Radiation dose reduction in parasinus CT by spectral shaping.

INTRODUCTION: Spectral shaping aims to narrow the X-ray spectrum of clinical CT. The aim of this study was to determine the image quality and the extent of radiation dose reduction that can be achieved by tin prefiltration for parasinus CT. METHODS: All scans were performed with a third generation dual-source CT scanner. A study protocol was designed using 100 kV tube voltage with tin prefiltration (200 mAs) that provides image noise levels comparable to a low-dose reference protocol using 100 kV without spectral shaping (25 mAs). One hundred consecutive patients were prospectively enrolled and randomly assigned to the study or control group. All patients signed written informed consent. The study protocol was approved by the local Institutional Review Board and applies to the HIPAA. Subjective and objective image quality (attenuation values, image noise, and contrast-to-noise ratio (CNR)) were assessed. Radiation exposure was assessed as volumetric CT dose index, and effective dose was estimated. Mann-Whitney U test was performed for radiation exposure and for image noise comparison. RESULTS: All scans were of diagnostic image quality. Image noise in air, in the retrobulbar fat, and in the eye globe was comparable between both groups (all p > 0.05). CNReye globe/air did not differ significantly between both groups (p = 0.7). Radiation exposure (1.7 vs. 2.1 mGy, p < 0.01) and effective dose (0.055 vs. 0.066 mSv, p < 0.01) were significantly reduced in the study group. CONCLUSION: Radiation dose can be further reduced by 17% for low-dose parasinus CT by tin prefiltration maintaining diagnostic image quality.

Third-generation dual-source 70-kVp chest CT angiography with advanced iterative reconstruction in young children: image quality and radiation dose reduction.

BACKGROUND: Many technical updates have been made in multi-detector CT. OBJECTIVE: To evaluate image quality and radiation dose of high-pitch second- and third-generation dual-source chest CT angiography and to assess the effects of different levels of advanced modeled iterative reconstruction (ADMIRE) in newborns and children. MATERIALS AND METHODS: Chest CT angiography (70 kVp) was performed in 42 children (age 158 ± 267 days, range 1-1,194 days). We evaluated subjective and objective image quality, and radiation dose with filtered back projection (FBP) and different strength levels of ADMIRE. For comparison were 42 matched controls examined with a second-generation 128-slice dual-source CT-scanner (80 kVp). RESULTS: ADMIRE demonstrated improved objective and subjective image quality (P < .01). Mean signal/noise, contrast/noise and subjective image quality were 11.9, 10.0 and 1.9, respectively, for the 80 kVp mode and 11.2, 10.0 and 1.9 for the 70 kVp mode. With ADMIRE, the corresponding values for the 70 kVp mode were 13.7, 12.1 and 1.4 at strength level 2 and 17.6, 15.6 and 1.2 at strength level 4. Mean CTDIvol, DLP and effective dose were significantly lower with the 70-kVp mode (0.31 mGy, 5.33 mGy*cm, 0.36 mSv) compared to the 80-kVp mode (0.46 mGy, 9.17 mGy*cm, 0.62 mSv; P < .01). CONCLUSION: The third-generation dual-source CT at 70 kVp provided good objective and subjective image quality at lower radiation exposure. ADMIRE improved objective and subjective image quality.

Dose reduction of the female breast in chest CT.

OBJECTIVE: Organ-based tube current modulation has been shown to significantly reduce the radiation dose to the female breast in phantom studies. We sought to assess the proportions of female breast and glandular tissues that are within the range of organ-based tube current modulation in different age groups and whether these proportions could be optimized by clothing. The secondary objective of our study was to determine whether metal parts of brassieres cause artifacts that impair the diagnostic value. SUBJECTS AND METHODS: Five hundred seventy-eight female patients undergoing chest CT were included in this study. Two hundred nine patients were prospectively examined wearing a brassiere (group A), and the control patients (group B; n = 369) were scanned according to our previous standard without wearing a brassiere during CT. The two groups were subdivided according to cup size (A-E). For CT data acquisition, an angle-dependent tube current modulation, which reduces the tube current for anterior tube position to minimize direct exposure to anteriorly located organs, was used. The proportion of breast tissue and glandular tissue located within and outside the region of tube current reduction was assessed. RESULTS: The results showed that 60.4% of total breast tissue and 67.1% of glandular tissue was inside the region of tube current reduction in group B; the proportions were significantly improved, to an average of 91.3% and 96%, respectively, in group A. Diagnostically relevant artifacts were introduced in none of the patients. Patients' age correlated with this effect, with higher rates of improvement in the older patient group. Angle-dependent tube current modulation was most effective in patients with cup size A while wearing a brassiere. In this group, 97.5% of breast tissue and 98.1% of glandular tissue was inside the region of tube current reduction. Women with a cup size of E had the largest effect of wearing a brassiere, increasing the rate of breast tissue that was affected by angle-dependent tube current modulation from 30.0% to 83.3% and that of glandular tissue from 31.8% to 90.0%. CONCLUSION: We show that wearing a brassiere increases the percentage of breast tissue within the region of reduced tube current and, therefore, improves the performance of angle-dependent tube current modulation technique.

Automated tube voltage adaptation in head and neck computed tomography between 120 and 100 kV: effects on image quality and radiation dose.

INTRODUCTION: Low tube voltage allows for computed tomography (CT) imaging with increased iodine contrast at reduced radiation dose. We sought to evaluate the image quality and potential dose reduction using a combination of attenuation based tube current modulation (TCM) and automated tube voltage adaptation (TVA) between 100 and 120 kV in CT of the head and neck. METHODS: One hundred thirty consecutive patients with indication for head and neck CT were examined with a 128-slice system capable of TCM and TVA. Reference protocol was set at 120 kV. Tube voltage was reduced to 100 kV whenever proposed by automated analysis of the localizer. An additional small scan aligned to the jaw was performed at a fixed 120 kV setting. Image quality was assessed by two radiologists on a standardized Likert-scale and measurements of signal- (SNR) and contrast-to-noise ratio (CNR). Radiation dose was assessed as CTDIvol. RESULTS: Diagnostic image quality was excellent in both groups and did not differ significantly (p = 0.34). Image noise in the 100 kV data was increased and SNR decreased (17.8/9.6) in the jugular veins and the sternocleidomastoid muscle when compared to 120 kV (SNR 24.4/10.3), but not in fatty tissue and air. However, CNR did not differ statistically significant between 100 (23.5/14.4/9.4) and 120 kV data (24.2/15.3/8.6) while radiation dose was decreased by 7-8%. CONCLUSIONS: TVA between 100 and 120 kV in combination with TCM led to a radiation dose reduction compared to TCM alone, while keeping CNR constant though maintaining diagnostic image quality.

Comparison of lesion detection and quantitation of tracer uptake between PET from a simultaneously acquiring whole-body PET/MR hybrid scanner and PET from PET/CT.

PURPOSE: PET/MR hybrid scanners have recently been introduced, but not yet validated. The aim of this study was to compare the PET components of a PET/CT hybrid system and of a simultaneous whole-body PET/MR hybrid system with regard to reproducibility of lesion detection and quantitation of tracer uptake. METHODS: A total of 46 patients underwent a whole-body PET/CT scan 1 h after injection and an average of 88 min later a second scan using a hybrid PET/MR system. The radioactive tracers used were (18)F-deoxyglucose (FDG), (18)F-ethylcholine (FEC) and (68)Ga-DOTATATE (Ga-DOTATATE). The PET images from PET/CT (PET(CT)) and from PET/MR (PET(MR)) were analysed for tracer-positive lesions. Regional tracer uptake in these foci was quantified using volumes of interest, and maximal and average standardized uptake values (SUV(max) and SUV(avg), respectively) were calculated. RESULTS: Of the 46 patients, 43 were eligible for comparison and statistical analysis. All lesions except one identified by PET(CT) were identified by PET(MR) (99.2 %). In 38 patients (88.4 %), the same number of foci were identified by PET(CT) and by PET(MR). In four patients, more lesions were identified by PET(MR) than by PET(CT), in one patient PET(CT) revealed an additional focus compared to PET(MR). The mean SUV(max) and SUV(avg) of all lesions determined by PET(MR) were by 21 % and 11 % lower, respectively, than the values determined by PET(CT) (p < 0.05), and a strong correlation between these variables was identified (Spearman rho 0.835; p < 0.01). CONCLUSION: PET/MR showed equivalent performance in terms of qualitative lesion detection to PET/CT. The differences demonstrated in quantitation of tracer uptake between PET(CT) and PET(MR) were minor, but statistically significant. Nevertheless, a more detailed study of the quantitative accuracy of PET(MR) and the factors governing it is needed to ultimately assess its accuracy in measuring tissue tracer concentrations.

Optimized Camera-Based Patient Positioning in CT: Impact on Radiation Exposure.

OBJECTIVE: The aim of this study was to evaluate whether a 3-dimensional (3D) camera can outperform highly trained technicians in precision of patient positioning and whether this transforms into a reduction in patient exposure. MATERIALS AND METHODS: In a single-center study, 3118 patients underwent computer tomography (CT) scans of the chest and/or abdomen on a latest generation single-source CT scanner supported with an automated patient positioning system by 3D camera. One thousand five hundred fifty-seven patients were positioned laser-guided by a highly trained radiographer (camera off) and 1561 patients with 3D camera (camera on) guidance. Radiation parameters such as effective dose, organ doses, CT dose index, and dose length product were analyzed and compared. Isocenter accuracy and table height were evaluated between the 2 groups. RESULTS: Isocenter positioning was significantly improved with the 3D camera ( P < 0.001) as compared with visual laser-guided positioning. Absolute table height differed significantly ( P < 0.001), being higher with camera positioning (165.6 ± 16.2 mm) as compared with laser-guided positioning (170.0 ± 20.4 mm). Radiation exposure decreased using the 3D camera as indicated by dose length product (321.1 ± 266.6 mGy·cm; camera off: 342.0 ± 280.7 mGy·cm; P = 0.033), effective dose (3.3 ± 2.7 mSv; camera off: 3.5 ± 2.9; P = 0.053), and CT dose index (6.4 ± 4.3 mGy; camera off: 6.8 ± 4.6 mGy; P = 0.011). Exposure of radiation-sensitive organs such as colon ( P = 0.015) and red bone marrow ( P = 0.049) were also lower using the camera. CONCLUSIONS: The introduction of a 3D camera improves patient positioning in the isocenter of the scanner, which results in a lower and also better balanced dose reduction for the patients.

Acute stroke: a comparison of different CT perfusion algorithms and validation of ischaemic lesions by follow-up imaging.

OBJECTIVES: To compare ischaemic lesions predicted by different CT perfusion (CTP) post-processing techniques and validate CTP lesions compared with final lesion size in stroke patients. METHODS: Fifty patients underwent CT, CTP and CT angiography. Quantitative values and colour maps were calculated using least mean square deconvolution (LMSD), maximum slope (MS) and conventional singular value decomposition deconvolution (SVDD) algorithms. Quantitative results, core/penumbra lesion sizes and Alberta Stroke Programme Early CT Score (ASPECTS) were compared among the algorithms; lesion sizes and ASPECTS were compared with final lesions on follow-up MRI + MRA or CT + CTA as a reference standard, accounting for recanalisation status. RESULTS: Differences in quantitative values and lesion sizes were statistically significant, but therapeutic decisions based on ASPECTS and core/penumbra ratios would have been the same in all cases. CTP lesion sizes were highly predictive of final infarct size: Coefficients of determination (R (2)) for CTP versus follow-up lesion sizes in the recanalisation group were 0.87, 0.82 and 0.61 (P < 0.001) for LMSD, MS and SVDD, respectively, and 0.88, 0.87 and 0.76 (P < 0.001), respectively, in the non-recanalisation group. CONCLUSIONS: Lesions on CT perfusion are highly predictive of final infarct. Different CTP post-processing algorithms usually lead to the same clinical decision, but for assessing lesion size, LMSD and MS appear superior to SVDD. KEY POINTS: Following an acute stroke, CT perfusion imaging can help predict lesion evolution. Delay-insensitive deconvolution and maximum slope approach are superior to delay-sensitive deconvolution regarding accuracy. Different CT perfusion post-processing algorithms usually lead to the same clinical decision. CT perfusion offers new insights into the evolution of stroke.

Radiation dose considerations by intra-individual Monte Carlo simulations in dual source spiral coronary computed tomography angiography with electrocardiogram-triggered tube current modulation and adaptive pitch.

OBJECTIVES: To evaluate radiation dose levels in patients undergoing spiral coronary computed tomography angiography (CTA) on a dual-source system in clinical routine. METHODS: Coronary CTA was performed for 56 patients with electrocardiogram-triggered tube current modulation (TCM) and heart-rate (HR) dependent pitch adaptation. Individual Monte Carlo (MC) simulations were performed for dose assessment. Retrospective simulations with constant tube current (CTC) served as reference. Lung tissue was segmented and used for organ and effective dose (ED) calculation. RESULTS: Estimates for mean relative ED was 7.1 ± 2.1 mSv/100 mAs for TCM and 12.5 ± 5.3 mSv/100 mAs for CTC (P < 0.001). Relative dose reduction at low HR (≤60 bpm) was highest (49 ± 5%) compared to intermediate (60-70 bpm, 33 ± 12%) and high HR (>70 bpm, 29 ± 12%). However lowest ED is achieved at high HR (5.2 ± 1.5 mSv/100 mAs), compared with intermediate (6.7 ± 1.6 mSv/100 mAs) and low (8.3 ± 2.1 mSv/100 mAs) HR when automated pitch adaptation is applied. CONCLUSIONS: Radiation dose savings up to 52% are achievable by TCM at low and regular HR. However lowest ED is attained at high HR by pitch adaptation despite inferior radiation dose reduction by TCM. KEY POINTS: • Monte Carlo simulations allow for individual radiation dose calculations. • ECG-triggered tube current modulation (TCM) can effectively reduce radiation dose. • Slow and regular heart rates allow for highest dose reductions by TCM. • Adaptive pitch accounts for lowest radiation dose at high heart rates. • Women receive higher effective dose than men undergoing spiral coronary CT-angiography.

Coronary computed tomography angiography with a consistent dose below 1 mSv using prospectively electrocardiogram-triggered high-pitch spiral acquisition.

AIMS: We evaluated the feasibility and image quality of a new scan mode for coronary computed tomography angiography (CTA) with an effective dose of less than 1 mSv. METHODS AND RESULTS: In 50 consecutive patients (body weight

3D-Visualization of Neurovascular Compression at the Ventrolateral Medulla in Patients with Arterial Hypertension.

PURPOSE: Controversy exists on the association of arterial hypertension (HTN) and neurovascular compression (NVC) at the ventrolateral medulla (VLM). No standardized and reproducible technique has been introduced yet for detection of NVC in HTN. This study aimed to generate, analyze and compare different results of exact reproducible anatomical 3D-representations of the VLM in patients with HTN, based on magnetic resonance imaging (MRI). METHODS: A 3T scanner provided MRI (T2-constructive interference in steady state (CISS) high resolution imaging and three-dimensional Time-of-flight (3D-TOF) angiography) from the posterior fossa of 44 patients with clinical treatment-resistant HTN. Image processing consists of segmentation of the CISS data, registration and fusion of the CISS and TOF data and visualization. For each patient two 3D-visualizations (before and after fusion) were obtained. The reproduction quality of the vessels, flow-related signal variability and pulsation artifacts were analyzed and compared, using a ranking score. RESULTS: Integrating vascular information from TOF into CISS data reduced artifacts in 3D-visualizations of exclusively processed CISS data. The quality of 3D-visualization of the vessels near the brain stem was significantly improved (p = 0.004). The results were reproducible and reliable. The quality of the 3D-presentations of neurovascular relationships at the VLM improved significantly (p < 0.001). CONCLUSION: The 3D-visualization of fused image data provides an excellent overview of the relationship between cranial nerves and vessels at the VLM and simplifies the detection of NVC in HTN. It provides a powerful tool for future clinical and scientific research. Although microvascular decompression (MVD) in treatment resistant HTN is not a standard procedure, it can be discussed in selected patients with intractable severe HTN.

Atrial and ventricular functional and structural adaptations of the heart in elite triathletes assessed with cardiac MR imaging.

PURPOSE: To assess cardiac morphologic and functional adaptations in elite triathletes with magnetic resonance (MR) imaging and to compare findings to those in recreationally active control subjects. MATERIALS AND METHODS: The institutional review board approved the study, and written informed consent was obtained from all subjects. Twenty-six male triathletes (mean age ± standard deviation, 27.9 years ± 3.5; age range, 18-35 years) and 27 nonathletic male control subjects (mean age, 27.3 years ± 3.7; age range, 20-34 years) underwent cardiac MR imaging. Electrocardiographically gated steady-state free-precession cine MR imaging was used to measure indexed left ventricular (LV) and right ventricular (RV) myocardial mass, end-diastolic and end-systolic volumes, stroke volume, ejection fraction (EF), and cardiac index at rest. The ventricular remodeling index, which is indicative of the pattern of cardiac hypertrophy, was calculated. The maximum left atrial (LA) volume was calculated according to the biplane area-length method. Differences between means of athletes and control subjects were assessed by using the Student t test for independent samples. RESULTS: The atrial and ventricular volume and mass indexes in triathletes were significantly greater than those in control subjects (P < .001). In 25 of the 26 athletes, the LV and RV end-diastolic volumes were greater than the normal ranges reported in the literature for healthy, male, nonathletic control subjects (47-92 mL/m(2) and 55-105 mL/m(2), respectively). There was a strong positive correlation between end-diastolic volume and myocardial mass (P < .01). The mean LV and RV remodeling indexes of the athletes (0.73 g/mL ± 0.1 and 0.22 g/mL ± 0.01, respectively) were similar to those of the control subjects (0.71 g/mL ± 0.1 [P = .290] and 0.22 g/mL ± 0.01 [P = .614], respectively). There was a negative correlation between LA end-systolic volume and heart rate (P < .01). CONCLUSION: Changes in cardiac morphologic characteristics and function in elite triathletes, as measured with cardiac MR imaging, reflect a combination of eccentric and concentric remodeling with regulative enlargement of atrial and ventricular chambers. These findings are different from what has been observed in previous studies in other types of elite athletes.

Cardiac magnetic resonance assessment of left and right ventricular morphologic and functional adaptations in professional soccer players.

BACKGROUND: Professional, long-term physical training is associated with cardiac morphologic and functional changes that depend on the type of exercise performed. So far, the specific effect of soccer training on cardiac morphology has not been investigated with cardiac magnetic resonance imaging (CMRI). We sought to use CMRI to study left ventricular (LV) and right ventricular (RV) morphologic and functional adaptations in professional soccer players. METHODS: Twenty-nine male professional soccer players (mean age 24.6 +/- 3.9 years, range 18-31 years) in different playing positions and 29 nonathlete male controls (27.0 +/- 3.7 years, 21-34 years) underwent CMRI. Electrocardiographic-gated steady-state free-precession cine CMRI was used to measure myocardial mass (MM), end-diastolic volume (EDV) and end-systolic volume, stroke volume (SV), ejection fraction, and cardiac index at rest. We calculated the ventricular remodeling index (RI) to describe the pattern of cardiac hypertrophy. RESULTS: Ventricular volume and mass indices were significantly (P < .001) higher in athletes. LVEDV and RVEDV on MRI was above normal in 27/29 athletes. There was a strong positive correlation between EDV and myocardial mass (P < .01). The LVRI and RVRI were similar (0.73 +/- 0.1 g/mL; 0.22 +/- 0.01 g/mL) to that of controls (0.71 +/- 0.1 g/mL; 0.22 +/- 0.01 g/mL). No significant differences were observed for LV ejection fraction and cardiac index. Neither the comparison of athletes in different playing positions nor the comparison of younger and older players revealed statistically significant differences. CONCLUSION: Cardiac magnetic resonance imaging measurements enable studying the mechanisms of LV and RV adaptation in professional soccer players and reflect the ventricular response to combined endurance and strength based training.

Panoramic radiograph, computed tomography or magnetic resonance imaging. Which imaging technique should be preferred in bisphosphonate-associated osteonecrosis of the jaw? A prospective clinical study.

It was the aim of the present study to find out which radiological imaging techniques allow assessing the extent of bisphosphonate-associated osteonecrosis of the jaw (BONJ) in an adequate way. Twenty-four patients suffering from BONJ were included in the study. Before surgery, each patient was examined with panoramic radiograph, contrast-enhanced magnetic resonance imaging (MRI) and non-enhanced computed tomography. The detectability of BONJ was assessed for the three imaging techniques. The extent of the jaw region affected by BONJ was determined in MRI and CT scans and compared to the intra-operative situation. The detectability of BONJ lesions was 54% for panoramic radiographs, 92% for MRI scans and 96% for computed tomography (CT) scans. The intra-operatively assessed extent of BONJ correlated significantly with the measurements on CT scans (p = 0.0004) but did not correlate significantly with the measurements in MRI scans (p = 0.241). The intra-operatively measured extent of BONJ differed significantly from the CT measurements (p = 0.00003) but not from the MRI data (p = 0.137). Although MRI as well as CT have a high detectability for BONJ lesions that exceeds that of panoramic radiographs by far, both techniques show problems with the exact assessment of the extent of BONJ lesions in the individual patients. Therefore, the relevance of MRI and CT for the preoperative assessment of the extent of BONJ lesions is limited. Future research should focus on the identification of imaging techniques that allow assessing the extent of BONJ lesions with a higher accuracy.

Recent and Upcoming Technological Developments in Computed Tomography: High Speed, Low Dose, Deep Learning, Multienergy.

The advent of computed tomography (CT) has revolutionized radiology, and this revolution is still going on. Starting as a pure head scanner, modern CT systems are now able to perform whole-body examinations within a couple of seconds in isotropic resolution, single-rotation whole-organ perfusion, and temporal resolution to fulfill the needs of cardiac CT. Because of the increasing number of CT examinations in all age groups and overall medical-driven radiation exposure, dose reduction remains a hot topic. Although fast gantry rotation, broad detector arrays, and different dual-energy solutions were main topics in the past years, new techniques such as photon counting detectors, powerful x-ray tubes for low-kV scanning, automated image preprocessing, and machine learning algorithms have moved into focus today.The aim of this article is to give an overview of the technical specifications of up-to-date available CT systems and recent hardware and software innovations for CT systems in the near future.

Cardiac spiral dual-source CT with high pitch: a feasibility study.

Increase of pitch in spiral CT decreases data acquisition time; dual-source CT (DSCT) systems provide improved temporal resolution. We evaluated the combination of these two features. Measurements were performed using a commercial DSCT system equipped with prototype software allowing pitch factors from p = 0.35 to 3.0. We measured slice sensitivity profiles as a function of pitch to assess spatial resolution in the z-direction and the contrast of structures moved periodically to measure temporal resolution. Additionally we derived modulation transfer functions to provide objective parameters; both spatial and temporal resolution were essentially unchanged even at high pitch. CT of the cardiac region of three pigs was performed at p = 3.0. In vivo CT images confirmed good image quality; direct comparison with standard low-pitch phase-correlated CT image datasets showed no significant difference. For a normalized z-axis acquisition of 12 cm, the corresponding effective dose value was 2.0 mSv for the high-pitch CT protocol. We conclude that spiral DSCT imaging with a pitch of 3.0 can provide unimpaired image quality with respect to spatial and temporal resolution. Applications to cardiac and thoracic imaging with effective dose below 1 mSv are possible.

Evaluation of ventricular septal defects using high pitch computed tomography angiography of the chest in children with complex congenital heart defects below one year of age.

BACKGROUND: Aim of this study was to assess the accuracy of ventricular septal defects (VSD) using high pitch computed tomography angiography (CTA) of the chest in children below 1 year of age, compared to the intraoperative findings and echocardiography. METHODS: Out of 154 patients that underwent Dual-Source CTA of the chest using a high-pitch protocol at low tube voltages (70-80 kV), 55 underwent surgical repair of a VSD (median age 8 days, range 1-348 days). The margins of the VSDs and their relation to the surrounding structures were reproduced by en-face views using multiplanar reformations (MPR). Absolute diameter, normalized area and relative area compared to the aortic valve annulus were used for discrimination between restrictive and non-restrictive defects. Localization was classified into four subtypes. The results were compared to two-dimensional echocardiography and intraoperative findings. RESULTS: Median absolute size of VSDs did not differ significantly between CTA-measurements (10.8 mm, range 2.8-18.1 mm) and intraoperative findings (12.0 mm, 3.0-25.0 mm, p = 0.09). Echocardiographic values were significantly lower (9.6 mm, 3.0-18.5 mm, both p < 0.01). The classification of the location and orientation matched the intraoperative situs in 96.4% of all cases using CT and in 87.3% using echocardiography. Echocardiography missed the relation to valves in 11% of all cases. Pre-interventional sensitivity and specificity for detection of a VSD were 97.2/98.9% compared to echocardiography. Median radiation dose was 0.32 mSv (range 0.12-2.00 mSv) and differed significantly between second and third generation Dual-Source CT (0.43 vs. 0.22 mSv, p = 0.003). CONCLUSION: Size and subtype of VSDs can be accurately assessed by CTA of the chest in patients with complex congenital heart defects at a very low radiation dose.

Cervical CT angiography comparing routine noncontrast and a late venous scan as masks for automated bone subtraction: feasibility study and examination of the influence of patient motion on image quality.

OBJECTIVES: Bone subtraction techniques have been shown to enhance cranial computed tomography angiography (CTA). The aims of this study were to assess the feasibility of bone subtraction CTA (BSCTA) in cervical CTA, test whether a late venous CT (LVCT) scan can be used as bone mask instead of a low-dose nonenhanced CT (NECT), and to evaluate the impact of patient motion on image quality. MATERIALS AND METHODS: Thirty-six patients underwent BSCTA for the evaluation of the neck vessels with a 64-slice CT system using commercially available software. Eighteen patients had a low-dose NECT scan before CTA, and 18 patients had an LVCT scan after CTA. Subtraction quality for vascular segments was evaluated independently by 2 examiners. Cohen's Kappa was applied to evaluate interobserver reliability, and Wilcoxon signed rank test was used to test for differences between the 2 groups. Motion between the 2 scans was measured and correlated to image quality. RESULTS: BSCTA using both NECT and LVCT scans as masks was successfully applied in all patients. Image quality did not differ significantly between the 2 groups, and interobserver agreement was high (k 0.5-1). Motion between the scans was highest for the jaw and hyoid, and lowest for the upper and lower spine. Decreased image quality on the subtracted images was associated with increased motion for the external carotid and vertebral artery, independent of mask type (P = 0.002-0.04). CONCLUSIONS: BSCTA techniques can be successfully applied in the neck. If parenchymal phase imaging is indicated, the LVCT can be used as a bone subtraction mask and diagnostic scan, eg, for tumor imaging.

Thin-slice MDCT of the neck: impact on cancer staging.

OBJECTIVE: The objective of this study was to compare thin-slice multiplanar evaluation and conventional 3-mm axial evaluation of head and neck MDCT in tumor staging. MATERIALS AND METHODS: Ninety-six patients with histologically proven squamous cell carcinoma were evaluated independently, once using 3-mm axial images and once using 1-mm interactive multiplanar reformation (MPR) images. Tumor stage was assessed with both methods; histology served as the reference. Thirty-seven patients with hypopharyngeal and laryngeal tumors had en bloc resection, allowing direct comparison of tumor infiltration into designated anatomic structures. Two examiners independently assessed the data sets. Interobserver agreement was tested with a modified kappa test. The Wilcoxon signed rank test with continuity correction was applied to test the null hypothesis, which postulates the equality of both methods. The chi-square test was applied to compare the number of correctly classified tumors for the two methods and readers. RESULTS: Interobserver agreement was high (kappa = 0.88-0.91). Both methods allowed accurate tumor staging, and no significant differences between the two methods were found (reader A, p = 0.61; reader B, p = 1). With MPR assessment, more anatomic structures were rated positive for tumor infiltration, but diagnostic accuracy did not differ significantly in the subgroup of patients with histologic correlation from en bloc resection. CONCLUSION: Conventional 3-mm axial evaluation of head and neck MDCT proved to be sufficient in tumor staging.

Impact of Contrast Media Concentration on Low-Kilovolt Computed Tomography Angiography: A Systematic Preclinical Approach.

OBJECTIVES: Low peak kilovoltage (kVp) protocols in computed tomography angiography (CTA) demand a review of contrast media (CM) administration practices. The aim of this study was to systematically evaluate different iodine concentrations of CM in a porcine model. MATERIALS AND METHODS: Dynamic 70 kVp CTA was performed on 7 pigs using a third-generation dual-source CT system. Three CM injection protocols (A-C) with an identical total iodine dose and iodine delivery rate (150 mg I/kg, 12 s, 0.75 g I/s) differed in iodine concentration and flow rate (protocol A: 400 mg I/mL, 1.9 mL/s; B: 300 mg I/mL, 2.5 mL/s; C: 150 mg I/mL, 5 mL/s). All protocols were applied in a randomized order and compared intraindividually. Arterial enhancement at different locations in the pulmonary artery, the aorta, and aortic branches was measured over time. Time attenuation curves, peak enhancement, time to peak, and bolus tracking delay times needed for static CTA were calculated. The reproducibility of optimal parameters was tested in single-phase CTA. RESULTS: The heart rates of the pigs were comparable for all protocols (P > 0.7). The injection pressure was significantly higher for protocol A (64 ± 5 psi) and protocol C (55 ± 3 psi) compared with protocol B (39 ± 2 psi) (P < 0.001). Average arterial peak enhancement in the dynamic scans was 359 ± 51 HU (protocol A), 382 ± 36 HU (B), and 382 ± 60 HU (C) (A compared with B and C: P < 0.01; B compared with C: P = 0.995). Time to peak enhancement decreased with increasing injection rate. The delay time for bolus tracking depended on the injection rate as well and was highest for protocol A (4.7 seconds) and lowest for protocol C (3.9 seconds) (P = 0.038). The peak enhancement values of the dynamic scans highly correlated with those of the single-phase CTA scans. CONCLUSIONS: In 70 kVp CTA, 300 mg I/mL iodine concentrations showed to be superior to high-concentration CM when keeping the iodine delivery rate constant. Besides, iodine concentrations as low as 150 mg I/mL can be administered without compromising vascular enhancement. This opens up new possibilities in CM administration.

Evaluation of coronary stents and stenoses at different heart rates with dual source spiral CT (DSCT).

OBJECTIVES: Evaluation of coronary arteries at higher heart rates and in the presence of coronary stents remains problematic. The utilization of dual source computed tomography (DSCT) might improve the visualization of the coronary arteries under these conditions by imaging at a temporal resolution of 83 milliseconds, independent of heart rate. MATERIALS AND METHODS: Vessel phantoms (diameter 2-4 mm) were attached to a robotic device to simulate cardiac motion and scanned with a DSCT system. The phantoms had either inserts leading to 50% stenosis or carried stents. Images were evaluated for motion artifacts and measurements of the normal, stenotic, and in-stent lumen at different heart rates (50-120 bpm) were performed. Quantile regression analysis was performed to investigate heart rate dependence of the measurement errors. RESULTS: Visualization of the stenoses and stents was possible without motion artifacts at heart rates of up to 120 bpm. Image quality was similar for the static (0 bpm) and the dynamic (50-120 bpm) scans. Errors for diameter measurements of the vessel lumen and the stenotic lumen were low (3-mm vessel: 1-2%), but considerable for in-stent diameter measurements (3-mm stent: 27-32%). A window/level setting of 1500/300 Hounsfield units was more favorable for stent evaluation. No heart rate dependence was found. CONCLUSIONS: Depiction of coronary stents with DSCT is possible across a large range of simulated heart rates without motion artifacts and with image quality superior to that of previous generations of CT scanners.