Ines Valenta

Johns Hopkins University, Baltimore, Maryland, United States

Are you Ines Valenta?

Claim your profile

Publications (69)359.26 Total impact

  • [Show abstract] [Hide abstract]
    ABSTRACT: Conventional myocardial perfusion scintigraphy with SPECT/CT or with PET/CT has been established as pivotal clinical imaging modality for the identification of hemodynamically obstructive coronary artery disease (CAD) and risk stratification of patients with suspected or known CAD. While the assessment of the relative distribution of radiotracer uptake in the left-ventricular (LV) myocardium during vasomotor stress identifies the "culprit" or most severe CAD lesion in multivessel disease, flow-limiting effects of remaining but less severe epicardial lesions may be missed. This limitation principally may be overcome by the possibility of PET/CT with radiotracer-kinetic modeling to concurrently assess left-ventricular (LV) myocardial blood flow (MBF) in ml/g/min at rest and during vasomotor stress and the resulting myocardial flow reserve (MFR). While a stress-induced regional reduction in radiotracer uptake or perfusion identifies the most advanced epicardial lesion, flow-limiting effects of the other epicardial lesions may principally be identified by regional reductions in MFR. Conversely, reductions in MFR in CAD may be appreciated as suboptimal as they reflect not only the consequences of flow-limiting effects of epicardial stenosis but also of microvascular dysfunction. The relatively low specificity of a reduced therefore MFR may hamper a clear identification of the downstream hemodynamic effects of an epicardial lesion on hyperemic coronary flow increases. In this scenario, there is increasing evidence that the PET assessment of an abnormal decrease in MBF from the base to the apex of the LV during hyperemic flows, a so-called longitudinal flow gradient, is primarily related to fluid dynamic consequences of CAD-induced diffuse luminal and/or focal narrowing of the epicardial artery. The combined evaluation of the MFR and corresponding longitudinal MBF gradient could emerge as new a novel analytic concept to further optimize the identification and characterization of hemodynamic CAD burden in multivessel disease, which, however, warrants further clinical validation.
    Current Cardiology Reports 01/2015; 17(1):550. DOI:10.1007/s11886-014-0550-z
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: Myocardial perfusion imaging with SPECT/CT or with PET/CT is a mainstay in clinical practice for the diagnostic assessment of downstream, flow-limiting effects of epicardial lesions during hyperemic flows and for risk stratification of patients with known or suspected coronary artery disease (CAD). In patients with multivessel CAD, the relative distribution of radiotracer uptake in the left ventricular myocardium during stress and rest accurately identifies flow-limiting epicardial lesions or the most advanced, so called culprit, lesion. Often, less severe obstructive CAD lesions may go undetected or underdiagnosed. The concurrent ability of PET/CT with radiotracer kinetic modeling to determine myocardial blood flow (MBF) in absolute terms (mL/g/min) at rest and during vasomotor stress allows the computation of regional myocardial flow reserve (MFR) as an adjunct to the visual interpretation of myocardial perfusion studies. Adding the noninvasive evaluation and quantification of MBF and MFR by PET imaging to the visual analysis of myocardial perfusion may (1) identify subclinical CAD, (2) better characterize the extent and severity of CAD burden, and (3) assess "balanced" decreases of MBF in all 3 major coronary artery vascular territories. Recent investigations have demonstrated that PET-determined reductions in hyperemic MBF or MFR in patients with subclinical or clinically manifest CAD are predictive of increased relative risk of future cardiovascular events and clinical outcome. Quantifying MFR with PET enables the identification and characterization of coronary vasodilator dysfunction as functional precursor of the CAD process, which offers the unique opportunity to monitor its response to lifestyle or risk factor modification by preventive medical care. Whether an improvement or even normalization of hyperemic MBF or the MFR in subclinical or in clinically manifest CAD confers an improved long-term cardiovascular outcome remains untested. Nonetheless, given the recent growth in the clinical utilization of myocardial perfusion PET, image-guided and personalized preventive care of vascular health may become a reality in the near future.
    Seminars in Nuclear Medicine 07/2014; 44(4):274-293. DOI:10.1053/j.semnuclmed.2014.04.002 · 3.13 Impact Factor
  • [Show abstract] [Hide abstract]
    ABSTRACT: Objectives The purpose of this study was to evaluate the diagnostic value of a positron emission tomography (PET)/computed tomography (CT)–determined longitudinal decrease in myocardial blood flow (MBF) gradient during hyperemia and myocardial flow reserve (MFR) for the identification of epicardial stenosis ≥50%. Background Although PET-determined reductions in MFR are increasingly applied to identify epicardial lesions in coronary artery disease (CAD), it may be seen as a suboptimal approach due to the nonspecific origin of decreases in MFR. Methods In 24 patients with suspected or known CAD, MBF was measured with 13N-ammonia and PET/CT in ml/g/min at rest, during dipyridamole stimulation, and the corresponding MFR was calculated. MBF was also determined in the mid and mid-distal myocardium of the left ventricle (LV). A decrease in MBF from mid to mid-distal LV myocardium was defined as longitudinal MBF gradient. MBF parameters were determined in the myocardial region with stress-induced perfusion defect and with stenosis ≥50% (territory 1), without defect but with stenosis ≥50% (territory 2), or without stenosis ≥50% (territory 3). Results In territories 1 and 2 with focal stenosis ≥50%, the severity of epicardial artery stenosis correlated with the Δlongitudinal MBF gradient (stress-rest) (r = 0.52; p < 0.0001), while this association was less pronounced for corresponding MFR (r = −0.40; p < 0.003). On a vessel-based analysis, the sensitivity and specificity of the Δlongitudinal MBF gradient in the identification of epicardial lesions was higher than those for MFR (88% vs. 71%, p ≤ 0.044; and 81% vs. 63%, p = 0.134, respectively). Combining both parameters resulted in an optimal sensitivity of 100% and intermediate specificity of 75%. The diagnostic accuracy was highest for the combined analysis than for the Δlongitudinal MBF gradient or MFR alone (94% vs. 86%, p ≤ 0.003; and 94% vs. 70%, p ≤ 0.0002). Conclusions The combined evaluation of a Δlongitudinal MBF gradient and MFR may evolve as a new promising analytic approach to further optimize the identification of CAD lesions.
    JACC. Cardiovascular imaging 04/2014; 7(4). DOI:10.1016/j.jcmg.2014.01.001 · 6.99 Impact Factor
  • [Show abstract] [Hide abstract]
    ABSTRACT: Increases in intra-abdominal visceral adipose tissue have been widely appreciated as a risk factor for metabolic disorders such as dyslipidemia, hypertension, insulin resistance, and type 2 diabetes, whereas this is not the case for peripheral or subcutaneous obesity. While the underlying mechanisms that contribute to these differences in adipose tissue activity remain uncertain, increases in visceral fat commonly induce metabolic dysregulation, in part because of increased venous effluent of fatty acids and/or adipokines/cytokines to the liver. Increased body weight, paralleled by an increase in plasma markers of the insulin-resistance syndrome and chronic inflammation, is independently associated with coronary circulatory dysfunction. Recent data suggest that plasma proteins originating from the adipose tissue, such as endocannabinoids (EC), leptin, and adiponectin (termed adipocytes) play a central role in the regulation and control of coronary circulatory function in obesity. Positron emission tomography (PET) in concert with tracer kinetic modeling is a well established technique for quantifying regional myocardial blood flow at rest and in response to various forms of vasomotor stress. Myocardial flow reserve assessed by PET provides a noninvasive surrogate of coronary circulatory function. PET also enables the monitoring and characterization of coronary circulatory function in response to gastric bypass-induced weight loss in initially morbidly obese individuals, to medication and/or behavioral interventions related to weight, diet, and physical activity. Whether the observed improvement in coronary circulatory dysfunction via weight loss may translate to diminution in cardiovascular events awaits clinical confirmation.
    Current Cardiology Reports 01/2014; 16(1):433. DOI:10.1007/s11886-013-0433-8
  • [Show abstract] [Hide abstract]
    ABSTRACT: Conventional scintigraphic myocardial perfusion imaging with SPECT/CT or with PET/CT has evolved as an important clinical tool for the diagnostic assessment of flow-limiting epicardial lesions and risk stratification of patients with suspected CAD. By determining the relative distribution of radiotracer-uptake in the left-ventricular (LV) myocardium during stress, the presence of flow-limiting CAD lesions can be identified. While this approach successfully identifies epicardial coronary artery lesions, the presence of subclinical and non-obstructive CAD may go undetected. In this direction, the concurrent ability of PET/CT to assess absolute myocardial blood flow (MBF) in ml/g/min, rather that relative regional distribution of radiotracer-uptake, and myocardial flow reserve (MFR), expands the scope of conventional myocardial perfusion imaging from the identification of more advanced and flow-limiting epicardial lesions to (1) subclinical CAD, (2) an improved characterization of the extent and severity of CAD burden, and (3) the discovery of "balanced" reduction in myocardial blood flow as a consequence of 3 vessel CAD. Concurrent to the PET data, the CT component of the hybrid PET/CT allows the assessment of coronary artery calcification as an indirect surrogate for CAD burden, without contrast, or with contrast angiography to directly denote coronary stenosis and/or plaque morphology with CT. Hybrid PET/CT system, therefore, has the potential to not only identify and characterize flow-limiting epicardial lesions but also subclinical stages of functional and/or structural stages of CAD. Whether the application of PET/CT for an optimal assessment of coronary pathology, its downstream effects on myocardial perfusion, and coronary circulatory function will in effect lead to changes in clinical decision-making process, investiture in preventive health care, and improved long-term outcome, awaits scientific verification.
    Current Cardiology Reports 03/2013; 15(3):344. DOI:10.1007/s11886-012-0344-0
  • Source
    Ines Valenta, Thomas Hellmut Schindler
    European Journal of Nuclear Medicine 06/2012; 39(8):1231-2. DOI:10.1007/s00259-012-2154-4 · 4.53 Impact Factor
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: Quantification of myocardial blood flow (MBF) with generator-produced (82)Rb is an attractive alternative for centres without an on-site cyclotron. Our aim was to validate (82)Rb-measured MBF in relation to that measured using (15)O-water, as a tracer 100% of which can be extracted from the circulation even at high flow rates, in healthy control subject and patients with mild coronary artery disease (CAD). MBF was measured at rest and during adenosine-induced hyperaemia with (82)Rb and (15)O-water PET in 33 participants (22 control subjects, aged 30 ± 13 years; 11 CAD patients without transmural infarction, aged 60 ± 13 years). A one-tissue compartment (82)Rb model with ventricular spillover correction was used. The (82)Rb flow-dependent extraction rate was derived from (15)O-water measurements in a subset of 11 control subjects. Myocardial flow reserve (MFR) was defined as the hyperaemic/rest MBF. Pearson's correlation r, Bland-Altman 95% limits of agreement (LoA), and Lin's concordance correlation ρ (c) (measuring both precision and accuracy) were used. Over the entire MBF range (0.66-4.7 ml/min/g), concordance was excellent for MBF (r = 0.90, [(82)Rb-(15)O-water] mean difference ± SD = 0.04 ± 0.66 ml/min/g, LoA = -1.26 to 1.33 ml/min/g, ρ(c) = 0.88) and MFR (range 1.79-5.81, r = 0.83, mean difference = 0.14 ± 0.58, LoA = -0.99 to 1.28, ρ(c) = 0.82). Hyperaemic MBF was reduced in CAD patients compared with the subset of 11 control subjects (2.53 ± 0.74 vs. 3.62 ± 0.68 ml/min/g, p = 0.002, for (15)O-water; 2.53 ± 1.01 vs. 3.82 ± 1.21 ml/min/g, p = 0.013, for (82)Rb) and this was paralleled by a lower MFR (2.65 ± 0.62 vs. 3.79 ± 0.98, p = 0.004, for (15)O-water; 2.85 ± 0.91 vs. 3.88 ± 0.91, p = 0.012, for (82)Rb). Myocardial perfusion was homogeneous in 1,114 of 1,122 segments (99.3%) and there were no differences in MBF among the coronary artery territories (p > 0.31). Quantification of MBF with (82)Rb with a newly derived correction for the nonlinear extraction function was validated against MBF measured using (15)O-water in control subjects and patients with mild CAD, where it was found to be accurate at high flow rates. (82)Rb-derived MBF estimates seem robust for clinical research, advancing a step further towards its implementation in clinical routine.
    European Journal of Nuclear Medicine 03/2012; 39(6):1037-47. DOI:10.1007/s00259-012-2082-3 · 4.53 Impact Factor
  • [Show abstract] [Hide abstract]
    ABSTRACT: Among individuals with cardiovascular risk factors, reductions in coronary vasodilator capacity with or without diabetes mellitus (DM) carry important diagnostic and prognostic information. Positron emission tomography (PET) myocardial perfusion imaging in concert with tracer kinetic modeling allows the assessment of absolute regional myocardial blood flow (MBF) at rest and its response to various forms of vasomotor stress. Such noninvasive evaluation of myocardial flow reserve (MFR) or the vasodilator capacity of the coronary circulation expands the possibilities of conventional scintigraphic myocardial perfusion imaging from identifying flow-limiting epicardial coronary artery lesions to understanding the underlying pathophysiology of diabetic vasculopathy, microcirculatory dysfunction, and its atherothrombotic sequelae. Invaluable mechanistic insights were recently reported with PET by unraveling important effects of insulin resistance, obesity, and DM on the function of the coronary circulation. Such noninvasive assessment of coronary circulatory dysfunction enables monitoring its response to antidiabetic medication and/or behavioral interventions related to weight, diet, and physical activity that may evolve as a promising tool for an image-guided and personalized preventive diabetic vascular care. Whether PET-guided improvement or normalization of hyperemic MBF and/or MFR will translate into improved patient outcome in DM is a laudable goal to pursue next.
    Current Cardiology Reports 12/2011; 14(2):217-25. DOI:10.1007/s11886-011-0240-z
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: Ischemic coronary artery disease (CAD) is a major cause for morbidity and mortality resulting in a continuously increasing number of diagnostic interventions. We have validated a new hybrid imaging method using minimized radiation dose for rapid non-invasive prediction of invasive coronary angiography (CA) findings with regard to coronary lesion detection and revascularization. Forty patients referred for elective invasive coronary angiography (CA) due to suspected CAD were prospectively enrolled to undergo a low-dose CTCA with prospective ECG-triggering and a stress-only SPECT-MPI scan administering half of the standard low-dose stress (99m)Tc-tetrofosmin activity. The latter was acquired immediately after adenosine stress (omitting the standard 30-60 min waiting time). After fusing CTCA and SPECT-MPI decisions towards conservative management versus revascularization strategy based on hybrid images were compared to the decisions taken by the interventional operator in the catheterization laboratory based on CA. The latter served as standard of reference. Hybrid images yielded sensitivity, specificity, positive and negative predictive values and accuracy of 100%, 96.0%, 100%, 93.8% and 97.5% for predicting coronary revascularization. The estimated mean effective radiation doses were significantly lower for hybrid imaging (4.7 ± 1.0 mSv) than for invasive CA (8.7 ± 4.2 mSv; P<0.001 vs. hybrid). Total non-invasive protocol time was below 60 min, comparing favourably to standard SPECT protocols. Rapid cardiac hybrid imaging allows accurate prediction of invasive CA findings and of treatment decision despite minimized radiation dose and protocol time.
    International journal of cardiology 11/2011; 153(1):10-3. DOI:10.1016/j.ijcard.2010.08.023 · 6.18 Impact Factor
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: The aim was to prospectively characterise the effect of the level of breath-hold on heart rate in CT coronary angiography (CTCA) with prospective electrocardiogram (ECG) triggering and its impact on coronary artery attenuation. 260 patients (86 women; mean age 59 ± 11 years) underwent 64-slice CTCA using prospective ECG triggering. Prior to CTCA, heart rates were recorded during 15 s of breath-hold at three different levels of inspiration (normal, intermediate and deep). The inspiration level with the lowest heart rate was chosen for actual CTCA scanning. Coronary artery attenuation was measured, and the presence of backflow of contrast material into the inferior vena cava (as an indicator of increased intrathoracic pressure) was recorded. The mean heart rate at breath-hold was significantly different for the three inspiration levels (normal, 60 ± 8 bpm; intermediate, 59 ± 8 bpm; deep, 57 ± 7 bpm; p<0.001). The maximum heart rate reduction in each patient at breath-hold averaged 5.3 ± 5.1 bpm, and was observed at a normal inspiration depth in 23 (9%) patients, at an intermediate inspiration depth in 102 (39%) patients and at deep inspiration in 135 (52%) patients. Overall, there was no association between the level of breath-hold and coronary vessel attenuation (p-value was not significant). However, the backflow of contrast material into the inferior vena cava (n = 26) was found predominantly at deep inspiration levels (p<0.001), and, when it occurred, it was associated with reduced coronary attenuation compared with patients with no backflow (p<0.05). The breath-hold level to best reduce heart rate for CTCA should be individually assessed prior to scanning because a mean heart rate reduction of 5 bpm can be achieved.
    The British journal of radiology 09/2011; 84(1005):790-5. DOI:10.1259/bjr/29696915 · 1.53 Impact Factor
  • Source
    European Journal of Nuclear Medicine 04/2011; 38(6). DOI:10.1007/s00259-011-1805-1 · 4.53 Impact Factor
  • Source
    Journal of Nuclear Cardiology 02/2011; 18(2):201-3. DOI:10.1007/s12350-011-9357-0 · 2.65 Impact Factor
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: The aim of this study was to determine whether epicardial structural disease may affect the manifestation of a longitudinal decrease in myocardial blood flow (MBF) or MBF difference during hyperemia in cardiovascular risk individuals, and its dependency on the flow increase. In 54 cardiovascular risk individuals (at risk) and in 26 healthy controls, MBF was measured with (13)N-ammonia and PET/CT in mL/g/min at rest and during dipyridamole stimulation. Computed tomography coronary angiography (CTA) was performed using a 64-slice CT of a PET/CT system. Absolute MBFs during dipyridamole stimulation were mildly lower in the mid-distal than in the mid-LV myocardium in controls (2.20 ± .51 vs 2.29 ± .51, P < .0001), while it was more pronounced in at risk with normal and abnormal CTA (1.56 ± .42 vs 1.91 ± .46 and 1.18 ± .34 vs 1.51 ± .40 mL/g/min, respectively, P < .0001), resulting in a longitudinal MBF difference that was highest in at risk with normal CTA, intermediate in at risk abnormal CTA, and lowest in controls (.35 ± .16 and .22 ± .09 vs .09 ± .04 mL/g/min, respectively, P < .0001). On multivariate analysis, log-CCS and mid-LV hyperemic MBF increase, indicative of microvascular function, were independent predictors of the observed longitudinal MBF difference (P ≤ .004 by ANOVA). Epicardial structural disease and microvascular function are important determinants of an abnormal longitudinal MBF difference as determined with PET/CT.
    Journal of Nuclear Cardiology 12/2010; 17(6):1023-33. DOI:10.1007/s12350-010-9272-9 · 2.65 Impact Factor
  • [Show abstract] [Hide abstract]
    ABSTRACT: To validate the ultrafast assessment of left ventricular (LV) dyssynchrony by phase analysis using high-speed nuclear myocardial perfusion imaging (MPI) on a new gamma camera with cadmium-zinc-telluride (CZT) solid-state detector technology. In 46 patients rest MPI with 960 MBq (99m)Tc-tetrofosmin was acquired on a dual-head detector SPECT camera (Ventri, GE Healthcare) and an ultrafast CZT camera (Discovery NM 530c, GE Healthcare) with acquisition times of 15 and 5 min, respectively. LV dyssynchrony was assessed using the Emory Cardiac Toolbox with established values for histogram bandwidth (male <62.4°; female <49.7°) and standard deviations (male <24.4°; female <22.1°) as the gold standard. Evaluating CZT scan times of 0.5, 1, 2, 3 and 5 min (list mode) in 16 patients revealed the preferred scan time to be 5 min, which was then applied in all 46 patients. Intraclass correlation and the level of agreement in dyssynchrony detection between the CZT and Ventri cameras were assessed. In LV dyssynchrony the mean histogram bandwidths with the CZT camera (n = 8) and the Ventri camera (n = 9) were 123.3 ± 50.6° and 130.2 ± 43.2° (p not significant) and 42.4 ± 13.6° vs. 43.2 ± 12.7° (p not significant). Normal bandwidths and SD obtained with the CZT camera (35.9 ± 7.7°, 12.6 ± 3.5°) and the Ventri camera (34.8 ± 6.6°, 11.1 ± 2.1°, both p not significant) excluded dyssynchrony in 38 and 37 patients, respectively. Intraclass correlation and the level of agreement between the CZT camera with a 5-min scan time and the Ventri camera were 0.94 (p < 0.001, SEE 14.4) and 96% for histogram bandwidth and 0.96 (p < 0.001, SEE 3.9) and 98% for SD. This ultrafast CZT camera allows accurate assessment of LV dyssynchrony with a scan time of only 5 min, facilitating repeat measurements which would potentially be helpful for parameter optimization for cardiac resynchronization therapy.
    European Journal of Nuclear Medicine 11/2010; 37(11):2086-92. DOI:10.1007/s00259-010-1507-0 · 4.53 Impact Factor
  • [Show abstract] [Hide abstract]
    ABSTRACT: The aim of this study was to assess the ability of real-time breath-hold-triggered myocardial perfusion imaging (MPI) using a novel cadmium-zinc-telluride (CZT) gamma camera to discriminate artefacts from true perfusion defects. A group of 40 patients underwent a 1-day (99m)Tc-tetrofosmin pharmacological stress/rest imaging protocol on a conventional dual detector SPECT gamma camera with and without attenuation correction (AC), immediately followed by scanning on an ultrafast CZT camera with and without real-time breath-hold triggering (instead of AC) by intermittent scanning confined to breath-hold at deep inspiration (using list mode acquisition). We studied the use of breath-hold triggering on the CZT camera and its ability to discriminate artefacts from true perfusion defects using AC SPECT MPI as the reference standard. Myocardial tracer uptake (percent of maximum) from CZT was compared to AC SPECT MPI by intraclass correlation and by calculating Bland-Altman limits of agreement. AC of SPECT MPI identified 19 apparent perfusion defects as artefacts. Of these, 13 were correctly identified and 4 were partially unmasked (decrease in extent and/or severity) by breath-hold triggering of the CZT scan. All perfusion defects verified by SPECT MPI with AC were appropriately documented by CZT with and without breath-hold triggering. This was supported by the quantitative analysis, as the correlation (r) of myocardial tracer uptake between CZT and AC SPECT improved significantly from 0.81 to 0.90 (p<0.001) when applying breath-hold triggering. Similarly, Bland-Altman limits of agreement were narrower for CZT scans with breath-hold triggering. This novel CZT camera allows real-time breath-hold triggering as a potential alternative to AC to assist in the discrimination of artefacts from true perfusion defects.
    European Journal of Nuclear Medicine 10/2010; 37(10):1903-8. DOI:10.1007/s00259-010-1480-7 · 4.53 Impact Factor
  • [Show abstract] [Hide abstract]
    ABSTRACT: SPECT myocardial perfusion imaging (MPI) is commonly used for comprehensive interpretation of metabolic PET FDG imaging in ischemic dysfunctional myocardium. We evaluated the difference in scan interpretation introduced by CT attenuation correction (CTAC) of SPECT MPI in patients undergoing viability characterization by (99m)Tc SPECT MPI/PET FDG. In 46 consecutive patients (mean age 64, range 36-83 years) with dysfunctional myocardium, we analyzed viability from combined SPECT MPI and PET FDG scanning without attenuation correction (NC) and with CTAC for SPECT MPI. FDG uptake was classified in groups of percent uptake using the segment with maximum tracer in SPECT perfusion uptake as reference. Viability patterns were categorized as normal, mismatch, mild match and scar by relative comparison of SPECT and PET. Applying CTAC introduced a different reference segment for the normalization of PET FDG study in 57% of cases. As a result, the flow-metabolism pattern changed in 28% of segments, yielding a normal, mismatch, mild match and scar pattern in 462, 150, 123, and 47 segments with NC and 553, 86, 108, and 35 with CTAC, respectively (P = 0.001). Thus, by introducing CTAC for SPECT MPI 25% of segments originally classified as scar were reclassified and the number of normal segments increased by 20%. Introducing CTAC decreased by 54% the number of patients with possible indication for revascularization, from 26/46 to 12/46 (P < 0.001). Different interpretation of myocardial viability can be observed when using CTAC instead of NC SPECT MPI as reference for PET FDG scans.
    The international journal of cardiovascular imaging 10/2010; 27(6):913-21. DOI:10.1007/s10554-010-9719-8 · 2.32 Impact Factor
  • [Show abstract] [Hide abstract]
    ABSTRACT: The aim of this study was to validate attenuation correction (AC) using low-dose standard CT for myocardial perfusion imaging (MPI) on a novel ultra fast γ-camera with cadmium-zinc-telluride (CZT) detector technology. Sixty-six patients (body mass index ± SD, 27.2 ± 3.5 kg/m(2); range, 19.1-36.0 kg/m(2)) underwent a 1-d (99m)Tc-tetrofosmin adenosine stress-rest imaging protocol with 15-min acquisitions on a standard dual-head SPECT camera. All scans were repeated within minutes on the CZT camera, with 3-min acquisitions for stress (low dose) and 2-min acquisitions for rest (high dose) as recently established. We compared maximum myocardial uptake (20-segment model) from CZT versus standard SPECT MPI by intraclass correlation without and with CT AC. In addition, clinical agreement for each coronary territory for all scans from both devices was assessed, and Bland-Altmann (BA) limits of agreement for percentage uptake were calculated. The clinical agreement between CZT and standard SPECT cameras was 96% for noncorrected low- and high-dose images (r = 0.90 and BA = -18 to 15, and r = 0.91 and BA = -15 to 16, respectively), and agreement after AC was 96% for low- and 99% for high-dose images (r = 0.87 and BA = -16 to 14, and r = 0.88 and BA = -16 to 14, respectively). Our results support that AC of MPI on the novel CZT camera, compared with AC MPI on a conventional SPECT camera, is feasible because it provides a high correlation of segmental tracer uptake and an excellent clinical agreement.
    Journal of Nuclear Medicine 10/2010; 51(10):1539-44. DOI:10.2967/jnumed.110.078170 · 5.56 Impact Factor
  • [Show abstract] [Hide abstract]
    ABSTRACT: In patients with large total blood volume contrast material (CM) dilution decreases coronary attenuation in CT coronary angiography (CTCA). As increased blood volume is well paralleled by body surface area (BSA) we assessed a BSA-adapted CM protocol to compensate for dilution effects. Low-dose CTCA with prospective ECG-triggering was performed in 80 patients with a BSA-adapted CM bolus ranging 40-105 ml and injection rate ranging 3.5-5.0 ml/s for a BSA of <1.70 to >or=2.5 m(2). Eighty control patients matched for BSA who had previously undergone routine CTCA with a fixed CM protocol of 80 ml at 5 ml/s served as reference group. The average vessel attenuation from the proximal right (RCA) and the left main coronary artery (LMA) was assessed. Correlation of BSA with vessel attenuation was assessed in both groups. BSA-matching of all patients was successful (BSA-adapted group 1.98 +/- 0.15 m(2), range 1.66-2.39 m(2) versus reference group 1.98 +/- 0.17 m(2), range 1.59-2.38 m(2); P = 0.74). Mean CM bolus was significantly smaller in the BSA-adapted versus the reference group (70.9 +/- 14.1 vs. 80.0 +/- 0 ml, P < 0.001). There was no correlation in the BSA-adapted group (r = -0.07, P = 0.53, SEE = 0.15), while coronary attenuation was inversely related to BSA in the reference group (r = -0.59, P < 0.001, SEE = 0.14). We have successfully validated a BSA-adapted contrast material protocol which results in a comparable coronary contrast enhancement independent of individual BSA. This was achieved despite a significant reduction in the overall contrast material amount.
    The international journal of cardiovascular imaging 06/2010; 26(5):591-7. DOI:10.1007/s10554-010-9594-3 · 2.32 Impact Factor
  • [Show abstract] [Hide abstract]
    ABSTRACT: To assess the diagnostic performance of a novel ultrafast cardiac gamma camera with cadmium-zinc-telluride (CZT) solid-state semiconductor detectors for nuclear myocardial perfusion imaging (MPI). The study group comprised 75 consecutive patients (55 men, BMI range 19-45 kg/m(2)) who underwent a 1-day (99m)Tc-tetrofosmin adenosine-stress/rest imaging protocol. Scanning was performed first on a conventional dual-detector SPECT gamma camera (Ventri, GE Healthcare) with a 15-min acquisition time each for stress and rest. All scans were immediately repeated on an ultrafast CZT camera (Discovery 530 NMc, GE Healthcare) with a 3-min scan time for stress and a 2-min scan time for rest. Clinical agreement (normal, ischaemia, scar) between CZT and SPECT was assessed for each patient and for each coronary territory using SPECT MPI as the reference standard. Segmental myocardial tracer uptake values (percent of maximum) using a 20-segment model and left ventricular ejection fraction (EF) values obtained using CZT were compared with those obtained using conventional SPECT by intraclass correlation and by calculating Bland-Altman limits of agreement. There was excellent clinical agreement between CZT and conventional SPECT on a per-patient basis (96.0%) and on a per-vessel territory basis (96.4%) as shown by a highly significant correlation between segmental tracer uptake values (r=0.901, p<0.001). Similarly, EF values for both scanners were highly correlated (r=0.976, p<0.001) with narrow Bland-Altman limits of agreement (-5.5-10.6%). The novel CZT camera allows a more than fivefold reduction in scan time and provides clinical information equivalent to conventional standard SPECT MPI.
    European Journal of Nuclear Medicine 04/2010; 37(4):773-8. DOI:10.1007/s00259-009-1375-7 · 4.53 Impact Factor
  • Journal of the American College of Cardiology 03/2010; 55(10). DOI:10.1016/S0735-1097(10)60709-7 · 15.34 Impact Factor

Publication Stats

3k Citations
359.26 Total Impact Points


  • 2014
    • Johns Hopkins University
      • Department of Radiology
      Baltimore, Maryland, United States
  • 2010–2013
    • University of Geneva
      • • Division of Cardiology
      • • Department of Internal Medicine
      Genève, Geneva, Switzerland
  • 2006–2011
    • University of Zurich
      • Center for Integrative Human Physiology
      Zürich, Zurich, Switzerland