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.     

Correction for heart rate variability improves coronary magnetic resonance angiography

PURPOSE: To address degradation of coronary MR angiography (MRA) image quality due to heart rate variability (HRV)-associated variations in coronary artery position and motion. MATERIALS AND METHODS: Free-breathing navigator-gated and -corrected coronary MRA using subject-specific trigger delays and acquisition windows was combined with a real-time HRV correction algorithm, such as commonly used in left ventricular wall motion studies. Ten healthy adults underwent free-breathing navigator-gated and -corrected coronary MRA with and without HRV correction. Signal-to-noise (SNR), contrast-to-noise (CNR), vessel length, diameter, sharpness, and subjective image quality (on a five-point scale) were compared in a blinded fashion. RESULTS: Vessel sharpness improved significantly for both the left (LCA) and right (RCA) coronary artery systems (P = 0.016 and P = 0.015, respectively) with the use of HRV correction. Subjective image quality also improved significantly when HRV correction was used (P = 0.003). There were no significant differences with regard to SNR and CNR (P > 0.1). CONCLUSIONS: Preliminary results suggest that HRV correction improves objective and subjective image quality in coronary MRA. Continued studies in patients with known or suspected coronary artery disease are warranted to investigate the clinical impact of this technique.     

Impact of bulk cardiac motion on right coronary MR angiography and vessel wall imaging

The purpose of this study was to investigate the impact of in-plane coronary artery motion on coronary magnetic resonance angiography (MRA) and coronary MR vessel wall imaging. Free-breathing, navigator-gated, 3D-segmented k-space turbo field echo ((TFE)/echo-planar imaging (EPI)) coronary MRA and 2D fast spin-echo coronary vessel wall imaging of the right coronary artery (RCA) were performed in 15 healthy adult subjects. Images were acquired at two different diastolic time periods in each subject: 1) during a subject-specific diastasis period (in-plane velocity <4 cm/second) identified from analysis of in-plane coronary artery motion, and 2) using a diastolic trigger delay based on a previously implemented heart-rate-dependent empirical formula. RCA vessel wall imaging was only feasible with subject-specific middiastolic acquisition, while the coronary wall could not be identified with the heart-rate-dependent formula. For coronary MRA, RCA border definition was improved by 13% (P < 0.001) with the use of subject-specific trigger delay (vs. heart-rate-dependent delay). Subject-specific middiastolic image acquisition improves 3D TFE/EPI coronary MRA, and is critical for RCA vessel wall imaging.     

Improved three-dimensional free-breathing coronary magnetic resonance angiography using gadocoletic acid (B-22956) for intravascular contrast enhancement

PURPOSE: To evaluate gadocoletic acid (B-22956), a gadolinium-based paramagnetic blood pool agent, for contrast-enhanced coronary magnetic resonance angiography (MRA) in a Phase I clinical trial, and to compare the findings with those obtained using a standard noncontrast T2 preparation sequence. MATERIALS AND METHODS: The left coronary system was imaged in 12 healthy volunteers before B-22956 application and 5 (N = 11) and 45 (N = 7) minutes after application of 0.075 mmol/kg of body weight (BW) of B-22956. Additionally, imaging of the right coronary system was performed 23 minutes after B-22956 application (N = 6). A three-dimensional gradient echo sequence with T2 preparation (precontrast) or inversion recovery (IR) pulse (postcontrast) with real-time navigator correction was used. Assessment of the left and right coronary systems was performed qualitatively (a 4-point visual score for image quality) and quantitatively in terms of signal-to-noise ratio (SNR), contrast-to-noise ratio (CNR), vessel sharpness, visible vessel length, maximal luminal diameter, and the number of visible side branches. RESULTS: Significant (P < 0.01) increases in SNR (+42%) and CNR (+86%) were noted five minutes after B-22956 application, compared to precontrast T2 preparation values. A significant increase in CNR (+40%, P < 0.05) was also noted 45 minutes postcontrast. Vessels (left anterior descending artery (LAD), left coronary circumflex (LCx), and right coronary artery (RCA)) were also significantly (P < 0.05) sharper on postcontrast images. Significant increases in vessel length were noted for the LAD (P < 0.05) and LCx and RCA (both P < 0.01), while significantly more side branches were noted for the LAD and RCA (both P < 0.05) when compared to precontrast T2 preparation values. CONCLUSION: The use of the intravascular contrast agent B-22956 substantially improves both objective and subjective parameters of image quality on high-resolution three-dimensional coronary MRA. The increase in SNR, CNR, and vessel sharpness minimizes current limitations of coronary artery visualization with high-resolution coronary MRA.     

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.     

Non-invasive coronary angiography with 16-slice spiral computed tomography: image quality in patients with high heart rates

The purpose of this study was to assess segment image quality at high heart rates using 16-slice computed tomography and differential reconstruction for major coronary vessels. According to the following protocol, 16-slice CT coronary angiography in 46 patients with a mean heart rate of 86.3+/-11.8 was reconstructed. At three transverse planes, preview series were obtained and motion artifacts evaluated in 5% increments from 0-95% within the cardiac cycle. Relying on image quality in the previews, reconstructions were performed at three z-positions for each patient. Segment image quality was assessed in terms of artifacts and visibility. The effects of heart rate and trigger delay on image quality were analyzed. Optimal image quality was achieved at 25 to 35% of the cardiac cycle for the left circumflex (CX) and right coronary artery (RCA) or 30 to 40% for the left main (LM) and left anterior descending artery (LAD). Sixteen-slice CT and differential reconstruction produced good image quality with a low percentage of motion-degraded proximal and middle segments (8.8%). Grades were 1.5 for the LM, 1.9 for the LAD, 2.0 for the CX and 2.3 for the RCA. At high heart rates, good image quality of the coronary arteries is achieved by 16-slice CT and a sophisticated reconstruction strategy at peak to late systole.     

3D radial sampling and 3D affine transform‐based respiratory motion correction technique for free‐breathing whole‐heart coronary MRA with 100% imaging efficiency

The navigator gating and slice tracking approach currently used for respiratory motion compensation during free‐breathing coronary magnetic resonance angiography (MRA) has low imaging efficiency (typically 30–50%), resulting in long imaging times. In this work, a novel respiratory motion correction technique with 100% scan efficiency was developed for free‐breathing whole‐heart coronary MRA. The navigator signal was used as a reference respiratory signal to segment the data into six bins. 3D projection reconstruction k‐space sampling was used for data acquisition and enabled reconstruction of low resolution images within each respiratory bin. The motion between bins was estimated by image registration with a 3D affine transform. The data from the different respiratory bins was retrospectively combined after motion correction to produce the final image. The proposed method was compared with a traditional navigator gating approach in nine healthy subjects. The proposed technique acquired whole‐heart coronary MRA with 1.0 mm³ isotropic spatial resolution in a scan time of 6.8 ± 0.9 min, compared with 16.2 ± 2.8 min for the navigator gating approach. The image quality scores, and length, diameter and sharpness of the right coronary artery (RCA), left anterior descending coronary artery (LAD), and left circumflex coronary artery (LCX) were similar for both approaches (P > 0.05 for all), but the proposed technique reduced scan time by a factor of 2.5. Magn Reson Med, 2011. © 2011 Wiley‐Liss, Inc.     

Nitrate-induced coronary vasodilation by stress-magnetic resonance imaging: a novel noninvasive test of coronary vasomotion

PURPOSE: To evaluate the feasibility of assessing coronary vasodilation following exogenous nitrates, using magnetic resonance angiography (MRA). The assessment of coronary response to exogenous nitrovasodilators may have a diagnostic and prognostic impact in patients with coronary artery disease. To date, stress imaging of coronary artery vasomotion has been confined to the catheterization laboratory. MRA is emerging as a noninvasive tool for coronary artery imaging. MATERIALS AND METHODS: Coronary MRA was performed in 20 healthy volunteers (12 males, age = 33 +/- 8). We used spiral spoiled gradient echo (SSGE) sequences for imaging of coronary artery lumen. After the baseline short-axis view of the coronary artery was obtained, sublingual nitroglycerin (NTG) (0.3 mg) was administered. In all subjects, short-axis views of the coronary artery were acquired repetitively (8-10 times) from 1 up to 10 minutes after NTG administration. Measurements were obtained by two independent investigators. RESULTS: Interpretable short-axis view of left anterior descending artery (LAD) was obtained in 15 subjects (75%); in the remaining five subjects the right coronary artery (RCA) was examined. The interobserver variability was 15%, and the intraobserver variability 4%. The NTG-induced maximal vasodilation was 43 +/- 22%. The vasodilator response over time after NTG was maximal on average at 279 +/- 112 seconds, but with substantial heterogeneity. CONCLUSION: Entity and time course of nitrate-induced coronary vasodilation in the left anterior descending and/or RCA can be assessed using MRA with high feasibility and reproducibility. Coronary MRA has potential for dynamic imaging of coronary vasomotion.     

多层螺旋CT和三维屏气MR冠状动脉成像的对比研究

目的比较16层螺旋CT（16 multi-detector CT,16-MDCT）冠状动脉血管造影（CTA）和三维屏气冠状动脉MR血管造影（MRA）的图像质量以及诊断冠状动脉显著性狭窄（＞50%）的准确性.方法40例疑有冠心病患者在3 d内均行冠状动脉CTA和MRA检查,其中31例患者在2周内行冠状动脉造影检查.将冠状动脉分成9个节段（右冠状动脉近、中、远段,左冠状动脉主干,前降支近、中、远段和旋支近、远段）,由2名影像科医生共同对各个节段的图像质量按0～4级评分,比较CTA和MRA上各个节段的图像质量.以冠状动脉造影为标准,计算并比较CTA和MRA诊断31例冠状动脉显著性狭窄（＞50%）各项准确性指标.结果CTA在右冠状动脉中段的图像质量低于MRA,右冠状动脉近段二者无区别,其他节段均优于MRA.冠状动脉造影显示31例患者共有43个节段狭窄＞50%,CTA和MRA分别正确诊断出36和27个,其敏感性、特异性、阳性预测值和阴性预测值分别为83%、84%、49%、97%和63%、90%、55%、93%.结论除右冠状动脉中段,CTA大部分节段的图像质量优于MRA.CTA诊断冠状动脉显著性狭窄的敏感性高于MRA,但特异性低于MRA.冠状动脉CTA和MRA均表现了较高的阴性预测值,对排除冠状动脉狭窄具有临床价值.     

Coronary MR angiography at 3T during diastole and systole

PURPOSE: To investigate the impact of end-systolic imaging on quality of right coronary magnetic resonance angiography (MRA) in comparison to diastolic and to study the effect of RR interval variability on image quality. MATERIALS AND METHODS: The right coronary artery (RCA) of 10 normal volunteers was imaged at 3T using parallel imaging (sensitivity encoding [SENSE]). Navigator-gated three-dimensional (3D) gradient echo was used three times: 1) end-systolic short acquisition (SS): 35-msec window; 2) diastolic short (DS): middiastolic acquisition using 35-msec window; and 3) diastolic long (DL): 75-msec diastolic acquisition window. Vectorcardiogram (VCG) data was used to analyze RR variability. Vessel sharpness, length, and diameter were compared to each other and correlated with RR variability. Blinded qualitative image scores of the images were compared. RESULTS: Quantitative and qualitative parameters were not significantly different and showed no significant correlation with RR variability. CONCLUSION: Imaging the RCA at 3T during the end-systolic rest period using SENSE is possible without significant detrimental effect on image quality. Breaking away from the standard of imaging only during diastole can potentially improve image quality in tachycardic patients or used for simultaneous imaging during both periods in a single scan.     

Real-time motion correction in navigator-gated free-breathing double-oblique submillimeter 3D right coronary artery magnetic resonance angiography

RATIONALE AND OBJECTIVES: The purpose of this study was the investigation of the impact of real-time adaptive motion correction on image quality in navigator-gated, free-breathing, double-oblique three-dimensional (3D) submillimeter right coronary magnetic resonance angiography (MRA). MATERIALS AND METHODS: Free-breathing 3D right coronary MRA with real-time navigator technology was performed in 10 healthy adult subjects with an in-plane spatial resolution of 700 x 700 microm. Identical double-oblique coronary MR-angiograms were performed with navigator gating alone and combined navigator gating and real-time adaptive motion correction. Quantitative objective parameters of contrast-to-noise ratio (CNR) and vessel sharpness and subjective image quality scores were compared. RESULTS: Superior vessel sharpness, increased CNR, and superior image quality scores were found with combined navigator gating and real-time adaptive motion correction (vs. navigator gating alone; P < 0.01 for all comparisons). CONCLUSION: Real-time adaptive motion correction objectively and subjectively improves image quality in 3D navigator-gated free-breathing double-oblique submillimeter right coronary MRA.     

A fast 3D approach for coronary MRA.

Two-dimensional (2D)-breath-hold coronary magnetic resonance angiography (MRA) has been shown to be a fast and reliable method to depict the proximal coronary arteries. Recent developments, however, allow for free-breathing navigator gated and navigator corrected three-dimensional (3D) coronary MRA. These 3D approaches have potential for improved signal-to-noise ratio (SNR) and allow for the acquisition of adjacent thin slices without the misregistration problems known from 2D approaches. Still, a major impediment of a 3D acquisition is the increased scan time. The purpose of this study was the implementation of a free-breathing navigator gated and corrected ultra-fast 3D coronary MRA technique, which allows for scan times of less than 5 minutes. Twelve healthy adult subjects were examined in the supine position using a navigator gated and corrected ECG triggered ultra-fast 3D interleaved gradient echo planar imaging sequence (TFE-EPI). A 3D slab, consisting of 20 slices with a reconstructed slice thickness of 1.5 mm, was acquired with free-breathing. The diastolic TFE-EPI acquisition block was preceded by a T2prep pre-pulse, a diaphragmatic navigator pulse, and a fat suppression pre-pulse. With a TR of 19 ms and an effective TE of 5.4 ms, the duration of the data acquisition window duration was 38 ms. The in-plane spatial resolution was 1.0-1.3 mm*1.5-1.9 mm. In all cases, the entire left main (LM) and extensive portions of the left anterior descending (LAD) and right coronary artery (RCA) could be visualized with an average scan time for the entire 3D-volume data set of 2:57 +/- 0:51 minutes. Average contiguous vessel length visualized was 53 +/- 11 mm (range: 42 to 75 mm) for the LAD and 84 +/- 14 mm (range: 62 to 112 mm) for the RCA. Contrast-to-noise between coronary blood and myocardium was 5.0 +/- 2.3 for the LM/LAD and 8.0 +/- 2.9 for the RCA, resulting in an excellent suppression of myocardium. We present a new approach for free-breathing 3D coronary MRA, which allows for scan times superior to corresponding 2D coronary MRA approaches, and which takes advantage of the enhanced SNR of 3D acquisitions and the post-processing benefits of thin adjacent slices. The robust image quality and the short average scanning time suggest that this approach may be useful for screening the major coronary arteries or identification of anomalous coronary arteries. J. Magn. Reson. Imaging 1999;10:821-825.     

Volume‐targeted and whole‐heart coronary magnetic resonance angiography using an intravascular contrast agent

Purpose

To compare volume‐targeted and whole‐heart coronary magnetic resonance angiography (MRA) after the administration of an intravascular contrast agent.

Materials and Methods

Six healthy adult subjects underwent a navigator‐gated and ‐corrected (NAV) free breathing volume‐targeted cardiac‐triggered inversion recovery (IR) 3D steady‐state free precession (SSFP) coronary MRA sequence (t‐CMRA) (spatial resolution = 1 × 1 × 3 mm³) and high spatial resolution IR 3D SSFP whole‐heart coronary MRA (WH‐CMRA) (spatial resolution = 1 × 1 × 2 mm³) after the administration of an intravascular contrast agent B‐22956. Subjective and objective image quality parameters including maximal visible vessel length, vessel sharpness, and visibility of coronary side branches were evaluated for both t‐CMRA and WH‐CMRA.

Results

No significant differences (P = NS) in image quality were observed between contrast‐enhanced t‐CMRA and WH‐CMRA. However, using an intravascular contrast agent, significantly longer vessel segments were measured on WH‐CMRA vs. t‐CMRA (right coronary artery [RCA] 13.5 ± 0.7 cm vs. 12.5 ± 0.2 cm; P < 0.05; and left circumflex coronary artery [LCX] 11.9 ± 2.2 cm vs. 6.9 ± 2.4 cm; P < 0.05). Significantly more side branches (13.3 ± 1.2 vs. 8.7 ± 1.2; P < 0.05) were visible for the left anterior descending coronary artery (LAD) on WH‐CMRA vs. t‐CMRA. Scanning time and navigator efficiency were similar for both techniques (t‐CMRA: 6.05 min; 49% vs. WH‐CMRA: 5.51 min; 54%, both P = NS).

Conclusion

Both WH‐CMRA and t‐CMRA using SSFP are useful techniques for coronary MRA after the injection of an intravascular blood‐pool agent. However, the vessel conspicuity for high spatial resolution WH‐CMRA is not inferior to t‐CMRA, while visible vessel length and the number of visible smaller‐diameter vessels and side‐branches are improved. J. Magn. Reson. Imaging 2009;30:1191–1196. © 2009 Wiley‐Liss, Inc.     

Influence of heart rate on vessel visibility in noninvasive coronary angiography using new multislice computed tomography: experience in 94 patients

OBJECTIVES: Initial reports indicate that coronary artery lesions might be visualized with high sensitivity and specificity by the use of recently introduced multislice computed tomography (MSCT). Current CT technology offers a temporal resolution of 250 ms. In case of heart rates (HRs) >65 beats/min (bpm), however, the reconstruction software switches from a single-phase algorithm (using data from one heart cycle only) to a biphase algorithm using image data of two consecutive heart cycles, improving temporal resolution to down to 125 ms. Thus, it was the aim of the present study to evaluate the influence of the patients' (pts) HR on image quality expressed by vessel segment visibility. METHODS AND RESULTS: MSCT scans (Somatom VZ) were performed in 94 pts. Ten coronary segments were analyzed in each patient with regard to image quality (RCA: segments [sgts] 1-4, LMS: sgt 5, LAD: sgts 5-8, LCX: sgts 11, 12). A total of 697 of 940 (74.1%) sgts were accurately visualizable (RCA: 244/376 [64.9%], LMS: 94/94 [100%], LAD: 232/283 (82.3%), LCX: 146/188 [77.7%]). Beta-blocker therapy had a significant influence on mean HR (65 pts on beta-blocker, HR 65.1+/-10.7 bpm vs. 29 pts, HR 71.6+/-12.2 bpm, P=.01). A significant inverse correlation between HR and segmental visibility was found (r=-.48, P<.0001), with best visibility in pts with lower HRs (n=14 pts with 10 analyzable sgts, HR 60+/-10.1 vs. n=8 pts with 4 analyzable sgts, HR 79.9+/-6.9, P<.0001). CONCLUSIONS: Our results indicate that vessel visibility is highly dependent on the pts HR. Best vessel visibility was found in pts with HR <65 bpm with single-phase image reconstruction. Thus, it appears to be advisable to evaluate, and if needed, to lower the pts HRs before undergoing MSCT coronary angiography in order to achieve best image quality.     

64层螺旋CT冠状动脉成像的心率变化及其对图像质量的影响

目的探讨64层螺旋CT冠状动脉成像的心率变化及心率变化对图像质量的影响。方法回顾性分析138例64层螺旋CT冠状动脉成像资料,记录扫描期间的心率变化,根据不同的心率变化分组。A组心率变化0~4次/min,B组心率变化5~9次/min,C组心率变化10~20次/min,D组心率变化>20次/min。比较不同组间的冠状动脉各节段图像质量差异。结果64层螺旋CT冠状动脉成像心率变化在10次/min以内者占89%,RCA1、RCA3、PDA、LMA、LAD、LCX1及LCX2的图像质量A、B、C组间无显著差异(P>0.05),D组与A、B、C组对比图像质量明显下降(P<0.05);RCA2的A、B、C、D组间对比图像质量有显著差异(P<0.05),呈下降趋势。结论64层螺旋CT冠状动脉成像心率变化幅度小,心率变化>20次/min,才引起冠状动脉成像质量明显下降,RCA2段图像质量易受心率波动的影响。     

Usefulness of 64-slice MDCT for follow-up of young children with coronary artery aneurysm due to Kawasaki disease: initial experience

To evaluate the initial application and value of 64-slice multidetector computed tomography as an alternative diagnostic modality in the follow-up of young children with coronary artery aneurysm due to Kawasaki disease. Twelve boys (mean age 5.1 years, range 1.8-7.8 years) for follow-up (time range from 1.1 to 5.1 years) of known Kawasaki disease and coronary artery aneurysm underwent 64-slice MDCT ECG-gated coronary angiography. All data were acquired without breath holding. Two pediatric radiologists independently assessed image quality and the diameter of all coronary segments were measured for each patient. The number, position, shape and size of each coronary artery aneurysm were observed and compared with those of ECHO performed previously. A total of 118/156 segments permitted visualization with diagnostic image quality, the CT measurements showed good inter-observer and intra-observer reliability, coefficients were 0.93 and 0.88, respectively. A total of 30 coronary artery aneurysms were identified with measured mean of 7.5+/-3.8 mm in diameter, and of 12.4+/-9.1 mm in longitudinal lengths.10 tumors were small, 8 tumors were medium and 12 tumors were giant aneurysm. The affected segments included LM7/12(58.3%), 9/12(75%) of LAD1, 4/12(33.3%) of LAD2, 2/12(16.7%) of LCX1; 6/12(50%) of RCA1, 9/12(75%) of RCA2 and 4/12(33.3%) of RCA3, including affected two segments in 9 tumors and three segments in 1 tumor. Calcifications were found in 5 aneurysms and 3/5 with thrombosis; six stenotic segments were found. ECHO failed to detect 8 tumors with 2/8 in LAD, 1/8 in LCX and 5/8 in RCA, and those included 4 small aneurysms. The use of 64-slice MDCT angiography proved valuable for monitoring young children with Kawasaki disease. However, further study is necessary to specify the sensitivity and specificity of MDCT in the follow-up.     

Free-breathing 3D coronary MRA: the impact of "isotropic" image resolution

During conventional x-ray coronary angiography, multiple projections of the coronary arteries are acquired to define coronary anatomy precisely. Due to time constraints, coronary magnetic resonance angiography (MRA) usually provides only one or two views of the major coronary vessels. A coronary MRA approach that allowed for reconstruction of arbitrary isotropic orientations might therefore be desirable. The purpose of the study was to develop a three-dimensional (3D) coronary MRA technique with isotropic image resolution in a relatively short scanning time that allows for reconstruction of arbitrary views of the coronary arteries without constraints given by anisotropic voxel size. Eight healthy adult subjects were examined using a real-time navigator-gated and corrected free-breathing interleaved echoplanar (TFE-EPI) 3D-MRA sequence. Two 3D datasets were acquired for the left and right coronary systems in each subject, one with anisotropic (1.0 x 1.5 x 3.0 mm, 10 slices) and one with "near" isotropic (1.0 x 1.5 x 1.0 mm, 30 slices) image resolution. All other imaging parameters were maintained. In all cases, the entire left main (LM) and extensive portions of the left anterior descending (LAD) and the right coronary artery (RCA) were visualized. Objective assessment of coronary vessel sharpness was similar (41% +/- 5% vs. 42% +/- 5%; P = NS) between in-plane and through-plane views with "isotropic" voxel size but differed (32% +/- 7% vs. 23% +/- 4%; P < 0.001) with nonisotropic voxel size. In reconstructed views oriented in the through-plane direction, the vessel border was 86% more defined (P < 0.01) for isotropic compared with anisotropic images. A smaller (30%; P < 0.001) improvement was seen for in-plane reconstructions. Vessel diameter measurements were view independent (2.81 +/- 0.45 mm vs. 2.66 +/- 0.52 mm; P = NS) for isotropic, but differed (2.71 +/- 0.51 mm vs. 3.30 +/- 0.38 mm; P < 0.001) between anisotropic views. Average scanning time was 2:31 +/- 0:57 minutes for anisotropic and 7:11 +/- 3:02 minutes for isotropic image resolution (P < 0.001). We present a new approach for "near" isotropic 3D coronary artery imaging, which allows for reconstruction of arbitrary views of the coronary arteries. The good delineation of the coronary arteries in all views suggests that isotropic 3D coronary MRA might be a preferred technique for the assessment of coronary disease, although at the expense of prolonged scan times. Comparative studies with conventional x-ray angiography are needed to investigate the clinical utility of the isotropic strategy.     

Coronary anomalies assessed by whole‐heart isotropic 3D magnetic resonance imaging for cardiac morphology in congenital heart disease

Purpose

To determine the value of whole‐heart three‐dimensional magnetic resonance imaging (MRI) for coronary artery imaging in children/adolescents with congenital heart disease (CHD).

Materials and Methods

Forty children/adolescents (median age: 14 years, range 2.6–25.8) with CHD underwent free‐breathing navigator‐gated isotropic three‐dimensional steady‐state free‐precession (3D‐SSFP) MRI for cardiac morphology. Two observers independently evaluated visibility of origin, course, vessel lengths, image quality (IQ), and contrast between coronary lumen and myocardium. A subgroup was compared with cardiac catheter.

Results

The total scan time was 6.3 ± 3.2 minutes (mean ± SD, at mean heart rate 76 ± 15/min). The mean vessel length for right coronary artery (RCA) by observer 1 was 97 ± 43 mm (observer 2: 94 ± 37 mm), for left main and anterior descending artery (LM/LAD) 91 ± 40 mm (observer 2: 90 ± 40 mm), and for left circumflex artery (LCX) 64 ± 28mm (observer 2: 66 ± 28 mm). The mean vessel contrast was 0.34 ± 0.05 (range: 0.23–0.45; maximum = 1, minimum = 0). On a 4‐level score (1 = nondiagnostic, 4 = excellent), mean IQ scores ranged between 2.3–2.9 (±0.8–1.0). Both observers agreed on the presence/proximal course of RCA in 40/40, LM/LAD in 38/40, and LCX in 36/40 patients. There was complete agreement with invasive coronary angiography available in 12/40 patients (six anomalies).

Conclusion

Isotropic whole‐heart 3D‐MRI for cardiac morphology allows reliable discrimination between normal and abnormal coronary anatomy in children/adolescents with CHD. J. Magn. Reson. Imaging 2009;29:320–327. © 2009 Wiley‐Liss, Inc.     

屏气三维快速平衡稳态进动序列在磁共振冠状动脉成像中的可靠性研究

目的 :评价屏气三维快速平衡稳态进动 ( 3D FIESTA)序列在冠状动脉磁共振成像 (CMRA)中的可靠性。材料和方法 :67例受检者 ,采用心电触发的三维FIESTA序列 ,呼气末屏气采样 ,在 8个不同层面方向定位显示冠状动脉各主支 ,包括右冠 (RCA)、左主支 (LM)、左前降支 (LAD)和左回旋支 (LCX) ,以 0 -IV级图像质量体系为参照 ,评分II级以上作为可接受标准 ,采用美国心脏协会 (AHA)的冠状动脉分段标准评价其显示的长度和范围。结果 :67例受检者能够屏气配合完成检查的 65例 ,检查适用率为 97.0 % ;对AHA 18、19段 (RCA近段和中段 )、AHA 1、2 (LM)、AHA 3、5、7段 (LAD近段和中段 ) ,AHA 10段 (LCX近段 )的显示可重复性为 10 0 % ;对AHA 9、14、2 1段 (LAD、LCX和RCA的远段 )的显示可重复性分别为 95 .3 8%、72 .3 1%、96.92 %。结论 :此三维FIESTA序列可以稳定显示冠状动脉主要分支的近段和中段 ,初步具备临床应用的价值。     

Evaluation of the optimal image reconstruction interval for coronary artery imaging using 64-slice computed tomography

BACKGROUND: Cardiac computed tomography (CT) has become an established complement in cardiac imaging. Thus, optimized image quality is diagnostically crucial. PURPOSE: To prospectively evaluate whether, by using 64-slice CT, a specific reconstruction interval can be identified providing best image quality for all coronary artery segments and each individual coronary artery. MATERIAL AND METHODS: 311 coronary segments of 14 men and seven women were analyzed using 64-slice CT. Data reconstruction was performed in 5% increments from 5-100% of the R-R interval. Four experienced observers independently evaluated image quality of the coronary arteries according to the AHA classification. A three-point ranking scale was applied: 1, very poor, no evaluation possible; 2, diagnostically sufficient quality; 3, highest image quality, no artifacts. RESULTS: The best reconstruction point for all segments was found to be 65% of the R-R interval (mean value 2.4+/-0.5; P<0.05). On a per-artery basis, best image quality was again achieved at 65% of the R-R interval: RCA 2.2+/-0.4, LCA 2.4+/-0.5, LM 2.5+/-0.2, LAD 2.3+/-0.4, LCX 2.3+/-0.5. CONCLUSION: By using 64-slice CT, the need for adjusting the reconstruction point to each coronary segment might be overcome. Best image quality was achieved with image reconstruction at 65% of the R-R interval for all coronary segments as well as each coronary artery.