Ultra-low Radiation Dose Research Articles

Ultra-low-dose CT coronary angiography using 128-slice dual source CT with low concentration contrast agent: initial experience.

To optimize and evaluate an ultra-low-dose (ULD) technique for CT coronary angiography (CTCA). Eighty-two patients were randomly divided into two groups. ULD and routine CTCA were performed in groups A and B. Image quality, radiation dose and contrast agent were evaluated. The effective dose (ED) was 0.20±0.01mSv for the ULD technique, a decrease of 87% (t=-21.182, P<0.001) compared with the control group. The total iodine content was 8.10±0g, a decrease of 62% (t=-73.458, P<0.001) compared with 21.10±1.15g for the control group. The assessment rates for both groups were the same (99.26 vs 99.64%, χ 2 =0.727, P=0.394). The contrast-to-noise ratio was 19.31±7.95 for group A and 20.73±5.07 for group B: the difference was not statistically significant (t=-1.678, P=0.095). Using an ultra-low radiation dose and contrast agent technique, while maintaining an assessable image and improving the safety of the medical examination, was a feasible and reliable method for CTCA.

Comparison of low- and ultralow-dose computed tomography protocols for quantitative lung and airway assessment.

Quantitative computed tomography (CT) measures are increasingly being developed and used to characterize lung disease. With recent advances in CT technologies, we sought to evaluate the quantitative accuracy of lung imaging at low- and ultralow-radiation doses with the use of iterative reconstruction (IR), tube current modulation (TCM), and spectral shaping. We investigated the effect of five independent CT protocols reconstructed with IR on quantitative airway measures and global lung measures using an invivo large animal model as a human subject surrogate. A control protocol was chosen (NIH-SPIROMICS+TCM) and five independent protocols investigating TCM, low- and ultralow-radiation dose, and spectral shaping. For all scans, quantitative global parenchymal measurements (mean, median and standard deviation of the parenchymal HU, along with measures of emphysema) and global airway measurements (number of segmented airways and pi10) were generated. In addition, selected individual airway measurements (minor and major inner diameter, wall thickness, inner and outer area, inner and outer perimeter, wall area fraction, and inner equivalent circle diameter) were evaluated. Comparisons were made between control and target protocols using difference and repeatability measures. Estimated CT volume dose index (CTDIvol) across all protocols ranged from 7.32mGy to 0.32mGy. Low- and ultralow-dose protocols required more manual editing and resolved fewer airway branches; yet, comparable pi10 whole lung measures were observed across all protocols. Similar trends in acquired parenchymal and airway measurements were observed across all protocols, with increased measurement differences using the ultralow-dose protocols. However, for small airways (1.9±0.2mm) and medium airways (5.7±0.4mm), the measurement differences across all protocols were comparable to the control protocol repeatability across breath holds. Diameters, wall thickness, wall area fraction, and equivalent diameter had smaller measurement differences than area and perimeter measurements. In conclusion, the use of IR with low- and ultralow-dose CT protocols with CT volume dose indices down to 0.32mGy maintains selected quantitative parenchymal and airway measurements relevant to pulmonary disease characterization.

Computer-aided detection (CAD) of solid pulmonary nodules in chest x-ray equivalent ultralow dose chest CT - first in-vivo results at dose levels of 0.13 mSv

ObjectivesTo determine the value of computer-aided detection (CAD) for solid pulmonary nodules in ultralow radiation dose single-energy computed tomography (CT) of the chest using third-generation dual-source CT at 100kV and fixed tube current at 70 mAs with tin filtration. Methods202 consecutive patients undergoing clinically indicated standard dose chest CT (1.8±0.7 mSv) were prospectively included and scanned with an additional ultralow dose CT (0.13±0.01 mSv) in the same session. Standard of reference (SOR) was established by consensus reading of standard dose CT by two radiologists. CAD was performed in standard dose and ultralow dose CT with two different reconstruction kernels. CAD detection rate of nodules was evaluated including subgroups of different nodule sizes (<5, 5–7, >7mm). Sensitivity was further analysed in multivariable mixed effects logistic regression. ResultsThe SOR included 279 solid nodules (mean diameter 4.3±3.4mm, range 1–24mm). There was no significant difference in per–nodule sensitivity of CAD in standard dose with 70% compared to 68% in ultralow dose CT both overall and in different size subgroups (all p>0.05). CAD led to a significant increase of sensitivity for both radiologists reading the ultralow dose CT scans (all p<0.001). In multivariable analysis, the use of CAD (p<0.001), and nodule size (p<0.0001) were independent predictors for nodule detection, but not BMI (p=0.933) and the use of contrast agents (p=0.176). ConclusionsComputer-aided detection of solid pulmonary nodules using ultralow dose CT with chest X-ray equivalent radiation dose has similar sensitivities to those from standard dose CT. Adding CAD in ultralow dose CT significantly improves the sensitivity of radiologists.

25 - Ultralow Dose Radiation 3D Intraoperative Imaging: How Low Can We Go? An O-Arm®, CT Scan, Cadaveric Study

25 - Ultralow Dose Radiation 3D Intraoperative Imaging: How Low Can We Go? An O-Arm®, CT Scan, Cadaveric Study

Coronary CT angiography with 80 kV tube voltage and low iodine concentration contrast agent in patients with low body weight

BackgroundCoronary CT angiography (CTA) is gaining widespread acceptance for the non-invasive evaluation of coronary arteries. However, radiation exposure and administration of iodinated contrast agents are still reasons of some concern. The 80 kV tube voltage increases the attenuation of iodine, allowing to use lower iodine concentration contrast agents for coronary CTA. ObjectiveWe evaluated the diagnostic accuracy of coronary CTA performed with 64-slice scanner, 80 kV tube voltage, iterative reconstruction algorithm and ultra-low concentration contrast medium to reduce iodine load and radiation dose. MethodsWe enrolled 45 patients with low body weight and indication for elective invasive coronary angiography (ICA). All patients received an 80 ml bolus of Iodixanol-270 at an infusion rate of 5 mL/s and underwent coronary CTA (80 kV and 500–550 mA) with prospective ECG-triggering. Image quality score, type of artifacts, coronary CTA evaluability, diagnostic accuracy and radiation exposure were assessed. ResultsPre-test probability of CAD was low-to-intermediate (48%). Accordingly, the prevalence of obstructive CAD was 47% (21 out of 45 patients). Most (93%) of the patients were pre-treated with intravenous metoprolol before scanning and achieved a heart rate suitable for prospective ECG-triggering coronary CTA (53 ± 3 bpm). The mean effective dose and iodine load were 1.1 ± 0.4 mSv and 21.6 gI, respectively. We rated 443 out of 720 coronary segments as being of excellent image quality. In a segment-based model, coronary evaluability (number of coronary segments evaluable/total number of coronary segments), was 97% (699/720 segments). In a segment-based analysis, sensitivity, specificity, positive predictive value, negative predictive value and accuracy for >50% coronary stenosis identification vs. ICA were 89%, 99%, 89%, 99% and 99%, respectively. In a patient-based analysis, sensitivity, specificity, positive predictive value, negative predictive value and accuracy were 94%, 89%, 83%, 96% and 91%, respectively. ConclusionsIn patients with low body weight, image quality and diagnostic accuracy of ultra-low radiation dose and low-iodine load coronary CTA are good and similar to values reported in the literature for standard tube voltage and iodine load protocols.

Performance of ultralow-dose CT with iterative reconstruction in lung cancer screening: limiting radiation exposure to the equivalent of conventional chest X-ray imaging.

To investigate the detection rate of pulmonary nodules in ultralow-dose CT acquisitions. In this lung phantom study, 232 nodules (115 solid, 117 ground-glass) of different sizes were randomly distributed in a lung phantom in 60 different arrangements. Every arrangement was acquired once with standard radiation dose (100 kVp, 100 references mAs) and once with ultralow radiation dose (80 kVp, 6 mAs). Iterative reconstruction was used with optimized kernels: I30 for ultralow-dose, I70 for standard dose and I50 for CAD. Six radiologists examined the axial 1-mm stack for solid and ground-glass nodules. During a second and third step, three radiologists used maximum intensity projection (MIPs), finally checking with computer-assisted detection (CAD), while the others first used CAD, finally checking with the MIPs. The detection rate was 95.5% with standard dose (DLP 126mGy*cm) and 93.3% with ultralow-dose (DLP: 9mGy*cm). The additional use of either MIP reconstructions or CAD software could compensate for this difference. A combination of both MIP reconstructions and CAD software resulted in a maximum detection rate of 97.5% with ultralow-dose. Lung cancer screening with ultralow-dose CT using the same radiation dose as a conventional chest X-ray is feasible. • 93.3% of all lung nodules were detected with ultralow-dose CT. • A sensitivity of 97.5 % is possible with additional image post-processing. • The radiation dose is comparable to a standard radiography in two planes. • Lung cancer screening with ultralow-dose CT is feasible.

Dynamic and static tensile mechanical properties of myocardial tissue.

Event Abstract Back to Event Dynamic and static tensile mechanical properties of myocardial tissue. Sherif Ramadan1, 2, 3, Hani Naguib1, 2, 3 and Narinder Paul3, 4 1 University of Toronto, Mechanical and Industrial Engineering, Canada 2 University of Toronto, Smart and Adaptive Polymers Lab, Canada 3 University of Toronto, Institute of Biomaterials and Biomedical Engineering, Canada 4 Toronto General Hospital, Joint Department of Medical Imaging, Canada Introduction: Heart disease is a significant cause of morbidity and mortality that affects 1.3 million Canadians annually[1]. Coronary artery disease (CAD) is a leading cause of heart disease and is due to progressive accumulation of arterial plaque resulting in occlusion of the arterial lumen and abnormal myocardial contractility[2]. Computed Tomography Coronary Angiography (CTCA) is used to exclude significant CAD in patients with low-intermediate pre-test probability[3],[4]. However, dynamic anthropomorphic CT phantom devices that realistically mimic normal and diseased cardiac tissues are required to test new imaging techniques and algorithms that target ultralow radiation dose and high resolution CTCA. This study aims to quantify the mechanical properties of myocardial tissue to allow for the fabrication of phantoms that mimic the behaviour of heart tissue under varying hemodynamic conditions. Materials and Methods: The elasticity of myocardial tissue was tested under static and dynamic conditions. Tensile testing was performed to obtain the Young’s modulus and a dynamic mechanical analyzer (DMA) induced a frequency sweep to determine the complex (dynamic) modulus. A frequency range of 0.5Hz to 3.5Hz was analyzed as these frequencies correspond to human heart rates of 30 to 210bpm. Multiple tissue samples were taken from each pig and lamb heart, these animal models were chosen as they are close human analogues and are commonly used as replacements for human tissue[5],[6].The heart tissue was tested while freshly sacrificed without any intervening freeze-thaw cycles to ensure the integrity of the muscle tissue. The tissue was placed in a balanced salt solution and tested at 37°C to simulate in vitro conditions[7]. Results and Discussion: Preliminary data (mean ± SD): The tensile and complex moduli were tested on 6 pig and lamb hearts; tensile modulus of lamb = 0.06 ±0.03 (n=15 samples) and for pig =0.04 ± 0.03 (n=11 samples); the complex modulus for lamb = 0.03Mpa at 0.5Hz to 0.06 Mpa at 3.5Hz ± 0.02 (n=15 samples) and for pig = 0.03Mpa at 0.5Hz to 0.06 Mpa at 3.5Hz ± .01 (n=15 samples) and both exhibited a linear trend. These values indicate that myocardial tissue behaves similarly to soft rubbers and stiffens under higher frequency loads. Moreover, for tensile testing there was no statistical difference between individual hearts or animals (P values of 0.235, 0.483, and 0.73 between the animals, pig hearts, and lamb hearts respectively). Conclusions: The static and dynamic moduli of myocardial tissue in pig and lamb hearts is between 0.02 and 0.1Mpa which is similar to soft, rubber-like materials. This quantitative data will inform selection and fabrication of customized biomaterials for construction of the myocardium in a dynamic anthropomorphic tissue realistic heart phantom.

Approaches to ultra-low radiation dose coronary artery calcium scoring based on 3rd generation dual-source CT: A phantom study

ObjectivesTo investigate to what extent 3rd generation dual-source computed tomography (DSCT) can reduce radiation dose in coronary artery calcium scoring. MethodsImage acquisition was performed using a stationary calcification phantom. Prospectively electrocardiogram (ECG)-triggered 120kV sequential, and 120 and Sn100kV ultra-high pitch (UHP) acquisitions were performed with different tube currents (80, 60, 40, 20mA). Images were reconstructed using filtered back projection (FBP) and 3rd generation iterative reconstruction (IR). Contrast-to-noise ratio (CNR), Agatston score, calcium volume, and radiation dose were assessed. For statistical analysis Friedman tests and Wilcoxon rank sum tests were used. ResultsEven at reduced tube currents, the three acquisition techniques did not show significant differences in Agatston score (p=0.4) or calcium volume (p=0.08) with FBP reconstruction. Calcium volumes were significantly lower for 3rd generation IR compared to FBP reconstructions (p<0.01). CTDIvol for the 120kV sequential, 120 and Sn100kV UHP acquisitions at 80 and 20mA were 1.2–0.37, 0.48–0.17, and 0.07–0.02 mGy, respectively. Conclusion3rd generation DSCT enabled a reduction of tube current in both the sequential and UHP acquisitions without significantly affecting coronary calcium scoring. Tin filtered 100kV scanning may allow accurate quantification of calcium score without correction of the HU threshold.

The potential use of ultra-low radiation dose images in digital mammography--a clinical proof-of-concept study in craniocaudal views.

To estimate the potential of low-dose images in digital mammography by analysing the effect of substantial dose reduction in craniocaudal (CC) views on clinical performance. At routine mammography, additional CC views were obtained with about 10% of the standard dose. Five radiologists retrospectively read the standard [mediolateral oblique (MLO) + CC] and combination low-dose mammograms (standard MLO + low-dose CC). If present, lesion type, conspicuity and suggested work-up were recorded. Final diagnoses were made by histology or follow up. A t-test or χ(2) test was used to compare results. 421 cases were included, presenting 5 malignancies, 66 benign lesions and multiple non-specific radiologic features. Using MLO with low-dose CC, all lesions were detected by at least one reader, but altogether less often than with standard mammography (sensitivity, 73.9% vs 81.5%). Missed lesions concerned all types. Lesions detected with both protocols were described similarly (p = 0.084) with comparable work-up recommendations (p = 0.658). Mammography with ultra-low-dose CC images particularly influences detection. While sensitivity decreased, specificity was unaffected. In this proof-of-concept study a lower limit was to be determined that is not intended nor applicable for clinical practice. This should facilitate further research in optimization of a low-dose approach, which has potential in a relatively young and largely asymptomatic population. Tungsten/silver-acquired mammography images might facilitate substantial dose reduction. Ultra-low-dose CC images reduce sensitivity, but not specificity. Low-dose images have potential in a largely young and asymptomatic population; a baseline is set for further research in optimization of a low-dose approach.

Feasibility of ultra-low radiation dose reduction for renal stone CT using model-based iterative reconstruction: prospective pilot study

PurposeTo compare dose, reader assessments, and noise between ultra-low-dose (ULD) and low-dose (LD) renal stone computed tomography (CT) using multiple reconstruction methods. Materials and methodsProspective study of 19 patients having noncontrast LD and ULD renal stone CT reconstructed using filtered back projection, adaptive statistical iterative reconstruction (ASIR), and model-based iterative reconstruction (MBIR). Dose, noise measurements, and subjective image assessments were recorded. ResultsULD volume CT dose index was 61% less. Noise was 50% less with ULD MBIR than with LD ASIR (P<.001); no other significant differences existed. ConclusionULD MBIR is comparable to our standard of care, LD ASIR, with 61% lower dose and 50% less noise.

Ultralow-Dose Chest Computed Tomography for Pulmonary Nodule Detection

The purpose of this study was to evaluate the image quality and sensitivity of ultralow radiation dose single-energy computed tomography (CT) with tin filtration for spectral shaping and iterative reconstructions for the detection of pulmonary nodules in a phantom setting. Single-energy CT was performed using third-generation dual-source CT (SOMATOM Force; 2 × 192 slices) at 70 kVp, 100 kVp with tin filtration (100Sn kVp), and 150Sn kV with tube current-time product adjustments resulting in standard dose (CT volume dose index, 3.1 mGy/effective dose, 1.3 mSv at a scan length of 30 cm), 1/10th dose level (0.3 mGy/0.13 mSv), and 1/20th dose level (0.15 mGy/0.06 mSv). An anthropomorphic chest phantom simulating an intermediate-sized adult with randomly distributed solid pulmonary nodules of various sizes (2-10 mm; attenuation, 75 HU at 120 kVp) was used. Images were reconstructed with advanced model-based iterative reconstruction (ADMIRE; strength levels 3 and 5) and were compared with those acquired with second-generation dual-source CT at 120 kVp (reconstructed with filtered back projection) and sinogram-affirmed iterative reconstruction (strength level 3) at the lowest possible dose at 120 kVp (CT volume dose index, 0.28 mGy). One blinded reader measured image noise, and 2 blinded, independent readers determined overall image quality on a 5-grade scale (1 = nondiagnostic to 5 = excellent) and marked nodule localization with confidence rates on a 5-grade scale (1 = unsure to 5 = high confidence). The constructional drawing of the phantom served as reference standard for calculation of sensitivity. Two patients were included, for proof of concept, who were scanned with the 100Sn kVp protocol at the 1/10th and 1/20th dose level. Image noise was highest in the images acquired with second-generation dual-source CT and reconstructed with filtered back projection. At both the 1/10th and 1/20th dose levels, image noise at a tube voltage of 100Sn kVp was significantly lower than in the 70 kVp and 150Sn kV data sets (ADMIRE 3, P < 0.01; ADMIRE 5, P < 0.05). Sensitivity of nodule detection was lowest in images acquired with second-generation dual-source CT at 120 kVp and the lowest possible dose. Protocols at 100Sn kVp and ADMIRE 5 showed highest sensitivity at the 1/10th and 1/20th dose levels. Highest numbers of false-positives occurred in second-generation dual-source CT images (range, 12-15), whereas lowest numbers occurred in the 1/10th and 1/20th dose data sets acquired with third-generation dual-source CT at 100Sn kVp and reconstructed with ADMIRE strength levels 3 and 5 (total of 1 and 0 false-positives, respectively). Diagnostic confidence at 100Sn kVp was significantly higher than at 70 kVp or 150Sn kV (ADMIRE 3, P < 0.05; ADMIRE 5, P < 0.01) at both the 1/10th and 1/20th dose levels. Images of the 2 patients scanned with 100Sn kVp at the 1/10th and 1/20th dose levels were of diagnostic quality. Our study suggests that chest CT for the detection of pulmonary nodules can be performed with third-generation dual-source CT producing high image quality, sensitivity, and diagnostic confidence at a very low effective radiation dose of 0.06 mSv when using a single-energy protocol at 100 kVp with spectral shaping and when using advanced iterative reconstruction techniques.

809 In Vivo Colonic Insufflation via a Disposable CO2 Insufflation System

Background: One of the major obstacles (~30%) of screening colonoscopy is the hurdle of preparation. The standard technologies demands aggressive bowel cleansing that hamper patient's compliance. Aim: To test the safety and proof of concept of a novel prep-less XRay imaging capsule (Check Cap Ltd, Israel) for colon cancer screening. Material and Methods: The capsule (approximately 34 mm in length and 11.5 mm in diameter, similar in size to optical imaging capsules) utilizes a novel ultra-low dose (0.03 mSv) low energy (56 70 Kev) X-ray-based imaging technology to safely generate high resolution 3-D imagery of the colon without bowel cleansing or other aggressive preparation. 10 capsules were swallowed by volunteers (M=7, F=3) (ages 37 66) and were tracked during the whole passage of the capsule in the body using radio frequency telemetry and an Electromagnetic Localization System (ELS). The capsules were programed to perform scans when movement in the colon is detected and transmit the imaging data to an external recorder unit worn by the patients. The study was approved by the IRB of the Tel Aviv Medical Center. Total transit time and total X-ray exposure to the patients were calculated to assess the safety profile of the x-ray capsule imaging technology in human subjects. Results: All capsules were swallowed and naturally exerted by the volunteers without any minor or major side effect. The average transit time of 68 ±31 hours. The volunteers were exposed to an ultralow total radiation dose (Average total exposure (0.03 ± 0.007 mSv), two orders of magnitude less than CTC (with 1 outlier due to manufacturing fault). Data from scans in the colon combined with ELS positioning information was used to reconstruct 3D colon segments in un-prepped colon. Fig1 and Fig.2 are examples of such 3D scans. Laboratory data form synthetic colon phantoms with and without polyps as well as data from cow colon phantom with induced tissue made polyp Fig.3 and Fig.4 have shown reconstruction accuracy of 2 3 mm in colon diameter measurements. (All figure dimensions in mm) Conclusions: A safety and proof of concept study has been performed using a novel prep-less x-ray imaging capsule for colon cancer screening. Quantitative ultra-low dose x-ray 3D imaging was achieved in the colon of human subjects. The efficacy will be confirmed in a multi-center study.

Safety, efficacy, and feasibility of an ultra-low dose radiation protocol for CT-guided percutaneous needle biopsy of pulmonary lesions: Initial experience

To prospectively determine efficacy and complication rates following an ultra-low dose (ULD) protocol for computed tomography (CT)-guided percutaneous needle biopsy (PNB) of lung lesions. The use of an ULD protocol (100kV, 7.5mAs) for CT-guided lung biopsy was initiated, as a quality assurance initiative. All patients who underwent lung lesion biopsies under ULD were evaluated prospectively. For the purposes of comparison, a retrospective review was conducted to obtain data from patients who underwent the standard-dose protocol for CT-guided PNB of lung lesions. Total dose received, length of procedure, technical success, and complications were evaluated. The overall technical success rate using the ULD protocol was 95.8%. There was a statistically significant 57.5% reduction in radiation dose in the ULD group. There was no significant difference in average length of procedure between the two groups. Complication rates between the two groups were comparable, with 42% in the standard-dose group and 32% in the ULD group; no major complications occurred. Within the ULD group, smaller sized lesions were found to be correlated with higher complication rates, but lesion size had no effect on the total dose of radiation received. Radiation dose to the chest during CT-guided lung PNB is reduced significantly by 57.5% through the use of an ULD protocol. Reducing the CT radiation dose does not negatively impact patient safety or biopsy diagnostic rates in PNB.

Coronary computed tomography angiography with model-based iterative reconstruction using a radiation exposure similar to chest X-ray examination

AimsTo evaluate the feasibility and image quality of coronary computed tomography angiography (CCTA) acquisition with a submillisievert fraction of effective radiation dose using model-based iterative reconstruction (MBIR) for noise reduction.Methods and resultsIn 42 patients undergoing standard low-dose (100–120 kV; 450–700 mA) and additional ultra-low-dose CCTA (80–100 kV; 150–210 mA) reconstructed with MBIR, segmental image quality was graded on a four-point scale [(i): non-evaluative, (ii): good, (iii): adequate, and (iv): excellent]. Signal-to-noise ratio (SNR) was calculated dividing left main artery (LMA) and right coronary artery (RCA) attenuation by the aortic root noise. Over a wide range of body mass index (18–40 kg/m2), the estimated median radiation dose exposure was 1.19 mSv [interquartile range (IQR): 1.07–1.30 mSv] for standard and 0.21 mSv (IQR: 0.18–0.23 mSv) for ultra-low-dose CCTA (P < 0.001). The median image quality score per segment was 3.5 (IQR: 3.0–4.0) in standard CCTA vs. 3.5 (IQR: 2.5–4.0) in ultra-low dose with MBIR (P = 0.29). Diagnostic image quality (scores 2–4) was found in 98.7 vs. 97.8% coronary segments (P = 0.36). Introduction of MBIR for ultra-low-dose CCTA resulted in a significant increase in SNR (P < 0.001) for LMA (from 15 ± 5 to 29 ± 7) and RCA (from 14 ± 4 to 27 ± 6) despite 82% dose reduction.ConclusionCoronary computed tomography angiography acquisition with diagnostic image quality is feasible at an ultra-low radiation dose of 0.21 mSv, e.g. in the range reported for a postero-anterior and lateral chest X-ray.

Image quality of ultra-low-dose dual-source CT angiography using high-pitch spiral acquisition and iterative reconstruction in young children with congenital heart disease

BackgroundObtaining diagnostic CT image quality with ultra-low radiation dose in young children with congenital heart disease remains challenging. ObjectiveWe evaluated the feasibility and image quality of prospectively electrocardiogram (ECG)-triggered high-pitch spiral acquisition with iterative reconstruction for pediatric cardiovascular CT angiography. MethodsSixty-two consecutive pediatric patients younger than 2 years with congenital heart disease underwent prospectively ECG-triggered high-pitch spiral dual-source CT acquisition. Patients were randomly assigned into 2 groups: full tube current (40–70 mAs) scans with filtered back projection reconstruction (group A) and half tube current (20–35 mAs) scans with sinogram-affirmed iterative reconstruction (group B). Attenuation, noise, signal-to-noise ratio (SNR), contrast-to-noise ratio (CNR), and subjective image quality were compared between the 2 groups. Effective radiation dose was also estimated for both groups. ResultsNo significant difference was found in the attenuation, image noise, SNR, and CNR between the 2 groups in the same evaluated anatomic regions, whereas the attenuation and image noise were slightly lower, and the SNR and CNR were slightly higher in group B. No significant difference was found in subjective image quality between the 2 groups (4.27 ± 0.73 vs. 4.34 ± 0.42; P = .813). Effective dose was 0.06 ± 0.03 mSv in group B and 0.13 ± 0.04 mSv in group A, reflecting dose savings of 53.8% by using iterative reconstruction. ConclusionsA combination of prospectively ECG-triggered high-pitch spiral acquisition, low tube current, and iterative reconstruction may offer diagnostic image quality in pediatric cardiovascular CT angiography with effective radiation dose < 0.1 mSv.

3:46 PM Abstract No. 225 - Ultra-low radiation dose reduction for post EVAR (endovascular aneurysm repair) CT angiography using model-based iterative reconstruction (MBIR)

Purpose Model-based iterative reconstruction (MBIR) is a CT reconstruction algorithm that has the potential to provide high quality diagnostic images at very low radiation doses. The purpose of this study is to compare radiation dose, image quality and noise using an ultra low radiation dose (ULD) protocol reconstructed with MBIR to our current standard radiation dose (SD) protocol. Materials and Methods A prospective evaluation of 20 patients (20M;0F; mean age=75 yrs) undergoing surveillance post-EVAR enhanced CT was performed. All patients underwent SD and ULD venous phase imaging (SD/ULD: noise index = 36/51, min mA=100/50, max mA=450/225, kV=100/100). SD images were reconstructed using ASIR (Adaptive Statistical Iterative Reconstruction) per standard of care and compared with ULD images reconstructed with ASIR and MBIR. The volume CT Dose Index (CTDI) was recorded. Quantitative measurements of image noise using the HU standard deviation in 5 separate locations were recorded and averaged. Subjective image assessment (1=worst, 5 = best) of two radiologists blinded to scanning protocol and reconstruction algorithm was performed evaluating diagnostic confidence, image noise, vessel sharpness and aneurysm size. Results The CTDIvol was 73% lower using the ULD protocol (3.4 mGy vs 12.8 mGy for SD). Quantitative image noise measurements were 34% lower with ULD MBIR compared to SD ASIR and 55% lower when compared to ULD ASIR. ULD MBIR and SD ASIR showed no significant difference in averaged subjective noise (3.8 vs 4.0, p=.25). Although vessel sharpness (3.3 vs 4.1, p Conclusion An ULD MBIR protocol performed at 73% lower dose than standard of care imaging provides identical assessment of aneurysm size, high diagnostic confidence and lower image noise and should be considered for post EVAR CT follow-up.

CT coronary angiography at an ultra-low radiation dose (&lt;0.1 mSv): feasible and viable in times of constraint on healthcare costs

Computed tomography coronary angiography (CTCA) has reached very high standards both in terms of diagnostic performance and radiation dose reduction. This commentary follows a report on CTCA using less than 0.1 mSv in selected patients. This is an extraordinary accomplishment, both for technology and for medicine. The difficult task is now to implement this tool in clinical practice so it can play the best possible role. CTCA can improve diagnostic pathways, can save money for healthcare systems and could even improve pharmacological therapy. All of this may happen, but it will require the combined effort of all the experienced operators in this field, including the referring clinicians. In times of financial constraint, CTCA may also help to restrict ineffective medical expenses.

Clinical validation of coronal and sagittal spinal curve measurements based on three-dimensional vertebra vector parameters

For many decades, visualization and evaluation of three-dimensional (3D) spinal deformities have only been possible by two-dimensional (2D) radiodiagnostic methods, and as a result, characterization and classification were based on 2D terminologies. Recent developments in medical digital imaging and 3D visualization techniques including surface 3D reconstructions opened a chance for a long-sought change in this field. Supported by a 3D Terminology on Spinal Deformities of the Scoliosis Research Society, an approach for 3D measurements and a new 3D classification of scoliosis yielded several compelling concepts on 3D visualization and new proposals for 3D classification in recent years. More recently, a new proposal for visualization and complete 3D evaluation of the spine by 3D vertebra vectors has been introduced by our workgroup, a concept, based on EOS 2D/3D, a groundbreaking new ultralow radiation dose integrated orthopedic imaging device with sterEOS 3D spine reconstruction software. Comparison of accuracy, correlation of measurement values, intraobserver and interrater reliability of methods by conventional manual 2D and vertebra vector-based 3D measurements in a routine clinical setting. Retrospective, nonrandomized study of diagnostic X-ray images created as part of a routine clinical protocol of eligible patients examined at our clinic during a 30-month period between July 2007 and December 2009. In total, 201 individuals (170 females, 31 males; mean age, 19.88 years) including 10 healthy athletes with normal spine and patients with adolescent idiopathic scoliosis (175 cases), adult degenerative scoliosis (11 cases), and Scheuermann hyperkyphosis (5 cases). Overall range of coronal curves was between 2.4 and 117.5°. Analysis of accuracy and reliability of measurements was carried out on a group of all patients and in subgroups based on coronal plane deviation: 0 to 10° (Group 1; n=36), 10 to 25° (Group 2; n=25), 25 to 50° (Group 3; n=69), 50 to 75° (Group 4; n=49), and above 75° (Group 5; n=22). All study subjects were examined by EOS 2D imaging, resulting in anteroposterior (AP) and lateral (LAT) full spine, orthogonal digital X-ray images, in standing position. Conventional coronal and sagittal curvature measurements including sagittal L5 vertebra wedges were determined by 3 experienced examiners, using traditional Cobb methods on EOS 2D AP and LAT images. Vertebra vector-based measurements were performed as published earlier, based on computer-assisted calculations of corresponding spinal curvature. Vertebra vectors were generated by dedicated software from sterEOS 3D spine models reconstructed from EOS 2D images by thesame three examiners. Manual measurements were performed by each examiner, thrice for sterEOS 3D reconstructions and twice for vertebra vector-based measurements. Means comparison ttest, Pearson bivariate correlation analysis, reliability analysis by intraclass correlation coefficients for intraobserver reproducibility and interrater reliability were performed using SPSS v16.0 software. In comparison with manual 2D methods, only small and nonsignificant differences were detectable in vertebra vector-based curvature data for coronal curves and thoracic kyphosis, whereas the found difference in L1-L5 lordosis values was shown to be strongly related to the magnitude of corresponding L5 wedge. Intraobserver reliability was excellent for both methods, and interrater reproducibility was consistently higher for vertebra vector-based methods that was also found to be unaffected by the magnitude of coronal curves or sagittal plane deviations. Vertebra vector-based angulation measurements could fully substitute conventional manual 2D measurements, with similar accuracy and higher intraobserver reliability and interrater reproducibility. Vertebra vectors represent a truly 3D solution for clear and comprehensible 3D visualization of spinal deformities while preserving crucial parametric information for vertebral size, 3D position, orientation, and rotation. The concept of vertebra vectors may serve as a starting point to a valid and clinically useful alternative for a new 3D classification of scoliosis.

Liver perfusion CT during hepatic arteriography for the hepatocellular carcinoma: Dose reduction and quantitative evaluation for normal- and ultralow-dose protocol

ObjectivesThe purpose of this study was to investigate whether substantial reduction of the computed tomography (CT) dose is possible in liver CT perfusion imaging by comparing the results of ultralow-dose CT perfusion imaging with those of conventional CT perfusion imaging the same patients and under the same conditions. Materials and methodsThe study was composed following two parts: computer simulation and patients study. In computer simulation, noise was added to the images so that the standard deviation (SD) of the CT values in the liver parenchyma became various values using ImageJ. Time density curves (TDCs) were created from the simulated data, and the influence of difference in the SDs on the shapes of the TDCs was investigated. In the patient study, CT perfusion during intra-arterial injection was performed in 30 consecutive patients undergoing transcatheter arterial chemoembolization. CT perfusion images were acquired twice, at 100mA (CTDIvol, 300mGy) for normal and at 20mA (CTDIvol, 60mGy) for the ultralow radiation doses, under the same conditions. ResultsNo change was observed in the shape of the TDCs and peak values in the analysis of simulation images. A very good correlation was observed between the normal- and ultralow-dose CT images for all analyzed values (R2=0.9885 for blood flow, 0.9269 for blood volume, and 0.8424 for mean transit time). ConclusionsOur results demonstrated that there was no significant difference in the analysis results of perfusion CT between ultralow-dose CT performed using 20% of the conventional dose and normal-dose CT perfusion.

The EOS™ imaging system and its uses in daily orthopaedic practice

The EOS™ X-ray machine, based on a Nobel prize-winning invention in physics in the field of particle detection, is capable of a simultaneous capture of biplanar X-ray images by slot scanning of the whole body in an upright, physiological load-bearing position, using ultra-low radiation doses. The simultaneous capture of spatially calibrated anterioposterior and lateral images provides a three-dimensional (3D) surface reconstruction of the skeletal system using a special software. Parts of the skeletal system in X-ray images and 3D-reconstructed models appear in true 1:1scale for size and volume, thus spinal and vertebral parameters, lower limb axis lengths and angles, as well as any relevant clinical parameters in orthopaedic practice can be very precisely measured and calculated. Visualisation of 3D reconstructed models in various views by sterEOS 3D software enables presentation of top view images to help analyse rotational conditions of lower limbs, joints and spine deformities in the horizontal plane, providing revolutionary novel possibilities in orthopaedic surgery, especially in spine surgery. Our department has been extensively using the very first commercially available EOS™ imaging system worldwide for routine orthopaedic diagnostics since June 2007. During this period of about 4.5years, more than 5,700 standard examinations have been carried out, about a third of them in spine deformity cases and the rest in lower limb orthopaedic cases. In this mini-review, general principles and uses of this groundbreaking integrated orthopaedic solution is reviewed with a few highlighted examples from our own clinical practice.