1. FM Lavender, RT Meades, A Al-Nahhas, KS Nijran Imperial College Healthcare NHS Trust, London, UK

2.  Quantitation software: uses thresholding, binarization, and clusterification to estimate position of myocardial surfaces.  Left ventricular ejection fraction : LVEF = (EDV-ESV )x100% EDV  The LVEF provides quantitative functional information about the heart.  Comparison of the LVEF at rest/stress gives a measure of the level of reversible ischaemia.  Comparison of the LVEF between successive scans gives an indication of the level of deterioration or response to treatment.

3. The aims of this study were to compare the effects of: 1. Quantitation software : 101 patients Quantitative Gated SPECT vs 4DMSPECT 2. Pre-reconstruction filtering : 32 patients Butterworth filter of varying order and cut-off frequency on LVEF quantification.

4. 101 patients Acquisition method:  Siemens ECAM dual-head gamma camera  SPECT acquisition: 32 projections, 30second/projection.  400-750MBq Tc99m Tetrofosmin  64x64 matrix, 6.59mm pixel size  ECG gated into 8 time bins

5. Gated SPECT AutoCardiac 4DMSPECT University of Michigan QGS Cedars-Sinai Medical Centre ReconstructionQuantitationAcquisition Hermes workstation esoft workstation

8. Range +21% to -28%

9. ESV≤30ml [1], 53 patientsESV>30ml, 48 patients [1] Hambye et al. Eur J Nucl Med Mol Imaging. 2004; 31(12):1606-13

10.  Small hearts: EF>50% for ALL patients  Partial volume effect  ESV estimation of 5ml is unlikely to be accurate.  Khalil et al. reported that LVEF of small hearts was overestimated by 12% compared to gated blood pool [2]. [2] Khalil et al., Nucl Med Commun. 2006 Apr; 27(4):321-32.

11. ESV≤30ml Mean difference ±SD -0.2 ± 6.4% ESV>30ml Mean difference ±SD 4.7 ± 6.2%

12. Manual correction necessary in 5% QGS and 4% 4DMSPECT

13. High uptake of tracer in the gut QGS 5/101 High uptake of tracer in the gut Inaccurate valve plane positioning [3] 4DMSPECT 4/101 Surface that intersects most basal myocardial points Surface perpendicular to the long axis of heart [3] Nakajima et al. J Nucl Med. 2001 Oct;42(10):1571-8

14. Manual contour correction to exclude activity in the gut

15.  The effect of perfusion defects on LVEF is controversial.  Vanhove 2002: gated blood pool imaging  Concluded that the accuracy of QGS was dependent on the severity but not the extent of perfusion defects [4].  Valejo 2000: MRI  Perfusion defects led to an increase in overestimation of EF by QGS [5]. [4] Vanhove et al. Eur J Nucl Med Mol Imag 2002 Jun;29(6):735-41 [5] Valejo et al. J Nucl Med. 2000 May;41(5):874-82

16. (a)(b)(c)(d) Short axis and vertical long axis slices from a patient exhibiting high tracer uptake in the gut. Order 5 Butterworth filter at cut-off frequencies of (a, b) 0.5cycles/cm, (c) 0.6cycles/cm, (d) 0.7cycles/cm. 0.5cycles/cm0.6cyc/cm0.7cyc/cm

17.  Van Laere comments that, “Recommended choices for a SPECT filter in the scarce literature on this subject are almost as numerous as the number of authors.” [6]  As the cut-off frequency is increased, larger volumes and smaller LVEFs were estimated using QGS [7].  The volumes and LVEF reported to plateau above 0.50cyc/cm [8]. [6] Van Laere et al. Comput Med Imaging Graph. 2001 Mar-Apr;25(2):127-33. Review. [7] Kakhki et al. Clin Nucl Med. 2007 May;32(5):404-6. [8] Nakajima et al. Eur J Nucl Med. 2000 Sep;27(9):1372-9.

18.  32 patients  Reconstruction performed using Hermes FBP SPET  Pre-reconstruction filter:  Butterworth  Orders 5 and 10  Cut-off frequencies 0.5 to 1.2 cycles/cm in steps of 0.1cycles/cm.  512 reconstructions

19.  No obvious plateau  Effect of cut-off frequency on EF is very patient specific

20.  At cut-off frequency of 0.5cyc/cm, maximum difference index was 42%.  At cut-off frequencies ≤ 0.8cyc/cm, the EF was overestimated compared to higher cut-off frequencies in 26/30 patients. Difference index= For z=0.5 to 1.2cyc/cm

21.  Why do we get large variations?  Reconstruction process is not fully automated.  Image is filtered, then axes have to be re- aligned for each reconstruction.

33. Method:  Repeated filtering for first ten patients (320 reconstructions) Results:  Average difference between initial and repeated results was <0.1% for both orders  Therefore manual axes alignment does not significantly affect LVEF estimation.

34.  4DMSPECT and QGS estimate significantly different EFs (range 21% to -28%) and should not be used interchangeably.  The agreement between the packages is worse for small hearts (ESV≤30ml) and may also be affected by severe perfusion defects and manual contour correction.  LVEF is dependent on the cut-off frequency used during pre-reconstruction filtering but the dependency is very patient specific.  Changing the cut-off frequency by as little as 0.1cyc/cm sometimes resulted in changes to the EF of >10 absolute EF percentage points.