Browsing by Author "Kunze, Karl P."

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    3D joint T 1/T 1 ρ/T 2 mapping and water-fat imaging for contrast-agent free myocardial tissue characterization at 1.5T.
    (2025) Crabb, Michael G.; Kunze, Karl P.; Littlewood, Simon J.; Tripp, Donovan; Fotaki, Anastasia; Prieto Vásquez, Claudia; Botnar, René Michael
    PURPOSE: To develop a novel, free-breathing, 3D joint T 1 $$ {T}_1 $$ / T 1 ρ $$ {T}_{1\rho } $$ / T 2 $$ {T}_2 $$ mapping sequence with Dixon encoding to provide co-registered 3D T 1 $$ {T}_1 $$ , T 1 ρ $$ {T}_{1\rho } $$ , and T 2 $$ {T}_2 $$ maps and water-fat volumes with isotropic spatial resolution in a single ≈ 7 $$ \approx 7 $$ min scan for comprehensive contrast-agent-free myocardial tissue characterization and simultaneous evaluation of the whole-heart anatomy. METHODS: An interleaving sequence over 5 heartbeats is proposed to provide T 1 $$ {T}_1 $$ , T 1 ρ $$ {T}_{1\rho } $$ , and T 2 $$ {T}_2 $$ encoding, with 3D data acquired with Dixon gradient-echo readout and 2D image navigators to enable 100 % $$ 100\% $$ respiratory scan efficiency. Images were reconstructed with a non-rigid motion-corrected, low-rank patch-based reconstruction, and maps were generated through dictionary matching. The proposed sequence was compared against conventional 2D techniques in phantoms, 10 healthy subjects, and 1 patient. RESULTS: The proposed 3D T 1 $$ {T}_1 $$ , T 1 ρ $$ {T}_{1\rho } $$ , and T 2 $$ {T}_2 $$ measurements showed excellent correlation with 2D reference measurements in phantoms. For healthy subjects, the mapping values of septal myocardial tissue were T 1 = 1060 ± 48 ms $$ {T}_1=1060\pm 48\kern0.2778em \mathrm{ms} $$ , T 1 ρ = 48 . 1 ± 3 . 9 ms $$ {T}_{1\rho }=48.1\pm 3.9\kern0.2778em \mathrm{ms} $$ , and T 2 = 44 . 2 ± 3 . 2 ms $$ {T}_2=44.2\pm 3.2\kern0.2778em \mathrm{ms} $$ for the proposed sequence, against T 1 = 959 ± 15 ms $$ {T}_1=959\pm 15\kern0.2778em \mathrm{ms} $$ , T 1 ρ = 56 . 4 ± 1 . 9 ms $$ {T}_{1\rho }=56.4\pm 1.9\kern0.2778em \mathrm{ms} $$ , and T 2 = 47 . 3 ± 1 . 5 ms $$ {T}_2=47.3\pm 1.5\kern0.2778em \mathrm{ms} $$ for 2D MOLLI, 2D T 1 ρ $$ {T}_{1\rho } $$ -prep bSSFP and 2D T 2 $$ {T}_2 $$ -prep bSSFP, respectively. Promising results were obtained when comparing the proposed mapping to 2D references in 1 patient with active myocarditis. CONCLUSION: The proposed approach enables simultaneous 3D whole-heart joint T 1 $$ {T}_1 $$ / T 1 ρ $$ {T}_{1\rho } $$ / T 2 $$ {T}_2 $$ mapping and water/fat imaging in ≈ $$ \approx $$ 7 min scan time, demonstrating good agreement with conventional mapping techniques in phantoms and healthy subjects and promising results in 1 patient with suspected cardiovascular disease.
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    3D whole-heart grey-blood late gadolinium enhancement cardiovascular magnetic resonance imaging
    (2021) Milotta, Giorgia; Munoz, Camila; Kunze, Karl P.; Neji, Radhouene; Figliozzi, Stefano; Chiribiri, Amedeo; Hajhosseiny, R.; Masci, Pier Giorgio; Prieto Vásquez, Claudia; Botnar, René Michael
    Abstract Purpose To develop a free-breathing whole-heart isotropic-resolution 3D late gadolinium enhancement (LGE) sequence with Dixon-encoding, which provides co-registered 3D grey-blood phase-sensitive inversion-recovery (PSIR) and complementary 3D fat volumes in a single scan of < 7 min. Methods A free-breathing 3D PSIR LGE sequence with dual-echo Dixon readout with a variable density Cartesian trajectory with acceleration factor of 3 is proposed. Image navigators are acquired to correct both inversion recovery (IR)-prepared and reference volumes for 2D translational respiratory motion, enabling motion compensated PSIR reconstruction with 100% respiratory scan efficiency. An intermediate PSIR reconstruction is performed between the in-phase echoes to estimate the signal polarity which is subsequently applied to the IR-prepared water volume to generate a water grey-blood PSIR image. The IR-prepared water volume is obtained using a water/fat separation algorithm from the corresponding dual-echo readout. The complementary fat-volume is obtained after water/fat separation of the reference volume. Ten patients (6 with myocardial scar) were scanned with the proposed water/fat grey-blood 3D PSIR LGE sequence at 1.5 T and compared to breath-held grey-blood 2D LGE sequence in terms of contrast ratio (CR), contrast-to-noise ratio (CNR), scar depiction, scar transmurality, scar mass and image quality. Results Comparable CRs (p = 0.98, 0.40 and 0.83) and CNRs (p = 0.29, 0.40 and 0.26) for blood-myocardium, scar-myocardium and scar-blood respectively were obtained with the proposed free-breathing 3D water/fat LGE and 2D clinical LGE scan. Excellent agreement for scar detection, scar transmurality, scar mass (bias = 0.29%) and image quality scores (from 1: non-diagnostic to 4: excellent) of 3.8 ± 0.42 and 3.6 ± 0.69 (p > 0.99) were obtained with the 2D and 3D PSIR LGE approaches with comparable total acquisition time (p = 0.29). Similar agreement in intra and inter-observer variability were obtained for the 2D and 3D acquisition respectively. Conclusion The proposed approach enabled the acquisition of free-breathing motion-compensated isotropic-resolution 3D grey-blood PSIR LGE and fat volumes. The proposed approach showed good agreement with conventional 2D LGE in terms of CR, scar depiction and scan time, while enabling free-breathing acquisition, whole-heart coverage, reformatting in arbitrary views and visualization of both water and fat information.
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    Efficient non-contrast enhanced 3D Cartesian cardiovascular magnetic resonance angiography of the thoracic aorta in 3 min
    (2022) Fotaki, Anastasia; Munoz, Camila; Emanuel, Yaso; Hua, Alina; Bosio, Filippo; Kunze, Karl P.; Neji, Radhouene; Masci, Pier Giorgio; Botnar, Rene M.; Prieto, Claudia
    Background: The application of cardiovascular magnetic resonance angiography (CMRA) for the assessment of thoracic aortic disease is often associated with prolonged and unpredictable acquisition times and residual motion artefacts. To overcome these limitations, we have integrated undersampled acquisition with image-based navigators and inline non-rigid motion correction to enable a free-breathing, contrast-free Cartesian CMRA framework for the visualization of the thoracic aorta in a short and predictable scan of 3 min.
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    Evaluation of accelerated motion-compensated 3d water/fat late gadolinium enhanced MR for atrial wall imaging
    (SPRINGER, 2021) Munoz, Camila; Sim, Iain; Neji, Radhouene; Kunze, Karl P.; Masci, Pier Giorgio; Schmidt, Michaela; O'Neill, Mark; Williams, Steven; Botnar, Rene M.; Prieto, Claudia
    Objective 3D late gadolinium enhancement (LGE) imaging is a promising non-invasive technique for the assessment of atrial fibrosis. However, current techniques result in prolonged and unpredictable scan times and high rates of non-diagnostic images. The purpose of this study was to compare the performance of a recently proposed accelerated respiratory motion-compensated 3D water/fat LGE technique with conventional 3D LGE for atrial wall imaging. Materials and methods 18 patients (age: 55.7 +/- 17.1 years) with atrial fibrillation underwent conventional diaphragmatic navigator gated inversion recovery (IR)-prepared 3D LGE (dNAV) and proposed image-navigator motion-corrected water/fat IR-prepared 3D LGE (iNAV) imaging. Images were assessed for image quality and presence of fibrosis by three expert observers. The scan time for both techniques was recorded. Results Image quality scores were improved with the proposed compared to the conventional method (iNAV: 3.1 +/- 1.0 vs. dNAV: 2.6 +/- 1.0, p = 0.0012, with 1: Non-diagnostic to 4: Full diagnostic). Furthermore, scan time for the proposed method was significantly shorter with a 59% reduction is scan time (4.5 +/- 1.2 min vs. 10.9 +/- 3.9 min, p < 0.0001). The images acquired with the proposed method were deemed as inconclusive less frequently than the conventional images (expert 1/expert 2: 4/7 dNAV and 2/4 iNAV images inconclusive). Discussion The motion-compensated water/fat LGE method enables atrial wall imaging with diagnostic quality comparable to the current conventional approach with a significantly shorter scan of about 5 min.
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    Evaluation of myocarditis with a free-breathing three-dimensional isotropic whole-heart joint T1 and T2 mapping sequence
    (ELSEVIER SCIENCE INC, 2024) Hua, Alina; Velasco, Carlos; Munoz, Camila; Milotta, Giorgia; Fotaki, Anastasia; Bosio, Filippo; Granlund, Inka; Sularz, Agata; Chiribiri, Amedeo; Kunze, Karl P.; Botnar Rene, Michael; Prieto Vásquez, Claudia Del Carmen; Ismail, Tevfik F.
    Background: The diagnosis of myocarditis by cardiovascular magnetic resonance (CMR) requires the use of T2 and T1 weighted imaging, ideally incorporating parametric mapping. Current two-dimensional (2D) mapping sequences are acquired sequentially and involve multiple breath-holds resulting in prolonged scan times and anisotropic image resolution. We developed an isotropic free-breathing three-dimensional (3D) whole-heart sequence that allows simultaneous T1 and T2 mapping and validated it in patients with suspected myocarditis. Methods: Eighteen healthy volunteers and 28 patients with suspected myocarditis underwent conventional 2D T1 and T2 mapping with whole-heart coverage and 3D joint T1/T2 mapping on a 1.5T scanner. Acquisition time, image quality, and diagnostic performance were compared. Qualitative analysis was performed using a 4-point Likert scale. Bland-Altman plots were used to assess the quantitative agreement between 2D and 3D sequences. Results: The 3D T1/T2 sequence was acquired in 8 min 26 s under free breathing, whereas 2D T1 and T2 sequences were acquired with breath-holds in 11 min 44 s (p = 0.0001). All 2D images were diagnostic. For 3D images, 89% (25/ 28) of T1 and 96% (27/28) of T2 images were diagnostic with no significant difference in the proportion of diagnostic images for the 3D and 2D T1 (p = 0.2482) and T2 maps (p = 1.0000). Systematic bias in T1 was noted with biases of 102, 115, and 152 ms for basal-apical segments, with a larger bias for higher T1 values. Good agreement between T2 values for 3D and 2D techniques was found (bias of 1.8, 3.9, and 3.6 ms for basal-apical segments). The sensitivity and specificity of the 3D sequence for diagnosing acute myocarditis were 74% (95% confidence interval [CI] 49%-91%) and 83% (36%-100%), respectively, with a c-statistic (95% CI) of 0.85 (0.79-0.91) and no statistically significant difference between the 2D and 3D sequences for the detection of acute myocarditis for T1 (p = 0.2207) or T2 (p = 1.0000). Conclusion: Free-breathing whole-heart 3D joint T1/T2 mapping was comparable to 2D mapping sequences with respect to diagnostic performance, but with the added advantages of free breathing and shorter scan times. Further work is required to address the bias noted at high T1 values, but this did not significantly impact diagnostic accuracy.
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    Free-breathing, Contrast Agent-free Whole-Heart MTC-BOOST Imaging: Single-Center Validation Study in Adult Congenital Heart Disease
    (2023) Fotaki, Anastasia; Pushparajah, Kuberan; Hajhosseiny, Reza; Schneider, Alina; Alam, Harith; Ferreira, Joana; Neji, Radhouene; Kunze, Karl P.; Frigiola, Alessandra; Botnar, Rene M.; Prieto, Claudia
    Purpose: To assess the clinical performance of the three-dimensional, free-breathing, Magnetization Transfer Contrast Bright-and-black blOOd phase-SensiTive (MTC-BOOST) sequence in adult congenital heart disease (ACHD).Materials and Methods: In this prospective study, participants with ACHD undergoing cardiac MRI between July 2020 and March 2021 were scanned with the clinical T2-prepared balanced steady-state free precession sequence and proposed MTC-BOOST sequence. Four cardiologists scored their diagnostic confidence on a four-point Likert scale for sequential segmental analysis on images acquired with each sequence. Scan times and diagnostic confidence were compared using the Mann-Whitney test. Coaxial vascular dimensions at three anatomic landmarks were measured, and agreement between the research sequence and the corresponding clinical sequence was assessed with Bland-Altman analysis.Results: The study included 120 participants (mean age, 33 years +/- 13 [SD]; 65 men). The mean acquisition time of the MTC-BOOST sequence was significantly lower compared with that of the conventional clinical sequence (9 minutes +/- 2 vs 14 minutes +/- 5; P < .001). Diagnostic confidence was higher for the MTC-BOOST sequence compared with the clinical sequence (mean, 3.9 +/- 0.3 vs 3.4 +/- 0.7; P < .001). Narrow limits of agreement and mean bias less than 0.08 cm were found between the research and clinical vascu-lar measurements.Conclusion: The MTC-BOOST sequence provided efficient, high-quality, and contrast agent-free three-dimensional whole-heart imag-ing in ACHD, with shorter, more predictable acquisition time and improved diagnostic confidence compared with the reference stan-dard clinical sequence.
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    Free-breathing, non-contrast, 3D whole-heart coronary MRI for the identification of culprit and vulnerable atherosclerotic plaque
    (2025) Hajhosseiny, Reza; Hartley, Adam; Cole, Graham; Munoz, Camilla; Sethi, Amarjit; Al-Lamee, Rasha; Khawaja, Saud; Zaman, Sameer; Howard, James; Gopalan, Deepa; Ariff, Ben; Kaprielian, Raffi; Neji, Radhouene; Kunze, Karl P.; Kaura, Amit; Prieto Vásquez, Claudia; Khamis, Ramzi; Botnar, René Michael
    BACKGROUND: Detection of vulnerable coronary plaque can predict future myocardial infarctions. We have developed a novel, non-contrast cardiovascular magnetic resonance sequence (iT2prep-BOOST), enabling simultaneous, co-registered coronary angiography and plaque detection.OBJECTIVES: To validate iT2prep-BOOST in patients with non-ST-segment elevation myocardial infarction (NSTEMI).METHODS: 41 patients with suspected NSTEMI were recruited. Invasive coronary angiography ± intravascular imaging was used to classify coronary segments into the following categories: normal, non-culprit and culprit segments; stenosed segments as well as segments with vulnerable plaque features (lipid, calcium, fibroatheroma, thin cap fibroatheroma (TCFA), plaque-rupture and thrombus). The plaque/myocardial signal intensity ratio (PMR) in each coronary segment was analyzed on iT2prep-BOOST.RESULTS: The mean ± standard deviation PMR of culprit segments was significantly higher than non-culprit segments and normal segments (1.01 ± 0.14 vs. 0.67 ± 0.18 vs. 0.35 ± 0.24, P<0.001 respectively). Coronary segments with lipid, calcium and fibroatheroma had a significantly higher PMR compared to normal coronary segments (P<0.001), but significantly lower than segments with plaque-rupture and intraluminal thrombus (P<0.05). There was a progressive increase in PMR with increasing coronary segment stenosis (P<0.001). There was a significant association on multivariable analysis between HbA1c as well as family history of coronary artery disease and mean PMR (P=0.05 and P=0.04 respectively).CONCLUSIONS: iT2prep-BOOST has the potential to simultaneously visualize coronary artery lumen and plaque and differentiate normal segments from non-culprit and culprit plaque segments non-invasively and without contrast. The prognostic value of PMR needs to be investigated in a prospective multicenter study.
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    Free‐breathing 3D whole‐heart joint T1/T2 mapping and water/fat imaging at 0.55 T
    (2024) Si, Dongyue; Crabb, Michael G.; Kunze, Karl P.; Littlewood, Simon J.; Prieto Vasquez, Claudia Del Carmen; Botnar, René M.
    To develop and validate a highly efficient motion compensated free-breathingisotropic resolution 3D whole-heart joint T 1 /T2 mapping sequence with anatomicalwater/fat imaging at 0.55 T.Methods: The proposed sequence takes advantage of shorter T1 at 0.55 T to acquirethree interleaved water/fat volumes with inversion-recovery preparation, no prepara-tion, and T 2 preparation, respectively. Image navigators were used to facilitate nonrigidmotion-compensated image reconstruction. T1 and T2 maps were jointly calculated bya dictionary matching method. Validations were performed with simulation, phantom,and in vivo experiments on 10 healthy volunteers and 1 patient. The performance ofthe proposed sequence was compared with conventional 2D mapping sequences includ-ing modified Look-Locker inversion recovery and T2 -prepared balanced steady-SSFPsequence.Results: The proposed sequence has a good T1 and T2 encoding sensitivity in simula-tion, and excellent agreement with spin-echo reference T 1 and T2 values was observedin a standardized T1 /T2 phantom (R2 = 0.99). In vivo experiments provided good-qualityco-registered 3D whole-heart T1 and T2 maps with 2-mm isotropic resolution in ashort scan time of about 7 min. For healthy volunteers, left-ventricle T1 mean andSD measured by the proposed sequence were both comparable with those of modi-fied Look-Locker inversion recovery (640 ± 35 vs. 630 ± 25 ms [p = 0.44] and 49.9 ± 9.3vs. 54.4 ± 20.5 ms [p = 0.42]), whereas left-ventricle T2 mean and SD measured by theproposed sequence were both slightly lower than those of T2 -prepared balanced SSFP(53.8 ± 5.5 vs. 58.6 ± 3.3 ms [p < 0.01] and 5.2 ± 0.9 vs. 6.1 ± 0.8 ms [p = 0.03]). MyocardialT 1 and T2 in the patient measured by the proposed sequence were in good agreementwith conventional 2D sequences and late gadolinium enhancement.Conclusion: The proposed sequence simultaneously acquires 3D whole-heart T1 and T2mapping with anatomical water/fat imaging at 0.55 T in a fast and efficient 7-min scan.Further investigation in patients with cardiovascular disease is now warranted
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    High-resolution 3D whole-heart bright- and black-blood imaging with co-registered T2 mapping at 0.55 T
    (Cambridge University Press, 2025) Kokhanovskyi, Ivan; Castillo Passi, Carlos; Crabb, Michael G.; Ganter, Carl; Littlewood, Simon J.; Kunze, Karl P.; Karampinos, Dimitrios C.; Makowski, Marcus R.; Rueckert, Daniel; Prieto Vásquez, Claudia; Botnar, René Michael
    Conventional CMR exams for assessment of cardiac anatomy and tissue characterization require multiple sequential 2D acquisitions under breath-hold in different orientations, in addition to being limited to 1.5 T and 3 T. Methods: In this study, we sought to develop a novel 3D motion-compensated free-breathing sequence for comprehensive high-resolution whole-heart assessment of cardiovascular anatomy via simultaneous bright- and black-blood imaging and co-registered (Formula presented.) myocardial tissue quantification in a one-click scan at 0.55 T. Results: Good agreement with a spin-echo reference sequence was found in the phantom for (Formula presented.) mapping. In-vivo, the proposed research sequence was evaluated in 10 healthy subjects, providing great delineation of cardiac and vascular structures, good visibility of coronary arteries and accurate (Formula presented.) parametric mapping in a clinically feasible time of less than 9 min.
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    High-resolution non-contrast free-breathing coronary cardiovascular magnetic resonance ngiography for detection of coronary artery disease: validation against invasive coronary angiography
    (2022) Nazir, Muhummad Sohaib; Bustin, Aurelien; Hajhosseiny, Reza; Yazdani, Momina; Ryan, Matthew; Vergani, Vittoria; Neji, Radhouene; Kunze, Karl P.; Nicol, Edward; Masci, Pier Giorgio; Perera, Divaka; Plein, Sven; Chiribiri, Amedeo; Botnar, Rene; Prieto, Claudia
    Background: Coronary artery disease (CAD) is the single most common cause of death worldwide. Recent technological developments with coronary cardiovascular magnetic resonance angiography (CCMRA) allow high-resolution free-breathing imaging of the coronary arteries at submillimeter resolution without contrast in a predictable scan time of similar to 10 min. The objective of this study was to determine the diagnostic accuracy of high-resolution CCMRA for CAD detection against the gold standard of invasive coronary angiography (ICA).
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    High-resolution non-contrast free-breathing coronary cardiovascular magnetic resonance angiography for detection of coronary artery disease : validation against invasive coronary angiography
    (2022) Nazir, Muhummad S.; Bustin, Aurélien; Hajhosseiny, Reza; Yazdani, Momina; Ryan, Matthew; Vergani, Vittoria; Neji, Radhouene; Kunze, Karl P.; Perera, Divaka; Botnar, René Michael; Prieto Vásquez, Claudia
    Coronary artery disease (CAD) is the single most common cause of death worldwide. Recent technological developments with coronary cardiovascular magnetic resonance angiography (CCMRA) allow high-resolution free-breathing imaging of the coronary arteries at submillimeter resolution without contrast in a predictable scan time of ~ 10 min. The objective of this study was to determine the diagnostic accuracy of high-resolution CCMRA for CAD detection against the gold standard of invasive coronary angiography (ICA). Methods: Forty-five patients (15 female, 62 ± 10 years) with suspected CAD underwent sub-millimeter-resolution (0.6 mm3) non-contrast CCMRA at 1.5T in this prospective clinical study from 2019–2020. Prior to CCMR, patients were given an intravenous beta blockers to optimize heart rate control and sublingual glyceryl trinitrate to promote coronary vasodilation. Obstructive CAD was defined by lesions with ≥ 50% stenosis by quantitative coronary angiography on ICA. Results: The mean duration of image acquisition was 10.4 ± 2.1 min. On a per patient analysis, the sensitivity, specificity, positive predictive value and negative predictive value (95% confidence intervals) were 95% (75–100), 54% (36–71), 60% (42–75) and 93% (70–100), respectively. On a per vessel analysis the sensitivity, specificity, positive predictive value and negative predictive value (95% confidence intervals) were 80% (63–91), 83% (77–88), 49% (36–63) and 95% (90–98), respectively. Conclusion: As an important step towards clinical translation, we demonstrated a good diagnostic accuracy for CAD detection using high-resolution CCMRA, with high sensitivity and negative predictive value. The positive predictive value is moderate, and combination with CMR stress perfusion may improve the diagnostic accuracy. Future multicenter evaluation is now required
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    Highly efficient free-breathing 3D whole-heart imaging in 3-min: single center study in adults with congenital heart disease
    (2024) Fotaki, Anastasia; Pushparajah, Kuberan; Rush, Christopher; Muñoz, Camila; Velasco, Carlos; Neji, Radhouene; Kunze, Karl P.; Botnar, René Michael; Prieto Vásquez, Claudia Del Carmen
    Background: Three dimensional, whole-heart (3DWH) MRI is an established non-invasive imaging modality in patients with congenital heart disease (CHD) for the diagnosis of cardiovascular morphology and for clinical decision making. Current techniques utilise diaphragmatic navigation (dNAV) for respiratory motion correction and gating and are frequently limited by long acquisition times. This study proposes and evaluates the diagnostic performance of a respiratory gating-free framework, which considers respiratory image-based navigation (iNAV), and highly accelerated variable density Cartesian sampling in concert with non-rigid motion correction and low-rank patch-based denoising (iNAV-3DWH-PROST). The method is compared to the clinical dNAV-3DWH sequence in adult patients with CHD. Methods: In this prospective single center study, adult patients with CHD who underwent the clinical dNAV-3DWH MRI were also scanned with the iNAV-3DWH-PROST. Diagnostic confidence (4-point Likert scale) and diagnostic accuracy for common cardiovascular lesions was assessed by three readers. Scan times and diagnostic confidence were compared using the Wilcoxon-signed rank test. Co-axial vascular dimensions at three anatomic landmarks were measured, and agreement between the research and the corresponding clinical sequence was assessed with Bland-Altman analysis. Results: The study included 60 participants (mean age ± [SD]: 33 ± 14 years; 36 men). The mean acquisition time of iNAV-3DWH-PROST was significantly lower compared with the conventional clinical sequence (3.1 ± 0.9 min vs 13.9 ± 3.9 min, p < 0.0001). Diagnostic confidence was higher for the iNAV-3DWH-PROST sequence compared with the clinical sequence (3.9 ± 0.2 vs 3.4 ± 0.8, p < 0.001), however there was no significant difference in diagnostic accuracy. Narrow limits of agreement and mean bias less than 0.08 cm were found between the research and the clinical vascular measurements. Conclusions: The iNAV-3DWH-PROST framework provides efficient, high quality and robust 3D whole-heart imaging in significantly shorter scan time compared to the standard clinical sequence.
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    Highly efficient image navigator based 3D whole-heart cardiac MRA at 0.55T
    (2024) Castillo-Passi, Carlos; Kunze, Karl P.; Crabb, Michael G.; Munoz, Camila; Fotaki, Anastasia; Neji, Radhouene; Irarrazaval, Pablo; Prieto, Claudia; Botnar, Rene M.
    PurposeTo develop and evaluate a highly efficient free-breathing and contrast-agent-free three-dimensional (3D) whole-heart Cardiac Magnetic Resonance Angiography (CMRA) sequence at 0.55T.MethodsFree-breathing whole-heart CMRA has been previously proposed at 1.5 and 3T. Direct application of this sequence to 0.55T is not possible due to changes in the magnetic properties of the tissues. To enable free-breathing CMRA at 0.55T, pulse sequence design and acquisition parameters of a previously proposed whole-heart CMRA framework are optimized via Bloch simulations. Image navigators (iNAVs) are used to enable nonrigid respiratory motion-correction and 100% respiratory scan efficiency. Patch-based low-rank denoising is employed to accelerate the scan and account for the reduced signal-to-noise ratio at 0.55T. The proposed approach was evaluated on 11 healthy subjects. Image quality was assessed by a clinical expert (1: poor to 5: excellent) for all intrapericardiac structures. Quantitative evaluation was performed by assessing the vessel sharpness of the proximal right coronary artery (RCA).ResultsOptimization resulted in an imaging flip angle of 110 degrees$$ 11{0}<^>{\circ } $$, fat saturation flip angle of 180 degrees$$ 18{0}<^>{\circ } $$, and six k-space lines for iNAV encoding. The relevant cardiac structures and main coronary arteries were visible in all subjects, with excellent image quality (mean 4.9/5.0$$ 4.9/5.0 $$) and minimal artifacts (mean 4.9/5.0$$ 4.9/5.0 $$), with RCA vessel sharpness (50.3%+/- 9.8%$$ 50.3\%\pm 9.8\% $$) comparable to previous studies at 1.5T.ConclusionThe proposed approach enables 3D whole-heart CMRA at 0.55T in a 6-min scan (5.9 +/- 0.7 min$$ 5.9\pm 0.7\;\min $$), providing excellent image quality, minimal artifacts, and comparable vessel sharpness to previous 1.5T studies. Future work will include the evaluation of the proposed approach in patients with cardiovascular disease.
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    Isotropic, high-resolution, whole-chest inversion recovery contrast-enhanced magnetic resonance angiography in under 4.5 min using image-based navigator fluoro trigger
    (2025) Craft, Jason; Parikh, Roosha; Cheng, Josh Y.; Diaz, Nancy; Kunze, Karl P.; Schmidt, Michaela; Neji, Radhouene; Leung, Amanda; Weber, Suzanne; Weber, Jonathan; Carter, Timothy; Biso, Sylvia; Yamashita, Ann-Marie; Wolff, Eric H.; Prieto Vásquez, Claudia Del Carmen; Botnar, Rene Michael
    BACKGROUND: Serial assessment of the thoracic aorta with magnetic resonance angiography (MRA) is desirable due to 3D volumetric dataset, high spatial resolution, and lack of ionizing radiation. Electrocardiogram (ECG) gated, contrast-enhanced (CE), inversion recovery gradient echo MRA is efficient and historically provides low artifact burden, but the window for imaging with weak albumin binding extracellular gadolinium based contrast agents is small. Our purpose was to acquire whole-chest gated CE-MRA with 1.2 mm 3 resolution using image-based navigator (iNAV) for motion correction/contrast monitoring, and variable density sampling in 4-5 min. Image quality and vessel diameter reproducibility are assessed against time resolved MRA (TR-MRA). METHODS: iNAV CE-MRA and TR-MRA were obtained prospectively in 40 patients and reviewed by 3 blinded cardiologists for vessel diameter and image quality rated on a four point scale: (1) non-diagnostic; (2) poor-significant blurring; (3) good-mild blurring; and (4) excellent. Reproducibility and image quality were evaluated using the concordance correlation statistic and Cohen's kappa with mean differences evaluated using paired t-tests and repeat-measures ANOVA. RESULTS: iNAV CE-MRA scan time was 4.2 ± 0.7 min. iNAV CE-MRA quality score was higher ( p  
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    Motion corrected 3D whole-heart SAVA T 1 mapping at 0.55 T.
    (2025) De la Sotta, Rafael I.; Crabb, Michael G.; Kunze, Karl P.; Botnar, René M.; Prieto, Claudia
    PURPOSE: To propose a novel highly efficient isotropic-resolution 3D whole-heart saturation-recovery and variable-flip-angle (SAVA) T 1 mapping sequence at 0.55 T, incorporating image navigator (iNAV)-based non-rigid motion correction and dictionary matching. METHODS: The proposed iNAV-based isotropic-resolution 3D whole-heart SAVA T 1 mapping sequence at 0.55 T acquires three gradient echo T 1-weighted volumes sequentially: an equilibrium contrast with 4° flip angle, and two saturation recovery T 1-weighted contrasts with 10° flip angles and different saturation delays. Sequence parameters were optimized for the lower field strength by simulations and phantom experiments. Two-dimensional iNAVs are acquired at each heartbeat to enable respiratory motion estimation and correction and 100% respiratory scan efficiency. The T 1 mapping is computed by dictionary matching, using subject-specific dictionaries based on Bloch equations simulations. Non-rigid motion correction is implemented based on respiratory bins reconstructed by iterative-SENSE and subsequent patch-based low-rank denoising, for each contrast separately. The proposed approach was evaluated in a standardized T 1 phantom and 10 healthy subjects, in comparison to spin-echo reference and 2D MOLLI, respectively. RESULTS: Excellent agreement is observed between iNAV-based SAVA T 1 mapping at 0.55 T and spin echo reference in phantom, with a R 2 = 0.998 $$ {R}^2=0.998 $$ for all phantom vials. Good image quality was obtained in vivo for the contrast images and corresponding T 1 maps in a scan time of 6:30 min ±40 s. Average and SD of myocardial T 1 values across subjects and segments was 706 ± 41 ms, which is comparable to acquired 2D MOLLI values of 681 ± 26 ms, and previously reported 2D MOLLI values of 701 ± 24 ms. Coefficient of variation values (12%) are higher than those previously reported for diaphragmatic navigator-based non-isotropic SAVA T 1 mapping at 3 T (7.4%). CONCLUSION: The proposed iNAV-based SAVA approach achieves free-breathing motion-corrected 3D whole-heart T 1 mapping at 0.55 T in approximately 7 min scan time for an isotropic resolution of 2 mm. In vivo experiments showed that the proposed sequence achieves good map quality, with comparable T 1 values and spatial variability compared to 2D MOLLI T 1 mapping. Further evaluation is warranted in patients with cardiovascular disease.
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    Motion-corrected whole-heart PET-MR for the simultaneous visualisation of coronary artery integrity and myocardial viability: an initial clinical validation
    (2018) Muñoz, Camila; Kunze, Karl P.; Neji, Radhouene; Vitadello, Teresa; Rischpler, Christoph; Botnar, René Michael; Nekolla, Stephan G.; Prieto Vásquez, Claudia
    Purpose: Cardiac PET-MR has shown potential for the comprehensive assessment of coronary heart disease. However, image degradation due to physiological motion remains a challenge that could hinder the adoption of this technology in clinical practice. The purpose of this study was to validate a recently proposed respiratory motion-corrected PET-MR framework for the simultaneous visualisation of myocardial viability (18F-FDG PET) and coronary artery anatomy (coronary MR angiography, CMRA) in patients with chronic total occlusion (CTO). Methods: A cohort of 14 patients was scanned with the proposed PET-CMRA framework. PET and CMRA images were reconstructed with and without the proposed motion correction approach for comparison purposes. Metrics of image quality including visible vessel length and sharpness were obtained for CMRA for both the right and left anterior descending coronary arteries (RCA, LAD), and relative increase in 18F-FDG PET signal after motion correction for standard 17-segment polar maps was computed. Resulting coronary anatomy by CMRA and myocardial integrity by PET were visually compared against X-ray angiography and conventional Late Gadolinium Enhancement (LGE) MRI, respectively. Results: Motion correction increased CMRA visible vessel length by 49.9% and 32.6% (RCA, LAD) and vessel sharpness by 12.3% and 18.9% (RCA, LAD) on average compared to uncorrected images. Coronary lumen delineation on motion-corrected CMRA images was in good agreement with X-ray angiography findings. For PET, motion correction resulted in an average 8% increase in 18F-FDG signal in the inferior and inferolateral segments of the myocardial wall. An improved delineation of myocardial viability defects and reduced noise in the 18F-FDG PET images was observed, improving correspondence to subendocardial LGE-MRI findings compared to uncorrected images. Conclusion: The feasibility of the PET-CMRA framework for simultaneous cardiac PET-MR imaging in a short and predictable scan time (~11 min) has been demonstrated in 14 patients with CTO. Motion correction increased visible length and sharpness of the coronary arteries by CMRA, and improved delineation of the myocardium by 18F-FDG PET, resulting in good agreement with X-ray angiography and LGE-MRI.
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    MRI-Guided Motion-Corrected PET Image Reconstruction for Cardiac PET/MRI
    (SOC NUCLEAR MEDICINE INC, 2021) Munoz, Camila; Ellis, Sam; Nekolla, Stephan G.; Kunze, Karl P.; Vitadello, Teresa; Neji, Radhouene; Botnar, Rene M.; Schnabel, Julia A.; Reader, Andrew J.; Prieto, Claudia
    Simultaneous PET/MRI has shown potential for the comprehensive assessment of myocardial health from a single examination. Furthermore, MRI-derived respiratory motion information, when incorporated into the PET image reconstruction, has been shown to improve PET image quality. Separately, MRI-based anatomically guided PET image reconstruction has been shown to effectively denoise images, but this denoising has so far been demonstrated mainly in brain imaging. To date, the combined benefits of motion compensation and anatomic guidance have not been demonstrated for myocardial PET/MRI. This work addressed this lack by proposing a single cardiac PET/MRI image reconstruction framework that fully utilizes MRI-derived information to allow both motion compensation and anatomic guidance within the reconstruction. Methods: Fifteen patients underwent an F-18-FDG cardiac PET/MRI scan with a previously introduced acquisition framework. The MRI data processing and image reconstruction pipeline produces respiratory motion fields and a high-resolution respiratory motion-corrected MR image with good tissue contrast. This MRI-derived information was then included in a respiratory motion-corrected, cardiac-gated, anatomically guided image reconstruction of the simultaneously acquired PET data. Reconstructions were evaluated by measuring myocardial contrast and noise and were compared with images from several comparative intermediate methods using the components of the proposed framework separately. Results: Including respiratory motion correction, cardiac gating, and anatomic guidance significantly increased contrast. In particular, myocardiumto-blood pool contrast increased by 143% on average (P < 0.0001), compared with conventional uncorrected, non-guided PET images. Furthermore, anatomic guidance significantly reduced image noise, by 16.1%, compared with nonguided image reconstruction (P < 0.0001). Conclusion: The proposed framework for MRI-derived motion compensation and anatomic guidance of cardiac PET data significantly improved image quality compared with alternative reconstruction methods. Each component of the reconstruction pipeline had a positive impact on the final image quality. These improvements have the potential to improve clinical interpretability and diagnosis based on cardiac PET/MR images.
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    Non-rigid motion-compensated 3D whole-heart T2 mapping in a hybrid 3T PET-MR system
    (2024) Schneider, Alina; Munoz, Camila; Hua, Alina; Ellis, Sam; Jeljeli, Sami; Kunze, Karl P.; Neji, Radhouene; Reader, Andrew J.; Reyes, Eliana; Ismail, Tevfik F.; Botnar, Rene M.; Prieto, Claudia
    Purpose: Simultaneous PET-MRI improves inflammatory cardiac disease diagnosis. However, challenges persist in respiratory motion and mis-registration between free-breathing 3D PET and 2D breath-held MR images. We propose a free-breathing non-rigid motion-compensated 3D T-2-mapping sequence enabling whole-heart myocardial tissue characterization in a hybrid 3T PET-MR system and provides non-rigid respiratory motion fields to correct also simultaneously acquired PET data.Methods: Free-breathing 3D whole-heart T-2-mapping was implemented on a hybrid 3T PET-MRI system. Three datasets were acquired with different T-2-preparation modules (0, 28, 55 ms) using 3-fold under sampled variable-density Cartesian trajectory. Respiratory motion was estimated via virtual 3D image navigators, enabling multi-contrast non-rigid motion-corrected MR reconstruction. T-2-maps were computed using dictionary-matching. Approach was tested in phantom, 8 healthy subjects, 14 MR only and 2 PET-MR patients with suspected cardiac disease and compared with spin echo reference (phantom) and clinical 2D T-2-mapping (in-vivo).Results: Phantom results show a high correlation (R-2 = 0.996) between proposed approach and gold standard 2D T-2 mapping. In-vivo 3D T-2-mapping average values in healthy subjects (39.0 +/- 1.4 ms) and patients (healthy tissue) (39.1 +/- 1.4 ms) agree with conventional 2D T-2-mapping (healthy = 38.6 +/- 1.2 ms, patients = 40.3 +/- 1.7 ms). Bland-Altman analysis reveals bias of 1.8 ms and 95% limits of agreement (LOA) of -2.4-6 ms for healthy subjects, and bias of 1.3 ms and 95% LOA of -1.9 to 4.6 ms for patients.Conclusion: Validated efficient 3D whole-heart T-2-mapping at hybrid 3T PET-MRI provides myocardial inflammation characterization and non-rigid respiratory motion fields for simultaneous PET data correction. Comparable T-2 values were achieved with both 3D and 2D methods. Improved image quality was observed in the PET images after MR-based motion correction.
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    Simultaneous 3D aortic lumen and vessel wall imaging at 0.55 T at either systole or diastole
    (John Wiley & Sons, 2025) Paredes Gálvez, Matías Ignacio; Castillo Passi, Carlos; Kunze, Karl P.; Fotaki, Anastasia; Littlewood, Simon; Botnar, René Michael; Prieto Vásquez, Claudia
    Purpose: To evaluate the feasibility of a novel, non-contrast enhanced, 3D, simultaneous bright-blood, and black-blood sequence (iT2prep-BOOST) for aortic imaging at 0.55 T at either systole or diastole. Methods: Simultaneous contrast-free 3D aortic lumen and vessel wall imaging at 0.55 T is achieved using the recently introduced iT2prep-BOOST framework that interleaves the acquisition of two bright blood images (with inversion recovery T-2 preparation [T2prep-IR] and no preparation). To enable either systolic or diastolic aortic imaging, three T-2 preparation pulses were investigated-an adiabatic RF pulse and two Malcolm-Levitt (MLEV) pulses (MLEV4 and MLEV8)-to improve image quality in regions with high flow and susceptibility. The proposed approach was evaluated in phantom, 10 healthy subjects and 3 patients with suspected cardiovascular disease. Bright- and black-blood images resulting from the three different T-2 preparation pulses were compared both qualitatively and quantitatively, using a 4-point Likert scale for vessel sharpness and presence of blood artifacts. Additionally, the contrast ratio between the lumen and myocardium was computed. Aortic measurements, including the aortic annulus area at systole and diastole, cusp-commissure measurement at the aortic root level during diastole, and aortic diameter at the ascending aortic level during diastole were also performed. Results: Excellent or good image quality scores were obtained for both bright- and black-blood images with iT2prep-BOOST at 0.55 T with all three preparation pulses. The use of MLEV8 T-2 preparation scheme improves systolic image quality, reducing the presence of artifacts with a significant difference (p < 0.05) at the mid descending aorta level. This scheme also increases the contrast ratio between aortic lumen and myocardium, compared to the previously used adiabatic RF T-2 preparation. The aortic root diameter and area were consistent with values reported in the literature for healthy subjects at 1.5 T. Conclusion: The feasibility of a novel, non-contrast-enhanced, 3D aortic imaging framework for simultaneous bright-blood and black-blood imaging was demonstrated at 0.55 T for either systole or diastole, with a scan time of 7 min. Good image quality scores and aortic measurements in agreement with literature values at 1.5 T were achieved with the MLEV8 T-2 preparation. Studies in a larger cohort of healthy subjects and patients with aortopathies are warranted.
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    Simultaneous 3D T1,T2, and fat-signal-fraction mapping with respiratory-motion correction for comprehensive liver tissue characterization at 0.55 T
    (2024) Tripp, Donovan P.; Kunze, Karl P.; Crabb, Michael G.; Prieto, Claudia; Neji, Radhouene; Botnar, Rene M.
    Purpose: To develop a framework for simultaneous three-dimensional (3D) mapping of T-1, T-2, and fat signal fraction in the liver at 0.55T. Methods: The proposed sequence acquires four interleaved 3D volumes with a two-echo Dixon readout. T-1 and T-2 are encoded into each volume via preparation modules, and dictionary matching allows simultaneous estimation of T-1, T-2, and M0 for water and fat separately. 2D image navigators permit respiratory binning, and motion fields from nonrigid registration between bins are used in a non rigid respiratory-motion-corrected reconstruction, enabling 100% scan efficiency from a free-breathingacquisition.Theintegratednatureoftheframeworkensures the resulting maps are always co-registered. Results: T-1, T-2, and fat-signal-fraction measurements in phantoms correlated strongly (adjusted r(2) > 0.98) with reference measurements. Mean liver tissue parameter values in 10 healthy volunteers were 427 +/- 22, 47.7 +/- 3.3ms, and 7 +/- 2% for T-1, T-2, and fat signal fraction, giving biases of 71,-30.0 ms, and -5 percentage points, respectively, when compared to conventional methods. Conclusion: A novel sequence for comprehensive characterization of liver tissue at 0.55T was developed. The sequence provides co-registered 3D T-1, T-2, and fat-signal-fraction maps with full coverage of the liver, from a single nine-and-a-half-minute free-breathing scan. Further development is needed to achieve accurate proton-density fat fraction (PDFF) estimation in vivo.