Influence of CT dose reduction on AI-driven malignancy estimation of incidental pulmonary nodules.

OBJECTIVES: The purpose of this study was to determine the influence of dose reduction on a commercially available lung cancer prediction convolutional neuronal network (LCP-CNN). METHODS: CT scans from a cohort provided by the local lung cancer center (n = 218) with confirmed pulmonary malignancies and their corresponding reduced dose simulations (25% and 5% dose) were subjected to the LCP-CNN. The resulting LCP scores (scale 1-10, increasing malignancy risk) and the proportion of correctly classified nodules were compared. The cohort was divided into a low-, medium-, and high-risk group based on the respective LCP scores; shifts between the groups were studied to evaluate the potential impact on nodule management. Two different malignancy risk score thresholds were analyzed: a higher threshold of ≥ 9 ("rule-in" approach) and a lower threshold of > 4 ("rule-out" approach). RESULTS: In total, 169 patients with 196 nodules could be included (mean age ± SD, 64.5 ± 9.2 year; 49% females). Mean LCP scores for original, 25% and 5% dose levels were 8.5 ± 1.7, 8.4 ± 1.7 (p > 0.05 vs. original dose) and 8.2 ± 1.9 (p < 0.05 vs. original dose), respectively. The proportion of correctly classified nodules with the "rule-in" approach decreased with simulated dose reduction from 58.2 to 56.1% (p = 0.34) and to 52.0% for the respective dose levels (p = 0.01). For the "rule-out" approach the respective values were 95.9%, 96.4%, and 94.4% (p = 0.12). When reducing the original dose to 25%/5%, eight/twenty-two nodules shifted to a lower, five/seven nodules to a higher malignancy risk group. CONCLUSION: CT dose reduction may affect the analyzed LCP-CNN regarding the classification of pulmonary malignancies and potentially alter pulmonary nodule management. CLINICAL RELEVANCE STATEMENT: Utilization of a "rule-out" approach with a lower malignancy risk threshold prevents underestimation of the nodule malignancy risk for the analyzed software, especially in high-risk cohorts. KEY POINTS: • LCP-CNN may be affected by CT image parameters such as noise resulting from low-dose CT acquisitions. • CT dose reduction can alter pulmonary nodule management recommendations by affecting the outcome of the LCP-CNN. • Utilization of a lower malignancy risk threshold prevents underestimation of pulmonary malignancies in high-risk cohorts.

Minor head trauma in infants - how accurate is cranial ultrasound performed by trained radiologists?

Correct management of infants after minor head trauma is crucial to minimize the risk to miss clinically important traumatic brain injury (ciTBI). Current practices typically involve CT or in-hospital surveillance. Cranial ultrasound (CUS) provides a radiation-free and fast alternative. This study examines the accuracy of radiologist-performed CUS to detect skull fracture (SF) and/or intracranial hemorrhage (ICH). An inconspicuous CUS followed by an uneventful clinical course would allow exclusion of ciTBI with a great certainty. This monocentric, retrospective, observational study analyzed CUS in infants (< 12 months) after minor head trauma at Bern University Children's Hospital, between 7/2013 and 8/2020. The primary outcome was the sensitivity and specificity of CUS in detecting SF and/or ICH by comparison to the clinical course and to additional neuroimaging. Out of a total of 325 patients, 73% (n = 241) had a normal CUS, 17% (n = 54) were found with SF, and ICH was diagnosed in 2.2% patients (n = 7). Two patients needed neurosurgery and three patients deteriorated clinically during surveillance. Additional imaging was performed in 35 patients. The sensitivity of CUS was 93% ([0.83, 0.97] 95% CI) and the specificity 98% ([0.95, 0.99] 95% CI). All false-negative cases originated in missed SF without clinical deterioration; no ICH was missed.  Conclusion: This study shows high accuracy of CUS in exclusion of SF and ICH, which can cause ciTBI. Therefore, CUS offers a reliable method of neuroimaging in infants after minor head trauma and gives reassurance to reduce the duration of in-hospital surveillance. What is Known: • Minor head trauma can cause clinically important traumatic brain injury in infants, and the management of these cases is a challenge for the treating physician. • Cranial ultrasound (CUS) is regularly used in neonatology, but its accuracy after head trauma in infants is controversial. What is New: • CUS performed by a trained radiologist can exclude findings related to clinically important traumatic brain injury (ciTBI) with high sensitivity and specificity. It therefore offers reassurance in the management of infants after minor head trauma.

MRI Shows Lung Perfusion Changes after Vaping and Smoking.

Background Evidence regarding short-term effects of electronic nicotine delivery systems (ENDS) and tobacco smoke on lung ventilation and perfusion is limited. Purpose To examine the immediate effect of ENDS exposure and tobacco smoke on lung ventilation and perfusion by functional MRI and lung function tests. Materials and Methods This prospective observational pilot study was conducted from November 2019 to September 2021 (substudy of randomized controlled trial NCT03589989). Included were 44 healthy adult participants (10 control participants, nine former tobacco smokers, 13 ENDS users, and 12 active tobacco smokers; mean age, 41 years ± 12 [SD]; 28 men) who underwent noncontrast-enhanced matrix pencil MRI and lung function tests before and immediately after the exposure to ENDS products or tobacco smoke. Baseline measurements were acquired after 2 hours of substance abstinence. Postexposure measurements were performed immediately after the exposure. MRI showed semiquantitative measured impairment of lung perfusion (RQ) and fractional ventilation (RFV) impairment as percentages of affected lung volume. Lung clearance index (LCI) was assessed by nitrogen multiple-breath washout to capture ventilation inhomogeneity and spirometry to assess airflow limitation. Absolute differences were calculated with paired Wilcoxon signed-rank test and differences between groups with unpaired Mann-Whitney test. Healthy control participants underwent two consecutive MRI measurements to assess MRI reproducibility. Results MRI was performed and lung function measurement was acquired in tobacco smokers and ENDS users before and after exposure. MRI showed a decrease of perfusion after exposure (RQ, 8.6% [IQR, 7.2%-10.0%] to 9.1% [IQR, 7.8%-10.7%]; P = .03) and no systematic change in RFV (P = .31) among tobacco smokers. Perfusion increased in participants who used ENDS after exposure (RQ, 9.7% [IQR, 7.1%-10.9%] to 9.0% [IQR, 6.9%-10.0%]; P = .01). RFV did not change (P = .38). Only in tobacco smokers was LCI elevated after smoking (P = .02). Spirometry indexes did not change in any participants. Conclusion MRI showed a decrease of lung perfusion after exposure to tobacco smoke and an increase of lung perfusion after use of electronic nicotine delivery systems. © RSNA, 2022 Online supplemental material is available for this article. See also the editorial by Kligerman in this issue.

Diagnostic validation of a deep learning nodule detection algorithm in low-dose chest CT: determination of optimized dose thresholds in a virtual screening scenario.

OBJECTIVES: This study was conducted to evaluate the effect of dose reduction on the performance of a deep learning (DL)-based computer-aided diagnosis (CAD) system regarding pulmonary nodule detection in a virtual screening scenario. METHODS: Sixty-eight anthropomorphic chest phantoms were equipped with 329 nodules (150 ground glass, 179 solid) with four sizes (5 mm, 8 mm, 10 mm, 12 mm) and scanned with nine tube voltage/current combinations. The examinations were analyzed by a commercially available DL-based CAD system. The results were compared by a comparison of proportions. Logistic regression was performed to evaluate the impact of tube voltage, tube current, nodule size, nodule density, and nodule location. RESULTS: The combination with the lowest effective dose (E) and unimpaired detection rate was 80 kV/50 mAs (sensitivity: 97.9%, mean false-positive rate (FPR): 1.9, mean CTDIvol: 1.2 ± 0.4 mGy, mean E: 0.66 mSv). Logistic regression revealed that tube voltage and current had the greatest impact on the detection rate, while nodule size and density had no significant influence. CONCLUSIONS: The optimal tube voltage/current combination proposed in this study (80 kV/50 mAs) is comparable to the proposed combinations in similar studies, which mostly dealt with conventional CAD software. Modification of tube voltage and tube current has a significant impact on the performance of DL-based CAD software in pulmonary nodule detection regardless of their size and composition. KEY POINTS: • Modification of tube voltage and tube current has a significant impact on the performance of deep learning-based CAD software. • Nodule size and composition have no significant impact on the software's performance. • The optimal tube voltage/current combination for the examined software is 80 kV/50 mAs.

Full core technology versus notch sampling technology: evaluation of the diagnostic accuracy and the risk of a pneumothorax after transthoracic needle biopsy of suspicious lung lesions.

BACKGROUND: Percutaneous needle biopsy of the lung (PCBL) under image guidance has become a safe and effective minimal invasive method to obtain a specimen related histological diagnosis of pulmonary lesions. PURPOSE: To evaluate the diagnostic yield and safety of two different coaxial biopsy technologies: full core and notch sampling technology. The former allowing the removal of full punch cylinders and the latter using a cutting-edge mechanism. MATERIAL AND METHODS: A retrospective analysis of 48 consecutive PCBL procedures has been carried out for this prognostic study, involving patients with a documented pulmonary nodule or mass lesion on previous computed tomography (CT) scans. The study population included 38 men and 10 women (mean age = 67 years). Of these 48 patients who underwent a procedure with a co-axial cutting system, 24 have been performed with notch sampling technology and 24 with full core technology. RESULTS: Out of the 48 biopsy procedures, 46 yielded specimens were adequate for histopathological evaluation, consistent with a technical success rate of 96%. The most common induced image-guided biopsy complication was a pneumothorax, occurring in 14 patients (35%). Seven patients with a pneumothorax were attributed to the full core technology and seven to the notch sampling technology (odds ratio = 1, 95% confidence interval = 0.28-3.51, P = 1). CONCLUSION: In the setting of full core versus notch sampling percutaneous CT-guided coaxial needle biopsy of the lung, no significant difference in the diagnostic accuracy and the incidence of pneumothoraces could be shown, while both technologies have an excellent diagnostic performance.

Ionic and non-ionic intravenous X-ray contrast media: antibacterial agents?

X-ray contrast media have been reported to have inhibitory effects on bacterial growth. Despite its potentially beneficial effect on patients, these features of contrast media have received relatively little attention in the medical literature in the past decades. The aim of this review is to evaluate the literature concerning the bactericidal and bacteriostatic effects of X-ray contrast media, specifically if there is a known difference concerning these effects between ionic and non-ionic contrast media. Systematic literature review was performed for the years of publication between 1911 and 2019. Since the publication of Grossich in 1911, the effect of iodine on the treatment of superficial infections in surgical procedures has been established clinical knowledge. Bacteriostatic and bactericidal effects of ionic X-ray contrast media are well established. However, non-ionic contrast agents have been the subject of little research in this respect. In past decades, the hypothesis emerged in the literature that mainly the concentration of free iodine might be responsible for any bacteriostatic or bactericidal effect of ionic X-ray contrast media. Nowadays, however, only non-ionic contrast media are used. The question regarding the mechanism and magnitude of bacteriostatic or bactericidal effects of these, non-ionic contrast media, could not be answered conclusively from this review. Non-ionic contrast media could be used intentionally when a local antibacterial effect is intended (e.g. in percutaneous abscess drainage), as well as to reduce the overall dose of antibiotics administered to a patient. Thus, this question remains relevant and might constitute the area of future research.

A comprehensive review of imaging findings in COVID-19 - status in early 2021.

Medical imaging methods are assuming a greater role in the workup of patients with COVID-19, mainly in relation to the primary manifestation of pulmonary disease and the tissue distribution of the angiotensin-converting-enzyme 2 (ACE 2) receptor. However, the field is so new that no consensus view has emerged guiding clinical decisions to employ imaging procedures such as radiography, computer tomography (CT), positron emission tomography (PET), and magnetic resonance imaging, and in what measure the risk of exposure of staff to possible infection could be justified by the knowledge gained. The insensitivity of current RT-PCR methods for positive diagnosis is part of the rationale for resorting to imaging procedures. While CT is more sensitive than genetic testing in hospitalized patients, positive findings of ground glass opacities depend on the disease stage. There is sparse reporting on PET/CT with [18F]-FDG in COVID-19, but available results are congruent with the earlier literature on viral pneumonias. There is a high incidence of cerebral findings in COVID-19, and likewise evidence of gastrointestinal involvement. Artificial intelligence, notably machine learning is emerging as an effective method for diagnostic image analysis, with performance in the discriminative diagnosis of diagnosis of COVID-19 pneumonia comparable to that of human practitioners.

Non-contrast-enhanced 3-Tesla Magnetic Resonance Imaging Using Surface-coil and Sonography for Assessment of Hidradenitis Suppurativa Lesions.

Hidradenitis suppurativa has a substantial negative effect on quality of life of affected persons. Diagnosis is based mainly on clinical examination. However, physi-cal examination alone might underestimate disease severity compared with imaging modalities. We report here the application of non-contrast-enhanced 3-Tesla magnetic resonance imaging using surface-coil and sonography for assessment of hidradenitis suppurativa lesions based on topographic assessment of skin lesions. In addition, we review the literature regarding the application of ultrasound and magnetic resonance imaging in hidradenitis suppurativa.

Radiologists and nuclear medicine physicians are looking forward to a cross-curricular training.

OBJECTIVES: To obtain an overview of the attitudes toward interdisciplinary further education of residents and consultants in radiology and nuclear medicine and preferences regarding a future joint training curriculum in Switzerland. METHODS: A 34-item questionnaire was sent electronically (SurveyMonkey online survey tool) to 1244 radiologists and nuclear physicians (residents and consultants) in Switzerland. The items asked about the motivation for further education in each other's specialty and preferences regarding a joint further education curriculum in radiology and nuclear medicine. RESULTS: Overall, 370 questionnaires were analyzed (370/1244, 30%). There were 280 (76%) board-certified physicians in either radiology (238/370, 64%) or nuclear medicine (42/370, 12%) and 65 (18%) residents (radiology 54/370, 15%; nuclear medicine 11/370, 3%). More than half of all residents (34/65, 52%) stated their conviction that a wide range of expertise in both disciplines could be fully guaranteed through adequate cross-curricular training. For responders already at a consultant level in radiology or nuclear medicine, the willingness to undergo further training in each other's specialty significantly increased with a shorter training period. The preferred option for a possible future joint training curriculum was a combination of a 5-year radiology training program with 2 years of further training in nuclear medicine. CONCLUSIONS: Both residents and board-certified physicians in Switzerland are highly interested in a cross-curricular training curriculum in radiology and nuclear medicine. KEY POINTS: • A systematic survey was conducted to obtain information on interest in cross-curricular training in radiology and nuclear medicine and preferences regarding a future joint training curriculum. • More than half of radiology and nuclear medicine residents would be interested in further training in the other specialty. • There is a strong desire for a shorter training program when combining training in both radiology and nuclear medicine.

What you should know about prophylaxis and treatment of radiographic and magnetic resonance contrast medium extravasation.

In addition to anaphylactic reactions induced by contrast media (CM), extravasation is an adverse reaction that occurs immediately, requires special treatment, and attention. Since radiologists are often not familiar with either prophylactic or treatment modalities, the goal of this paper is to summarize the major facts and recommendations with respect to CM extravasation under practical clinical aspects.

In vitro T2 relaxivities of the Gd-based contrast agents (GBCAs) in human blood at 1.5 and 3 T.

BACKGROUND: The availability of data in the medical literature for the T2 relaxivities of the Gd-based contrast agents (GBCAs) is limited. A comprehensive comparison between the agents available commercially (other than in Europe) is lacking, with no data available that most closely reflect the clinic, which is in human whole blood at body temperature. PURPOSE: To complement the existing literature by determining T2 relaxivity data for eight GBCAs in vitro. MATERIAL AND METHODS: The relaxivities of eight GBCAs diluted in human whole blood at 1.5 and 3 T were determined at 37 ± 0.5 °C. Gd was in the range of 0-4 mM. Multi-echo sequences with variable echo times were acquired using a phantom containing a dilution series with each agent, and SigmaPlot 12.0 was used to calculate the R2 relaxation rate and finally r2. Statistical comparisons between agents and field strengths were conducted. RESULTS: The relationship between R2 vs. Gd was observed to be linear at 1.5 and 3 T, with a mild increase in r2 from 1.5 to 3 T for all GBCAs. T2 relaxivity data were compared with prior results. The GBCAs are closely clustered into two groups, with higher r2 noted for the two lipophilic (those with partial hepatobiliary excretion) compounds. CONCLUSION: The r2 values at 1.5 and 3 T, determined for the eight GBCAs still clinically available (other than in Europe), provide a definitive baseline for future evaluations, including theoretical calculations of signal intensity and their clinical impact on T2-weighted scans.

Improved identification of DNA double strand breaks: γ-H2AX-epitope visualization by confocal microscopy and 3D reconstructed images.

Currently, in the context of radiology, irradiation-induced and other genotoxic effects are determined by visualizing DSB-induced DNA repair through γ-H2AX immunofluorescence and direct counting of the foci by epifluorescence microscopy. This procedure, however, neglects the 3D nature of the nucleus. The aim of our study was to use confocal microscopy and 3D reconstructed images to improve documentation and analysis of γ-H2AX fluorescence signals after diagnostic examinations. Confluent, non-dividing MRC-5 lung fibroblasts were irradiated in vitro with a Cs-137 source and exposed to radiation doses up to 1000 mGy before fixation and staining with an antibody recognizing the phosphorylated histone variant γ-H2AX. The 3D distribution of γ-H2AX foci was visualized using confocal laser scanning microscopy. 3D reconstruction of the optical slices and γ-H2AX foci counting were performed using Imaris Image Analysis software. In parallel, γ-H2AX foci were counted visually by epifluorescence microscopy. In addition, whole blood was exposed ex vivo to the radiation doses from 200 to 1600 mGy. White blood cells (WBCs) were isolated and stained for γ-H2AX. In fibroblasts, epifluorescence microscopy alone visualized the entirety of fluorescence signals as integral, without correct demarcation of single foci, and at 1000 mGy yielded on average 11.1 foci by manual counting of 2D images in comparison to 36.1 foci with confocal microscopy and 3D reconstruction (p < 0.001). The procedure can also be applied for studies on WBCs. In contrast to epifluorescence microscopy, confocal microscopy and 3D reconstruction enables an improved identification of DSB-induced γ-H2AX foci, allowing for an unbiased, ameliorated quantification.

Subspecialization in radiology: effects on the diagnostic spectrum of radiologists and report turnaround time in a Swiss university hospital.

PURPOSE: To analyze the changes in the work profiles of radiologists and the reporting time after the implementation of professional subspecialization in the radiology department of a Swiss university hospital. METHODS: In a retrospective analysis, the overall number of different radiologic examinations performed in the department of radiology of the largest Swiss university hospital was documented for 2014 and 2016 before and after the implementation of subspecialized reporting (subspecialities: abdominal, musculoskeletal, cardiothoracic, emergency, and pediatric imaging) in May 2015. For six selected radiologists, the number and types of reported examinations as well as the related radiology report turnaround times (RTATs) were analyzed in detail and compared between the two 1-year periods. RESULTS: Overall, there was a significant increase of 10.3% in the total number of examinations performed in the whole department in 2016 compared with 2014. For four of the six radiologists, the range of different types of examinations significantly decreased with the introduction of subspecialized reporting (p < 0.05). Furthermore, there was a significant change in the subset of the ten most commonly reported types of examinations reported by each of the six radiologists. Mean overall RTATs significantly increased for five of the six radiologists (p < 0.05). CONCLUSIONS: Implementation of subspecialized reporting led to a change in the structure and a decrease in the range of different examination types reported by each radiologist. Mean RTAT increased for most radiologists. Subspecialized reporting allows the individual radiologist to focus on a special field of professional competence but can result in longer overall RTAT.

Automated Billing Code Retrieval from MRI Scanner Log Data.

Although the level of digitalization and automation steadily increases in radiology, billing coding for magnetic resonance imaging (MRI) exams in the radiology department is still based on manual input from the technologist. After the exam completion, the technologist enters the corresponding exam codes that are associated with billing codes in the radiology information system. Moreover, additional billing codes are added or removed, depending on the performed procedure. This workflow is time-consuming and we showed that billing codes reported by the technologists contain errors. The coding workflow can benefit from an automated system, and thus a prediction model for automated assignment of billing codes for MRI exams based on MRI log data is developed in this work. To the best of our knowledge, it is the first attempt to focus on the prediction of billing codes from modality log data. MRI log data provide a variety of information, including the set of executed MR sequences, MR scanner table movements, and given a contrast medium. MR sequence names are standardized using a heuristic approach and incorporated into the features for the prediction. The prediction model is trained on 9754 MRI exams and tested on 1 month of log data (423 MRI exams) from two MRI scanners of the radiology site for the Swiss medical tariffication system Tarmed. The developed model, an ensemble of classifier chains with multilayer perceptron as a base classifier, predicts medical billing codes for MRI exams with a micro-averaged F1-score of 97.8% (recall 98.1%, precision 97.5%). Manual coding reaches a micro-averaged F1-score of 98.1% (recall 97.4%, precision 98.8%). Thus, the performance of automated coding is close to human performance. Integrated into the clinical environment, this work has the potential to free the technologist from a non-value adding an administrative task, therefore enhance the MRI workflow, and prevent coding errors.

Dynamic non-invasive ASL perfusion imaging of a normal pancreas with secretin augmented MR imaging.

OBJECTIVES: To investigate prospectively the repeatability of pancreatic perfusion measurements using arterial spin labelling (ASL) and to determine the increase in perfusion due to secretin stimulation. MATERIAL AND METHODS: An (FAIR)-TrueFISP ASL sequence was applied to determine the perfusion of the pancreatic head in a 3T MRI scanner. Ten healthy volunteers (four men, six women: mean age 28.5 ± 4.6 years; age range 25-40 years) were investigated twice within 1 week. The inter-individual variability was calculated using the standard deviation. Intra-individual agreement between the first and second scan was estimated using the Pearson correlation coefficient. A paired Wilcoxon rank-sum test was used to compare perfusion at baseline (BL) and during secretin stimulation. RESULTS: The mean BL perfusion of the pancreatic head was 285 ± 96 mL/100 g/min with an intra-individual correlation coefficient of 0.67 (strong) for repeated measurements. Secretin stimulation led to a significant increase (by 81%) in perfusion of the pancreatic head to 486 ±156 mL/100 g/min (p=0.002) with an intra-individual correlation of 0.29 (weak). A return to BL values was observed after 239 ± 92 s with a moderate intra-individual correlation coefficient of 0.42 for repeat measurements. CONCLUSION: Dynamic non-invasive ASL imaging of the pancreas permitted quantification of pancreatic perfusion in a clinically applicable setting. KEY POINTS: • ASL imaging of the pancreas permitted quantification of pancreatic perfusion • Secretin stimulation led to a significant increase in pancreatic perfusion • The intra-individual correlation coefficient for baseline perfusion was strong for repeated measurements.

Dynamic Contrast-Enhanced Magnetic Resonance Imaging of Ocular Melanoma as a Tool to Predict Metastatic Potential.

PURPOSE: This study explores the capability of dynamic contrast-enhanced magnetic resonance imaging (DCE-MRI) to differentiate tumor characteristics of metastatic and nonmetastatic choroidal melanoma as a potential tool for patient management. MATERIALS AND METHODS: A total of 13 patients (69 ± 9 years) with choroidal melanoma were imaged using DCE-MRI on a 3-T MRI system with a 16-channel head coil. The Tofts 2-compartment model was chosen for quantification, and parameters K (the transfer constant from the blood plasma to the extracellular space) and Kep (the transfer constant from the extracellular space to the blood plasma) were calculated and compared. Metastasis was excluded by subsequent clinical work-up or confirmed by histology after targeted biopsy. RESULTS: Six patients were diagnosed with metastatic melanoma and 7 without. All orbital tumors were at least larger than 2 mm. A significant difference was identified in K between patients with (0.73 ± 0.18/min) and without (1.00 ± 0.21/min) metastatic melanoma (P = 0.03), whereas the difference was not significantly shown in Kep (2.58 ± 1.54/min of metastatic patients vs 2.98 ± 1.83/min of nonmetastatic patients, P = 0.67). CONCLUSIONS: Dynamic contrast-enhanced magnetic resonance imaging has the potential to differentiate orbital melanomas with metastatic and nonmetastatic spread. Thus, DCE-MRI has the potential to be an in vivo imaging technique to predict early which patients are prone to metastatic disease.

Intravenous Iodinated Contrast Agents Amplify DNA Radiation Damage at CT.

PURPOSE: To determine the effect of the use of iodinated contrast agents on the formation of DNA double-strand breaks during chest computed tomography (CT). MATERIALS AND METHODS: This study was approved by the institutional review board, and written informed consent was obtained from all patients. This single-center study was performed at a university hospital. A total of 179 patients underwent contrast material-enhanced CT, and 66 patients underwent unenhanced CT. Blood samples were taken from these patients prior to and immediately after CT. In these blood samples, the average number of phosphorylated histone H2AX (γH2AX) foci per lymphocyte was determined with fluorescence microscopy. Significant differences between the number of foci that developed in both the presence and the absence of the contrast agent were tested by using an independent sample t test. RESULTS: γH2AX foci levels were increased in both groups after CT. Patients who underwent contrast-enhanced CT had an increased amount of DNA radiation damage (mean increase ± standard error of the mean, 0.056 foci per cell ± 0.009). This increase was 107% ± 19 higher than that in patients who underwent unenhanced CT (mean increase, 0.027 foci per cell ± 0.014). CONCLUSION: The application of iodinated contrast agents during diagnostic x-ray procedures, such as chest CT, leads to a clear increase in the level of radiation-induced DNA damage as assessed with γH2AX foci formation.

Lung nodule detection by microdose CT versus chest radiography (standard and dual-energy subtracted).

OBJECTIVE: The purpose of this study was to investigate the feasibility of microdose CT using a comparable dose as for conventional chest radiographs in two planes including dual-energy subtraction for lung nodule assessment. MATERIALS AND METHODS: We investigated 65 chest phantoms with 141 lung nodules, using an anthropomorphic chest phantom with artificial lung nodules. Microdose CT parameters were 80 kV and 6 mAs, with pitch of 2.2. Iterative reconstruction algorithms and an integrated circuit detector system (Stellar, Siemens Healthcare) were applied for maximum dose reduction. Maximum intensity projections (MIPs) were reconstructed. Chest radiographs were acquired in two projections with bone suppression. Four blinded radiologists interpreted the images in random order. RESULTS: A soft-tissue CT kernel (I30f) delivered better sensitivities in a pilot study than a hard kernel (I70f), with respective mean (SD) sensitivities of 91.1%±2.2% versus 85.6%±5.6% (p=0.041). Nodule size was measured accurately for all kernels. Mean clustered nodule sensitivity with chest radiography was 45.7%±8.1% (with bone suppression, 46.1%±8%; p=0.94); for microdose CT, nodule sensitivity was 83.6%±9% without MIP (with additional MIP, 92.5%±6%; p<10(-3)). Individual sensitivities of microdose CT for readers 1, 2, 3, and 4 were 84.3%, 90.7%, 68.6%, and 45.0%, respectively. Sensitivities with chest radiography for readers 1, 2, 3, and 4 were 42.9%, 58.6%, 36.4%, and 90.7%, respectively. In the per-phantom analysis, respective sensitivities of microdose CT versus chest radiography were 96.2% and 75% (p<10(-6)). The effective dose for chest radiography including dual-energy subtraction was 0.242 mSv; for microdose CT, the applied dose was 0.1323 mSv. CONCLUSION: Microdose CT is better than the combination of chest radiography and dual-energy subtraction for the detection of solid nodules between 5 and 12 mm at a lower dose level of 0.13 mSv. Soft-tissue kernels allow better sensitivities. These preliminary results indicate that microdose CT has the potential to replace conventional chest radiography for lung nodule detection.