

CONCLUSIONS

A brief educational session provided to health professions students early in their education showed an increased awareness and knowledge of the utility, limitations, and risks associated with medical imaging. Incorporation of a best imagining practice educational session early during medical education may promote more thoughtful imaging decisions for future medical providers.

Contrast-Induced Acute Kidney Injury: Pathophysiology, Manifestations, Prevention, and Management

Contrast-induced acute kidney injury is a phenomenon that has been extensively studied throughout the years. There is a large volume of literature documenting this risk, and most radiology departments and radiologists use this information when making decisions regarding contrast administration. A review of the current information on the topic of contrast-induced acute kidney injury is necessary to ensure that the risks of intravenous contrast are properly weighed against the benefits of a contrast-enhanced computed tomography scan.

Negative D-dimer testing excludes pulmonary embolism in non-high risk patients in the emergency department

PURPOSE

The purpose of this study was to assess the ability of d-dimer testing to obviate the need for cross-sectional imaging for patients at "non-high risk" for pulmonary embolism (PE).

METHODS

This is a retrospective study of emergency department patients at an academic medical center who underwent cross-sectional imaging (MRA or CTA) to evaluate for PE from 2008 to 2013. The primary outcome was the NPV of d-dimer testing when used in conjunction with clinical decision instruments (CDIs = Wells', Revised Geneva, and Simplified Revised Geneva Scores). The reference standard for PE status included image test results and a 6-month chart review follow-up for venous thromboembolism as a proxy for false negative imaging. Secondary analyses included ROC curves for each CDI and calculation of PE prevalence in each risk stratum.

RESULTS

Of 459 patients, 41 (8.9%) had PE. None of the 76 patients (16.6%) with negative d-dimer results had PE. Thus, d-dimer testing had 100% sensitivity and NPV, and there were no differences in CDI performance. Similarly, when evaluated independently of d-dimer results, no CDI outperformed the others (areas under the ROC curves ranged 0.53-0.55). There was a significantly higher PE prevalence in the high versus "non-high risk" groups when stratified by the Wells' Score (p = 0.03).

CONCLUSIONS

Negative d-dimer testing excluded PE in our retrospective cohort. Each CDI had similar NPVs, whether analyzed in conjunction with or independently of d-dimer results. Our results confirm that PE can be safely excluded in patients with "non-high risk" CDI scores and a negative d-dimer.