Radiation dose of chaperones during common pediatric computed tomography examinations.

BACKGROUND: One main challenge in pediatric imaging is to reduce motion artifacts by calming young patients. To that end, the Radiological Society of North America (RSNA) as early as 1997 stated the necessity of adults accompanying their child during the child's examination. Nonetheless, current research lacks data regarding radiation dose to these chaperones. OBJECTIVE: The aim of this study was to measure the radiation dose of accompanying adults during state-of-the-art pediatric CT protocols. MATERIALS AND METHODS: In addition to a 100-kV non-contrast-enhanced chest CT (Protocol 1), we performed a 70-kV contrast-enhanced chest protocol (Protocol 2) using a third-generation dual-source CT. We acquired data on the radiation dose around the scanner using digital dosimetry placed right at the gantry, 1 m away, as well as beside the gantry. We acquired the CT-surrounding radiation dose during scanning of a pediatric phantom as well as 12 pediatric patients. RESULTS: After conducting 10 consecutive phantom scans using Protocol 1, we found the location with the highest cumulative dose acquired was right next to the gantry opening, at 3 µSv. Protocol 2 showed highest cumulative dose of 2 µSv at the same location. For Protocol 1, the location with the highest radiation doses during pediatric scans was right next to the gantry opening, with doses of 0.75±0.70 µSv. For Protocol 2, the highest radiation was measured 1 m away at 0.50±0.60 µSv. No radiation dose was measured at any time beside the gantry. CONCLUSION: Our results provide proof that chaperones receive low radiation doses during state-of-the-art CT examinations. Given knowledge of these values as well as the optimal spots with the lowest radiation doses, parents as well as patients might be more relaxed during the examination.

Direct communication between radiologists and patients following imaging examinations. Should radiologists rethink their patient care?

OBJECTIVES: To investigate patients' perception of the radiology service when the radiologist communicates the findings to patients. METHODS: After routine MRI, patients in group 1 (n = 101) were given the opportunity to discuss the findings with the radiologist. Patients in group 2 (n = 101) left the radiology department without any personal communication. Subsequently, by means of a questionnaire designed by an expert psychologist, both groups were asked regarding their anxiety, emotional attachment to the institute and subjective assessment of competence. RESULTS: Overall 76 % of all patients were concerned about their imaging findings without significant difference between both groups (p = 0.179). Significantly more patients in group 1 (81%) versus group 2 (14%; p < 0.001) perceived the opportunity to discuss their imaging findings with a radiologist to be a characteristic of a good radiology consultation. A larger number of patients in group 1 experienced significantly higher bonding and only wanted in the future to be examined in the department with communication (p = 0.001) (93%/75%). Significantly more patients in group 1 regarded the radiology department they attended as being more competent (mean score 4.72/4.09, p < 0.001). CONCLUSION: Direct communication of imaging findings from radiologists to patients after an MRI examination leads to increased confidence in the radiology service and higher bonding between the patient and radiologist. Radiologists who refrain from direct communication have a lower bonding to patients and are assessed to have lower competence from the patient's point of view. KEY POINTS: • Communication between radiologists and patients leads to an increased bonding affinity. • Direct communication leads to increased patient confidence in the radiology service. • Patients perceived discussion with a radiologist of high value.

Free-breathing Sparse Sampling Cine MR Imaging with Iterative Reconstruction for the Assessment of Left Ventricular Function and Mass at 3.0 T.

Purpose To prospectively evaluate the accuracy of left ventricle (LV) analysis with a two-dimensional real-time cine true fast imaging with steady-state precession (trueFISP) magnetic resonance (MR) imaging sequence featuring sparse data sampling with iterative reconstruction (SSIR) performed with and without breath-hold (BH) commands at 3.0 T. Materials and Methods Ten control subjects (mean age, 35 years; range, 25-56 years) and 60 patients scheduled to undergo a routine cardiac examination that included LV analysis (mean age, 58 years; range, 20-86 years) underwent a fully sampled segmented multiple BH cine sequence (standard of reference) and a prototype undersampled SSIR sequence performed during a single BH and during free breathing (non-BH imaging). Quantitative analysis of LV function and mass was performed. Linear regression, Bland-Altman analysis, and paired t testing were performed. Results Similar to the results in control subjects, analysis of the 60 patients showed excellent correlation with the standard of reference for single-BH SSIR (r = 0.93-0.99) and non-BH SSIR (r = 0.92-0.98) for LV ejection fraction (EF), volume, and mass (P < .0001 for all). Irrespective of breath holding, LV end-diastolic mass was overestimated with SSIR (standard of reference: 163.9 g ± 58.9, single-BH SSIR: 178.5 g ± 62.0 [P < .0001], non-BH SSIR: 175.3 g ± 63.7 [P < .0001]); the other parameters were not significantly different (EF: 49.3% ± 11.9 with standard of reference, 48.8% ± 11.8 with single-BH SSIR, 48.8% ± 11 with non-BH SSIR; P = .03 and P = .12, respectively). Bland-Altman analysis showed similar measurement errors for single-BH SSIR and non-BH SSIR when compared with standard of reference measurements for EF, volume, and mass. Conclusion Assessment of LV function with SSIR at 3.0 T is noninferior to the standard of reference irrespective of BH commands. LV mass, however, is overestimated with SSIR. © RSNA, 2016 Online supplemental material is available for this article.

Closing in on the K edge: coronary CT angiography at 100, 80, and 70 kV-initial comparison of a second- versus a third-generation dual-source CT system.

PURPOSE: To prospectively evaluate radiation and contrast medium requirements for performing high-pitch coronary computed tomographic (CT) angiography at 70 kV using a third-generation dual-source CT system in comparison to a second-generation dual-source CT system. MATERIALS AND METHODS: All patients gave informed consent for this institutional review board-approved study. Forty-five patients (median age, 52 years; 27 men) were imaged in high-pitch mode with a third-generation dual-source CT system at 70 kV (n = 15) or with a second-generation dual-source CT system at 80 or 100 kV (n = 15 for each). Tube voltage was based on body mass index: 80 or 70 kV for less than 26 kg/m(2) versus 100 kV for 26-30 kg/m(2). For the 80- and 100-kV protocols, 80 mL of contrast material was injected, versus 45 mL for the 70-kV protocol. Data were reconstructed by using a second-generation iterative reconstruction algorithm for second-generation dual-source CT and a recently introduced third-generation iterative reconstruction algorithm for third-generation dual-source CT. Objective image quality was measured for various regions of interest, and subjective image quality was evaluated with a five-point Likert scale. RESULTS: The signal-to-noise ratio of the coronary CT angiography studies acquired with 70 kV was significantly higher (70 kV: 14.3-17.6 vs 80 kV: 7.1-12.9 vs 100 kV: 9.8-12.9; P < .0497) than those acquired with the other two protocols for all coronary arteries. Qualitative image quality analyses revealed no significant differences between the three CT angiography protocols (median score, 5; P > .05). The mean effective dose was 75% and 108% higher (0.92 mSv ± 0.3 [standard deviation] and 0.78 mSv ± 0.2 vs 0.44 mSv ± 0.1; P < .0001), respectively, for the 80- and 100-kV CT angiography protocols than for the 70-kV CT angiography protocol. CONCLUSION: In nonobese patients, third-generation high-pitch coronary dual-source CT angiography at 70 kV results in robust image quality for studying the coronary arteries, at significantly reduced radiation dose (0.44 mSv) and contrast medium volume (45 mL), thus enabling substantial radiation dose and contrast medium savings as compared with second-generation dual-source CT.

Incidence of transient interruption of contrast (TIC) - A retrospective single-centre analysis in CT pulmonary angiography exams acquired during inspiratory breath-hold with the breathing command: "Please inspire gently!"

OBJECTIVES: To assess the occurrence of transient interruption of contrast (TIC) phenomenon in pulmonary computed tomography angiography (CTPA) exams performed in inspiratory breath-hold after patients were told to inspire gently. METHODS: In this retrospective single-centre study, CTPA exams of 225 consecutive patients scanned on a 16-slice CT scanner system were analysed. A-priori to measurements, exams were screened for inadequate pulmonary artery contrast due to incorrect bolus tracking or failure of i.v. contrast administration. Those exams were excluded. Attenuation values in the thoracic aorta and in the pulmonary trunk were assessed in duplicate measurements (M1 and M2) and the aorto-pulmonary density ratio was calculated. An aorto-pulmonary ratio > 1 with still contrast inflow being visible within the superior vena cava was defined as TIC. RESULTS: 3 patients were excluded due to incorrect bolus tracking. Final analysis was performed in 222 patients (mean age 65 ± 19 years, range 18 to 99 years). Mean density in the pulmonary trunk was 275±17 HU, in the aorta 208 ± 15 HU. Mean aorto-pulmonary ratio was 0.81± 0.29. 48 patients (21.6%) had an aorto-pulmonary ratio >1. Correlation of mean aorto-pulmonary ratio and age was: -0.213 (p = 0.001). Age was not significantly different for an aorto-pulmonary ratio >1 vs. ≤1 (p = 0.122). Both in M1 and M2, 33/222 patients presented with absolute HU values of < 200 HU within the pulmonary artery. In M1 measurements, 24 of these 33 patients (72%) fulfilled TIC criteria (M2: 25/33 patients (75%)). CONCLUSIONS: TIC is a common phenomenon in CTPA studies with inspiratory breath-hold commands after patients were told to inspire gently with an incidence of 22% in our retrospective cohort. Occurrence of TIC shows a significant negative correlation with increasing age and disproportionately often occurs in patients with lower absolute contrast density values within their pulmonary arteries.

Variability and Reproducibility of 3rd-generation dual-source dynamic volume perfusion CT Parameters in Comparison to MR-perfusion Parameters in Rectal Cancer.

To compare in patients with untreated rectal cancer quantitative perfusion parameters calculated from 3rd-generation dual-source dynamic volume perfusion CT (dVPCT) with 3-Tesla-MR-perfusion with regard to data variability and tumour differentiation. In MR-perfusion, plasma flow (PF), plasma volume (PV) and mean transit time (MTT) were assessed in two measurements (M1 and M2) by the same reader. In dVPCT, blood flow (BF), blood volume (BV), MTT and permeability (PERM) were assessed respectively. CT dose values were calculated. 20 patients (60 ± 13 years) were analysed. Intra-individual and intra-reader variability of duplicate MR-perfusion measurements was higher compared to duplicate dVPCT measurements. dVPCT-derived BF, BV and PERM could differentiate between tumour and normal rectal wall (significance level for M1 and M2, respectively, regarding BF: p < 0.0001*/0.0001*; BV: p < 0.0001*/0.0001*; MTT: p = 0.93/0.39; PERM: p < 0.0001*/0.0001*), with MR-perfusion this was true for PF and PV (p-values M1/M2 for PF: p = 0.04*/0.01*; PV: p = 0.002*/0.003*; MTT: p = 0.70/0.27*). Mean effective dose of CT-staging incl. dVPCT was 29 ± 6 mSv (20 ± 5 mSv for dVPCT alone). In conclusion, dVPCT has a lower data variability than MR-perfusion while both dVPCT and MR-perfusion could differentiate tumour tissue from normal rectal wall. With 3rd-generation dual-source CT dVPCT could be included in a standard CT-staging without exceeding national dose reference values.

Imaging of Patients with Complex Hemodialysis Arterio-Venous Fistulas using Time-Resolved Dynamic CT Angiography: Comparison with Duplex Ultrasound.

To evaluate the feasibility and potential on therapy management of time-resolved dynamic computed tomography angiography (dCTA) in patients with forearm arterio-venous fistula (AVF)/arterio-venous grafts (AVG). Thirty-five patients with complex failing forearm AVF/AVGs were examined with ultrasound and a dCTA protocol. Diagnosis and therapy management was evaluated versus duplex ultrasound (DUS) in three different readouts: 1. all dCTA datasets; 2. one arterial phase of the dCTA dataset; 3. one arterial and one venous dataset out of the dCTA dataset. All reads were performed >30 days apart from each other. Using all data of the dCTA examination, 20 patients were classified as having a stenosis >50%, 12 high-shunt flow, 11 partial thrombosis, 5 venous aneurysms and 5 complete thrombosis of their AVF/AVG grafts. This lead to 13 additional pathologic findings not visible on DUS and reclassification as normal in one patient with suspected AVF stenosis and complete thrombus on DUS. These additional findings lead to a direct change of therapeutic management in 8 patients. Compared to readout 1 (53 pathologies), readout number 2 and 3 revealed only 33 and 41 pathologies, respectively. dCTA provides additional information, improving diagnostic confidence and leading to changes in therapy management when compared to DUS alone.

Comparison of perfusion models for quantitative T1 weighted DCE-MRI of rectal cancer.

In this work, the two compartment exchange model and two compartment uptake model were applied to obtain quantitative perfusion parameters in rectum carcinoma and the results were compared to those obtained by the deconvolution algorithm. Eighteen patients with newly diagnosed rectal carcinoma underwent 3 T MRI of the pelvis including a T1 weighted dynamic contrastenhanced (DCE) protocol before treatment. Mean values for Plasma Flow (PF), Plasma Volume (PV) and Mean Transit Time (MTT) were obtained for all three approaches and visualized in parameter cards. For the two compartment models, Akaike Information Criterion (AIC) and [Formula: see text] were calculated. Perfusion parameters determined with the compartment models show results in accordance with previous studies focusing on rectal cancer DCE-CT (PF2CX = 68 ± 44 ml/100 ml/min, PF2CU = 55 ± 36 ml/100 ml/min) with similar fit quality (AIC:169 ± 81/179 ± 77, [Formula: see text]:10 ± 12/9 ± 10). Values for PF are overestimated whereas PV and MTT are underestimated compared to results of the deconvolution algorithm. Significant differences were found among all models for perfusion parameters as well as between the AIC and [Formula: see text] values. Quantitative perfusion parameters are dependent on the chosen tracer kinetic model. According to the obtained parameters, all approaches seem capable of providing quantitative perfusion values in DCE-MRI of rectal cancer.

Radiation Dose Comparison Between 70 kVp and 100 kVp With Spectral Beam Shaping for Non-Contrast-Enhanced Pediatric Chest Computed Tomography: A Prospective Randomized Controlled Study.

OBJECTIVE: The aim of this prospective randomized controlled study was to compare 2 techniques for radiation dose reduction in non-contrast-enhanced pediatric chest computed tomography (CT): low peak kilovoltage imaging at 70 kVp and spectral beam shaping at 100 kVp using a dedicated tin filter (100-kVp Sn). MATERIALS AND METHODS: All chest CT examinations were performed on a third-generation dual-source CT system (SOMATOM Force; Siemens Healthineers, Germany). Fifty children (mean age, 6.8 ± 5.1 years) were examined using the 100-kVp Sn protocol, whereas 25 children received the 70-kVp protocol (mean age, 5.7 ± 5.2 years; 2:1 randomization scheme). Radiation metrics and organ doses were compared between acquisition techniques using commercially available radiation dose analysis software (Radimetrics Inc, Bayer AG, Toronto, Ontario, Canada). Objective image quality, expressed by signal-to-noise ratio and subjective image quality based on a 4-point scale (1, best; 4, worst image quality), were compared. RESULTS: Volume CT dose index and size-specific dose estimate were significantly lower in the 100-kVp Sn group compared with the 70-kVp group (0.19 ± 0.12 mGy vs 0.81 ± 0.70 mGy and 0.34 ± 0.13 mGy vs 1.48 ± 1.11 mGy; P < 0.0001 for both). Accordingly, mean effective dose was significantly lower for the 100-kVp Sn examinations (0.21 ± 0.10 mSv) compared with the 70-kVp examinations (0.83 ± 0.49 mSv; P < 0.0001). Calculated organ doses were also significantly lower using the 100-kVp Sn protocol when compared with the 70-kVp protocol; for example, breast dose was reduced by a factor of 4.3. Signal-to-noise ratio was slightly superior for 70-kVp images while lung image quality of the 100-kVp Sn protocol was preferred in subjective analysis (P = 0.0004). CONCLUSIONS: Pediatric chest CT performed at 100 kVp with an additional tin filter for spectral shaping significantly reduces radiation dose when compared with low peak kilovoltage imaging at 70 kVp and therefore should be preferred in non-contrast-enhanced pediatric chest CT examinations, particularly (given the improved subjective image quality) when the main focus is evaluation of the lung parenchyma.

Radiation Dose Levels of Retrospectively ECG-Gated Coronary CT Angiography Using 70-kVp Tube Voltage in Patients with High or Irregular Heart Rates.

RATIONALE AND OBJECTIVES: Despite ongoing technical refinements, coronary computed tomography angiography (cCTA) remains challenging in its diagnostic value by electrocardiographic (ECG) misregistration and motion artifacts, which commonly occur in patients with atrial fibrillation and high or irregular heart rates. The aim of this study was to evaluate the radiation dose and the number of inconclusive coronary segments at cCTA using retrospective ECG gating at 100 and 70 kV. MATERIALS AND METHODS: With institutional review board approval, 154 patients (median age 54 years, 98 men) with high or irregular heart rate prospectively underwent retrospectively ECG-gated cCTA without tube current modulation on a third-generation dual-source computed tomography (DSCT) system at 70 kV (n = 103) or on a second-generation DSCT system at 100 kV (n = 51). Images were reconstructed in best diastolic phase (BDP), best systolic phase (BSP), and in all phases (APs) at 10% intervals across the R-R cycle. Objective and subjective image qualities were evaluated as well as the presence of motion artifacts with the three different reconstruction approaches. RESULTS: The mean heart rate was 93 ± 16 bpm. The mean effective radiation dose was 4.5 mSv for 70 kV compared to 8.4 mSv for 100 kV (P < 0.05). At BDP reconstruction, 71% (n = 110) of the patients showed motion artifacts in one or more coronary segments. At BSP reconstruction, the number of patients with motion artifacts decreased to 37% (n = 57). In contrast, if images were reconstructed with the AP approach, all vessels and coronary segments were evaluable with both cCTA protocols. CONCLUSIONS: Retrospectively ECG-gated cCTA at 70 kV results in 52% decreased radiation dose. Further using the AP algorithm allowed for diagnostic evaluation of all coronary segments for stenosis, in contrast to BDP or BSP phase alone.

Spectral optimization of iodine-enhanced CT: Quantifying the effect of tube voltage on image quality and radiation exposure determined at an anthropomorphic phantom.

PURPOSE: To provide an experimental basis for spectral optimization of iodine-enhanced CT by a quantitative analysis of image quality and radiation dose characteristics consistently measured for a large variety of scan settings at an anthropomorphic phantom. METHODS: CT imaging and thermoluminescent dosimetry were performed at an anthropomorphic whole-body phantom with iodine inserts for different tube voltages (U, 70-140kV) and current-time products (Q, 60-300mAs). For all U-Q combinations, the iodine contrast (C), the noise level (N) and, from these, the contrast-to-noise ratio (CNR) of reconstructed CT images were determined and parameterized as a function of U, Q or the measured absorbed dose (D). Finally, two characteristic curves were derived that give the relative increase of CNR at constant D and the relative decrease of D at constant CNR when lowering U. RESULTS: Lowering U affects the measured CNR only slightly but markedly reduces D. For example, reducing U from 120kV to 70kV increases the CNR at constant D by a factor of nearly 1.8 or, alternatively, reduces D at constant CNR by a factor of nearly 5. CONCLUSION: Spectral optimization by lowering U is an effective approach to attain the necessary CNR for a specific diagnostic task at hand while at the same time reducing radiation exposure as far as practically achievable. The characteristic curves derived in this study from extensive measurements at a reference 'person' can support CT users in an easy-to-use manner to select an appropriate voltage for various clinical scenarios.

Sparse Reconstruction Techniques in Magnetic Resonance Imaging: Methods, Applications, and Challenges to Clinical Adoption.

The family of sparse reconstruction techniques, including the recently introduced compressed sensing framework, has been extensively explored to reduce scan times in magnetic resonance imaging (MRI). While there are many different methods that fall under the general umbrella of sparse reconstructions, they all rely on the idea that a priori information about the sparsity of MR images can be used to reconstruct full images from undersampled data. This review describes the basic ideas behind sparse reconstruction techniques, how they could be applied to improve MRI, and the open challenges to their general adoption in a clinical setting. The fundamental principles underlying different classes of sparse reconstructions techniques are examined, and the requirements that each make on the undersampled data outlined. Applications that could potentially benefit from the accelerations that sparse reconstructions could provide are described, and clinical studies using sparse reconstructions reviewed. Lastly, technical and clinical challenges to widespread implementation of sparse reconstruction techniques, including optimization, reconstruction times, artifact appearance, and comparison with current gold standards, are discussed.

Rapid functional cardiac imaging after gadolinium injection: Evaluation of a highly accelerated sequence with sparse data sampling and iterative reconstruction.

To generate a patient-friendly, time-efficient cardiac MRI examination protocol, a highly accelerated real-time CINE MR sequence (SSIR) was acquired in the idle time in between contrast injection and late gadolinium enhancement phase. 20 consecutive patients underwent a cardiac MRI examination including a multi-breath-hold sequence as gold standard (Ref) as well as SSIR sequences with (SSIR-BH) and without breath-hold (SSIR-nonBH). SSIR sequences were acquired 4 minutes after gadolinium injection. Right- (RV) and left-ventricular (LV) volumetric functional parameters were evaluated and compared between Ref and SSIR sequences. Despite reduced contrast between myocardium and intra-ventricular blood, volumetric as well as regional wall movement assessment revealed high agreement between both SSIR sequences and Ref. Excellent correlation and narrow limits of agreements were found for both SSIR-BH and SSIR-nonBH when compared to Ref for both LV (mean LV ejection fraction [EF] Ref: 52.8 ± 12.6%, SSIR-BH 52.3 ± 12.9%, SSIR-nonBH 52.5 ± 12.6%) and RV (mean RV EF Ref: 52.7 ± 9.4%, SSIR-BH 52.0 ± 8.1%, SSIR-nonBH 52.2 ± 9.3%) analyses. Even when acquired in the idle time in between gadolinium injection and LGE acquisition, the highly accelerated SSIR sequence delivers accurate volumetric and regional wall movement information. It thus seems ideal for very time-efficient and robust cardiac MR imaging protocols.

Right Ventricular Imaging in 25 Seconds: Evaluating the Use of Sparse Sampling CINE With Iterative Reconstruction for Volumetric Analysis of the Right Ventricle.

OBJECTIVE: The aim of this study was to prospectively evaluate a 2-dimensional real-time CINE TrueFISP magnetic resonance sequence using sparse data sampling with iterative reconstruction (SSIR) for right ventricular (RV) volumetry in comparison to the criterion standard (CS) acquired at 3 T. MATERIALS AND METHODS: Ten healthy controls and 20 consecutive patients scheduled for cardiac magnetic resonance imaging on a 3-T system (Magnetom Skyra; Siemens Healthcare Sector, Germany) underwent undersampled SSIR sequences with a single breath-hold (BH) as well as with shallow free breathing (NBH) and a fully sampled multi-BH sequence as CS. Right ventricular volumetry was performed with dedicated cardiac magnetic resonance software (cvi42; Circle Cardiovascular Imaging Inc, Calgary, Alberta, Canada). Agreement of SSIR with and without BH and CS for RV functional parameters (end-systolic volume [RVESV], end-diastolic volume [RVEDV], stroke volume [RVSV], and ejection fraction [RVEF]) were assessed with Bland-Altman analysis and paired t test. RESULTS: Analysis of the 30 individuals (19 male; 48 ± 14 years) revealed no significant differences when comparing CS and BH measurements for RVEDV (153.7 vs 153.6 mL, P = 0.96), RVESV (71.6 vs 72.1 mL, P = 0.78), RVSV (82.0 vs 81.6 mL, P = 0.65), and RVEF (54.9% vs 54.2%, P = 0.19). Similar results were shown when comparing CS and NBH measurements for RVEDV (153.7 vs 152.2 mL, P = 0.34), RVESV (71.6 vs 72.8 mL, P = 0.30), RVSV (82.0 vs 81.0 mL, P = 0.46), and RVEF (54.9 vs 54.4, P = 0.48). Time taken for acquisition was 350 seconds for the CS, 34 seconds for BH, and 25 seconds for NBH measurements. Additional time required for iterative reconstruction was 2 minutes and 30 seconds for the sparse sampled data sets. CONCLUSIONS: Our results demonstrate that accurate RV volumetry with SSIR data at 3 T is feasible in clinical routine within 25 seconds even without BH, which is of particular importance in patients with dyspnea.

Ultra-high pitch chest computed tomography at 70 kVp tube voltage in an anthropomorphic pediatric phantom and non-sedated pediatric patients: Initial experience with 3rd generation dual-source CT.

PURPOSE: Minimizing radiation dose while at the same time preserving image quality is of particular importance in pediatric chest CT. Very recently, CT imaging with a tube voltage of 70 kVp has become clinically available. However, image noise is inversely proportional to the tube voltage. We aimed to investigate radiation dose and image quality of pediatric chest CT performed at 70 kVp in an anthropomorphic pediatric phantom as well as in clinical patients. METHODS AND MATERIALS: An anthropomorphic pediatric phantom, which resembles a one-year-old child in physiognomy, was scanned on the 3rd generation dual-source CT (DSCT) system at 70 kVp and 80 kVp and a fixed ultra low tube-current of 8 mAs to solely evaluate the impact of lowering tube voltage. After the phantom measurements, 18 pediatric patients (mean 29.5 months; range 1-91 months; 21 examinations) underwent 3.2 high-pitch chest CT on the same DSCT system at 70 kVp tube voltage without any sedation. Radiation dose and presence of motion artifacts was compared to a retrospectively identified patient cohort examined at 80 kVp on a 16-slice single-source-CT (SSCT; n=15; 14/15 with sedation; mean 30.7 months; range 0-96 months; pitch=1.5) or on a 2nd generation DSCT without any sedation (n=6; mean 32.8 months; range 4-61 months; pitch=3.2). RESULTS: Radiation dose in the phantom scans was reduced by approximately 40% when using a tube voltage of 70 kVp instead of 80 kVp. In the pediatric patient group examined at 70 kVp age-specific effective dose (ED; mean 0.5±0.2 mSv) was significantly lower when compared to the retrospective cohort scanned at 80 kVp on the 16-slice-SSCT (mean ED: 1.0±0.3 mSv; p<0.0001) and also considerably lower when compared to the cohort scanned at 80 kVp on the 2nd generation DSCT (mean ED: 0.9±0.5 mSv). None of the prospective, sedation-free CT examinations showed any motion artifacts whereas 13/15 examinations of the retrospective patient cohort scanned at 80 kVp with a pitch of 1.5 showed motion artifacts. CONCLUSION: 3.2 high-pitch chest CT performed with 70 kVp significantly reduces radiation dose when compared to 80 kVp while at the same time provides good image quality without any motion artifacts even without sedation.

Carotid dual-energy CT angiography: Evaluation of low keV calculated monoenergetic datasets by means of a frequency-split approach for noise reduction at low keV levels.

BACKGROUND AND PURPOSE: Calculated monoenergetic ultra-low keV datasets did not lead to improved contrast-to-noise ratio (CNR) due to the dramatic increase in image noise. The aim of the present study was to evaluate the objective image quality of ultra-low keV monoenergetic images (MEIs) calculated from carotid DECT angiography data with a new monoenergetic imaging algorithm using a frequency-split technique. MATERIALS AND METHODS: 20 patients (12 male; mean age 53±17 years) were retrospectively analyzed. MEIs from 40 to 120 keV were reconstructed using the monoenergetic split frequency approach (MFSA). Additionally MEIs were reconstructed for 40 and 50 keV using a conventional monoenergetic (CM) software application. Signal intensity, noise, signal-to-noise ratio (SNR) and CNR were assessed in the basilar, common, internal carotid arteries. RESULTS: Ultra-low keV MEIs at 40 keV and 50 keV demonstrated highest vessel attenuation, significantly greater than those of the polyenergetic images (PEI) (all p-values <0.05). The highest SNR level and CNR level was found at 40 keV and 50 keV (all p-values <0.05). MEIs with MFSA showed significantly lower noise levels than those processed with CM (all p-values <0.05) and no significant differences in vessel attenuation (p>0.05). Thus MEIs with MFSA showed significantly higher SNR and CNR compared to MEIs with CM. CONCLUSION: Combining the lower spatial frequency stack for contrast at low keV levels with the high spatial frequency stack for noise at high keV levels (frequency-split technique) leads to improved image quality of ultra-low keV monoenergetic DECT datasets when compared to previous monoenergetic reconstruction techniques without the frequency-split technique.

Dual-energy snap-shot perfusion CT in suspect pulmonary nodules and masses and for lung cancer staging.

Dual energy computed tomography (DECT) has proven its clinical usefulness for improved tissue characterization within the past years. In thoracic oncology, DECT can be used to differentiate between benign and malignant pulmonary nodules and masses. In patients with known lung cancer, DECT can add incremental functional information to staging scans, therapeutic response evaluation, as well as to the assessment of lung function. This review aims to give an overview on the current clinical utilities of DECT of the chest, its multiple post-processing applications and dose saving options. Furthermore, this review highlights promising applications of DECT that merit implementation in future clinical routine.

Unenhanced third-generation dual-source chest CT using a tin filter for spectral shaping at 100kVp.

OBJECTIVE: To prospectively investigate image quality and radiation dose of 100kVp spectral shaping chest CT using a dedicated tin filter on a 3rd generation dual-source CT (DSCT) in comparison to standard 100kVp chest CT. METHODS: Sixty patients referred for a non-contrast chest on a 3rd generation DSCT were prospectively included and examined at 100kVp with a dedicated tin filter. These patients were retrospectively matched with patients that were examined on a 2nd generation DSCT at 100kVp without tin filter. Objective and subjective image quality was assessed in various anatomic regions and radiation dose was compared. RESULTS: Radiation dose was decreased by 90% using the tin filter (3.0 vs 0.32mSv). Soft tissue attenuation and image noise was not statistically different for both examination techniques (p>0.05), however image noise was found to be significantly higher in the trachea when using the additional tin filter (p=0.002). SNR was found to be statistically similar in pulmonary tissue, significantly lower when measured in air and significantly higher in the aorta for the scans on the 3rd generation DSCT. Subjective image quality with regard to overall quality and image noise and sharpness was not statistically significantly different (p>0.05). CONCLUSION: 100kVp spectral shaping chest CT by means of a tube-based tin-filter on a 3rd generation DSCT allows 90% dose reduction when compared to 100kVp chest CT on a 2nd generation DSCT without spectral shaping.

Where do we stand? Functional imaging in acute and chronic pulmonary embolism with state-of-the-art CT.

Nowadays, CT pulmonary angiography (CTPA) is the diagnostic imaging modality of choice for acute and chronic pulmonary embolism (PE) in order to assess vascular anatomy and parenchymal morphology. Over the past decade, several prognostic CTPA markers associated with an increased risk of adverse clinical events and in-hospital mortality have been evaluated, namely cardiac chamber dimensions, obstruction scores, and visualization of iodinated contrast material in the lung parenchyma by dual-energy (DE) CTPA. This article reviews the current status and potential prognostic advantages of CTPA or DE CTPA with its recent developments for accessing right ventricular dysfunction and the assessment of first pass lung perfusion with DE CTPA in the diagnosis of acute and chronic PE.

Mitral annular plane systolic excursion is an easy tool for fibrosis detection by late gadolinium enhancement cardiovascular magnetic resonance imaging in patients with hypertrophic cardiomyopathy.

BACKGROUND: Hypertrophic cardiomyopathy (HCM) causes various degrees of fibrosis resulting in left ventricular function impairment, which can be measured using mitral annular plane systolic excursion (MAPSE). AIMS: To determine the values for septal, lateral and average MAPSE using cardiovascular magnetic resonance (CMR) in healthy controls and patients with HCM; and to investigate whether MAPSE correlated with the extent of fibrosis. METHODS: Patients with HCM and healthy controls underwent CMR. RESULTS: In 50 healthy controls, septal and lateral MAPSE were comparable and showed excellent intra- and inter-observer reliability. Patients with HCM had significantly reduced septal, lateral and average MAPSE compared to healthy controls. Furthermore, in patients with HCM, septal MAPSE measurements were significantly reduced compared to lateral ones. Correspondingly, the septal myocardial segments showed significantly more late gadolinium enhancement (LGE) than lateral ones. No significant differences were found between echocardiographic and CMR MAPSE measurements in healthy controls and patients with HCM. Patients who suffered a major adverse cardiac event or stroke revealed a significantly reduced MAPSE and a significantly greater LGE extent compared to event-free patients with HCM. CONCLUSIONS: MAPSE measurement using CMR is feasible, reproducible and comparable to echocardiography in healthy controls and patients with HCM. The asymmetric and mainly septal distribution of myocardial hypertrophy and fibrosis detected by LGE in patients with HCM was reflected by significantly reduced septal versus lateral MAPSE. Therefore, reduced MAPSE seems to be an easily determinable marker of fibrosis accumulation leading to left ventricular mechanical dysfunction and also seems to have a prognostic implication.