Real-time gated-SPECT myocardial perfusion imaging with CZT detectors: A promising tool for monitoring left ventricular function
Real-time gated-SPECT myocardial perfusion imaging with CZT detectors: A promising tool for monitoring left ventricular function
Roberta Assante 0 1
Alberto Cuocolo 0
0 Reprint requests: Alberto Cuocolo, MD, Department of Advanced Biomedical Sciences, University Federico II , Via Pansini 5, 80131 Naples , Italy
1 Department of Advanced Biomedical Sciences, University Federico II , Naples , Italy
The use of stress single-photon emission computed
tomography (SPECT) cardiac imaging for the
assessment of myocardial perfusion has become one of the
most used noninvasive approaches for the management
of patients with known or suspected coronary artery
disease (CAD).1 The possibility to perform
gatedSPECT as a routine part of clinical protocols offers the
advantage to add to perfusion data functional
parameters, such as left ventricular (LV) volumes, ejection
fraction (EF), and regional wall motion, increasing the
diagnostic accuracy and clinical utility of cardiac
SPECT imaging.2,3 The assessment of LV volumes and
EF represents a powerful and reliable method for the
prediction of long-term prognosis and for clinical
decision making in patients with heart diseases.4,5 There are
many automated algorithms for quantification of SPECT
parameters of myocardial perfusion and LV function,
which have demonstrated accuracy and reproducibility.6
For the assessment of LV volumes and function, cardiac
magnetic resonance (CMR) is considered the reference
standard noninvasive method for validation of other
imaging techniques. It is due to the characteristics of
CMR imaging, a method that does not depend on
geometric assumptions of LV shape.7 This approach is
characterized by high reproducibility, excellent temporal
and spatial resolution, and low interobserver and
intraobserver variability.8 A good agreement of LV
functional parameters between gated-SPECT by
conventional Anger camera and CMR imaging has been
demonstrated both at rest and post-stress. However, it
has also been shown that gated-SPECT LV volumes and
functional parameters may be underestimated by using
standard cameras compared to CMR, showing high
variability.9,10 Probably, the underestimation of
end-diastolic and end-systolic volumes may be mainly
explained by the limited SPECT temporal and spatial
resolution. Other factors that may contribute to the
discrepancies between these two modalities include the use
of different algorithms and the possibility that in patients
with large perfusion defects, severe reduction or absence
of photon counts in a myocardial region may lead to an
underestimation of regional wall motion, due to
inadequate visualization.11 Using conventional Anger camera
with waiting periods after stress tracer injection of at
least 15 minutes, but sometimes also up to 60 minutes,
post-stress LV function and volumes may be
underestimated and early ischemic functional changes after stress
test might be not identifiable. In addition, acquisition
time with conventional cameras is very long and this
may lead to a resolution of the LV function during this
long time. All these characteristics do not allow to
identifying post-stress LV function and wall motion
abnormalities, which have been demonstrated to be
correlated with severe obstructive CAD.12
The introduction of new dedicated cardiac cameras
based on cadmium-zinc-telluride (CZT) semiconductor
technology, characterized by a higher photon sensitivity
and higher temporal and spatial resolution than standard
systems, could overcome most of the limitations of
conventional Anger cameras. The use of CZT camera
technology enables a significant reduction in both
radiation exposure and acquisition time without loss of
image quality.13 Previous studies have demonstrated
excellent agreement between CZT SPECT and CMR
imaging for the measurement of LVEF, although
significant differences were found in the measurement of
ventricular volumes.14 For the determination of LVEF
and regional wall motion estimation, 16-frame
reformatted images appear to be more accurate than 8-frame
In the current issue of the Journal, Nkoulou et al16
evaluated the feasibility of LVEF measurements and its
accuracy to detect clinically relevant changes in systolic
function during standard dobutamine stress protocol
assessed by real-time high-speed gated-SPECT using
CMR as standard of reference. The study was conducted
in 50 patients referred for SPECT MPI using a hybrid
CZT/CT device. All SPECT images were acquired at
rest after injection of 320 MBq of 99mTc-tetrofosmin
twice consecutively over 3 minutes each and after
dobutamine stress test. In particular, stress SPECT was
performed during low-dose dobutamine and at peak
stress during maximum dobutamine dose. Finally, gated
post-stress images were acquired after 5 minutes of
injection of 960 MBq of 99mTc-tetrofosmin. In this way,
the authors performed real-time LV function
assessment, in addition to assess perfusion images at rest and
at high-dose stress. Moreover, in 20 patients an
additional rest/dobutamine CMR was performed within two
weeks from SPECT imaging. The authors found an
excellent agreement between CMR and gated-SPECT
for rest LVEF, end-diastolic, and end-systolic volumes.
At peak stress, gated-SPECT identified 14 of 16 patients
with a change in LVEF C 5%, and 3 of 4 patients with
stable or decreasing LVEF by stress CMR with an
agreement rate of 85%. On the contrary, LVEF derived
from post-stress SPECT, reflecting standard SPECT
acquisition with conventional camera, showed only a
modest agreement (45%), allowing identifying 8 of 16
patients with increasing LVEF, and 1 of 4 with stable or
decreasing LVEF by stress CMR. The results of this
study highlight the opportunity to obtain highly
repeatable LV function measurements by using new CZT
camera with short acquisition time, allowing clinical
follow-up of patients. Moreover, the protocol proposed
by Nkoulou et al16 might represent a valid method in
patients with multivessel disease, allowing evaluation of
regional stress-induced contractile dysfunction. CZT
SPECT technology improves sensitivity and spatial
resolution compared to conventional gamma cameras.
This new technology allows obtaining fast imaging with
high myocardial count rate, which lead to a good image
quality and improved diagnostic accuracy. In addition,
owing to the possibility to perform the procedure in a
very short acquisition time, there is low rate of motion
artifact with high patient throughput.17 A CZT system
also allows performing several acquisitions as dynamic
imaging or dual isotope acquisition. Recently, Brodov
et al18 demonstrated the feasibility of measuring LVEF
reserve by short, successive acquisitions, starting 5
minutes after regadenoson injection by using a novel
high-efficiency SPECT camera with solid state
cardiacfocused detectors. The authors found a negative, early
LVEF reserve among ischemic patients, compared to a
positive LVEF reserve among nonischemic patients.18
Other imaging modalities are available for
evaluation of LV function in patients with CAD.
Echocardiography is the most commonly imaging
modality used by cardiologists for evaluating ventricular
function.19 It is characterized by short procedure time,
low cost, and availability. Moreover, it is noninvasive
and radiation free; however, this test technique shows
significant variability, because it is subjective and
experience-dependent, and in some cases, the acoustic
window is limited.20 Several studies have compared
LVEF values obtained from echocardiography and
gated-SPECT, reporting variable results. Particularly
some studies reported no significant differences between
values obtained with SPECT and those obtained with
echocardiography.21 On the contrary, other studies
reported higher values of LVEF measured with SPECT
as compared to echocardiography.22 One of the strengths
of the work proposed by Nkoulou et al16 is the use of
CMR imaging as standard reference. CMR is
characterized by a high reproducibility with low variability, but
also higher cost that limits the larger availability. The
use of cardiac nuclear imaging with CZT SPECT
technology has lead to a reduced dose of radiation for the
patient, making these methods very feasible. As also
acknowledged by the authors,16 one of the most
important drawbacks of the proposed protocol is the
limitation for the assessment of transient ischemic
dilatation. This parameter reflects a combination of LV
dilation and diffused subendocardial ischemia and
provides incremental diagnostic and prognostic information
to standard perfusion analysis in patients with known or
suspected CAD.23,24 Although obtained in a limited
number of patients, the results reported by Nkoulou
et al16 are very interesting and open the way for wider
applications of SPECT imaging. Additional and larger
studies are clearly needed to assess the clinical
applicability of the proposed approach.
M. Petretta and A. Cuocolo declare that they have no
conflict of interest.
1. Thomas GS , Miyamoto MI , Morello AP 3rd, Majmundar H , Thomas JJ , Sampson CH , et al. Technetium 99m sestamibi myocardial perfusion imaging predicts clinical outcome in the community outpatient setting. The Nuclear Utility in the Community (NUC) Study . J Am Coll Cardiol . 2004 ; 43 : 213 - 23 .
2. Cuocolo A , Petretta M , Acampa W , De Falco T. Gated SPECT myocardial perfusion imaging: The further improvements of an excellent tool . Q J Nucl Med Mol Imaging . 2010 ; 54 : 129 - 44 .
3. Klocke FJ , Baird MG , Lorell BH , Bateman TM , Messer JV , Berman DS , et al. ACC/AHA/ASNC guidelines for the clinical use of cardiac radionuclide imaging-executive summary: A report of the American College of Cardiology/American Heart Association Task Force on Practice Guidelines (ACC/AHA/ASNC Committee to Revise the 1995 Guidelines for the Clinical Use of Cardiac Radionuclide Imaging) . J Am Coll Cardiol 2003 ; 42 : 1318 - 33 .
4. Sharir T , Germano G , Kavanagh PB , Lai S , Cohen I , Lewin HC , et al. Incremental prognostic value of post-stress left ventricular ejection fraction and volume by gated myocardial perfusion single photon emission computed tomography . Circulation . 1999 ; 100 : 1035 - 42 .
5. Petretta M , Acampa W , Daniele S , Zampella E , Assante R , Nappi C , et al. Long-term survival benefit of coronary revascularization in patients undergoing stress myocardial perfusion imaging . Circ J . 2016 ; 80 : 485 - 93 .
6. Xu Y , Hayes S , Ali I , Ruddy TD , Wells RG , Berman DS , et al. Automatic and visual reproducibility of perfusion and function measures for myocardial perfusion SPECT . J Nucl Cardiol . 2010 ; 17 : 1050 - 7 .
7. Grover S , Leong DL , Selvanayagam JB . Evaluation of left ventricular function using cardiac magnetic resonance imaging . J Nucl Cardiol . 2011 ; 18 : 351 - 65 .
8. Demir H , Tan YZ , Kozdag G , Isgoren S , Anik Y , Ural D , et al. Comparison of gated SPECT, echocardiography and cardiac magnetic resonance imaging for the assessment of left ventricular ejection fraction and volumes . Ann Saudi Med . 2007 ; 27 : 415 - 20 .
9. Kuroiwa Y , Nagamachi S , Miyati T , Yamaguchi K , Nishii R , Kuga N , et al. The agreement of left ventricular function parameters between (99m)Tc-tetrofosmin gated myocardial SPECT and gated myocardial MRI . Ann Nucl Med . 2012 ; 26 : 147 - 63 .
10. Hedeer F , Palmer J , Arheden H , Ugander M. Gated myocardial perfusion SPECT underestimates left ventricular volumes and shows high variability compared to cardiac magnetic resonance imaging-A comparison of four different commercial automated software packages . BMC Med Imaging . 2010 ; 10 : 10 .
11. Fathala A. Comparison of cardiac magnetic resonance with gated SPECT for evaluation of left ventricular function and volumes in patients with severe and multiple myocardial perfusion defects . J Saudi Heart Assoc . 2010 ; 22 : 203 - 8 .
12. Taillefer R . Should early post-stress imaging be performed on a routine clinical basis for myocardial perfusion studies? J Nucl Cardiol . 2014 ; 21 : 1177 - 80 .
13. Duvall WL , Croft LB , Ginsberg ES , Einstein AJ , Guma KA , George T , et al. Reduced isotope dose and imaging time with a high-efficiency CZT SPECT camera . J Nucl Cardiol . 2011 ; 18 : 847 - 57 .
14. Cochet H , Bullier E , Gerbaud E , Durieux M , Godbert Y , Lederlin M , et al. Absolute quantification of left ventricular global and regional function at nuclear MPI using ultrafast CZT SPECT: Initial validation versus cardiac MR . J Nucl Med . 2013 ; 54 : 556 - 63 .
15. Giorgetti A , Masci PG , Marras G , Rustamova YK , Gimelli A , Genovesi D , et al. Gated SPECT evaluation of left ventricular function using a CZT camera and a fast low-dose clinical protocol: Comparison to cardiac magnetic resonance imaging . Eur J Nucl Med Mol Imaging . 2013 ; 40 : 1869 - 75 .
16. Nkoulou R , Wolfrum M , Pazhenkottil AP , Fiechter M , Buechel RR , Gaemperli O , et al. Gated SPECT myocardial perfusion imaging with Cadmium-Zinc-Telluride detectors allows real-time assessment of dobutamine-stress-induced wall motion abnormalities . J Nucl Cardiol . 2018 . https://doi.org/10.1007/s12350-018- 1187-x.
17. Imbert L , Poussier S , Franken PR , Songy B , Verger A , Morel O , et al. Compared performance of high-sensitivity cameras dedicated to myocardial perfusion SPECT: A comprehensive analysis of phantom and human images . J Nucl Med . 2012 ; 53 : 1897 - 903 .
18. Brodov Y , Fish M , Rubeaux M , Otaki Y , Gransar H , Lemley M , et al. Quantitation of left ventricular ejection fraction reserve from early gated regadenoson stress Tc-99m high-efficiency SPECT . J Nucl Cardiol . 2016 ; 23 : 1251 - 61 .
19. Gargiulo P , Cuocolo A , Dellegrottaglie S , Prastaro M , Savarese G , Assante R , et al. Nuclear assessment of right ventricle . Echocardiography . 2015 ; 32 : S69 - 74 .
20. Nagueh SF , Bhatt R , Vivo RP , Krim SR , Sarvari SI , Russell K , et al. Echocardiographic evaluation of hemodynamics in patients with decompensated systolic heart failure . Circ Cardiovasc Imaging . 2011 ; 4 : 220 - 7 .
21. Berk F , Isgoren S , Demir H , Kozdag G , Sahin T , Ural D , et al. Assessment of left ventricular function and volumes for patients with dilated cardiomyopathy using gated myocardial perfusion SPECT and comparison with echocardiography . Nucl Med Commun . 2005 ; 26 : 701 - 10 .
22. Mistry N , Halvorsen S , Hoffmann P , Mu¨ller C , Bøhmer E , Kjeldsen SE , et al. Assessment of left ventricular function with magnetic resonance imaging vs. echocardiography, contrast echocardiography, and single-photon emission computed tomography in patients with recent ST-elevation myocardial infarction . Eur J Echocardiogr . 2010 ; 11 : 793 - 800 .
23. Petretta M , Acampa W , Daniele S , Petretta MP , Nappi C , Assante R , et al. Transient ischemic dilation in SPECT myocardial perfusion imaging for prediction of severe coronary artery disease in diabetic patients . J Nucl Cardiol . 2013 ; 20 : 45 - 52 .
24. Petretta M , Acampa W , Daniele S , Petretta MP , Plaitano M , Cuocolo A . Transient ischemic dilation in patients with diabetes mellitus: Prognostic value and effect on clinical outcome after coronary revascularization . Circ Cardiovasc Imaging . 2013 ; 6 : 908 - 15 .