Assessment of radiation exposure: An in-depth analysis of dose evaluation in contrast-enhanced computed tomography abdomen imaging

INTRODUCTION

Contrast-enhanced computed tomography (CECT) of the abdomen is a technique for accurately visualizing anatomy and achieving precise diagnosis by the use of radiopaque dye. Despite having invaluable diagnostic information it offers, the consideration of radiation exposure becomes essential, requiring careful management. Conversely to conventional X-rays computed tomography (CT), CT scans utilize highly energetic ionizing radiation to generate detailed images, which presents inherent risks, including the potential for long-term adverse effects such as radiation-induced cancer. In the complex field of abdominal imaging, the concept of “differential dose” emerges as a crucial factor to be taken into account. Differential dosing in CECT abdomen cases involves customizing the administration of contrast agents and radiation dosage according to individual patient characteristics and diagnostic needs. This refined strategy enables healthcare providers to refine imaging protocols, guaranteeing both diagnostic precision and patient well-being. While exploring the domain of differential dosing in CECT abdomen cases, it reveals a complex terrain that includes clinical indications and imaging objectives. Effective comprehension and application of these dosing strategies empower healthcare providers to refine diagnostic accuracy, reduce radiation exposure, and ultimately enhance patient outcomes. It is crucial to consider the associated radiation dose when conducting these examinations to ensure patient safety and optimize imaging protocols. When considering CT imaging, especially for younger female patients, it’s essential to weigh the advantages against the potential risks posed by radiation exposure.¹ Due to the use of high-density contrast agents, the dose received in the CECT is much higher (30%) than the noncontrast scans.² Significant apprehensions have arisen due to the possible escalation in long-term radiation-induced cancer, leading some researchers to assert that the diagnostic application of CT scans could contribute to a notable number of fatalities annually. Based on the figures, 1 in every 250 CECT examinations may result in the development of cancer.³ The advantages of CT scans outweigh the negative impacts of radiation exposure in patients, and the rising radiation doses across the population make a strong argument for lowering exposure from CT scans. Photon counting detector-CT facilitates oncologic abdominal CT scans with a substantially lower dose, maintaining image quality comparable to that of a -second-generation Dual Slice CT scanner.⁴ In abdominal pelvic CT scans, direct radiation exposure affects the prostate and uterus, potentially posing health hazards to patients. A research investigation illustrated a notable linear dose-response relationship concerning prostate cancer, indicating an estimated excess relative risk per Gy of 0.57. This study’s findings led to the conclusion that “the observed dose-response reinforces the evidence suggesting a radiation impact on the likelihood of prostate cancer incidence among atomic bomb survivors.”⁵ There is no distinction in diagnostic efficacy between hepatic venous phase (HVP)-CT alone and multiphasic CT for identifying the causes of abdominal pain in patients admitted to the emergency department without preexisting chronic conditions or neoplasms.⁶ It is possible to maintain the amplitude of signal and contrast to noise ratios while achieving a balance between the radiation and contrast dose.⁷ In routine contrast-enhanced CT scans of the abdomen and pelvis, an extra delayed phase is included that is of minimal importance, especially when dependable follow-up imaging is accessible to provide further clarification of ambiguous findings.⁸ Obtaining a low-dose scan necessitates collaborative efforts, involving customizing the scan to suit the patient and medical inquiry, alongside ongoing quality improvement to incorporate evolving strategies for optimizing dose.⁹ Due to multiple scans in CT, the radiation increases subsequently, unlike X-rays, producing higher absorbed doses; hence, radiologists need to ensure that the patient’s benefit is much greater than the risk produced by the exposures, which may depend on the patient.¹⁰ The radiation should be kept lower than the diagnostic reference levels (DRLs) to increase patient safety and maintain image quality resulting in precise diagnosis.¹¹ DRL is an existing standard for specific imaging procedures designed to optimize radiation exposure levels and ensure they remain within a safe and acceptable range. The relationship between DRL and computed tomography dose index (CTDI) is that DRL serves as a reference point to evaluate CTDI values, ensuring that they remain within acceptable limits and that radiation exposure is optimized and safe.

Aim and Objectives: This study is aimed to assess radiation exposure levels associated with CECT scans of the abdomen, and also to estimate DRL for CECT abdomen studies. The primary objective of this study was to measure levels of radiation exposure related to CECT abdomen and to compare radiation dose among the genders.

MATERIAL AND METHODS

RESULTS

This study revolves around two sections, including the sociodemographic characteristics of the participants as well as parameters associated with radiation exposure and dose evaluation comprising 296 patients (211 males and 85 females). Males comprised an age range of 18–83 years while females of 20–86 years; the average age of males was 47.8 years, and 51.2 years for females. A majority of the patients had a history of abdominal pain (n = 162), constipation (n = 65), recurrent vomiting (n = 37), and follow-up of different diagnosis (n = 17) and others (n = 15), respectively [Table 1].

Tube voltages ranged from 80 kVp to 140 kVp, pitch of 1 mm, tube current-time ranged from 150 mAs to 280 mAs, slice thickness of 5 mm, contrast amount of 1.2 mL per kg of body weight with a flow rate of 3–4 mL per second. These factors of radiation exposure, including current and potential of tube, thickness of slices, slice number, and pitch, were taken into account [Table 2].

The minimum and maximum CTDIvol for abdominal CT were found to be 5 mGy and 26.42 mGy in males and 4.96 mGy and 21.9 mGy in females, with a mean of 11.54 and 12.77 mGy in males and females, correspondingly. The minimum and maximum DLP for CECT abdomen was 1004.62 mGy.cm and 6484.2 for males and 1040 mGy.cm and 4964.1 mGy.cm for females, respectively, with a mean of 2734.56 mGy.cm. and 2842.61 mGy.cm. The minimum and maximum effective dose was determined to be 15.06 mSv and 97.2 mSv for males and 15.6 mSv and 74.4 mSv for females, respectively, with a mean of 40.93 mSv for males and 42.63 mSv for females [Table 3].

The DRLs for CTDIvol and DLP values were established for this study; DRLs for CTDIvol: 34 mGy, 45.9 mGy, and 56.4 mGy for the 25th, 50th, and 75th percentile, respectively, and the proposed DRLs for DLP are 2018.7 mGy.cm, 2679.4 mGy.cm, and 3363.125 mGy.cm for 25th, 50th, and 75th percentile, respectively. The established local DRL for CECT abdomen is shown in Table 4.

An independent sample t-test was done to check if there was any statistically significant difference between the radiation dose with sex, but it was not statistically significant. There was a difference in the calculated mean values of the effective dose that could have possibly occurred due to the different exposure settings and patient aspects.

DISCUSSION

Ever since its introduction into clinical practice, CT scanning has been acknowledged as a diagnostic imaging technique associated with higher radiation doses compared to other modalities. As scanner technology has evolved and its utilization has become increasingly widespread, concerns regarding patient radiation doses from CT scans have escalated.¹² Switching from conventional X-rays to CT results in a very sharp increase in the effective doses received by the patient. A study done by Yadav et al. (2023) examined 92 adult patients undergoing abdominal CT scans at a Nepalese medical imaging department from August 2018 to January 2019 using a 16-slice CT scanner. Radiation doses were assessed using CTDIvol, DLP, and effective dose and analyzed with SPSS version 20, which were 7.31 mGy, 421.46 mGy.cm, and 6.31 mSv, representing a lower value than the standards established by European guidelines and International Atomic Energy Agency. A direct relation was found between the dose and body mass indexof individuals in multiple scan types.¹³ Choudhary et al. (2019) used a 16-slice scanner and evaluated radiation exposure in the head, thorax, abdomen, and pelvis. The CTDI results were adjusted for patient size using the size-specific dose estimate (SSDE) technique. The CTDIvol readings of 26.76 mGy, 16.27 mGy, 14.74 mGy, and 29.81 mGy were observed, respectively. A 4–8% variance from American Association of Physicists in Medicine-reported CTDI values were indicated by SSDE-calculated median doses, which raised concerns about depending exclusively on CTDI for accurate patient dose determination during CT operations.¹⁴ The CTDI and SSDEs among the 75 patients in El Mansouri et al.’s (2022) study were also determined using an algorithm that showed the values for CTDI varied from 4.8 mGy to 12.2 mGy and for SSDE from 8.01 mGy to 14.15 mGy.¹⁵

The variation in mA and scan volume DLP value variations were calculated in this study. In the majority of cases, the radiation dose and mA were linear. As a result, lowering the tube current value lowered the radiation dose to the patient. Table 2 provides details of mean and range values for CTDIvol (mGy), DLP (mGy*cm), and effective (mSv). For males and females, the mean effective dose was around 40.93 mSv and 42.63 mSv, respectively. Women’s effective dose was slightly greater (42.63 mSv) than men (40.93 mSv). Compared to 32- and 64-slice CT scanners, 16-slice CT scanners gave patients the least amount of radiation and produced images good enough for diagnosis.¹⁶ This study investigated the sociodemographic characteristics and parameters related to radiation exposure and dose evaluation in 296 patients undergoing abdominal CT scans. The patients presented with symptoms such as abdominal pain, constipation, and recurrent vomiting. Factors including tube voltage, tube current, slice thickness, and contrast amount were considered in assessing radiation exposure. Analysis revealed a range of CTDIvol, DLP, and effective dose values, with slight variations between males and females. While statistical analysis did not show a significant difference in radiation dose by sex, differences in effective dose may be attributed to varying exposure parameters and patient body. The findings highlight the need for dose optimization techniques to reduce exposure while maintaining diagnostic accuracy. Establishing DRLs for CT scans is an essential tool for optimizing and ensuring safe radiation exposure for patients. This study has established DRLs for CTDIvol and DLP values, which are crucial for evaluating patient radiation doses during CT examinations. The proposed CTDIvol DRLs are 34 mGy, 45.9 mGy, and 56.4 mGy for the 25th, 50th, and 75th percentiles, respectively, comparable to those in similar studies, indicating our CT scanner’s compliance with acceptable dose limits. These values help radiologists and radiographers optimize scanning protocols and minimize patient radiation exposure. The proposed DRLs for DLP are 2018.7 mGy.cm, 2679.4 mGy.cm, and 3363.125 mGy.cm for the 25th, 50th, and 75th percentiles, respectively, suggesting our scanner delivers acceptable doses. DLP values provide a comprehensive assessment of radiation exposure by considering scan length. These DRLs significantly impact radiation safety in our imaging department, guiding protocol optimization, reducing patient exposure, and improving care quality. They also serve as benchmarks for other departments, promoting radiation safety and dose optimization.

CONCLUSION

CECT scans are vital for diagnosing abdominal conditions, yet their high radiation doses pose risks to sensitive organs. Significant dose variation was observed throughout the study and this variation may have been due to differences in the scan protocol and parameters associated with the scanners and patient demographics. Radiology departments must monitor doses and follow standardized protocols to optimize radiation levels across facilities. Refining imaging protocols is crucial to reducing patient exposure without compromising diagnostic accuracy. Collaboration among radiologists, physicists, and technologists is essential for ongoing improvement. Establishing national DRLs for CT examinations is recommended to ensure consistency in dose optimization efforts. DRLs in CT imaging serve as benchmark radiation dose levels for standard procedures, aiding in optimizing patient safety. This practice helps standardizing radiation doses across different institutions, promoting consistent and safe imaging practices. Implementing these measures enhances patient safety and mitigates risks associated with radiation exposure during CECT abdomen imaging.