Iodine Dose of Administered Contrast Media Affects the Level of Radiation-Induced DNA Damage During Cardiac CT Scans.

OBJECTIVE. The purpose of this study is to investigate the contributing effect of contrast media (CM) iodine dose on radiation-induced DNA damage in blood lymphocytes during a cardiac CT scan. MATERIALS AND METHODS. The minipigs were exposed 12 times in total to a fixed cardiac CT scan protocol. An unenhanced and two CM injection protocols were considered, the latter with 50% saline diluted (160 mg I/mL) and standard iodixanol. Blood samples were collected before and after CT, and radiation-induced DNA double-strand breaks were assessed using γ-H2AX (H2A histone family member X) immunofluorescent staining of the blood lymphocytes. Significant differences in foci numbers were investigated with an independent sample t test. In addition, a numeric dosimetry model was applied that simulates the cardiac CT scan, with the heart represented by a blood volume containing a mixture of six iodine concentrations (0, 10, 20, 30, 40, and 50 mg I/mL). RESULTS. Compared with the unenhanced (0 mg I/mL) protocol, the number of γ-H2AX foci per cell increased significantly (p < 0.038), by 56.1% for the reduced iodine dose (160 mg I/mL) and by 141.1% for the standard iodine dose (320 mg I/mL) protocols. These in vivo results are confirmed by the dosimetry simulation model, in which 78.8% and 133.7% increases in locally absorbed blood dose in the left ventricle were observed for the reduced and standard iodine dose protocols, respectively. CONCLUSION. Administration of CM during a cardiac CT examination significantly increases radiation-induced DNA damage in blood lymphocytes. Moreover, a lower CM iodine dose results in a reduced level of DNA damage, at constant radiation exposure.

Potential Heating Effect in the Gravid Uterus by Using 3-T MR Imaging Protocols: Experimental Study in Miniature Pigs.

Purpose To determine the changes in temperature within the gravid miniature pig uterus during magnetic resonance (MR) imaging at 3 T. Materials and Methods The study received ethics committee approval for animal experimentation. Fiber-optic temperature sensors were inserted into the fetal brain, abdomen, bladder, and amniotic fluid of miniature pigs (second trimester, n = 2; third trimester, n = 2). In the first trimester (n = 2), the sensors were inserted only into the amniotic fluid (three sacs per miniature pig, for a total of six sacs). Imaging was performed with a 3-T MR imager by using different imaging protocols in a random order for animal, each lasting approximately 15 minutes. The first regimen consisted of common sequences used for human fetal MR examination, including normal specific absorption rate (SAR). The second regimen consisted of five low-SAR sequences, for which three gradient-echo sequences were interspersed with two diffusion-weighted imaging series. Finally, a high-SAR regimen maximized the radiofrequency energy deposition (constrained by the 2-W per kilogram of body weight SAR limitations) by using five single-shot turbo spin-echo sequences. Differences in temperature increases between the three regimens and between the three trimesters were evaluated by using one-way analysis of variance. The maximum cumulative temperature increase over 1 hour was also evaluated. Results Low-SAR regimens resulted in the lowest temperature increase (mean ± standard deviation, -0.03°C ± 0.20), normal regimens resulted in an intermediate increase (0.31°C ± 0.21), and high-SAR regimens resulted in the highest increase (0.56°C ± 0.20) (P < .0001). Mean temperature increase in the third trimester was 0.38°C ± 0.27, with no significant differences compared with the first (0.23°C ± 0.27) and second (0.25°C ± 0.32) trimesters (P = .07). The cumulative temperature increase over 1-hour imaging time with high SAR can reach 2.5°C. Conclusion In pregnant miniature pigs, the use of 3-T magnets for diagnostic MR imaging with normal SAR regimens does not lead to temperature increases above 1°C if imaging time is kept below 30 minutes. Longer imaging time, especially with high-SAR regimens, can lead to an increase of 2.5°C. (©) RSNA, 2015 Online supplemental material is available for this article.

Contrast agent and radiation dose reduction in abdominal CT by a combination of low tube voltage and advanced image reconstruction algorithms.

OBJECTIVES: To assess image quality in abdominal CT at low tube voltage combined with two types of iterative reconstruction (IR) at four reduced contrast agent dose levels. METHODS: Minipigs were scanned with standard 320 mg I/mL contrast concentration at 120 kVp, and with reduced formulations of 120, 170, 220 and 270 mg I/mL at 80 kVp with IR. Image quality was assessed by CT value, dose normalized contrast and signal to noise ratio (CNRD and SNRD) in the arterial and venous phases. Qualitative analysis was included by expert reading. RESULTS: Protocols with 170 mg I/mL or higher showed equal or superior CT values: aorta (278-468 HU versus 314 HU); portal vein (205-273 HU versus 208 HU); liver parenchyma (122-146 HU versus 115 HU). In the aorta, all 170 mg I/mL protocols or higher yielded equal or superior CNRD (15.0-28.0 versus 13.7). In liver parenchyma, all study protocols resulted in higher SNRDs. Radiation dose could be reduced from standard CTDIvol = 7.8 mGy (6.2 mSv) to 7.6 mGy (5.2 mSv) with 170 mg I/mL. CONCLUSION: Combining 80 kVp with IR allows at least a 47 % contrast agent dose reduction and 16 % radiation dose reduction for images of comparable quality. KEY POINTS: • There is a balance between image quality, contrast dose and radiation dose. • Iterative reconstruction has a major, positive impact on this balance. • Both contrast dose and radiation dose can be reduced in abdominal CT. • The trade-off can be quantitatively described by a 3D model. • Contrast and radiation dose can be tailored according to specific safety concerns.

Bony palmar ridges of the phalanges of the human fingers.

PURPOSE: On imaging studies, bony ridges can be seen at the palmar aspect of the phalanges of the fingers. Our purpose was to address the following: (1) which structures insert on to the ridges and what is the histological appearance? (2) Is there a difference between the different fingers? (3) Is there a correlation between the ridges and age? MATERIALS AND METHODS: Two observers retrospectively evaluated 270 radiographs (135 men; 135 women; mean age 44 years), and 33 CT scans (22 men; 11 women; mean age 46 years). Three cadaveric hands were also studied. The ridges were graded using a 4-point scale. A Chi-square test was used to compare the different fingers (p < 0.05) and to study the prominence of the ridges in relation to age (p < 0.05). RESULTS: On histology with routine stains the A2 pulley was inserted on the ridges of the proximal phalanx, and the flexor superficialis and A4 pulley on the ridges of the middle phalanx. On histology, the insertion showed a transition zone consisting of fibrocartilage. The prominence of the ridges was significantly different between fingers with III and IV categorized higher than II and III. There was a significant correlation with age for all fingers except for the middle phalanx of II and III. CONCLUSION: The bony palmar ridges have characteristics of enthesophytes. They correspond to the insertion site of the A2 pulley, and the flexor superficialis tendon and A4 pulley, at the proximal and middle phalanx, respectively. The ridges become more prominent with age, and their prominence is different between the fingers with III and IV categorized higher than II and V.

Potential increase in radiation-induced DNA double-strand breaks with higher doses of iodine contrast during coronary CT angiography.

PURPOSE: To investigate the contrast media iodine dose dependency of radiation-induced DNA double-strand breaks (DSBs) during a coronary computed tomography angiography (CCTA) scan. METHODS: This prospective patient study was approved by the ethical committee. Between November 2018 and July 2019, 50 patients (31 males and 19 females, mean age 64 years) were included in the study, 45 CCTA and five noncontrast-enhanced (NCE) cardiac computed tomography (CT) patients. A single-heartbeat scan protocol with a patient-tailored contrast media injection protocol was used, administering a patient-specific iodine dose. DNA double-strand breaks were quantified using a γH2AX foci assay on peripheral blood lymphocytes. The net amount of γH2AX/cell was normalized to the individual patient CT dose by the size-specific dose estimate (SSDE). Correlation between the administered and blood-iodine dose and the SSDE normalized amount of DNA DSBs was investigated using a Pearson correlation test. RESULTS: CCTA patients were scanned with a mean CTDIvol of 10.6 ± 5.6 mGy, corresponding to a mean SSDE of 11.3 ± 5.3 mGy while the NCE cardiac CT patients were scanned with a mean CTDIvol of 6.00 ± 1.8 mGy, corresponding to a mean SSDE of 6.6 ± 2.7 mGy. The administered iodine dose ranged from 16.5 to 34.0 gI in the CCTA patients, resulting in a blood-iodine dose range from 5.1 to 15.0 gI in the exposed blood volume. A significant linear relationship (r = 0.79, p-value < 0.001) was observed between the blood iodine dose and SSDE normalized radiation-induced DNA DSBs. A similar significant linear relationship (r = 0.62, p-value < 0.001) was observed between the administered iodine dose and SSDE normalized radiation-induced DNA DSBs. CONCLUSIONS: This study shows that contrast media iodine dose increases the level of radiation-induced DNA DSBs in peripheral blood lymphocytes in a linear dose-dependent manner with CCTA. Importantly, the level of DNA DSBs can be reduced by lowering the administered iodine dose.

Improved enhancement in CT angiography with reduced contrast media iodine concentrations at constant iodine dose.

The study objective is to investigate the impact of a wide range of contrast media (CM) iodine concentrations on CT enhancement at constant total iodine dose (TID) and iodine delivery rate (IDR). Seven injection protocols, based on different iodine concentrations ranging from 120 to 370 mg I/mL, were assessed on 4 minipigs at a constant TID of 320 mg I/kg and IDR of 0.64 g I/s. Dynamic images were acquired on a clinical 64-slice MDCT scanner for 120 s with the abdominal aorta, vena cava inferior and liver parenchyma in the field-of-view. Maximal enhancement, time-to-peak and peak width were assessed. The enhancement curve characteristics were correlated with CM iodine concentration. In particular, CM with lower iodine concentrations yielded a significant increased maximal enhancement and peak width compared to the standard-of-care concentrations: e.g. in the aorta, 245 HU maximal enhancement and 9.2 s peak width with the 320 mg I/mL iodine concentration increased to 291 HU and 16.1 s with 160 mg I/mL. When maintaining a constant TID and IDR, by compensating injection rate and volume, injection of a CM with reduced iodine concentration results in a diagnostically beneficial higher maximal enhancement and longer enhancement peak duration.

The Impact of Combining a Low-Tube Voltage Acquisition with Iterative Reconstruction on Total Iodine Dose in Coronary CT Angiography.

OBJECTIVES: To assess the impact of combining low-tube voltage acquisition with iterative reconstruction (IR) techniques on the iodine dose in coronary CTA. METHODS: Three minipigs underwent CCTA to compare a standard of care protocol with two alternative study protocols combining low-tube voltage and low iodine dose with IR. Image quality was evaluated objectively by the CT value, signal-to-noise ratio (SNR), and contrast-to-noise ratio (CNR) in the main coronary arteries and aorta and subjectively by expert reading. Statistics were performed by Mann-Whitney U test and Chi-square analysis. RESULTS: Despite reduced iodine dose, both study protocols maintained CT values, SNR, and CNR compared to the standard of care protocol. Expert readings confirmed these findings; all scans were perceived to be of at least diagnostically acceptable quality on all evaluated parameters allowing image interpretation. No statistical differences were observed (all p values > 0.11), except for streak artifacts (p = 0.02) which were considered to be more severe, although acceptable, with the 80 kVp protocol. CONCLUSIONS: Reduced tube voltage in combination with IR allows a total iodine dose reduction between 37 and 50%, by using contrast media with low iodine concentrations of 200 and 160 mg I/mL, while maintaining image quality.

Feasibility of markerless tumor tracking by sequential dual-energy fluoroscopy on a clinical tumor tracking system.

A novel approach to dual-energy imaging for markerless tumor tracking was proposed consisting of sequential dual-energy fluoroscopy, omitting the need for fast-switching kV generators. The implementation of this approach on a clinical tumor tracking system and its efficacy is shown feasible through optimization of the imaging parameters.