# A COMPARITIVE STUDY OF 16-FRAME AND 8-FRAME GATED SPECT IMAGING FOR DETERMINATION OF LEFT VENTRICULAR VOLUMES AND EJECTION FRACTION.

Byline: Abdul Kareem Khan, H. M. Noor ul Huda Khan Asghar, Zaheer Abbas Gilani, H. M. Ajmal, Muhammad Shahzad Shifa, Muhammad Nauman Usmani, M. Asghar and Jalil ur RehmanABSTRACT: Back Ground: The aim of this study was to compare the effect of 8-Frame and 16-Frame gated Single photon emission computerized tomography (SPECT) on measurement of left ventricular (LV) volumes.

Method: A total of 20 patients underwent technetium-99m-MIBI SPECT myocardial perfusion imaging using 16-frame per cardiac cycle acquisition. Eight-frame gated SPECT images were generated by summation of contiguous frames. Left ventricular end-diastolic volume (EDV), end-systolic volume (ESV) and ejection fraction (EF) were calculated from the 16-frame and 8-frame data sets.

Results: Imaging was performed with the advised dose of 20mCi. Sixteen frame per cardiac cycle acquisition resulted larger EDV (82.6 34.3 ml vs 80.9 42.5ml, P=NS) smaller ESV (34.7 31.4ml vs 38.9 40.1ml, P=NS but signif icant) and higher LVEF (63 14.1ml vs 59.1 15ml, P0.05 (NS). The more reliable method is the interval estimation. Thus 95% confidence Interval (CI) for mean difference in EDV8 and EDV16 is (-8.15220, 3.75220).

Correlation and Linear Regression Analysis of ESV

Table III: Regression analysis of ESV8 VS ESV16

Predictor###Coefficients###SE Coef###t-value###P-value

Constant###4.558###1.525###2.99###0.008

ESV8###0.77357###0.02764###27.99###0.000 (Significant)

Unusual Observations

Observations###ESV8###ESV16###Residual###Standardized

###Residual

4###47###26.00###-14.92###-3.17R

6###152###123.00###0.86###0.24 X

17###151###121.00###-0.37###-0.10 X

The scatter plot, Figure 5 used shows a straight line, but some points are little far from the regression lines. The Pearson correlation of EF8 and EF16 shows value r = 0.961, which indicate very high correlation between these EF variables. The Figure 5(c) - line chart indicates that some observation is getting very low in a process and shows the increasing or decreeing pattern for both variables EF8 and EF16. Figure 5 (b) dot plot shows that more than 2 points of each EF differ from the bulk of data. Figures 5 also suggest that shows a good confirmation that all the observations are very close to regression line, but some are aberrant or outlying from rest of the data.

The regression analysis suggests that the observations 6 and 17 are the outlying observations expected to show large influence while the observation 4 and 20 are having large residual. The regression equation is EF16 = 10.7 + 0.893 EF8 with R-Sq = 92.3%. The regression coefficient of EF8 is 0.89265 with positive sign and its t-value having shown that EF16 significantly depends on the values of EDV8. The high value of R-Sq = 92.3% shows a very good fit of regression as shown in table IV.

Table IV: Regression analysis of EF8 VS EF16

Predictor###Coefficients###SE Coef###t-value###P-value

Constant###10.735###3.662###2.93###0.009

EF8###0.89265###0.06064###14.72###0.000 (Significant)

Unusual Observations

EF8###EF16###Residual###St Resid

4###49.0###64.000###9.525###2.46R

6###24.0###33.000###0.841###0.25 X

17###18.0###23.000###-3.803###-1.25 X

4###69.0###62.000###-10.328###-2.67R

Table V: Mean SD analysis of EDV, ESV and EF

###16-frame ml###8-frame ml

###Observation assessment from Zonal charts

###EDV###82.60###80.40###Observation 6, 16 and17 are outside the Zone 1 in 8-

###34.29###43.14###frame Observation 6, 13, and 16 are outside the Zone

###1 in 16-frame

###ESV###34.65 31.40###38.90###Observation 6 and 16 are outside the Zone 1 in 8-

###40.14###frame

###Observation 6 and 16 are outside the Zone 1 in 16-

###frame

###EF###63.00###58.55###Observation 6, 11,13,16 and17 are outside the Zone I

###14.12###15.19###in 8-frame

###Observation 6, 163and17 are outside the Zone I in

###16-frame

Paired T-Test and Confidence Interval for EF8 and EF16, Two-tailed paired student t-test shows that te results are significant difference between EF8 and EF16 since the t-value is -4.70 with p-value = 0.000 <0.05 and the 95% confidence Interval (CI) for mean difference in EF8 and EF16 is (-6.43257, -2.46743).

Mean SD Analysis

In normal distribution and Student t-distribution (which is approximately normal) mean SD contains 68.26%, mean 2 SD contains 695.446% and mean 3 SD contains 99.73% of data. Data showing mean standard deviation (mean SD) for Zone1 are presented in the table V. Also the Zonal charts for variables EDV, ESV and EF for 8-frame and 16-frame are given in Figures 6, figure 7 and figure 8. The interpretation of mean SD rule for the whole data is also given in the last column of the table V.

It is quite interesting that all the three variables (EDV, ESV and EF) have shown significant results with high correlation coefficients (r =0.972, 0.989 and 0.961 with p-value=0.0000<0.05) such as for 16-frame and 8-frame method. This indicates that frame-16 observation which are actually simulated or produced from frame-8 have a strong positive relationship that is also observed in the line charts. Whether the 16-frame variables depend on 8-frame variables in case of EDV, ESV and %EF, we have found that in all cases the R-square value confirms the good fit ofregression. It is very surprising that in all the three regressions, some observations are outlying or highly influential, which require the use of regression diagnostics for further study. All the necessary calculation and graphs have been developed through SPSS v.10 and Minitab v 14.

We have also tried to study the data using Mean SD methodology and the statistical quality control technique from control charts i.e. Zonal study was implemented but found that some observation in each variable for 8-frame as well as 16-frame fall outside the limit of mean SD, so they can never show p-value 0.000. It will be better to consider the case for mean 2 SD or mean 3SD. It is expected that the criteria mean 3SD will surely give a p-value of 0.0000.

DISCUSSION:

Clinical Aspects: State of the art single-photon emission computerized tomography (SPECT) imaging provides combined information about myocardial perfusion and function, from the same image data. This became feasible after the introduction of teachnitum-99m MIBI and acquisition with electrocardiographic (ECG) gating. The present study shows that the LV volumes calculated from 16-frame imaging data similar significantly from those calculated from 8-frame imaging data. Sixteen frame studies result in larger EDVs, smaller ESVs and higher LVEFs as compared to 8-frame studies. The difference in LV volumes mentioned can be explained by the superior temporal resolution of 16-frame studies as compared with 8-frame studies. The end-systolic frame in an 8-frame study contains residual volume from systole/diastole on either side and hence is larger than that in a 16-frame study.

Higher temporal resolution of SPECT should result in more accurate determination of end-systolic and end-diastolic frames and hence more accurate assessment of ventricular volumes. We used stress/rest studies for our analysis, but mostly stress studies are routinely obtained by the 16-frame method in various institutions. Typically rest studies are obtained after a week if necessary.

Technical Aspects: The larger amount of computer storage space and longer acquisition and processing times required for 16-frame gated SPECT studies may result in an increase in costs as compared to 8-frame gated SPECT. The cost of storage media was a major concern 16-frame require 3 times larger data than 8 frames. The availability of faster and more sophisticated computers equipped with multiple processors and multi-tasking capability allows for fast and simultaneous acquisition and processing of multiple programs. This compensates for the longer acquisition and processing times necessary for 16-frame gated SPECT. The graph between frame and volume (time-volume curve) should be valley shape. But the curve obtained with 8-frame was not valley shaped properly. The study should be repeated if the results are same then it should not be reported.

Curves obtained with 8-frames were not properly valley shaped. However, curves obtained with 16-frame were properly valley shaped. So, this study was reliable and should be reported.

Statistical Analysis: Left ventricular parameters derived from 8-frame and 16-frame images were first-compared in the entire study group, and then in patients with administered dose studies, and in patients with and without myocardial perfusion defects by using Minitab software. Data are presented as mean standard deviation and P0.05), Smaller ESV (34.7 31.4ml vs 38.9 40.1ml, P>0.05), Higher LVEF (63 14.1ml vs 59.1 15ml, P>0.05) and our P values are greater than our assumed values. Hence our values were not significant.

Study Limitations: A limitation of the present study is that LV volumes and ejection fractions, derived from 16-Frame and 8-Frame gated SPECT, were not compared with an independent gold standard. Hence there is no direct proof that the larger EDV, higher LVEF and lower ESV from 16-frame gated SPECT are indeed more accurate. However, prior studies with 8-Frame gating have shown that calculated LV EDV and angiography or cine MRI. Thus the change in LV volumes and ejection fraction with 16-frame gating is in the direction that makes them more comparable with established standards. Another limitation of our study was absence of high storage computer and multi detector camera. We used single detector camera and low storage computer.

CONCLUSION:

Measurement of LV volumes may have an important impact on the management of patients with variety of cardiac disorders, such as coronary artery disease and valvular heart disease. ESV has been shown to be a powerful predictor of mortality in patients after myocardial infraction and coronary artery bypass surgery. Our study shows that 16-frame gated SPECT provides volume measurements that are significantly same than those provided by 8-frame gated SPECT. Sixteen frame gating provides better temporal resolution than 8-frame gating in the estimation of LV volumes and ejection fraction. Curves are valley shaped will 16 frame thus the acquisition of 16-frame per cycle may be preferred mode for gated SPECT studies. It will be common within few years with multi detector cameras and high storage computers.

ACKNOWLEDGEMENTS

I acknowledge Organization "BINO" and "BVH" at Bahawalpur Who provide me practically opportunity to do work on the Equipment to enhance the knowledge and data analysis.

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Publication: | Science International |
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Article Type: | Report |

Date: | Aug 31, 2017 |

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