Three-dimensional assessment of image distortion induced by active cardiac implants in 3.0T CMR.

CMR at 3.0T in the presence of active cardiac implants remains a challenge due to susceptibility artifacts. Beyond a signal void that cancels image information, magnetic field inhomogeneities may cause distorted appearances of anatomical structures. Understanding influencing factors and the extent of distortion are a first step towards optimizing the image quality of CMR with active implants at 3.0T. All measurements were obtained at a clinical 3.0T scanner. An in-house designed phantom with a 3D cartesian grid of water filled spheres was used to analyze the distortion caused by four representative active cardiac devices (cardiac loop recorder, pacemaker, 2 ICDs). For imaging a gradient echo (3D-TFE) sequence and a turbo spin echo (2D-TSE) sequence were used. The work defines metrics to quantify the different features of distortion such as changes in size, location and signal intensity. It introduces a specialized segmentation technique based on a reaction-diffusion-equation. The distortion features are dependent on the amount of magnetic material in the active implants and showed a significant increase when measured with the 3D TFE compared to the 2D TSE. This work presents a quantitative approach for the evaluation of image distortion at 3.0T caused by active cardiac implants and serves as foundation for both further optimization of sequences and devices but also for planning of imaging procedures.

Deep Learning Super-Resolution Reconstruction for Fast and Motion-Robust T2-weighted Prostate MRI.

Background Deep learning (DL) reconstructions can enhance image quality while decreasing MRI acquisition time. However, DL reconstruction methods combined with compressed sensing for prostate MRI have not been well studied. Purpose To use an industry-developed DL algorithm to reconstruct low-resolution T2-weighted turbo spin-echo (TSE) prostate MRI scans and compare these with standard sequences. Materials and Methods In this prospective study, participants with suspected prostate cancer underwent prostate MRI with a Cartesian standard-resolution T2-weighted TSE sequence (T2C) and non-Cartesian standard-resolution T2-weighted TSE sequence (T2NC) between August and November 2022. Additionally, a low-resolution Cartesian DL-reconstructed T2-weighted TSE sequence (T2DL) with compressed sensing DL denoising and resolution upscaling reconstruction was acquired. Image sharpness was assessed qualitatively by two readers using a five-point Likert scale (from 1 = nondiagnostic to 5 = excellent) and quantitatively by calculating edge rise distance. The Friedman test and one-way analysis of variance with post hoc Bonferroni and Tukey tests, respectively, were used for group comparisons. Prostate Imaging Reporting and Data System (PI-RADS) score agreement between sequences was compared by using Cohen κ. Results This study included 109 male participants (mean age, 68 years ± 8 [SD]). Acquisition time of T2DL was 36% and 29% lower compared with that of T2C and T2NC (mean duration, 164 seconds ± 20 vs 257 seconds ± 32 and 230 seconds ± 28; P < .001 for both). T2DL showed improved image sharpness compared with standard sequences using both qualitative (median score, 5 [IQR, 4-5] vs 4 [IQR, 3-4] for T2C and 4 [IQR, 3-4] for T2NC; P < .001 for both) and quantitative (mean edge rise distance, 0.75 mm ± 0.39 vs 1.15 mm ± 0.68 for T2C and 0.98 mm ± 0.65 for T2NC; P < .001 and P = .01) methods. PI-RADS score agreement between T2NC and T2DL was excellent (κ range, 0.92-0.94 [95% CI: 0.87, 0.98]). Conclusion DL reconstruction of low-resolution T2-weighted TSE sequences enabled accelerated acquisition times and improved image quality compared with standard acquisitions while showing excellent agreement with conventional sequences for PI-RADS ratings. Clinical trial registration no. NCT05820113 © RSNA, 2023 Supplemental material is available for this article. See also the editorial by Turkbey in this issue.

Assessment of pulmonary artery stiffness by multiparametric cardiac magnetic resonance-surrogate for right heart catheterization.

Background: Cardiac magnetic resonance (CMR) imaging allows for multiparametric assessment of healthy pulmonary artery (PA) hemodynamics. Gender- and aging-associated PA stiffness and pressure alterations have remained clinically unestablished, however may demonstrate epidemiological differences in disease development. The aim of this study is to evaluate the role of CMR as a surrogate for catheter examinations by providing a comprehensive CMR assessment of sex- and age-related reference values for PA stiffness, flow, and pressure. Methods and Results: PA hemodynamics were studied between gender and age groups (>/<50 years) using phase-contrast CMR. Corresponding correlation analyses were performed. 179 healthy volunteers with a median age of 32.6 years (range 11.3-68.2) were examined. Males demonstrated increased PA compliance (median [interquartile range] or mean ± standard deviation) (20.8 mm2/mmHg [16.6; 25.8] vs. 19.2 ± 7.1 mm2/mmHg; P < 0.033), higher pulse wave velocity (2.00 m/s [1.35; 2.87] vs. 1.73 m/s [1.19; 2.34]; P = 0.018) and a reduced full width half maximum (FWHM) (219 ± 22 ms vs. 235 ± 23 ms; P < 0.001) than females. Mean, systolic, diastolic PA pressure and pulmonary proportional pulse pressure were significantly elevated for males compared to females (P < 0.001). Older subjects (>50 years) exhibited reduced PA elasticity (41.7% [31.0; 52.9] vs. 66.4% [47.7; 83.0]; P < 0.001), reduced PA compliance (15.4 mm2/mmHg [12.3; 20.7] vs. 21.3 ± 6.8 mm2/mmHg; P < 0.001), higher pulse wave velocity (2.59 m/s [1.57; 3.59] vs. 1.76 m/s [1.24; 2.34]; P < 0.001) and a reduced FWHM (218 ± 29 ms vs. 231 ± 21 ms; P < 0.001) than younger subjects. Conclusions: Velocity-time profiles are dependent on age and gender. PA stiffness indices deteriorate with age. CMR has potential to serve as a surrogate for right heart catheterization.

Signal voids of active cardiac implants at 3.0 T CMR.

Recent technical advancements allow cardiac MRI (CMR) examinations in the presence of so-called MRI conditional active cardiac implants at 3.0 T. However, the artifact burden caused by susceptibility effects remain an obstacle. All measurements were obtained at a clinical 3.0 T scanner using an in-house designed cubic phantom and optimized sequences for artifact evaluation (3D gradient echo sequence, multi-slice 2D turbo spin echo sequence). Reference sequences according to the American Society for Testing and Materials (ASTM) were additionally applied. Four representative active cardiac devices and a generic setup were analyzed regarding volume and shape of the signal void. For analysis, a threshold operation was applied to the grey value profile of each data set. The presented approach allows the evaluation of the signal void and shape even for larger implants such as ICDs. The void shape is influenced by the orientation of the B0-field and by the chosen sequence type. The distribution of ferromagnetic material within the implants also matters. The void volume depends both on the device itself, and on the sequence type. Disturbances in the B0 and B1 fields exceed the visual signal void. This work presents a reproducible and highly defined approach to characterize both signal void artifacts at 3.0 T and their influencing factors.

Assessment of coronary artery disease by post-mortem cardiac MR.

OBJECTIVES: Minimally invasive or virtual autopsies are being advocated as alternative to traditional autopsy, but have limited abilities to detect coronary artery disease. It was the objective of this study to assess if the occurrence of chemical shift artifacts (CSA) along the coronary arteries on non-contrast, post-mortem cardiac MR may be used to investigate coronary artery disease. METHODS: We retrospectively compared autopsy and CT findings of 30 cases with significant (≥75%), insignificant (<75%), or absent coronary artery stenosis to post-mortem cardiac MR findings. The chi-square test was used to investigate if the occurrence of CSA depends on the presence or absence of stenosis. Sensitivity, specificity and predictive values were calculated for each finding. RESULTS: CSA indicates the absence of (significant) stenosis (p<0.001). The occurrence of paired dark bands in lieu of CSA on post-mortem cardiac MR suggests (significant) coronary arteries stenosis (p<0.001). Both findings have a high specificity but low sensitivity. CONCLUSIONS: CSA is a marker of vessel patency. The presence of paired dark bands indicates stenosis. These criteria improve the ability of minimally invasive or virtual autopsy to detect coronary artery disease related deaths.

The influence of body temperature on image contrast in post mortem MRI.

OBJECTIVE: To assess the temperature dependency of tissue contrast on post mortem magnetic resonance (PMMR) images both objectively and subjectively; and to visually demonstrate the changes of image contrast at various temperatures. MATERIALS AND METHODS: The study was approved by the responsible justice department and the ethics committee. The contrast of water, fat, and muscle was measured using regions of interest (ROI) in the orbit of 41 human corpses to assess how body temperature (range 2.1-39.8 °C) relates to image contrast of T1-weighted (T1W) and T2-weighted (T2W) sequences on PMMR. Regressions were calculated using the method of least squares. Three readers judged visible changes of image contrast subjectively by consensus. RESULTS: There was a positive relationship between temperature and contrast on T1-weighted (T1W) images and between temperature and the contrast of fat/muscle on T2-weighted (T2W) images. There was a negative relationship between temperature and the contrast of water/fat and water/muscle on T2W images. Subjectively, the influence of temperature became visible below 20 °C on T2W images, and below 10 °C on T1W images. CONCLUSION: Image contrast on PMMR depends on the temperature of a corpse. Radiologists involved in post mortem imaging must be aware of temperature-related changes in MR image contrast. To preserve technical quality, scanning corpses below 10 °C should be avoided.

Assessment of magnetization transfer effects in myocardial tissue using balanced steady-state free precession (bSSFP) cine MRI.

Magnetization transfer imaging (MTI) by means of MRI exploits the mobility of water molecules in tissue and offers an alternative contrast mechanism beyond the more commonly used mechanisms based on relaxation times. A cardiac MTI method was implemented on a commercially available 1.5 T MR imager. It is based on the acquisition of two sets of cardiac-triggered cine balanced steady-state free precession (bSSFP) images with different levels of RF power deposition. Reduction of RF power was achieved by lengthening the RF excitation pulses of a cine bSSFP sequence from 0.24 ms to 1.7 ms, while keeping the flip angle constant. Normal volunteers and patients with acute myocardial infarcts were imaged in short and long axis views. Normal myocardium showed an MT ratio (MTR) of 33.0 +/- 3.3%. In acute myocardial infarct, MTR was reduced to 24.5 +/- 9.2% (P < 0.04), most likely caused by an increase in water content due to edema. The method thus allows detection of acute myocardial infarct without the administration of contrast agents.

Disparity between ratios of diameters and blood flows in central pulmonary arteries in postoperative congenital heart disease using MRI.

PURPOSE: To compare the relative severity of stenoses of right or left pulmonary arteries with differences in flow to each lung after repair of congenital heart disease (CHD). MATERIALS AND METHODS: A total of 15 patients with postoperative congenital heart disease underwent MRI to evaluate branch pulmonary artery stenoses. Spin-echo images and MR angiography were used to assess morphology, and velocity-encoded cine (VEC) MRI was used to measure flow in the right and left pulmonary arteries. The ratios of the narrowest diameters of the right to left pulmonary arteries (R/L size) and right to left pulmonary arterial flow (R/L flow) were compared using Spearman's correlation. F test was used to assess the significance of the regression coefficients. RESULTS: R/L size ratio varied from 0.50 to 2.66, while the R/L flow ratio varied from 0.36 to 12.02. There was an exponential relationship between R/L size and R/L flow, with r2=0.78 and P=0.001. However, severity of morphologic stenoses was not clinically useful for predicting flow reduction. Prediction residuals ranged from -136% to 54% of the true R/L flow. CONCLUSION: Anatomical evaluation of the pulmonary arteries does not predict accurately differential blood flow in patients with pulmonary stenoses. Therefore, blood flow measurements are essential when considering the need for further surgical or interventional procedures.

MR evaluation of cardiovascular physiology in congenital heart disease: flow and function.

Cardiovascular magnetic resonance (CMR) has become the method of choice in the evaluation of a number of questions in congenital heart disease. In addition to morphology, modern CMR techniques allow the visualization of function and flow in a temporally resolved manner. Among the pathologies where these methods play a major role are shunts, septal defects, aortic coarctation, anomalies of the pulmonary arteries, and valvular regurgitation. This paper explains the basics of functional and flow encoded CMR and discusses their application in the assessment of several types of congenital heart disease.

Placement of deep brain stimulator electrodes using real-time high-field interventional magnetic resonance imaging.

A methodology is presented for placing deep brain stimulator electrodes under direct MR image guidance. The technique utilized a small, skull-mounted trajectory guide that is optimized for accurate alignment under MR fluoroscopy. Iterative confirmation scans are used to monitor device alignment and brain penetration. The methodology was initially tested in a human skull phantom and proved capable of achieving submillimeter accuracy over a set of 16 separate targets that were accessed. The maximum error that was obtained in this preliminary test was 2 mm, motivating use of the technique in a clinical study. Subsequently, a total of eight deep brain stimulation electrodes were placed in five patients. Satisfactory placement was achieved on the first pass in seven of eight electrodes, while two passes were required with one electrode. Mean error from the intended target on the first pass was 1.0 +/- 0.8 mm (range = 0.1-1.9 mm). All procedures were considered technical successes and there were no intraoperative complications; however, one patient did develop a postoperative infection.

Carotid stent delivery in an XMR suite: immediate assessment of the physiologic impact of extracranial revascularization.

BACKGROUND AND PURPOSE: Patients undergoing stent placement as treatment for severe stenosis of the internal carotid artery (ICA) were assessed with MR imaging in a combined MR-radiographic (XMR) angiography suite. MR imaging was performed before and immediately following conventional radiography-guided stent placement. Changes in MR imaging measurable properties, including flow and perfusion, resulting from stent placement were evaluated. PATIENTS AND TECHNIQUES: MR imaging analysis was performed for 12 patients with >70% stenosis of the ICA before and after conventional radiography-guided deployment of a carotid stent. MR imaging acquisitions included angiography, quantitative flow analysis, perfusion, diffusion, and turbo-fluid-attenuated inversion recovery (FLAIR). These acquisitions were all performed immediately before and following stent placement by using conventional techniques. RESULTS: MR angiography proved sufficient for identifying the target lesion and permitting targeted flow analysis. MR flow analysis demonstrated a marked increase in flow in the treated carotid artery (+2.2 +/- 1.2 mL/s) and little change in other extracranial arteries. MR perfusion imaging showed no significant differences in relative cerebral blood volume between hemispheres before or after treatment, but there was a modest decrease in mean transit time and time to peak evident in the treated hemisphere after stent placement. Diffusion imaging did not demonstrate any ischemic foci resulting from carotid stent treatment. Hyperintensity of the CSF was noted on turbo-FLAIR acquisitions in the ipsilateral hemisphere following stent placement in 75% of patients. CONCLUSION: MR imaging reliably reflects the state of the carotid artery and provides a means of monitoring and quantifying the effects of revascularization.

Free-breathing, three-dimensional coronary artery magnetic resonance angiography: comparison of sequences.

PURPOSE: To compare six free-breathing, three-dimensional, magnetization-prepared coronary magnetic resonance angiography (MRA) sequences. MATERIALS AND METHODS: Six bright-blood sequences were evaluated: Cartesian segmented gradient echo (C-SGE), radial SGE (R-SGE), spiral SGE (S-SGE), spiral gradient echo (S-GE), Cartesian steady-state free precession (C-SSFP), and radial SSFP (R-SSFP). The right coronary artery (RCA) was imaged in 10 healthy volunteers using all six sequences in randomized order. Images were evaluated by two observers with respect to signal-to-noise ratio (SNR), contrast-to-noise ratio (CNR), visible vessel length, vessel edge sharpness, and vessel diameter. RESULTS: C-SSFP depicted RCA over the longest distance with high vessel sharpness, good SNR, and excellent background suppression. S-GE provided best SNR and CNR in proximal segments, but more vessel blurring and poorer background suppression, resulting in poor visualization of distal segments. R-SSFP images showed good background suppression and best vessel sharpness, but only moderate SNR. C-SGE provided good SNR and reasonable CNR, but lowest vessel sharpness. S-SGE and R-SGE visualized the RCA over the smallest distance, mostly due to vessel blurring and low SNR, respectively. CONCLUSION: Overall, Cartesian SSFP provided the best image quality with excellent vessel sharpness, visualization of long vessel segments, and good SNR and CNR.

Whole-heart steady-state free precession coronary artery magnetic resonance angiography.

Current implementations of coronary artery magnetic resonance angiography (MRA) suffer from limited coverage of the coronary arterial system. Whole-heart coronary MRA was implemented based on a free-breathing steady-state free-precession (SSFP) technique with magnetization preparation. The technique was compared to a similar implementation of conventional, thin-slab coronary MRA in 12 normal volunteers. Three thin-slab volumes were prescribed: 1) a transverse slab, covering the left main (LM) artery and proximal segments of the left anterior ascending (LAD) and left circumflex (LCX) coronary arteries; 2) a double-oblique slab covering the right coronary artery (RCA); and 3) a double-oblique slab covering the proximal and distal segments of the LCX. The whole-heart data set was reformatted in identical orientations. Visible vessel length, vessel sharpness, and vessel diameter were determined and compared separately for each vessel. Whole-heart coronary MRA visualized LM/LAD (11.7 +/- 3.4 cm) and LCX (6.9 +/- 3.6 cm) over a significantly longer distance than the transverse volume (LM/LAD, 6.1 +/- 1.1 cm, P < 0.001; LCX, 4.2 +/- 1.2 cm, P < 0.05). Improvements in visible vessel length for RCA and LCX in the whole-heart approach vs. their respective targeted volumes were not significant. It is concluded that the whole-heart coronary MRA technique improves visible vessel length and facilitates high-quality coronary MRA of the complete coronary artery tree in a single measurement.

Experimental renal artery embolization in a combined MR imaging/angiographic unit.

PURPOSE: The purpose of this study was to use a combined x-ray angiography and MR imaging (XMR) system to manipulate intraarterial catheters and monitor the deposition of gadolinium (Gd)-impregnated embolic microspheres in vivo in a canine kidney model. MATERIALS AND METHODS: Seven anesthetized dogs (18-28 kg) were studied. The renal arteries were catheterized under fluoroscopic guidance. Renal blood flow rates were assessed with velocity-encoded cine MR imaging before and after renal artery embolization with Gd-impregnated microspheres (300-500 and 500-700 micro m in size). The particles were injected in vivo into 14 canine renal arteries under fast dynamic T1-weighted MR imaging guidance at one frame per second. Postembolic microsphere distributions were assessed with MR imaging and digital subtraction angiography (DSA). RESULTS: Gd-impregnated microsphere injection into the renal arteries was successful in all animals. Renal enhancement due to the deposition of the particles persisted for at least 1 hour after the injection. The distribution of MR signal enhancement in the kidneys differed for the smaller versus the larger microspheres. The 300-500- micro m microspheres deposited preferentially in the outer cortical regions, whereas the 500-700- micro m microspheres preferentially deposited in the medulla and inner cortex. Renal blood flow was significantly reduced after the administration of both the 300-500- micro m microspheres (from 3.9 to 1.0 mL/min/g) and the 500-700- micro m microspheres (from 3.5 to 0.2 mL/min/g). CONCLUSION: MR imaging permits real-time guidance of arterial embolization with Gd-impregnated microspheres.

Steady-state imaging for visualization of endovascular interventions.

Steady-state imaging techniques offer the potential to couple high spatial and temporal resolution with good signal-to-noise ratio (SNR), which makes them ideally suited for fluoroscopic applications. However, disturbance of the steady state can result in artifacts and substantially reduced signal levels. In this study the use of steady-state imaging techniques was investigated as a means of guiding endovascular interventions with fluoroscopic MRI. Devices containing localized susceptibility defects were shown to disturb the steady-state signal of spins that pass through the magnetic field disturbances. It was demonstrated that these effects are appreciable and can make delineation of interventional devices difficult in the presence of flow. T(1)-shortening contrast agents were shown to dramatically reduce these effects by reducing the time taken to achieve steady state. The addition of a blood pool agent in an in vivo model was found to be necessary for adequate visualization of a dysprosium-marked catheter.

Endovascular stents in pulmonary valve and artery in swine: feasibility study of MR imaging-guided deployment and postinterventional assessment.

PURPOSE: To assess the feasibility of using magnetic resonance (MR) imaging to guide stent deployment in the pulmonary valve and artery and evaluate, after stent deployment, the position and morphology of and blood flow through the stent. MATERIALS AND METHODS: Angiography and 1.5-T MR imaging were performed in a dual-imaging suite. Nitinol stents were placed in the pulmonary valve and main pulmonary artery in five pigs by using MR imaging guidance. For interactive MR imaging monitoring of catheter manipulation and stent delivery, balanced fast field-echo and T1-weighted turbo field-echo sequences were used. Visualization of the delivery system was based on T2* (with air as the contrast material) or T1 (with gadodiamide as the contrast material). After stent deployment, the position and morphology of and flow through the stent were verified with multiphase multisection balanced fast field-echo and velocity-encoded cine MR imaging. Findings at angiography and postmortem examination also helped verify stent placement. The paired Student t test was used for data analysis. RESULTS: The stent was successfully deployed in all animals. The stent was placed distal to the pulmonary valve in four animals and across the pulmonary valve in one animal. The position and morphology of the stent were clearly depicted on balanced fast field-echo images. In the animal with the stent placed across the pulmonary valve, the pulmonary regurgitant fraction was 37%; this was not seen in the animals with stents placed distal to the pulmonary valve. No complication (eg, stent migration, intramural injury, or vascular perforation) was noted during the intervention. Findings at angiography and postmortem examination confirmed the position of the stents. CONCLUSION: MR imaging has the potential to guide stent placement in the pulmonary valve or artery and to evaluate flow volume within the stent lumen after the intervention.

MR portal venography: preliminary results of fast acquisition without contrast material or breath holding.

RATIONALE AND OBJECTIVES: The authors performed this study to evaluate the feasibility of using the steady-state free precession (SSFP) sequence to perform magnetic resonance (MR) venography of the portal venous system without the use of contrast material or breath holding. MATERIALS AND METHODS: Eleven patients underwent MR venography with the SSFP technique. Coronal three-dimensional images were obtained with respiratory triggering. Contrast material and respiratory suspension were not used. All patients had recently undergone at least one other imaging study (conventional angiography, transhepatic portal venography, ultrasound, or contrast-enhanced computed tomography), and these findings were correlated with those from MR venography. The structures evaluated were the main portal vein, right portal vein, left portal vein, superior mesenteric vein, and splenic vein. RESULTS: MR venography with SSFP accurately depicted the status of these veins in all cases except one. In this patient, MR venography depicted portal vein thrombus but could not indicate that it was tumor thrombus. CONCLUSION: MR venography with SSFP accurately depicted the portal venous system in 10 of 11 patients without the use of respiratory suspension or contrast material.

Real-time MR properties of particulate embolic agents tested in a dynamic flow model.

PURPOSE: Interventional magnetic resonance (MR)-guided transcatheter embolization could potentially limit radiation exposure and improve visualization of target organs. The feasibility of monitoring injection and distribution of embolic agents was assessed in a dynamic flow model with real-time MR imaging. MATERIALS AND METHODS: MR-compatible flow models were constructed with use of clear plastic chambers containing 170-microm polyethylene tubular filters. Gadolinium (Gd)-impregnated polyvinyl alcohol (PVA) particles (355-500 and 500-710 microm in size) and Gd-impregnated microspheres (Embospheres, 300-500 and 500-700 microm in size) were injected into the flow circuit under real-time dynamic T1-weighted fast field echo guidance at four images per second. A dynamic steady-state free precession sequence at four images per second was used to monitor the injection of unmodified Embo-Gold 700-900- microm particles. High-resolution scans were obtained before and after each particle injection. RESULTS: MR signal enhancement on the dynamic T1-weighted fast field echo sequence was visible during the injection of Gd-impregnated microspheres. Gd-impregnated PVA particles were not detected by this sequence. After injection, microsphere and PVA localization to the filter chambers was confirmed by the high-resolution scans. On the high-resolution sequences, relative MR signal enhancement of the microspheres was higher than that of the PVA particles. The Embo-Gold particles were minimally detectable on the dynamic sequence and undetectable by the high-resolution scan. After particle injection, direct inspection of the filter chamber showed trapping of all particle types and sizes. CONCLUSION: Real-time MR tracking of Gd-impregnated embolic agents is possible in vitro.

Single breath-hold extended free-breathing navigator-gated three-dimensional coronary MRA.

PURPOSE: To acquire the center of k-space while extending three-dimensional free-breathing navigator-gated coronary magnetic resonance (MR) angiography by an initial single breath-hold. MATERIALS AND METHODS: This approach was successfully applied in eight healthy adult subjects. Resulting images were compared with conventionally acquired free-breathing navigator-gated MR angiograms. RESULTS: The acquisition of k-space center during the single breath-hold resulted in a 26% increase (P < 0.05) of signal-to-noise ratio. Visible length of the right coronary artery, as well as contrast-to-noise ratio between the blood and the myocardial muscle, were identical. CONCLUSION: The breath-hold extension was shown to be a valuable technique that may be combined with first-pass contrast-enhanced MR imaging.