Deep learning-based scan range optimization can reduce radiation exposure in coronary CT angiography.

OBJECTIVES: Cardiac computed tomography (CT) is essential in diagnosing coronary heart disease. However, a disadvantage is the associated radiation exposure to the patient which depends in part on the scan range. This study aimed to develop a deep neural network to optimize the delimitation of scan ranges in CT localizers to reduce the radiation dose. METHODS: On a retrospective training cohort of 1507 CT localizers randomly selected from calcium scoring and angiography scans and acquired between 2010 and 2017, optimized scan ranges were delimited by two radiologists in consensus. A neural network was trained to reproduce the scan ranges and was tested on two randomly selected and independent validation cohorts: an internal cohort of 233 CT localizers (January 2018-June 2020) and an external cohort from a nearby hospital of 298 CT localizers (July 2020-December 2020). Localizers where a bypass surgery was visible were excluded. The effective radiation dose to the patient was simulated using a Monte Carlo simulation. Scan ranges of radiographers, radiologists, and the network were compared using an equivalence test; likewise, the reduction in effective dose was tested using a superior test. RESULTS: The network replicated the radiologists' scan ranges with a Dice score of 96.5 ± 0.02 (p < 0.001, indicating equivalence). The generated scan ranges resulted in an effective dose reduction of 10.0% (p = 0.002) in the internal cohort and 12.6% (p < 0.001) in the external cohort compared to the scan ranges delimited by radiographers in clinical routine. CONCLUSIONS: Automatic delimitation of the scan range can result in a radiation dose reduction to the patient. CLINICAL RELEVANCE STATEMENT: Fully automated delimitation of the scan range using a deep neural network enables a significant reduction in radiation exposure during CT coronary angiography compared to manual examination planning. It can also reduce the workload of the radiographers. KEY POINTS: • Scan range delimitation for coronary computed tomography angiography could be performed with high accuracy by a deep neural network. • Automated scan ranges showed a high agreement of 96.5% with the scan ranges of radiologists. • Using a Monte Carlo simulation, automated scan ranges reduced the effective dose to the patient by up to 12.6% (0.9 mSv) compared to the scan ranges of radiographers in clinical routine.

Patterns of cardiac involvement in different muscular dystrophies assessed by magnetic resonance imaging.

BACKGROUND: In muscular dystrophies, it is not only skeletal muscles that can be affected, but also the myocardium. This cardiac involvement can represent a major cause of morbidity and mortality. PURPOSE: To investigate cardiac involvement in Duchenne (DMD), Becker (BMD), and limb girdle muscular dystrophy (LGMD) patients, and carriers of DMD/BMD by cardiac magnetic resonance (CMR) imaging and to search for differences in the pattern of cardiac involvement. MATERIAL AND METHODS: All patients with genetically or histologically proven DMD, BMD, and LGMD, or confirmed carriers of DMD/BMD who had undergone CMR at our clinic between January 2008 and November 2018 were retrospectively included and re-evaluated for regional and global left ventricular function, increased trabecularization, and late enhancement. RESULTS: A total of 26 DMD, 10 BMD, 11 LGMD, and seven DMD/BMD carriers were included. Only one carrier of DMD presented with normal CMR results; all other participants showed cardiac abnormalities. Regional wall motion abnormalities (RWMA; prevalence in LGMD patients: 55%) and late enhancement (prevalence in LGMD patients: 82%) were frequent. RWMA were accentuated basal inferolateral in DMD/BMD carriers, while in LGMD they were accentuated apical. In all groups late enhancement was located mainly subepicardial/midmyocardial with a basal inferolateral accentuation. Apart from the different RWMA distribution, no further group-specific differences were found. CONCLUSION: We found a high rate of cardiac involvement not only in DMD/BMD, but also in LGMD and DMD/BMD carriers with a different RWMA accentuation (apical in LGMD and basal inferolateral in DMD/BMD) as a single group-specific difference.

Pediatric age estimation from radiographs of the knee using deep learning.

OBJECTIVES: Age estimation, especially in pediatric patients, is regularly used in different contexts ranging from forensic over medicolegal to clinical applications. A deep neural network has been developed to automatically estimate chronological age from knee radiographs in pediatric patients. METHODS: In this retrospective study, 3816 radiographs of the knee from pediatric patients from a German population (acquired between January 2008 and December 2018) were collected to train a neural network. The network was trained to predict chronological age from the knee radiographs and was evaluated on an independent validation cohort of 423 radiographs (acquired between January 2019 and December 2020) and on an external validation cohort of 197 radiographs. RESULTS: The model showed a mean absolute error of 0.86 ± 0.72 years and 0.9 ± 0.71 years on the internal and external validation cohorts, respectively. Separating age classes (< 14 years from ≥ 14 years and < 18 years from ≥ 18 years) showed AUCs between 0.94 and 0.98. CONCLUSIONS: The chronological age of pediatric patients can be estimated with good accuracy from radiographs of the knee using a deep neural network. KEY POINTS: • Radiographs of the knee can be used for age estimations in pediatric patients using a standard deep neural network. • The network showed a mean absolute error of 0.86 ± 0.72 years in an internal validation cohort and of 0.9 ± 0.71 years in an external validation cohort. • The network can be used to separate the age classes < 14 years from ≥ 14 years with an AUC of 0.97 and < 18 years from ≥ 18 years with an AUC of 0.94.

Diagnostic reference levels for chest computed tomography in children as a function of patient size.

BACKGROUND: Radiation exposures from computed tomography (CT) in children are inadequately studied. Diagnostic reference levels (DRLs) can help optimise radiation doses. OBJECTIVE: To determine local DRLs for paediatric chest CT performed mainly on modern dual-source, multi-slice CT scanners as a function of patient size. MATERIALS AND METHODS: Five hundred thirty-eight chest CT scans in 345 children under 15 years (y) of age (median age: 8 y, interquartile range [IQR]: 4-13 y) performed on four different CT scanners (38% on third-generation and 43% on second-generation dual-source CT) between November 2013 and December 2020 were retrospectively analysed. Examinations were grouped by water-equivalent diameter as a measure of patient size. DRLs for volume CT dose index (CTDIvol) and dose-length product (DLP) were determined for six different patient sizes and compared to national and European DRLs. RESULTS: The DRLs for CTDIvol and DLP are determined for each patient size group as a function of water-equivalent diameter as follows: (I) < 13 cm (n = 22; median: age 7 months): 0.4 mGy, 7 mGy·cm; (II) 13 cm to less than 17 cm (n = 151; median: age 3 y): 1.2 mGy, 25 mGy·cm; (III) 17 cm to less than 21 cm (n = 211; median: age 8 y): 1.7 mGy, 44 mGy·cm; (IV) 21 cm to less than 25 cm (n = 97; median: age 14 y): 3.0 mGy, 88 mGy·cm; (V) 25 cm to less than 29 cm (n = 42; median: age 14 y): 4.5 mGy, 135 mGy·cm; (VI) ≥ 29 cm (n = 15; median: age 14 y): 8.0 mGy, 241 mGy·cm. Compared with corresponding age and weight groups, our size-based DRLs for DLP are 54% to 71% lower than national and 23% to 85% lower than European DRLs. CONCLUSION: We developed DRLs for paediatric chest CT as a function of patient size with substantially lower values than national and European DRLs. Precise knowledge of size-based DRLs may assist other institutions in further dose optimisation in children.

QRS-T angle in patients with Hypertrophic Cardiomyopathy - A comparison with Cardiac Magnetic Resonance Imaging.

Objective: We sought to investigate the possible association of a wide QRS-T angle on the surface EKG and myocardial fibrosis on contrast-enhanced cardiovascular magnetic (CMR) imaging in patients with hypertrophic cardiomyopathy (HCM). Background: Risk stratification in HCM patients is challenging. Late gadolinium enhancement (LGE) visualizes myocardial fibrosis with unique spatial resolution and is a strong and independent prognosticator in these patients. The QRS-T angle from the surface EKG is a promising prognostic marker in various cardiac pathologies. Methods: 70 patients with HCM obtained a standardized digital 12-lead EKG for the calculation of the QRS-T angle and underwent comprehensive CMR imaging for visualization of fibrosis by LGE. Patients were divided into groups according to the absence or presence of fibrosis on CMR. Results: 43 of 70 patients with HCM showed LGE on CMR following contrast administration. HCM patients with LGE (fibrosis) had wider QRS-T angles as compared to the patient group without LGE (100±54 vs. 46±31; <0.001). A QRS-T angle of 90 degrees or more was a strong predictor (OR 32.84, CI 4.08-264.47; p <0.001) of HCM with LGE. Conclusion: There is a strong association of a wide QRS-T angle and myocardial fibrosis in patients with HCM.

Third generation dual-energy CT with 80/150 Sn kV for head and neck tumor imaging.

BACKGROUND: Dual-energy CT (DECT) provides additional image datasets which enable improved tumor delineation or reduction of beam hardening artifacts in patients with head and neck squamous cell carcinoma (SCC). PURPOSE: To assess radiation dose and image quality of third-generation DECT of the head and neck in comparison to single-energy CT (SECT). MATERIAL AND METHODS: Thirty patients with SCC who underwent both SECT (reference tube voltage 120 kVp) and DECT (80/150 Sn kVp) of the head and neck region for staging were retrospectively selected. Attenuation measurements of the sternomastoid muscle, internal jugular vein, submandibular gland and tongue were compared. Image noise was assessed at five anatomic levels. Subjective image quality was evaluated by two radiologists in consensus. RESULTS: CTDIvol was 55% lower with DECT (4.2 vs. 9.3 mGy; P = 0.002). Median image noise was equal or lower in DECT at all levels (nasopharynx: 3.9 vs. 5.8, P < 0.0001; floor of mouth: 3.6 vs. 4.5, P = 0.0002; arytenoids: 3.6 vs. 3.1, P = 0.096; lower thyroid: 4.4 vs. 5.7, P = 0.002; arch of aorta: 5.6 vs. 6.5, P = 0.001). Attenuation was significantly lower in DECT ( P < 0.05). Subjective image analysis revealed that DECT is equal or superior to SECT with regard to overall image quality (nasopharynx: 5 vs. 5, P = 1; floor of mouth: 5 vs. 5, P = 0.0041; arytenoids: 5 vs. 5, P = 0.6; lower thyroid: 5 vs. 3, P < 0.0001; arch of aorta: 5 vs. 4, P < 0.0001). CONCLUSION: Head and neck imaging with third-generation DECT can reduce radiation dose by half compared to SECT, while maintaining excellent image quality.

Abdominopelvic 1.5-T and 3.0-T MR Imaging in Healthy Volunteers: Relationship to Formation of DNA Double-Strand Breaks.

Purpose To investigate the relationship between abdominopelvic magnetic resonance (MR) imaging and formation of DNA double-strand breaks (DSBs) in peripheral blood lymphocytes among a cohort of healthy volunteers. Materials and Methods Blood samples were obtained from 40 healthy volunteers (23 women and 17 men; mean age, 27.2 years [range, 21-37 years]) directly before and 5 and 30 minutes after abdominopelvic MR imaging performed at 1.5 T (n = 20) or 3.0 T (n = 20). The number of DNA DSBs in isolated blood lymphocytes was quantified after indirect immunofluorescent staining of a generally accepted DSB marker, γ-H2AX, by means of high-throughput automated microscopy. As a positive control of DSB induction, blood lymphocytes from six volunteers were irradiated in vitro with x-rays at a dose of 1 Gy (70-90 keV). Statistical analysis was performed by using a Friedman test. Results No significant alteration in the frequency of DNA DSB induction was observed after MR imaging (before imaging: 0.22 foci per cell, interquartile range [IQR] = 0.54 foci per cell; 5 minutes after MR imaging: 0.08 foci per cell, IQR = 0.39 foci per cell; 30 minutes after MR imaging: 0.09 foci per cell, IQR = 0.63 foci per cell; P = .057). In vitro radiation of lymphocytes with 1 Gy led to a significant increase in DSBs (0.22 vs 3.43 foci per cell; P = .0312). The frequency of DSBs did not differ between imaging at 1.5 T and at 3.0 T (5 minutes after MR imaging: 0.23 vs 0.06 foci per cell, respectively [P = .57]; 30 minutes after MR imaging: 0.12 vs 0.08 foci per cell [P = .76]). Conclusion Abdominopelvic MR imaging performed at 1.5 T or 3.0 T does not affect the formation of DNA DSBs in peripheral blood lymphocytes.

Radiation exposure during CT-guided biopsies: recent CT machines provide markedly lower doses.

OBJECTIVES: To examine radiation dose levels of CT-guided interventional procedures of chest, abdomen, spine and extremities on different CT-scanner generations at a large multicentre institute. MATERIALS AND METHODS: 1,219 CT-guided interventional biopsies of different organ regions ((A) abdomen (n=516), (B) chest (n=528), (C) spine (n=134) and (D) extremities (n=41)) on different CT-scanners ((I) SOMATOM-Definition-AS+, (II) Volume-Zoom, (III) Emotion6) were included from 2013-2016. Important CT-parameters and standard dose-descriptors were retrospectively examined. Additionally, effective dose and organ doses were calculated using Monte-Carlo simulation, following ICRP103. RESULTS: Overall, radiation doses for CT interventions are highly dependent on CT-scanner generation: the newer the CT scanner, the lower the radiation dose imparted to patients. Mean effective doses for each of four procedures on available scanners are: (A) (I) 9.3mSv versus (II) 13.9mSv (B) (I) 7.3mSv versus (III) 11.4mSv (C) (I) 6.3mSv versus (II) 7.4mSv (D) (I) 4.3mSv versus (II) 10.8mSv. Standard dose descriptors [standard deviation (SD); CT dose indexvol (CTDIvol); dose-length product (DLPbody); size-specific dose estimate (SSDE)] were also compared. CONCLUSION: Effective dose, organ doses and SSDE for various CT-guided interventional biopsies on different CT-scanner generations following recommendations of the ICRP103 are provided. New CT-scanner generations involve markedly lower radiation doses versus older devices. KEY POINTS: • Effective dose, organ dose and SSDE are provided for CT-guided interventional examinations. • These data allow identifying organs at risk of higher radiation dose. • Detailed knowledge of radiation dose may contribute to a better individual risk-stratification. • New CT-scanner generations involve markedly lower radiation doses compared to older devices.

Whole-body ultra-low dose CT using spectral shaping for detection of osteolytic lesion in multiple myeloma.

OBJECTIVES: The aim of this study was to investigate the radiation dose and image quality of a whole-body low-dose CT (WBLDCT) using spectral shaping at 100 kV (Sn 100 kV) for the assessment of osteolytic lesions in patients with multiple myeloma. METHODS: Thirty consecutive patients were retrospectively selected, who underwent a WBLDCT on a third-generation dual-source CT (DSCT) (Sn 100 kV, ref. mAs: 130). They were matched with patients, who were examined on a second-generation DSCT with a standard low-dose protocol (100 kV, ref. mAs: 111). Objective and subjective image quality, radiation exposure as well as the frequency of osteolytic lesions were evaluated. RESULTS: All scans were of diagnostic image quality. Subjective overall image quality was significantly higher in the study group (p = 0.0003). Objective image analysis revealed that signal intensities, signal-to-noise ratio and contrast-to-noise ratio of the bony structures were equal or significantly higher in the control group. There was no significant difference in the frequency of osteolytic lesions (p = 0.259). The median effective dose of the study protocol was significantly lower (1.45 mSv vs. 5.65 mSv; p < 0.0001). CONCLUSION: WBLDCT with Sn 100 kV can obtain sufficient image quality for the depiction of osteolytic lesions while reducing the radiation dose by approximately 74%. KEY POINTS: • Spectral shaping using tin filtration is beneficial for whole-body low-dose CT • Sn 100 kV yields sufficient image quality for depiction of osteolytic lesions • Whole-body low-dose CT can be performed with a median dose of 1.5 mSv.

Feasibility of FDG-PET in myocarditis: Comparison to CMR using integrated PET/MRI.

OBJECTIVE: Besides cardiac sarcoidosis, FDG-PET is rarely used in the diagnosis of myocardial inflammation, while cardiac MRI (CMR) is the actual imaging reference for the workup of myocarditis. Using integrated PET/MRI in patients with suspected myocarditis, we prospectively compared FDG-PET to CMR and the feasibility of integrated FDG-PET/MRI in myocarditis. METHODS: A total of 65 consecutive patients with suspected myocarditis were prospectively assessed using integrated cardiac FDG-PET/MRI. Studies comprised T2-weighted imaging, late gadolinium enhancement (LGE), and simultaneous PET acquisition. Physiological glucose uptake in the myocardium was suppressed using dietary preparation. RESULTS: FDG-PET/MRI was successful in 55 of 65 enrolled patients: two patients were excluded due to claustrophobia and eight patients due to failed inhibition of myocardial glucose uptake. Compared with CMR (LGE and/or T2), sensitivity and specificity of PET was 74% and 97%. Overall spatial agreement between PET and CMR was κ = 0.73. Spatial agreement between PET and T2 (κ = 0.75) was higher than agreement between PET and LGE (κ = 0.64) as well as between LGE and T2 (κ = 0.56). CONCLUSION: In patients with suspected myocarditis, FDG-PET is in good agreement with CMR findings.

Verification of organ doses calculated by a dose monitoring software tool based on Monte Carlo Simulation in thoracic CT protocols.

Background The importance of monitoring of the radiation dose received by the human body during computed tomography (CT) examinations is not negligible. Several dose-monitoring software tools emerged in order to monitor and control dose distribution during CT examinations. Some software tools incorporate Monte Carlo Simulation (MCS) and allow calculation of effective dose and organ dose apart from standard dose descriptors. Purpose To verify the results of a dose-monitoring software tool based on MCS in assessment of effective and organ doses in thoracic CT protocols. Material and Methods Phantom measurements were performed with thermoluminescent dosimeters (TLD LiF:Mg,Ti) using two different thoracic CT protocols of the clinical routine: (I) standard CT thorax (CTT); and (II) CTT with high-pitch mode, P = 3.2. Radiation doses estimated with MCS and measured with TLDs were compared. Results Inter-modality comparison showed an excellent correlation between MCS-simulated and TLD-measured doses ((I) after localizer correction r = 0.81; (II) r = 0.87). The following effective and organ doses were determined: (I) (a) effective dose = MCS 1.2 mSv, TLD 1.3 mSv; (b) thyroid gland = MCS 2.8 mGy, TLD 2.5 mGy; (c) thymus = MCS 3.1 mGy, TLD 2.5 mGy; (d) bone marrow = MCS 0.8 mGy, TLD 0.9 mGy; (e) breast = MCS 2.5 mGy, TLD 2.2 mGy; (f) lung = MCS 2.8 mGy, TLD 2.7 mGy; (II) (a) effective dose = MCS 0.6 mSv, TLD 0.7 mSv; (b) thyroid gland = MCS 1.4 mGy, TLD 1.8 mGy; (c) thymus = MCS 1.4 mGy, TLD 1.8 mGy; (d) bone marrow = MCS 0.4 mGy, TLD 0.5 mGy; (e) breast = MCS 1.1 mGy, TLD 1.1 mGy; (f) lung = MCS 1.2 mGy, TLD 1.3 mGy. Conclusion Overall, in thoracic CT protocols, organ doses simulated by the dose-monitoring software tool were coherent to those measured by TLDs. Despite some challenges, the dose-monitoring software was capable of an accurate dose calculation.

Real-time SPARSE-SENSE cine MR imaging in atrial fibrillation: a feasibility study.

Background Cardiac magnetic resonance imaging (MRI) relies on correct ECG-gating, which is hindered in arrhythmia. Purpose To examine whether a prototype free-breathing real-time cine sequence using SPARSE-SENSE (SPARSE) improves left ventricular quantification in atrial fibrillation. Material and Methods On a 1.5T MR system left ventricular short-axis stacks were acquired of the SPARSE sequence and of a "reference" steady-state free precession (SSFP) sequence with arrhythmia rejection in 20 patients with atrial fibrillation. Two radiologists independently rated arrhythmia-caused artifact severity in both sequences using a 4-point scale. Coefficients of variation of myocardial signal intensity for both sequences were acquired. Volumetry was performed twice by one reader and once by another reader. Correlation between artifact severity and employed sequence was analyzed by modified Fisher's exact test. Coefficients of variation and volumetric data were compared by paired t-test and intraclass correlation. Results Median arrhythmia-caused artifact severity was 2 in both readers for SSFP and 0 (reader 1)/1 (reader 2) for SPARSE, being significantly lower in SPARSE ( P < 0.001). Mean coefficient of variance was significantly smaller in SPARSE (0.11 ± 0.04) compared to SSFP (0.22 ± 0.13, P = 0.003), which was interpreted as a hint for fewer artifacts in SPARSE. Only a small difference of 9 ± 15 mL was seen for end-systolic volume ( P = 0.019) between sequences, otherwise no significant difference was detected (end-diastolic volume, P = 0.200; stroke volume, P = 0.554; ejection fraction, P = 0.136; myocardial mass, P = 0.353). Intraclass correlation between sequences was good to excellent (range, 0.80-0.97). Conclusion Real-time MRI with SPARSE data sampling is promising in atrial fibrillation because it reduces arrhythmia-caused artifacts.

Compressed sensing cine imaging with high spatial or high temporal resolution for analysis of left ventricular function.

PURPOSE: To assess two compressed sensing cine magnetic resonance imaging (MRI) sequences with high spatial or high temporal resolution in comparison to a reference steady-state free precession cine (SSFP) sequence for reliable quantification of left ventricular (LV) volumes. MATERIALS AND METHODS: LV short axis stacks of two compressed sensing breath-hold cine sequences with high spatial resolution (SPARSE-SENSE HS: temporal resolution: 40 msec, in-plane resolution: 1.0 × 1.0 mm(2) ) and high temporal resolution (SPARSE-SENSE HT: temporal resolution: 11 msec, in-plane resolution: 1.7 × 1.7 mm(2) ) and of a reference cine SSFP sequence (standard SSFP: temporal resolution: 40 msec, in-plane resolution: 1.7 × 1.7 mm(2) ) were acquired in 16 healthy volunteers on a 1.5T MR system. LV parameters were analyzed semiautomatically twice by one reader and once by a second reader. The volumetric agreement between sequences was analyzed using paired t-test, Bland-Altman plots, and Passing-Bablock regression. RESULTS: Small differences were observed between standard SSFP and SPARSE-SENSE HS for stroke volume (SV; -7 ± 11 ml; P = 0.024), ejection fraction (EF; -2 ± 3%; P = 0.019), and myocardial mass (9 ± 9 g; P = 0.001), but not for end-diastolic volume (EDV; P = 0.079) and end-systolic volume (ESV; P = 0.266). No significant differences were observed between standard SSFP and SPARSE-SENSE HT regarding EDV (P = 0.956), SV (P = 0.088), and EF (P = 0.103), but for ESV (3 ± 5 ml; P = 0.039) and myocardial mass (8 ± 10 ml; P = 0.007). Bland-Altman analysis showed good agreement between the sequences (maximum bias ≤ -8%). CONCLUSION: Two compressed sensing cine sequences, one with high spatial resolution and one with high temporal resolution, showed good agreement with standard SSFP for LV volume assessment. J. Magn. Reson. Imaging 2016;44:366-374.

Real-time SPARSE-SENSE cardiac cine MR imaging: optimization of image reconstruction and sequence validation.

OBJECTIVES: Improved real-time cardiac magnetic resonance (CMR) sequences have currently been introduced, but so far only limited practical experience exists. This study aimed at image reconstruction optimization and clinical validation of a new highly accelerated real-time cine SPARSE-SENSE sequence. METHODS: Left ventricular (LV) short-axis stacks of a real-time free-breathing SPARSE-SENSE sequence with high spatiotemporal resolution and of a standard segmented cine SSFP sequence were acquired at 1.5 T in 11 volunteers and 15 patients. To determine the optimal iterations, all volunteers' SPARSE-SENSE images were reconstructed using 10-200 iterations, and contrast ratios, image entropies, and reconstruction times were assessed. Subsequently, the patients' SPARSE-SENSE images were reconstructed with the clinically optimal iterations. LV volumetric values were evaluated and compared between both sequences. RESULTS: Sufficient image quality and acceptable reconstruction times were achieved when using 80 iterations. Bland-Altman plots and Passing-Bablok regression showed good agreement for all volumetric parameters. CONCLUSIONS: 80 iterations are recommended for iterative SPARSE-SENSE image reconstruction in clinical routine. Real-time cine SPARSE-SENSE yielded comparable volumetric results as the current standard SSFP sequence. Due to its intrinsic low image acquisition times, real-time cine SPARSE-SENSE imaging with iterative image reconstruction seems to be an attractive alternative for LV function analysis. KEY POINTS: • A highly accelerated real-time CMR sequence using SPARSE-SENSE was evaluated. • SPARSE-SENSE allows free breathing in real-time cardiac cine imaging. • For clinically optimal SPARSE-SENSE image reconstruction, 80 iterations are recommended. • Real-time SPARSE-SENSE imaging yielded comparable volumetric results as the reference SSFP sequence. • The fast SPARSE-SENSE sequence is an attractive alternative to standard SSFP sequences.

Clinical evaluation of a dose monitoring software tool based on Monte Carlo Simulation in assessment of eye lens doses for cranial CT scans.

INTRODUCTION: The aim of this study was to verify the results of a dose monitoring software tool based on Monte Carlo Simulation (MCS) in assessment of eye lens doses for cranial CT scans. METHODS: In cooperation with the Federal Office for Radiation Protection (Neuherberg, Germany), phantom measurements were performed with thermoluminescence dosimeters (TLD LiF:Mg,Ti) using cranial CT protocols: (I) CT angiography; (II) unenhanced, cranial CT scans with gantry angulation at a single and (III) without gantry angulation at a dual source CT scanner. Eye lens doses calculated by the dose monitoring tool based on MCS and assessed with TLDs were compared. RESULTS: Eye lens doses are summarized as follows: (I) CT angiography (a) MCS 7 mSv, (b) TLD 5 mSv; (II) unenhanced, cranial CT scan with gantry angulation, (c) MCS 45 mSv, (d) TLD 5 mSv; (III) unenhanced, cranial CT scan without gantry angulation (e) MCS 38 mSv, (f) TLD 35 mSv. Intermodality comparison shows an inaccurate calculation of eye lens doses in unenhanced cranial CT protocols at the single source CT scanner due to the disregard of gantry angulation. On the contrary, the dose monitoring tool showed an accurate calculation of eye lens doses at the dual source CT scanner without gantry angulation and for CT angiography examinations. CONCLUSION: The dose monitoring software tool based on MCS gave accurate estimates of eye lens doses in cranial CT protocols. However, knowledge of protocol and software specific influences is crucial for correct assessment of eye lens doses in routine clinical use.

Integrated FDG PET/MR Imaging for the Assessment of Myocardial Salvage in Reperfused Acute Myocardial Infarction.

PURPOSE: To compare the size of the area with reduced myocardial fluorodeoxygluose (FDG) uptake with the endocardial surface area (ESA) method as a marker for the area at risk in patients with reperfused acute myocardial infarction. MATERIALS AND METHODS: The study was approved by the local institutional review board. All patients gave written informed consent prior to their examination. Twenty-five patients (mean age ± standard deviation, 54 years ± 14) underwent prospective cardiac positron emission tomography/magnetic resonance imaging after acute coronary occlusion and interventional reperfusion. On late gadolinium contrast enhancement images, the size of infarction and the area at risk, as determined with ESA, were assessed and compared with the area of reduced FDG uptake. Statistical analysis comprised paired t tests and Mann-Whitney U tests, as well as Pearson r and Spearman ρ for correlations. RESULTS: In patients with infarcted myocardium and reduced FDG uptake (n = 18), a good correlation between the area of reduced FDG uptake and the area at risk according to ESA was observed (r = .70, P = .001). The area of reduced FDG uptake (31% ± 11 of left ventricular myocardial mass) was larger than the size of the infarct (10% ± 10, P < .0001) and the area at risk according to ESA (17% ± 13, P < .0001). In six patients, no late contrast enhancement was seen, whereas all patients had an area of reduced FDG uptake (29% ± 8) in the perfusion territory of the culprit artery. CONCLUSION: In patients with reperfused acute myocardial infarction, the area of reduced FDG uptake correlates with the area at risk as determined with the ESA method and is localized in the perfusion territory of the culprit artery in the absence of necrosis, although the area of reduced FDG uptake largely overestimates the size of the infarct and the ESA-based area at risk.

Cardiac pathologies in female carriers of Duchenne muscular dystrophy assessed by cardiovascular magnetic resonance imaging.

OBJECTIVES: Duchenne muscular dystrophy (DMD) is the most common and severe dystrophinopathy. DMD carriers rarely present with clinical symptoms, but may suffer from cardiac involvement. Because echocardiographic findings are inconsistent and cardiac magnetic resonance imaging (CMRI) data are limited, this study sought to investigate asymptomatic carriers for cardiac abnormalities using CMRI. METHODS: Fifteen genetically confirmed DMD carriers (age, 32.3 ± 10.2 years) were prospectively examined on a 1.5T MR system. Cine, T2, and late-gadolinium-enhanced (LGE) images were acquired, and were evaluated in consensus by two experienced readers. Left ventricular (LV) parameters were analysed semiautomatically, normalized to BSA. RESULTS: Normalized LV end-diastolic volume was increased in 7% (73.7 ± 16.8 ml/m(2); range, 48-116 ml/m(2)) and normalized LV end-systolic volume in 20% (31.5 ± 13.3 ml/m(2); range, 15-74 ml/m(2)). EF was reduced in 33% (58.4 ± 7.6%; range, 37-69%) and normalized LV myocardial mass in 80% (40.5 ± 6.8 g/m(2); range, 31-55 g/m(2)). In 80%, regional myocardial thinning was detected in more than one segment. In 13% and 40%, apical-lateral accentuation of LV non-compaction was present. LGE was found in 60% (midmyocardial inferolateral accentuation). CONCLUSIONS: Given the high frequency of cardiac pathologies detected by CMRI, regular cardiac risk assessment is advisable for DMD carriers. Besides clinical examination, CMRI is an excellent tool for this purpose. KEY POINTS: • Fifteen Duchenne muscular dystrophy carriers investigated using CMRI all showed cardiac pathologies. • Myocardial mass reduction, regional myocardial thinning, and late gadolinium enhancement were common. • Regular cardiac risk assessment is thus advisable in Duchenne muscular dystrophy carriers. • Besides clinical examination, CMRI is an excellent tool for this purpose.

Reduction of QTD--A Novel Marker of Successful Reperfusion in NSTEMI. Pathophysiologic Insights by CMR.

BACKGROUND/OBJECTIVES: Non-ST segment elevation myocardial infarction (MI) poses similar detrimental long-term prognosis as ST-segment elevation MI. No marker on ECG is established to predict successful reperfusion in NSTEMI. QT dispersion is increased by myocardial ischemia and reduced by successful restoration of epicardial blood flow by PCI. Whether QT dispersion reduction translates to smaller infarcts and thus indicates successful reperfusion is unknown. We hypothesized that the relative reduction of QT dispersion (QTD-Rrel ) on a standard ECG in acutely reperfused NSTEMI is related to infarct size and infarct transmurality as assessed by delayed enhancement CMR (DE-CMR). METHODS AND RESULTS: 69 patients with a first acute NSTEMI were included. QTD-Rrel was stratified according to LV function and volumes, infarct transmurality and size as assessed by DE-CMR. Extensive myocardial infarction was defined as above median infarct size. LV function and end-systolic volume were only mildly related to QTD-Rrel . QTD-Rrel was inversely related to infarct size (r=-0.506,p=0.001) and infarct transmurality (r=-0.415, p=0.001). QTD-Rrel was associated with extensive myocardial infarction in univariate analysis (odds ratio (OR) 0.958, CI 0.935-0.982; p=0.001). Compared to clinical and angiographic data QTD-Rrel remained the only independent predictor of non-transmural infarcts (OR 1.110, CI 1.055-1.167; p=0.049). CONCLUSION: In patients with acute Non-ST-Segment Myocardial infarction QTd-Rrel calculated on a surface ECG prior and post PCI for restoration of epicardial blood flow detects small, non-transmural infarcts as assessed by delayed enhancement CMR. Thus, QTd-Rrel can indicate successful reperfusion therapy.

Volumetric measurements in patients with corrected tetralogy of Fallot: comparison of short-axis versus axial cardiac MRI and echocardiography.

BACKGROUND: Patients with corrected tetralogy of Fallot (cToF) are prone to develop pulmonary regurgitation and right ventricular enlargement resulting in long-term complications, thus correct right ventricular volumetric monitoring is crucial. However, it remains controversial which cardiovascular magnetic resonance imaging (CMRI) slice orientation is most appropriate in cToF for the analysis of the right ventricular volume. PURPOSE: To investigate which slice orientation is most suited for right ventricular volumetry in cToF we compared short-axis and axial slices, and furthermore we compared right ventricular data between CMRI and echocardiography. MATERIAL AND METHODS: Thirty CMRI examinations of 27 patients with cToF were included retrospectively. Right ventricular end-diastolic (EDV) and end-systolic volume (ESV) were derived from short-axis and axial cine CMRI planes. Furthermore, pulmonary trunk forward flow in phase-contrast CMRI and right ventricular inner diastolic diameter in echocardiography (R VIDdiast) were measured. By Bland-Altman and variance analysis intra- and inter-observer agreement were assessed for cine CMRI data. By Pearson correlation CMRI cine and phase-contrast data and CMRI cine and echocardiographic data were compared. RESULTS: Intra- and inter-observer variability for right ventricular EDV were significantly lower in axial slices (P = 0.016, P = 0.010). For right ventricular ESV a trend towards a lower intra- and inter-observer variability in axial slices was found (P = 0.063, P = 0.138). Right ventricular stroke volume in short-axis (r = 0.872, P < 0.001) and in axial (r = 0.914, P < 0.001) planes correlated highly, respectively very highly with pulmonary trunk forward flow in phase-contrast CMRI. R VIDdiast correlated highly with right ventricular EDV assessed by short-axis and axial CMRI (P < 0.001, P < 0.001). CONCLUSION: Due to lower intra- and inter-observer variability, axial slices are recommended for right ventricular volumetry in cToF.

Quantification of congenital aortic valve stenosis in pediatric patients: comparison between cardiac magnetic resonance imaging and transthoracic echocardiography.

Previous studies showed the reliability of cardiac magnetic resonance imaging (cMRI) in the quantification of aortic valve stenosis in adults. The aim of this retrospective study was to assess the ability of cMRI in the quantification of congenital aortic valve stenosis (CAS) in children. Nineteen patients (mean age 14.0 ± 3.2 years, 15 boys and 4 girls) with CAS were imaged by cMRI and transthoracic echocardiography (TTE). cMRI was performed on a 1.5-Tesla MR scanner (Magnetom Avanto; Siemens Healthcare, Erlangen, Germany) using cine steady-state free precession sequences for the assessment of the aortic valve area (AVA) by MR planimetry and left-ventricular function. Phase-contrast measurement was used in cMRI to assess peak flow velocity above the aortic valve. A positive correlation was found between maximum systolic pressure gradient (MPG) as assessed by cMRI and TTE (28.9 ± 21.2 vs. 41.3 ± 22.7 mmHg, r = 0.84, p = 0.001) with a mean underestimation of 12.4 mmHg by cMRI. Only a weak correlation could be observed between AVA by cMRI and MPG at the aortic valve by TTE (r = -0.50, p = 0.029) and cMRI (r = -0.27, p = 0.40). Furthermore, a positive correlation between myocardial mass (cMRI) and MPG (TTE, r = 0.57, p = 0.01), but not between myocardial mass (cMRI) and AVA (cMRI, r = 0.07, p = 0.77), was found. The assessment of MPG by cMRI in patients with CAS is feasible with a trend toward underestimatation compared with TTE. Moreover, MPG seems to be a more accurate parameter than AVA regarding the prediction of myocardial hypertrophy.