Radiation Risks from Exposure to Chest Computed Tomography

Prediction of breast dose in chest CT examinations using adaptive neuro-fuzzy inference system (ANFIS)

In chest computed tomography (CT), the breasts located within the scan range receive a substantial radiation dose. Due to the risk of breast-related carcinogenesis, analyzing the breast dose for justification of CT examinations seems necessary. The main goal of this study is to overcome the limitations of conventional dosimetry methods, such as thermoluminescent dosimeters (TLDs) by introducing the adaptive neuro-fuzzy inference system (ANFIS) approach. In this study, the breast dose of 50 adult female patients who underwent chest CT examinations was measured directly by TLDs. Then, the ANFIS model was developed with four inputs including dose length product (DLP), volumetric CT dose index (CTDIvol), total mAs, and size-specific dose estimate (SSDE), and one output (TLD dose). Additionally, multiple linear regression (MLR) as a traditional prediction model was used for linear modeling and its results were compared with the ANFIS. The TLD reader results showed that the breast dose value was 12.37 ± 2.46 mGy. Performance indices of the ANFIS model, including root mean square error (RMSE) and correlation coefficient (R), were calculated at 0.172 and 0.93 for the testing dataset, respectively. Also, the ANFIS model had superior performance in predicting the breast dose than the MLR model (R = 0.805). This study demonstrates that the proposed ANFIS model is efficient for patient dose prediction in CT scans. Therefore, intelligence models such as ANFIS are suggested to estimate and optimize patient dose in CT examinations.

Gender Differences in the Impact of Recommendations on Diagnostic Imaging Tests: A Retrospective Study 2007-2021

(1) Background: The frequency of imaging tests grew exponentially in recent years. This increase may differ according to a patient's sex, age, or socioeconomic status. We aim to analyze the impact of the Council Directive 2013/59/Euratom to control exposure to radiation for men and women and explore the impact of patients' age and socioeconomic status; (2) Methods: The retrospective observational study that includes a catchment population of 234,424. We included data of CT, mammography, radiography (conventional radiography and fluoroscopy) and nuclear medicine between 2007-2021. We estimated the associated radiation effective dose per test according using previously published evidence. We calculated a deprivation index according to the postcode of their residence. We divided the study in 2007-2013, 2014-2019 and 2020-2021 (the pandemic period). (3) Results: There was an increase in the number of imaging tests received by men and women after 2013 (p < 0.001), and this increase was higher in women than in men. The frequency of imaging tests decreased during the pandemic period (2020-2021), but the frequency of CT and nuclear medicine tests increased even during these years (p < 0.001) and thus, the overall effective mean dose. Women and men living in the least deprived areas had a higher frequency of imaging test than those living in the most deprived areas. (4) Conclusions: The largest increase in the number of imaging tests is due to CTs, which account for the higher amount of effective dose. The difference in the increase of imaging tests carried out in men and women and according to the socioeconomic status could reflect different management strategies and barriers to access in clinical practice. Given the low impact of the available recommendations on the population exposure to radiation and the performance of high-dose procedures such as CT, deserve special attention when it comes to justification and optimization, especially in women.

Should We Always Perform Preoperative Chest Computed Tomography in Patients with cT1a Renal Cell Carcinoma?

No definitive criteria regarding the performance of preoperative chest computed tomography (CT) in patients with cT1a renal cell carcinoma (RCC) exists. We aimed to establish an objective standard for the optimal timing of preoperative chest CT in patients with RCC. Data from 890 patients who underwent surgical treatment for RCC between January 2011 and December 2020 were retrospectively collected. The primary endpoint was detection of lung metastasis on chest CT before nephrectomy. A multivariable logistic regression model predicting positive chest CT scans was used. Predictors included preoperative cTN stage, presence of systemic symptoms, Charlson comorbidity index (CCI), platelet count/hemoglobin ratio, albumin/globulin ratio (AGR), and De Ritis ratio. The overall rate of positive chest CT scans before nephrectomy was 3.03% (27/890). Only one patient had lung metastasis before surgery for cT1a. cT stage (≥cT1b), CCI ≥4, and low AGR were associated with a higher risk of positive chest CT scans. The best cutoff value for AGR was 1.39. After 890-sample bootstrap validation, the concordance index was 0.80. The net benefit of the proposed strategy was superior to that of the select-all and select-none strategies according to decision curve analysis. Therefore, when chest CT scans were performed with a risk of a positive result ≥10%, 532 (59.8%) negative chest CT scans could be prevented. Only 24 (2.7%) potentially positive chest CT scans were misdiagnosed. Therefore, we recommend chest CT in patients with ≥cT1b disease, CCI ≥4, and low AGR.

Diagnosis of pulmonary embolism: Following the evidence from suspicion to certainty

Accurate, timely and cost-effective identification of pulmonary embolism remains a diagnostic challenge. This article reviews the pulmonary embolism diagnostic process with a focus on the best practice advice from the American College of Physicians. Benefits and risks of each diagnostic step are discussed. Emerging diagnostic tools, not included in the algorithm, are briefly reviewed.

Assessing the Prevalence of Incidental Findings Identified by CTPA in Women of Reproductive Age

Background and Objective

Though multiple studies have evaluated the prevalence of incidental findings identified by CTPA, none have done so with a focus on reproductive-age females with normal chest X-ray (CXR). Due to a comparatively lower breast radiation dose, the oft-recommended alternative to CTPA in this patient group is a V/Q scan. However, these are limited in their assessment of these alternate findings; therefore, it is of particular importance to evaluate the likelihood of these findings on CT in this patient group, which is the goal of this study.

Methods

Through a review of our PACS system, female patients aged 18-50 years who underwent diagnostic CTPA prior to April 1, 2017, were identified. The 100 most recent cases which had a normal CXR within 48 hours of CTPA were included. Incidental/non-PE findings were then divided into PE-positive (PE+) and PE-negative (PE-), and subcategorized into types I, II, III, and nil non-PE finding groups. Type I findings required immediate follow-up or intervention, type II findings required outpatient follow-up, and type III findings required no follow-up or were previously known.

Results

PE was detected in 15% of scans. Type I findings were found in 8% of patients (0% of PE+, 9.4% of PE-), type II findings in 10% of patients (13.3% of PE+, 9.4% of PE-), type III findings in 34% of patients (40% of PE+, 32.9% of PE-), and nil non-PE finding in 48% of patients (46.7% PE+, 48.2% of PE-).

Conclusion

While CTPA identifies incidental findings in the majority of patients, a small minority of these findings are likely to alter immediate management. In the context in increased radiation risk, this strengthens the argument that alternate imaging modalities such as V/Q should be strongly considered for the investigation of potential PE in women of reproductive age with normal CXR.

Follow-up after initial surgical treatment of soft tissue sarcomas in the extremities and trunk wall

BACKGROUND/OBJECTIVES

Evaluation of our surveillance program for soft tissue sarcomas (STS) and borderline tumors (BT) for identification of local recurrence and lung metastases the first 2 years postoperatively.

METHODS

We retrospectively assessed the medical files of all patients (n = 232) with STS and BT of the extremities and trunk wall who underwent surgery from 2010 to 2013. Two-hundred-and-thirty-two patients were included in the local recurrence study and 116 patients in the lung metastasis study. We extracted information on how local recurrence and lung metastases were detected. Kaplan-Meier survival analysis and 2 × 2-contingency table with Chi-square test were used. Local recurrence and lung metastases were analyzed separately.

RESULTS

Twenty-five of 232 patients experienced local recurrence and 19 of 116 patients experienced lung metastases. Compared to clinical examination, local imaging led to a larger amount of local recurrence suspicions (37/560 vs. 8/706). Suspicions occurring on local imaging were more accurate than on clinical examination (17/37 vs. 0/8 affirmed). Local imaging identified a larger amount of local recurrence than clinical examination (17/560 vs. 0/706). Thirty-three patients suspected local recurrence themselves, 8 were affirmed. Compared to x-ray, computerized tomography (CT) led to a larger amount of lung metastasis suspicions (22/284 vs. 6/276). Suspicions occurring on CT seemed more accurate than on x-ray (15/22 vs. 2/6 affirmed). CT found a larger amount of lung metastases than x-ray (15/284 vs. 2/276). Three patients suspected lung metastases themselves, 1 was affirmed.

CONCLUSION

Bi-annual local imaging and CT the first 2 years after surgery of STS detect local recurrence and lung metastases better than clinical examination and x-ray. Clinical examination and x-ray between these examinations is unnecessary. Patients' own suspicion of local recurrence and lung metastases is still important.

Low-Dose Radiation Risks of Computerized Tomography and Cone Beam Computerized Tomography: Reducing the Fear and Controversy

Regulations for protecting humans against stochastic biological effects from ionizing radiation are based on the linear no-threshold (LNT) risk assessment model, which states that any amount of radiation exposure may lead to cancer in a population. Based on the LNT model, risk from low-dose radiation increases linearly with increasing doses of radiation. Imaging procedures in medicine and dentistry are an important source of low-dose ionizing radiation. The increased use of computerized tomography (CT) and cone beam computerized tomography (CBCT) has raised health concerns regarding exposure to low-dose ionizing radiation. In oral and maxillofacial surgery and implant dentistry, CBCT is now at the forefront of this controversy. Although caution has been expressed, there have been no direct studies linking radiation exposure from CT and CBCT used in dental imaging with cancer induction. This article describes the concerns about radiation exposure in dental imaging regarding the use of CT.

Pulmonary ultrasound examination for edema, effusion, and thromboembolism

Bedside, or point-of-care, ultrasound (US) has increasingly been used in various clinical settings to provide clinicians with rapid clinical information without the use of ionizing radiation. Lung US has been demonstrated as a valuable tool in the diagnosis and evaluation of pulmonary edema, pleural effusions, and pulmonary thromboembolism. Lung US enables the clinician to more quickly identify and initiate treatment for these potentially life-threatening conditions without the need for patient transportation to the radiology suite. Additionally, lung US can repeatedly be implemented to assess clinical changes without concern for repeated radiation exposure and is cost-effective given its ability to decrease the need for additional radiological and laboratory testing to confirm a suspected diagnosis. This review focuses on the application of lung US in the evaluation and management of pulmonary edema, pleural effusions, and pulmonary thromboembolism.

Clinical implications of non-contrast-enhanced computed tomography for follow-up after endovascular abdominal aortic aneurysm repair

BACKGROUND

There is growing concern over the long-term radiation exposure from serial computed tomographic (CT) scan follow-up after endovascular aneurysm repair (EVAR) of abdominal aortic aneurysms (AAAs). Screening for endoleaks with non-contrast-enhanced volumetric CT has been shown to significantly reduce radiation doses. We evaluated the use of NCT as the primary method of follow-up after EVAR of AAAs.

METHODS

Our institutional post-EVAR CT protocol consisted of contrast-enhanced CT angiography (CTA) 1 month after repair, followed by NCT at 3 or 6 and 12 months, and annually thereafter. At each follow-up scan, immediate 3-dimensional volume analysis was performed. If the volume change was <2%, NCT follow-up was continued. If the volume increased by ≥2% on nonenhanced images, contrast-enhanced CT was performed immediately to identify potential endoleaks. All images were reviewed by an experienced cardiovascular radiologist. End points included identification of endoleak, reintervention, and rupture.

RESULTS

Over a 7-year period, 126 patients were followed. Serial CTA was performed in 59 patients, while 67 patients were followed with the NCT protocol. The mean follow-up was 2.07 years. There were no differences in age, sex, or initial aneurysm volume or size. There were 35 total endoleaks identified. Twenty of these were early endoleaks (<30 days post-EVAR). The remaining 15 leaks were late in nature (10 in the contrast group and 5 in the noncontrast group; P=0.17). NCT aneurysm sac volume changes prompted contrasted studies in all 5 late leaks. The mean volume change was 11.2 cm3, an average change of 5.88%. These findings were not significantly different than the late leaks found by routine contrast studies (8.9 cm3; 4.98% [P=0.58]). There were no delayed ruptures or emergent reinterventions in the NCT group.

CONCLUSIONS

Serial NCT appears to be safe and effective as the sole means of follow-up after EVAR for AAAs. AAA volume increases of ≥2% should prompt further contrast-enhanced CT imaging. Changes of <2% can be safely followed with serial NCT. This protocol requires dedicated cardiovascular radiologist involvement, and patients should be retained in the radiology suite until real-time image evaluation can be completed.

Diagnostic yield and renal complications after computed tomography pulmonary angiograms performed in a community-based academic hospital

Background

Venous thromboembolism and pulmonary embolism (VTE/PE) remain a diagnostic challenge. The computed tomography pulmonary angiogram (CTPA) has emerged as a popular diagnostic test for PE. However, there is limited data on diagnostic yield and complications in actual clinical settings. Our goal was to determine the diagnostic yield for PE and rate of renal complications following CTPA in a large community hospital setting.

Methods

A retrospective chart review of 1,514 patients who underwent CTPA in the emergency department or during the initial 24 hours of admission to a community-based academic hospital.

Results

Of 1,514 CTPAs, 125 were positive for VTE/PE yielding a positive diagnosis in 8.2%. Dyspnea was the most common symptom in patients and a normal physical exam was the most common finding. Among the 925 patients with adequate data to calculate the rate of contrast-induced nephropathy (CIN), 25.8% had an increase of at least 25% in serum creatinine following the CTPA. Pre-existing diabetes and age were the most important predictors of CIN.

Conclusions

CTPA has a low diagnostic yield for PE in a community setting, and in some patient populations, the rate of contrast-induced nephropathy may be higher than previously reported in the literature. Due to the retrospective nature of this study we were limited in using pre-test scoring systems and in measuring the impact of alternative CT diagnoses on patient management.

Early lung cancer detection using the self-evaluation scoring questionnaire and chest digital radiography: a 3-year follow-up study in China

The standard definition of high-risk individuals for lung cancer was not uniform and the value of chest digital radiography (DR) in lung cancer screening was still unproven. The aim of this study was to assess whether the original questionnaire named as "Self-evaluation Scoring Questionnaire for High-risk Individuals of Lung Cancer" combined with DR examinations could detect early stage of lung cancer effectively. The Self-evaluation Scoring Questionnaire for High-risk Individuals of Lung Cancer had been designed in previous studies. Subjects with scores over 116 points were regarded as high-risk individuals and underwent the current DR scans at least once a year from 2007 to 2009. Noncalcified nodules with a diameter over 30 mm, along with enlarged pulmonary hilus and atelectasis, were considered to be positive and subjected to further special examinations. Efficacy of the scoring questionnaire combined with DR scans was estimated by 3-year results. Among 1,537 subjects, 13, 11, and 7 were diagnosed with lung cancer in the first, second, and third year, respectively, indicating the detection rate of 2.02 % (31/1,537). In addition, 77.42 % (24/31) of the patients were in stage I and 51.61 % (16/31) were adenocarcinomas. For the 31 cases, 28 were defined as detected cancers, while the other three were interval ones, only accounting for 0.20 % (3/1,504) of individuals with negative judgments. The protocol of Self-evaluation Scoring Questionnaire for High-risk Individuals of Lung Cancer combined with DR scans is a cost-effective and safe approach to detect early stage of lung cancer.

Use of BMI guidelines and individual dose tracking to minimize radiation exposure from low-dose helical chest CT scanning in a lung cancer screening program

RATIONALE AND OBJECTIVES

The increasing use of computed tomography (CT) has been accompanied by rising concerns over potential radiation-related health risks, especially cancer, and a need to minimize such risks.

MATERIALS AND METHODS

We conducted 2186 low-dose helical chest CT scans among 1235 nuclear weapons workers at elevated risk of lung cancer, setting the CT scanner tube current at 30 mAs for all participants with BMI <35 kg/m(2) and permitting technologists to raise mAs levels for participants with BMI ≥35 kg/m(2). Dose-length product (DLP) was recorded from the CT scanner, permitting calculation of effective dose. Phantom-based estimates of effective dose were also made. A chest radiologist recorded acceptability of image quality.

RESULTS

The study population was significantly overweight: 79% exceeded a body mass index (BMI) >25 kg/m(2) and 37.1% exceeded a BMI ≥30 kg/m(2). Nearly 90% of CT scans were performed using a tube current setting of 30 mAs and had a mean DLP-based effective dose of 1.3 mSv. The phantom-based estimate of effective dose was lower at 1.1 mSv. Among participants with a BMI ≥35 kg/m(2), 92% were scanned at 40 or 50 mAs, which was associated with a DLP-based effective dose of 1.6 and 2.0 mSv, respectively. Image quality was satisfactory in 99.8% of scans.

CONCLUSION

Application of simple BMI-based guidelines and DLP tracking of low-dose helical chest CT scans in a lung cancer screening program minimizes radiation dose, even in a largely overweight population.