3D whole-heart coronary MR angiography at 1.5T in healthy volunteers: comparison between unenhanced SSFP and Gd-enhanced FLASH sequences

Accelerated 3D whole-heart non-contrast-enhanced mDIXON coronary MR angiography using deep learning-constrained compressed sensing reconstruction

OBJECTIVES

To investigate the feasibility of a deep learning-constrained compressed sensing (DL-CS) method in non-contrast-enhanced modified DIXON (mDIXON) coronary magnetic resonance angiography (MRA) and compare its diagnostic accuracy using coronary CT angiography (CCTA) as a reference standard.

METHODS

Ninety-nine participants were prospectively recruited for this study. Thirty healthy subjects (age range: 20-65 years; 50% female) underwent three non-contrast mDIXON-based coronary MRA sequences including DL-CS, CS, and conventional sequences. The three groups were compared based on the scan time, subjective image quality score, signal-to-noise ratio (SNR), and contrast-to-noise ratio (CNR). The remaining 69 patients suspected of coronary artery disease (CAD) (age range: 39-83 years; 51% female) underwent the DL-CS coronary MRA and its diagnostic performance was compared with that of CCTA.

RESULTS

The scan time for the DL-CS and CS sequences was notably shorter than that of the conventional sequence (9.6 ± 3.1 min vs 10.0 ± 3.4 min vs 13.0 ± 4.9 min; p < 0.001). The DL-CS sequence obtained the highest image quality score, mean SNR, and CNR compared to CS and conventional methods (all p < 0.001). Compared to CCTA, the accuracy, sensitivity, and specificity of DL-CS mDIXON coronary MRA per patient were 84.1%, 92.0%, and 79.5%; those per vessel were 90.3%, 82.6%, and 92.5%; and those per segment were 98.0%, 85.1%, and 98.0%, respectively.

CONCLUSION

The DL-CS mDIXON coronary MRA provided superior image quality and short scan time for visualizing coronary arteries in healthy individuals and demonstrated high diagnostic value compared to CCTA in CAD patients.

CRITICAL RELEVANCE STATEMENT

DL-CS resulted in improved image quality with an acceptable scan time, and demonstrated excellent diagnostic performance compared to CCTA, which could be an alternative to enhance the workflow of coronary MRA.

KEY POINTS

Current coronary MRA techniques are limited by scan time and the need for noise reduction. DL-CS reduced the scan time in coronary MR angiography. Deep learning achieved the highest image quality among the three methods. Deep learning-based coronary MR angiography demonstrated high performance compared to CT angiography.

Three-Dimensional Free-Breathing Whole-Heart Coronary Magnetic Resonance Angiography at 1.5 T: Gadobutrol-Enhanced Gradient-Echo Acquisition Sequence Versus Non-Contrast-Enhanced Steady-State Free Precession Sequence

OBJECTIVES

The objective of this study was to compare gadobutrol-enhanced gradient-echo sequence (GRE) acquisition with T2-prepared non-contrast-enhanced steady-state free precession (SSFP) in coronary magnetic resonance angiography at 1.5 T.

METHODS

Twenty-one subjects successfully completed GRE and SSFP acquisition. Signal-to-noise ratio (SNR), contrast-to-noise ratio, image quality, sharpness, visibility, length, and lumen diameter of vessels were analyzed by 2 experienced radiologists.

RESULTS

The SNR at whole left circumflex artery, left main artery, and proximal left descending artery (LAD) was significantly higher in SSFP acquisition (P < 0.05). The SNR of distal LAD was slightly higher in GRE acquisition (P < 0.05). The contrast-to-noise ratio at distal LAD, proximal and distal RCA were significantly higher with GRE acquisition (P < 0.05).

CONCLUSIONS

Double-dose gadobutrol-enhanced GRE and unenhanced SSFP coronary magnetic resonance angiography at 1.5 T have their own characteristics, and the combined use of the 2 methods may be taken into consideration.

Magnetic Resonance Imaging of Pulmonary Embolism: Diagnostic Accuracy of Unenhanced MR and Influence in Mortality Rates

OBJECTIVES

We evaluated the diagnostic value for pulmonary embolism (PE) of the True fast imaging with steady-state precession (TrueFISP) MRI, a method that allows the visualization of pulmonary vasculature without breath holding or intravenous contrast.

METHODS

This is a prospective investigation including 93 patients with suspected PE. All patients underwent TrueFISP MRI after undergoing CT pulmonary angiography (CTPA). Two independent readers evaluated each MR study, and consensus was obtained. CTPA results were analysed by a third independent reviewer and these results served as the reference standard. A fourth radiologist was responsible for evaluating if lesions found on MRI for both analysis were the same and if these were the correspondent lesions on the CTPA. Sensitivity, specificity, predictive values and accuracy were calculated. Evidence for death from PE within the 1-year follow-up was also assessed.

RESULTS

Two patients could not undergo the real-time MRI and were excluded from the study. PE prevalence was 22%. During the 1-year follow-up period, eight patients died, whereas PE was responsible for 12.5% of cases. Between patients who developed PE, only 5% died due to this condition. There were no differences between MR and CT embolism detection in these subjects. MR sequences had a sensitivity of 85%, specificity was 98.6% and accuracy was 95.6%. Agreement between readers was high (κ= 0.87).

CONCLUSIONS

Compared with contrast-enhanced CT, unenhanced MR sequences demonstrate good accuracy and no differences in the mortality rates in 1 year were detected.

Combined blood pool and extracellular contrast agents for pediatric and young adult cardiovascular magnetic resonance imaging

BACKGROUND

A comprehensive cardiac magnetic resonance (cardiac MR) study including both late gadolinium enhancement (LGE) and MR angiography may be indicated for patients with a history of acquired or congenital heart disease.

OBJECTIVE

To study the novel use of an extracellular agent for assessment of LGE combined with a blood pool contrast agent for detailed MR angiography evaluation to yield a comprehensive cardiac MR study in these patients.

MATERIALS AND METHODS

We reviewed clinical cardiac MR studies utilizing extracellular and blood pool contrast agents and noted demographics, clinical data and adverse events. We rated LGE image quality and MR angiography image quality for each vascular segment and calculated inter-rater variability. We also quantified contrast-to-noise ratio (CNR).

RESULTS

Thirty-three patients (mean age 13.9 ± 3 years) received an extracellular contrast agent (10 gadobenate dimeglumine, 23 gadopentetate dimeglumine) and blood pool contrast agent (33 gadofosveset trisodium). No adverse events were reported. MRI indications included Kawasaki disease (8), cardiomyopathy and coronary anatomy (15), repaired congenital heart disease (8), and other (2). Mean LGE quality was 2.6 ± 0.6 with 97% diagnostic imaging. LGE quality did not vary by type of contrast agent given (P = 0.07). Mean MR angiography quality score was 4.7 ± 0.6, with high inter-rater agreement (k = 0.6-0.8, P < 0.002). MR angiography quality did not vary by type of contrast agent used (P = 0.6).

CONCLUSION

Cardiac MR studies utilizing both extracellular and blood pool contrast agents are feasible and safe and provide excellent-quality LGE and MR angiography images. The use of two contrast agents allows for a comprehensive assessment of both myocardial viability and vascular anatomy during the same exam.

High-resolution coronary MR angiography for evaluation of patients with anomalous coronary arteries: visualization of the intramural segment

BACKGROUND

Anomalous origin of the coronary artery from the contralateral coronary sinus is a rare coronary anomaly associated with sudden death. The inter-arterial course is most closely associated with sudden death, but it has been suggested that the presence of an intramural segment of a right anomalous coronary is associated with more symptoms and therefore may be an important criterion for intervention in these patients.

OBJECTIVE

To demonstrate that MR angiography can accurately determine the presence or absence of an intramural segment in an anomalous coronary artery.

MATERIALS AND METHODS

All studies of children who underwent MR angiography for the evaluation of an anomalous coronary artery were retrospectively reviewed by two pediatric radiologists in consensus. Criteria for an intramural anomalous coronary artery were the presence of a small or slit-like ostium and the relative smaller size of the proximal intramural portion of the coronary artery in relation to the more distal epicardial coronary artery. The anomalous coronary artery was classified as not intramural if these two findings were absent. These findings were correlated with operative reports confirming the presence or absence of an intramural segment.

RESULTS

Twelve patients (86%) met MR angiography criteria for the presence of an intramural course. Only 2 patients (14%) met MR angiography criteria for a non-intramural course. When correlating with intraoperative findings, MR angiography was successful in distinguishing between intramural and non-intramural anomalous coronary arteries in all cases (P = 0.01).

CONCLUSION

MR angiography may be able to reliably identify the intramural segment of an anomalous coronary artery in older children using the imaging criteria of a small or slit-like ostium and relative decrease in size of the proximal portion of the anomalous coronary artery compared to the distal portion of the anomalous coronary artery. Determining the presence of the intramural segment may help with surgical planning and may be an important criterion for the determination of intervention in patients with inter-arterial anomalous right coronary arteries.

Optimizing the imaging protocol for ex vivo coronary artery wall using high-resolution MRI: an experimental study on porcine and human

Objective

To optimize the MR imaging protocol for coronary arterial wall depiction in vitro and characterize the coronary atherosclerotic plaques.

Materials and Methods

MRI examination was prospectively performed in ten porcine hearts in order to optimize the MR imaging protocol. Various surface coils were used for coronary arterial wall imaging with the same parameters. Then, the image parameters were further optimized for high-resolution coronary wall imaging. The signal-noise ratio (SNR) and contrast-noise ratio (CNR) of images were measured. Finally, 8 human cadaver hearts with coronary atherosclerotic plaques were prospectively performed with MRI examination using optimized protocol in order to characterize the coronary atherosclerotic plaques.

Results

The SNR and CNR of MR image with temporomandibular coil were the highest of various surface coils. High-resolution and high SNR and CNR for ex vivo coronary artery wall depiction can be achieved using temporomandibular coil with 512 × 512 in matrix. Compared with histopathology, the sensitivity and specificity of MRI for identifying advanced plaques were: type IV-V (lipid, necrosis, fibrosis), 94% and 95%; type VI (hemorrhage), 100% and 98%; type VII (calcification), 91% and 100%; and type VIII (fibrosis without lipid core), 100% and 98%, respectively.

Conclusion

Temporomandibular coil appears to be dramatically superior to eight-channel head coil and knee coil for ex vivo coronary artery wall imaging, providing higher spatial resolution and improved the SNR. Ex vivo high-resolution MRI has capability to distinguish human coronary atherosclerotic plaque compositions and accurately classify advanced plaques.

3.0-T whole-heart coronary magnetic resonance angiography: comparison of gadobenate dimeglumine and gadofosveset trisodium

Gadolinium enhanced coronary magnetic resonance angiography (MRA) at 3 T appears to be superior to non-contrast methods. Gadofosveset is an intravascular contrast agent that may be well suited to this application. The purpose of this study was to perform an intra-individual comparison of gadofosveset and gadobenate for coronary MRA at 3 T. In this prospective randomized study, 22 study subjects [8 (36%) male; 27.9 ± 6 years; BMI = 22.8 ± 2 kg/m(2)] underwent two studies using a contrast-enhanced inversion recovery three-dimensional fast low angle shot MRA at 3 T. The order of contrast agent administration was varied randomly, separated by an average of 30 ± 5 days, using either gadobenate dimeglumine (Gd-BOPTA; Bracco, 0.1 mmol/Kg) or gadofosveset trisodium (MS-325; Lantheus Med, 0.03 mmol/Kg). Acquisition time, signal-to-noise ratio (SNR) of coronary vessels and contrast-to-noise ratio (CNR) were evaluated. Of 308 coronary arteries and veins segment analyzed, overall SNR of coronary arteries and veins segments were not different for the two contrast agents (132 ± 79 for gadofosveset vs. 135 ± 78 for gadobenate, p = 0.69). Coronary artery CNR was greater for gadofosveset in comparison to gadobenate (73.5 ± 46.9 vs. 59.3 ± 75.7 respectively, p = 0.03). Gadofosveset-enhanced MRA images displayed better image quality than gadobenate-enhanced MRA images (2.77 ± 0.61 for gadofosveset vs. 2.11 ± 0.51, p < .001). Inter- and intra-reader variability was excellent (ICC > 0.90) for both contrast agents. Gadofosveset trisodium appears to show slightly better performance for coronary MRA at 3 T compared to gadobenate.