High-pitch dual-source CT angiography of the aortic valve-aortic root complex without ECG-synchronization

Purpose

To compare image quality and radiation dose of high-pitch computed tomography angiography(CTA) of the aortic valve-aortic root complex with and without prospective ECG-gating compared to a retrospectively ECG-gated standard-pitch acquisition.

Materials and Methods

120 patients(mean age 68?±?13 years) were examined using a 128-slice dual-source CT system using prospectively ECG-gated high-pitch(group A; n?=?40), non-ECG-gated high-pitch(group B; n?=?40) or retrospectively ECG-gated standard-pitch(C; n?=?40) acquisition techniques. Image quality of the aortic root, valve and ascending aorta including the coronary ostia was assessed by two independent readers. Image noise was measured, radiation dose estimates were calculated.

Results

Interobserver agreement was good(κ?=?0.64–0.78). Image quality was diagnostic in 38/40 patients(group A), 37/40(B) and 38/40(C) with no significant difference in number of patients with diagnostic image quality among all groups (p?=?0.56). Significantly more patients showed excellent image quality in group A compared to groups B and C(each, p?<?0.01). Average image noise was significantly different between all groups(p?<?0.05). Mean radiation dose estimates in groups A and B(each; 2.4?±?0.3 mSv) were significantly lower compared to group C(17.5?±?4.4 mSv; p?<?0.01).

Conclusion

High-pitch dual-source CTA provides diagnostic image quality of the aortic valve-aortic root complex even without ECG-gating at 86% less radiation dose when compared to a standard-pitch ECG-gated acquisition.     

High-pitch dual-source CT angiography of the whole aorta without ECG synchronisation: Initial experience

Objective

To investigate the feasibility, image quality and radiation dose for high-pitch dual-source CT angiography (CTA) of the whole aorta without ECG synchronisation.

Methods

Each group of 40 patients underwent CTA either on a 16-slice (group 1) or dual-source CT device with conventional single-source (group 2) or high-pitch mode with a pitch of 3.0 (group 3). The presence of motion or stair-step artefacts of the thoracic aorta was independently assessed by two readers.

Results

Subjective and objective scoring of motion and artefacts were significantly reduced in the high-pitch examination protocol (p?p?Conclusion High-pitch dual-source CT angiography of the whole aorta is feasible in unselected patients. As a significant advantage over regular pitch protocols, motion-free imaging of the aorta is possible without ECG synchronisation. Thus, this CT mode bears potential to become a standard CT protocol before trans-catheter aortic valve implantation (TAVI).

Key Points

? High-pitch CT angiography without ECG synchronisation can provide motion-free aortic imaging ? High-pitch CTA could become the standard protocol before trans-catheter aortic valve implantation ? Without ECG-gating, there is no need for special preparation of the patient     

Dual source multidetector CT-angiography before Transcatheter Aortic Valve Implantation (TAVI) using a high-pitch spiral acquisition mode

Objectives

Transcatheter Aortic Valve Implantation (TAVI) is an alternative to surgical valve replacement in high risk patients. Angiography of the aortic root, aorta and iliac arteries is required to select suitable candidates, but contrast agents can be harmful due to impaired renal function. We evaluated ECG-triggered high-pitch spiral dual source Computed Tomography (CT) with minimized volume of contrast agent to assess aortic root anatomy and vascular access.

Methods

42 patients (82?±?6?years) scheduled for TAVI underwent dual source (DS) CT angiography (CTA) of the aorta using a prospectively ECG-triggered high-pitch spiral mode (pitch?=?3.4) with 40?mL iodinated contrast agent. We analyzed aortic root/iliac dimensions, attenuation, contrast to noise ratio (CNR), image noise and radiation exposure.

Results

Aortic root/iliac dimensions and distance of coronary ostia from the annulus could be determined in all cases. Mean aortic and iliac artery attenuation was 320?±?70 HU and 340?±?77 HU. Aortic/iliac CNR was 21.7?±?6.8 HU and 14.5?±?5.4 HU using 100?kV (18.8?±?4.1 HU and 8.7?±?2.6 HU using 120?kV). Mean effective dose was 4.5?±?1.2?mSv.

Conclusions

High-pitch spiral DSCTA can be used to assess the entire aorta and iliac arteries in TAVI candidates with a low volume of contrast agent while preserving diagnostic image quality. Key Points ? Transcatheter Aortic Valve Implantation (TAVI) offers an alternative to surgical valve replacement in high risk patients. ? Such procedures require essential information about aortic root anatomy and vascular access. ? High pitch ECG-triggered dual source Computed Tomography (CT) can provide this information ? Sufficient image quality can be maintained even with low volumes of contrast agent and reduced x-ray exposure.     

Comparison of image quality and radiation dose of different pulmonary CTA protocols on a 128-slice CT: high-pitch dual source CT, dual energy CT and conventional spiral CT

Objectives

To compare image quality and radiation dose of high-pitch dual-source computed tomography (DSCT), dual energy CT (DECT) and conventional single-source spiral CT (SCT) for pulmonary CT angiography (CTA) on a 128-slice CT system.

Methods

Pulmonary CTA was performed with five protocols: high-pitch DSCT (100?kV), high-pitch DSCT (120?kV), DECT (100/140?kV), SCT (100?kV), and SCT (120?kV). For each protocol, 30 sex, age, and body-mass-index (mean 25.3?kg/m²) matched patients were identified. Retrospectively, two observers subjectively assessed image quality, measured CT attenuation (HU±SD) at seven central and peripheral levels, and calculated signal-to-noise-ratio (SNR) and contrast-to-noise-ratio (CNR). Radiation exposure parameters (CTDIvol and DLP) were compared.

Results

Subjective image quality was rated good to excellent in >92% (>138/150) with an interobserver agreement of 91.4%. The five protocols did not significantly differ in image quality, neither by subjective, nor by objective measures (SNR, CNR). By contrast, radiation exposure differed between protocols: significant lower radiation was achieved by using high-pitch DSCT at 100?kV (p?Conclusions SCT, high-pitch DSCT, and DECT protocols techniques result in similar subjective and objective image quality, but radiation exposure was significantly lower with high-pitch DSCT at 100?kV.

Key Points

• New CT protocols show promising results in pulmonary embolism assessment.
• High-pitch dual-source CT (DSCT) at 100?kV provides radiation dose savings for pulmonary CTA.
• High-pitch DSCT at 100?kV maintains diagnostic image quality for pulmonary CTA.
• Dual energy CT uses more radiation but also provides lung perfusion evaluation.
• Whether the additional perfusion data is worth the extra radiation remains undetermined.

     

Image quality of ultra-low radiation exposure coronary CT angiography with an effective dose <0.1 mSv using high-pitch spiral acquisition and raw data-based iterative reconstruction

Objectives

We evaluated the potential of prospectively ECG-triggered high-pitch spiral acquisition with low tube voltage and current in combination with iterative reconstruction to achieve coronary CT angiography with sufficient image quality at an effective dose below 0.1 mSv.

Methods

Contrast-enhanced coronary dual source CT angiography (2?×?128?×?0.6 mm, 80 kV, 50 mAs) in prospectively ECG-triggered high-pitch spiral acquisition mode was performed in 21 consecutive individuals (body weight <100 kg, heart rate ≤60/min). Images were reconstructed with raw data-based filtered back projection (FBP) and iterative reconstruction (IR). Image quality was assessed on a 4-point scale (1 = no artefacts, 4 = unevaluable).

Results

Mean effective dose was 0.06?±?0.01 mSv. Image noise was significantly reduced in IR (128.9?±?46.6 vs. 158.2?±?44.7 HU). The mean image quality score was lower for IR (1.9?±?1.1 vs. 2.2?±?1.0, P?<?0.0001). Of 292 coronary segments, 55 in FBP and 40 in IR (P?=?0.12) were graded “unevaluable”. In patients with a body weight ≤75 kg, both in FBP and in IR, the rates of fully evaluable segments were significantly higher in comparison to patients >75 kg.

Conclusions

Coronary CT angiography with an estimated effective dose <0.1 mSv may provide sufficient image quality in selected patients through the combination of high-pitch spiral acquisition and raw data-based iterative reconstruction.

Key Points

? Coronary CT angiography with an estimated effective dose <0.1 mSv is possible. ? Combination of high-pitch spiral acquisition with iterative reconstruction achieves sufficient image quality. ? Diagnostic accuracy remains to be assessed in future trials.     

Contrast agent bolus tracking with a fixed threshold or a manual fast start for coronary CT angiography

Objectives

Comparison of bolus tracking with a fixed threshold versus a manual fast start for coronary CT angiography.

Methods

We retrospectively analysed 320-row coronary CT angiography of 50 patients with suspected or known coronary artery disease. Twenty-five examinations were initiated by a bolus tracking method (group 1), 25 examinations with a manual fast surestart (group 2).

Results

Mean attenuation values in the ascending aorta were 519?±?111 Hounsfield units (HU) in group 1 and 476?±?65 HU in group 2 (p?=?0.10). Assessable vessel lengths were 171?±?44 mm vs 172?±?29 mm for the right coronary artery (p?=?0.91), 11?±?4 mm vs 12?±?4 mm for the left main (p?=?0.9), 163?±?28 mm vs 151?±?26 mm for the left anterior descending coronary artery (p?=?0.11) and 125?±?41 mm vs 110?±?37 mm for the left circumflex coronary artery (p?=?0.18). Image quality for all coronary arteries was not significantly different between the groups (p?>?0.41). The attenuation ratio between the left and right ventricle was 2.8?±?0.7 vs 3.6?±?1.0 (p?=?0.003). Significantly less contrast agent was used in group 2 (64?±?6 ml vs 80?±?0 ml; p?<?0.001).

Conclusions

Bolus tracking with a fixed threshold and with a manual fast start are both suitable methods; the fast start allowed a reduction of contrast agent volumes.

Key Points

? Fixed threshold bolus tracking is suitable for coronary 320-row CT angiography ? Manual fast start bolus tracking can reduce contrast agent volumes ? Manual fast start and fixed threshold initiation achieve good image quality ? Fixed threshold bolus tracking achieves a more reliable contrast bolus position     

Clinical evaluation of automatic tube voltage selection in chest CT angiography

Objective

To evaluate the clinical impact of automatic tube voltage selection on chest CT angiography (CTA).

Methods

Ninety-three patients were prospectively evaluated with a CT protocol aimed at comparing two successive CTAs acquired under similar technical conditions except for the kV selection: (1) the initial CTA was systematically obtained at 120 kVp and 90 ref mAs; (2) the follow-up CTA was obtained with an automatic selection of the kilovoltage (Care KV; Siemens Healthcare) for optimised CTA.

Results

At follow-up, 90 patients (97 %) underwent CTA with reduced tube voltage, 100 kV (n?=?26; 28 %) and 80 kV (n?=?64; 69 %), resulting in a significant dose-length-product reduction (follow-up: 87.27; initial: 141.88 mGy.cm; P?<?0.0001; mean dose reduction: 38.5 %) and a significant increase in the CNR at follow-up (follow-up: 11.5?±?3.5 HU; initial: 10.9?±?3.7 HU; P?=?0.03). The increase in objective image noise at follow-up (follow-up: 23.2?±?6.7 HU vs. 17.8?±?5.1 HU; P?<?0.0001) did not alter the diagnostic value of images.

Conclusion

Automatic tube voltage selection reduced the radiation dose delivered during chest CT angiograms by 38.5 % while improving the contrast-to-noise ratio of the examinations.

Key Points

? As low a dose as possible must be used for CT angiography. ? Automatic tube voltage selection permits reduced patient exposure. ? Lowering the kVp enables increased intravascular attenuation. ? Automatic tube voltage selection does not compromise the overall image quality.     

Accuracy, image quality and radiation dose comparison of high-pitch spiral and sequential acquisition on 128-slice dual-source CT angiography in children with congenital heart disease

Objectives

To compare accuracy, image quality and radiation dose between high-pitch spiral and sequential modes on 128-slice dual-source computed tomographic (DSCT) angiography in children with congenital heart disease (CHD).

Methods

Forty patients suspected with CHD underwent 128-slice DSCT angiography with high-pitch mode and sequential mode respectively. All the anomalies were confirmed by the surgical and/or the conventional cardiac angiography (CCA) findings. The diagnostic accuracy, the subjective and objective image quality and effective radiation doses were compared.

Results

There was no significant difference in diagnostic accuracy (χ ² ?=?0.963, P?>?0.05), the objective parameters for image quality (P?>?0.05) and the image quality of great vessels (u?=?167.500, P?>?0.05) between the two groups. The image quality of intracardiac structures and coronary arteries was significantly better in the sequential mode group than that in the high-pitch group (u?=?112.500 and 100.000, P?t?=?5.287, P?Conclusions Both the high-pitch and the sequential modes for 128-slice DSCT angiography provide high accuracy for the assessment of CHD in children, while the high-pitch mode, even with some image quality decrease, further significantly lowers the radiation dose.

Key Points

? Modern CT provides excellent anatomical detail of congenital heart disease. ? Dual source CT systems offer high-pitch spiral and sequential modes. ? The high-pitch mode provides high accuracy for the assessment of CHD. ? A few images using the high-pitch mode were occasionally slightly degraded. ? But the high-pitch mode significantly lowers the radiation dose.     

Reduced cardiac 123I-metaiodobenzylguanidine uptake in patients with spinocerebellar ataxia type 2: a comparative study with Parkinson’s disease

Purpose

Spinocerebellar ataxia type 2 (SCA2) is an autosomal dominant neurodegenerative disorder characterized by cerebellar ataxia, supranuclear ophthalmoplegia, and peripheral neuropathy. Autonomic nervous system dysfunction is often present. This study evaluated the cardiac sympathetic function in patients with SCA2 using ¹²³I-metaiodobenzylguanidine (MIBG) in comparison with patients with Parkinson’s disease (PD) and control subjects.

Methods

Nine patients with SCA2, nine patients with PD, and nine control subjects underwent ¹²³I-MIBG imaging studies from which early and late heart-to-mediastinum (H/M) ratios and myocardial washout rates were calculated.

Results

Early (F?=?12.3, p?<?0.0001) and late (F?=?16.8, p?<?0.0001) H/M ratios were significantly different among groups. In controls, early and late H/M ratios (2.2?±?0.12 and 2.1?±?0.20) were significantly higher than in patients with SCA2 (1.9?±?0.23 and 1.8?±?0.20, both p?<?0.05) and with patients with PD (1.7?±?0.29 and 1.4?±?0.35, both p?<?0.001). There was also a significant difference in washout rates among groups (F?=?11.7, p?<?0.0001). In controls the washout rate (19.9?±?9.6 %) was significantly lower (p?<?0.005) than in patients with PD (51.0?±?23.7 %), but not different from that in SCA2 patients (19.5?±?9.4 %). In SCA2 patients, in a multivariable linear regression analysis only the Scale for the Assessment and Rating of Ataxia score was independently associated with early H/M ratio (β?=??0.12, p?<?0.05).

Conclusion

¹²³I-MIBG myocardial scintigraphy demonstrated an impairment of cardiac sympathetic function in patients with SCA2, which was less marked than in PD patients. These results suggest that ¹²³I-MIBG cardiac imaging could become a useful tool for analysing the pathophysiology of SCA2.     

Dose–response relationship of locally applied nimodipine in an ex vivo model of cerebral vasospasm

Introduction

Cerebral vasospasm is a severe complication of subarachnoid hemorrhage (SAH). The calcium channel inhibitor nimodipine has been used for treatment of cerebral vasospasm. No evidence-based recommendations for local nimodipine administration at the site of vasospasm exist. The purpose of this study was to quantify nimodipine's local vasodilatory effect in an ex vivo model of SAH-induced vasospasm.

Methods

SAH-induced vasospasm was modeled by contracting isolated segments of rat superior cerebellar arteries with a combination of serotonin and a synthetic analog of prostaglandin A₂. A pressure myograph system was used to determine vessel reactivity of spastic as well as non-spastic arteries.

Results

Compared to the initial vessel diameter, a combination of serotonin and prostaglandin induced considerable vasospasm (55?±?2.5 % contraction; n?=?12; p?<?0.001). Locally applied nimodipine dilated the arteries in a concentration-dependent manner starting at concentrations as low as 1 nM (n?=?12; p?<?0.05). Concentrations higher than 100 nM did not relevantly increase the vasodilatory effect. Nimodipine's vasodilatory effect was smaller in spastic than in non-spastic vessels (n?=?12; p?<?0.05), which we assume to be due to structural changes in the vessel wall.

Conclusion

The described ex vivo model allows to investigate the dose-dependent efficacy of spasmolytic drugs prior to in vivo experiments. Low concentrations of locally applied nimodipine have a strong vasodilatory effect, which is of relevance when considering the local application of nimodipine in cerebral vasospasm.     

Quantification and characterisation of coronary artery plaque volume and adverse plaque features by coronary computed tomographic angiography: a direct comparison to intravascular ultrasound

Objective

We evaluated the performance of manual measures of coronary plaque volumes and atherosclerotic plaque features from coronary CT angiography (CTA), using intravascular ultrasound (IVUS) as the reference.

Methods

Thirty individual coronary plaques with suitable fiduciary markers were identified. Plaque volumes on coronary CTA were manually quantified by two observers and compared to IVUS plaque volumes as interpreted by an independent laboratory. The presence of adverse plaque characteristics—low attenuation plaque (LAP), positive remodelling (PR) and spotty calcification (SC)—on coronary CTA was evaluated and compared to IVUS.

Results

High correlation in plaque volumes was detected between observers (r?=?0.94, P?<?0.0001; 95 % limits of agreement <48.7 mm³, bias 6.6 mm³). Excellent correlation (r?=?0.95, P?<?0.0001) was noted in plaque volume between independent observers and IVUS (95 % limits of agreement <40.6 mm³, bias ?4.4 mm³) and did not differ from IVUS (105.0?±?56.7 vs. 109.4?±?60.7 mm³, P?=?0.2). The frequency of LAP (10 % vs. 17 %), PR (7 % vs. 10 %) and SC (27 % vs. 33 %) was similar between coronary CTA and IVUS (all P?=?NS).

Conclusions

Plaque volume on coronary CTA determined by manual methods demonstrates high correlation and modest agreement to IVUS. Further, coronary CTA demonstrates high accuracy for the identification of adverse plaque characteristics, including LAP, PR and SC.

Key Points

? Coronary CT angiography is a non-invasive test that enables coronary plaque assessment ? Plaque quantification by coronary CT angiography correlates well with intravascular ultrasound findings ? Coronary CT angiography can identify adverse plaque characteristics     

Reproducibility of aortic annulus measurements by computed tomography

Objectives

To evaluate a systematic approach for measurement of aortic annulus dimensions by cardiac computed tomography.

Methods

CT data sets of 64 patients were evaluated. An oblique cross-section aligned with the aortic root was created by systematically identifying the caudal insertion points of the three aortic cusps and sequentially aligning them in a double oblique plane. Aortic annulus dimensions, distances of coronary ostia and a suitable fluoroscopic projection angle were independently determined by two observers.

Results

Interobserver intraclass correlation coefficients (ICC) for aortic annulus diameters were excellent (ICC 0.89–0.93). Agreement for prosthesis size selection was excellent (??=?0.86 for mean, ??=?0.84 for area-derived and ??=?0.91 for circumference-derived diameter). Mean distances of the left/right coronary ostium were 13.4?±?2.4/14.4?±?2.8 mm for observer 1 and 13.2?±?2.7/13.5?±?3.2 mm for observer 2 (p?=?0.30 and p?=?0.0001, respectively; ICC 0.76/0.77 for left/right coronary artery). A difference of less than 10° for fluoroscopic projection angle was achieved in 84.3 % of patients.

Conclusions

A systematic approach to generate a double oblique imaging plane exactly aligned with the aortic annulus demonstrates high interobserver and intraobserver agreements for derived measurements which are not influenced by aortic root calcification.

Key Points

? Systematic approach to generate a double oblique imaging plane for TAVI evaluation. ? This method is straightforward and software independent. ? An approach with high reproducibility, not influenced by aortic root calcification.     

Assessment of coronary artery disease and calcified coronary plaque burden by computed tomography in patients with and without diabetes mellitus

Purpose

To compare the coronary atherosclerotic burden in patients with and without type-2 diabetes using CT Coronary Angiography (CTCA).

Methods and Materials

147 diabetic (mean age: 65?±?10?years; male: 89) and 979 nondiabetic patients (mean age: 61?±?13?years; male: 567) without a history of coronary artery disease (CAD) underwent CTCA. The per-patient number of diseased coronary segments was determined and each diseased segment was classified as showing obstructive lesion (luminal narrowing >50%) or not. Coronary calcium scoring (CCS) was assessed too.

Results

Diabetics showed a higher number of diseased segments (4.1?±?4.2 vs. 2.1?±?3.0; p??400 (p?p?p?p?=?0.003) and obstructive CAD (12.5% vs. 3.8%, p?=?0.01). Among patients with CCS????10 all diabetics with obstructive CAD had a zero CCS and one patient was asymptomatic.

Conclusions

Diabetes was associated with higher coronary plaque burden. The present study demonstrates that the absence of coronary calcification does not exclude obstructive CAD especially in diabetics.     

High-pitch computed tomography pulmonary angiography with iterative reconstruction at 80 kVp and 20 mL contrast agent volume

Objectives

To evaluate the image quality, radiation dose and diagnostic accuracy of 80kVp, high-pitch CT pulmonary angiography (CTPA) with iterative reconstruction using 20 ml of contrast agent.

Methods

One hundred patients with suspected pulmonary embolism (PE) were randomly divided into two groups (n?=?50 each; group A, 100 kVp, 1.2 pitch, 60 ml of contrast medium and filtered back projection algorithm; group B, 80 kVp, 2.2 pitch, 20 ml of contrast medium and sinogram affirmed iterative reconstruction). Image quality, diagnostic accuracy and radiation dose were evaluated and compared.

Results

Mean CT numbers of pulmonary arteries in group B were higher than those in group A (all P?P?P?=?0.807). The interobserver agreement was excellent (k?=?0.836). There was no significant difference in diagnostic accuracy between the two groups (P?>?0.05). Compared with group A, radiation dose of group B was reduced by 50.3 % (P?Conclusions High-pitch CTPA at 80 kVp can obtain sufficient image quality in normal-weight individuals with 20 ml of contrast agent and half the radiation dose of a conventional CTPA protocol.

Key Points

? CTPA is feasible at 80 kVp using only 20 ml of contrast agent. ? High-pitch CTPA at 80 kVp has an effective dose under 1 mSv. ? This CTPA protocol can obtain sufficient image quality in normal-weight individuals.     

Computed tomography angiography of carotid and coronary artery via a single-bolus injection protocol: a feasibility study using 320-row multidetector CT

Objectives

To investigate the feasibility of using a single-dose injection protocol in CT angiography (CTA) of the carotid and coronary artery with 320-row multidetector CT.

Methods

A total of 82 consecutive patients with suspected carotid artery disease underwent an original CTA protocol aiming at capturing the extra-cranial carotid arteries and coronary arteries simultaneously using 320-row MDCT. The image quality, attenuation, and CNRs of the carotid and coronary arteries were assessed. The lag time (between two separated volumetric acquisitions) was compared between patients with and without cardiac venous opacification (CVO). The contrast medium volume and radiation dose were recorded.

Results

The image quality was 99.4 % diagnostic in carotid and 86.9 % in coronary artery segments. The mean attenuation of carotid and coronary arteries ranged from 462.2 Hu to 533.7 Hu, 415.9 Hu to 454.7 Hu respectively. The mean CNR of the carotid and coronary artery ranged from 15.8 to 18.9 and 17.7 to 20.4 respectively. The lag time in patients with and without CVO was 5.75?±?1.64 s vs. 4.21?±?1.14 s (p?<?0.05). The mean radiation dose was 6.6?±?4.1 mSv.The mean contrast media volume was 71.9?±?9.1 ml.

Conclusions

The carotid and coronary artery can be imaged simultaneously via our original single-dose injection CTA protocol using 320-row CT with adequate image quality.

Key Points

? Carotid and coronary 320-row CTA can be achieved in a single-dose injection. ? Longer coverage was achieved with two or more volumes using 320-row CT. ? The single-dose protocol allows a reduced contrast agent dose of about 72 ml.     

Gated SPECT evaluation of left ventricular function using a CZT camera and a fast low-dose clinical protocol: comparison to cardiac magnetic resonance imaging

Purpose

CZT technology allows ultrafast low-dose myocardial scintigraphy but its accuracy in assessing left ventricular function is still to be defined.

Methods

The study group comprised 55 patients (23 women, mean age 63?±?9 years) referred for myocardial perfusion scintigraphy. The patients were studied at rest using a CZT camera (Discovery NM530c; GE Healthcare) and a low-dose ^99mTc-tetrofosmin clinical protocol (mean dose 264?±?38 MBq). Gated SPECT imaging was performed as a 6-min list-mode acquisition, 15 min after radiotracer injection. Images were reformatted (8-frame to 16-frame) using Lister software on a Xeleris workstation (GE Healthcare) and then reconstructed with a dedicated iterative algorithm. Analysis was performed using Quantitative Gated SPECT (QGS) software. Within 2 weeks patients underwent cardiac magnetic resonance imaging (cMRI, 1.5-T unit CVi; GE Healthcare) using a 30-frame acquisition protocol and dedicated software for analysis (MASS 6.1; Medis).

Results

The ventricular volumes obtained with 8-frame QGS showed excellent correlations with the cMRI volumes (end-diastolic volume (EDV), r?=?0.90; end-systolic volume (ESV), r?=?0.94; p?<?0.001). However, QGS significantly underestimated the ventricular volumes (mean differences: EDV, ?39.5?±?29 mL; ESV, ?15.4?±?22 mL; p?<?0.001). Similarly, the ventricular volumes obtained with 16-frame QGS showed an excellent correlations with the cMRI volumes (EDV, r?=?0.92; ESV, r?=?0.95; p?<?0.001) but with significant underestimations (mean differences: EDV, ?33.2?±?26 mL; ESV, ?17.9?±?20 mL; p?<?0.001). Despite significantly lower values (47.9?±?16 % vs. 51.2?±?15 %, p?<?0.008), 8-frame QGS mean ejection fraction (EF) was closely correlated with the cMRI values (r?=?0.84, p?<?0.001). The mean EF with 16-frame QGS showed the best correlation with the cMRI values (r?=?0.91, p?<?0.001) and was similar to the mean cMRI value (49.6?±?16 %, p not significant). Regional analysis showed a good correlation between both 8-frame and 16-frame QGS and cMRI wall motion score indexes (8-frame WMSI, r?=?0.85; 16-frame WMSI, r?=?0.89; p?<?0.01).

Conclusion

Low-dose gated SPECT with a CZT camera provides ventricular volumes that correlate well with cMRI results despite significant underestimation in the measure values. EF estimation appeared to be more accurate with 16-frame reformatted images than with 8-frame images.     

Myocardial oxidative metabolism is increased due to haemodynamic overload in patients with aortic valve stenosis: assessment using 11C-acetate positron emission tomography

Purpose

The relationship between myocardial oxidative metabolism and pressure overload in aortic valve stenosis (AS) is not fully elucidated. We identified the determinants of myocardial oxidative metabolism by measuring its changes after aortic valve replacement (AVR) in patients with AS.

Methods

Myocardial ¹¹C-acetate clearance rate constant (Kmono), an index of oxidative metabolism, was measured non-invasively by using positron emission tomography in 16 patients with moderate to severe AS and 7 healthy controls. The severity of AS was assessed by echocardiography. Of 16 patients, 5 were reexamined at 1 month after AVR.

Results

Kmono was significantly higher in patients with AS than healthy controls by 42% (0.068?±?0.014 vs 0.048?±?0.007/min, p?<?0.01). Kmono was significantly correlated with age (r?=?0.58, p?<?0.01), left ventricular (LV) mass index (r?=?0.61, p?<?0.01) and estimated systolic LV pressure (r?=?0.81, p?<?0.001) measured by echocardiography. By multivariate analysis, estimated LV systolic pressure was an independent predictor of Kmono (β?=?0.93, p?<?0.01). After AVR, Kmono (from 0.075?±?0.012 to 0.061?±?0.014/min, p?=?0.043) and LV mass index (from 183?±?49 to 124?±?41 g/ml², p?=?0.043) were significantly decreased despite no significant changes in rate-pressure product.

Conclusion

Myocardial oxygen metabolism was increased in patients with AS, which was decreased after AVR. The increased myocardial oxidative metabolism in AS was largely attributable to the pressure overload of the LV.     

Reverse blood flow-glucose metabolism mismatch indicates preserved oxygen metabolism in patients with revascularised myocardial infarction

Purpose

Positron emission tomography (PET) with ¹⁸F-fluorodeoxyglucose (FDG) has been reported to be unreliable for identifying viable myocardium in acute myocardial infarction (AMI), especially in areas with discordance in myocardial blood flow (MBF) and glucose metabolism. In myocardium with decreased FDG uptake but preserved MBF, referred to as exhibiting reverse mismatch, myocardial viability remains controversial and little is known about the metabolic state. The aims of this study were to clarify substrate use and to estimate myocardial viability in infarct areas exhibiting reverse mismatch.

Methods

Eighteen AMI patients with successful revascularisation were included in this study. Two weeks after onset, ¹¹C-acetate and ¹⁸F-FDG PET were performed to evaluate regional oxygen consumption (k _mono), MBF and glucose metabolism. Free fatty acid (FFA) metabolism was evaluated with ¹²³I-15-(p-iodophenyl)-3-(R, S)-methylpentadecanoic acid (BMIPP) single photon emission computed tomography (SPECT). To assess wall motion, movement in left ventricular endocardial surface was calculated using ECG-gated ^99mTc-tetrofosmin SPECT.

Results

The %k _mono values in reverse mismatch segments (52.6?±?13.6 %) were not significantly different from those in non-infarct segments (60.4?±?12.8 %, p?=?0.071) and normal match segments (preserved MBF and FDG uptake) (58.6?±?11.6 %, p?=?0.396), although regional wall motion was more severely impaired (3.06?±?2.52 mm vs 6.78?±?3.17 mm, p?<?0.0001, and vs 5.30?±?2.33 mm, p?=?0.042, respectively). Compared to segments with reduced match (reduced MBF and FDG uptake), %k _mono and %BMIPP uptake were significantly higher in reverse mismatch segments (52.6?±?13.6 % vs 37.4?±?8.9 %, p?=?0.0002, and 58.8?±?10.6 % vs 40.2?±?10.7 %, p?<?0.0001).

Conclusion

Reverse mismatch in reperfused AMI patients, high oxygen consumption and FFA metabolism were observed despite decreased glucose metabolism. We conclude that reverse mismatch indicated the myocardium with early restoration of MBF and aerobic FFA metabolism.     

Left and right ventricle assessment with Cardiac CT: validation study vs. Cardiac MR

Objectives

To compare Magnetic Resonance (MR) and Computed Tomography (CT) for the assessment of left (LV) and right (RV) ventricular functional parameters.

Methods

Seventy nine patients underwent both Cardiac CT and Cardiac MR. Images were acquired using short axis (SAX) reconstructions for CT and 2D cine b-SSFP (balanced-steady state free precession) SAX sequence for MR, and evaluated using dedicated software.

Results

CT and MR images showed good agreement: LV EF (Ejection Fraction) (52?±?14% for CT vs. 52?±?14% for MR; r?=?0.73; p?>?0.05); RV EF (47?±?12% for CT vs. 47?±?12% for MR; r?=?0.74; p?>?0.05); LV EDV (End Diastolic Volume) (74?±?21?ml/m2 for CT vs. 76?±?25?ml/m2 for MR; r?=?0.59; p?>?0.05); RV EDV (84?±?25?ml/m2 for CT vs. 80?±?23?ml/m2 for MR; r?=?0.58; p?>?0.05); LV ESV (End Systolic Volume)(37?±?19?ml/m2 for CT vs. 38?±?23?ml/m2 for MR; r?=?0.76; p?>?0.05); RV ESV (46?±?21?ml/m2 for CT vs. 43?±?18?ml/m2 for MR; r?=?0.70; p?>?0.05). Intra- and inter-observer variability were good, and the performance of CT was maintained for different EF subgroups.

Conclusions

Cardiac CT provides accurate and reproducible LV and RV volume parameters compared with MR, and can be considered as a reliable alternative for patients who are not suitable to undergo MR.

Key Points

? Cardiac-CT is able to provide Left and Right Ventricular function. ? Cardiac-CT is accurate as MR for LV and RV volume assessment. ? Cardiac-CT can provide accurate evaluation of coronary arteries and LV and RV function.