W E D N E S D A Y

P M

A P R I L

9

S 116 Abstracts Journal of Nuclear Cardiology Wednesday afternoon, April 9, 1997 January/February 1997, Part 2

100.13

COST-EFFECTIVE PREPARATION OF 99mTc- TETROFOSMIN BY REFORMULATION AND FRAC- TIONATION OF MYOVIEW ® KIT INTO MULTIDOSE COLD KITS. Ouhayoun, E.; Leconte, V.;. Coca, F.; Bastir, D.; Coulais, Y.; Esquerrr, J.P. and Tafani, J.A.M. Service central de Mrde- cine Nuclraire. Hrpital Purpan. Toulouse. France.

99mTc-Tetrofosmin is a new powerful radioligand es- pecially used for myocardial perfusion SPECT imaging. In order to use the expensive Myoview ® kit in a more cost- effective manner, we developped an original splitting method. Using aseptic techniques, the lyophilized compo- nents of the original kit were dissolved in 3,5 ml of 20 ~g/ml N2-purged SnCI2 in bicarbonate buffer solution (pH 8). The kit was then splitted into 0,5 ml aliqnots in six sepa- rate vials, overlayed with nitrogen. The fmctionated kits we- re frozen at -20°C during a four weeks evaluation period. Each of them was reconstituted with 1,5-2,5 ml of 100-250 mCi (3,70-9,25 GBq) 99mTc for a multi-dose use. The RCP of the fractionated kits was determined by two thin layer chromatography systems on silica gel plates using ace- tone/dichloromethane (35/65,v/v) and methanol/H20/TFA (70/30/0,1,v/v) as mobile phases. Over the four weeks period, the average RCP of fractionated 99mTc-Tetrofosmin prepa- rations was maintained at 96,4+2,5% (n=12) and all bacte- riological controls were negative. Moreover, image quality with fraetionated kits was equivalent to original kit.

100.15

3D PERFUSION STUDIES USING A MOBILE GAMMA CAMERA BASED ON ECTOMOGRAPHY S.Dale, D.Bone, L-A Brodin, H.Elmqvist, M.Holmberg, C.Lindstrrm, M.Persson, T.Ribbe, L. Jorfeldt Karolinska Institute, Stockholm, Sweden A mobile tomographic gamma camera has been developed to enable three-dimensionai perfusion studies in the emergency room and in the intensive care environment. The system, Cardiotom, is based on the limited view angle method Ectomography and comprises a modem detector head equipped with a rotating slant hole collimator, and specially developed hardware and sot~ware for data acqui- sition, processing and display. The mobile system is PC- based running Windows 3.1 and is totally self-contained. The collimator has different projection directions, so that several simultaneous projections are obtained. The acquisition time is reduced with a factor equal to the number of projection directions; with a 4 segment collimator, the acquisition time is typically 6 rain for a myocardial perfusion study using Te-99m sestamibi. System volume resolution depends on the collimator slant angle and increases from 0.8 em 3 at 5 cm to 7.2 cm 3 at 20 cm for a slant angle of 40 degrees. The system, with a total weight of 350 kg, is currently in use at the Karolinska hospital for a blind comparative study with SPECT and for infarction treatment assessment.

100.14

PERFORMANCE COMPAR/SON ON A DIGITAL GAMMA CAMERA MODIFIED FOR POSITRON IMAGING: 3/8 INCH VS 1/2 INCH CRYSTAL T. Hill, D. Wagenaar, Beth Israel-Deaconess Medical Center, Harvard Medical School, Boston, USA

Cardiac viability studies using F-18 Huorodeoxy- glucose (FDG) have become widely available with the use of gamma cameras modified with high energy collimators for positron imaging. The modifications of the fast generation camera systems were focused around the collimator. The second generation cameras are now including modifications such as changing the crystal thickness to improve the sensitivity of the imaging device. We compared performance measurements on a dual headed digital gamma camera with a 3/8 inch crystal and a modified version with 1/2 inch crystal. The sensitivity for 511 key improved by approximately 30%. Contribution from septal penetration in the sensitivity measuremeut were evaluated. Intrinsic spatial resolution was degraded to 3.4mm FWHM at 140 key from 2.7mm. Lesion visibility data for 511 key photons have been acquired for both crystals and gain in sensitivity enhanced lesion detection. Improvements in digital gamma camera design with thicker crystals can improve system performance for 511 key imaging without compromising its performance as a general purpose nuclear medicine gamma camera.

100.16

IMPROVED NORMAL DISTRIBUTIONS IN ATTENUATION CORRECTED TC-99M-SESTAMIBI CARDIAC SPECT WITH GD-153 TRANSMISSION SCANNING AND DOWNSCATTER CORRECTION SJ Cullom, MW Groch, WK Braymer, J Ye, SM Spies and RC Hendel, Emory University, Atlanta GA, U.S.A.

Attenuation correction (AC) of Tc-99m-sestamibi (MIBI) SPECT using simultaneous Gd-153 line source scanning (SC) significantly improves the specificity of cardiac SPECT. However, attenuation map errors may result from downscatter (DS)of Tc-99m photons into the Gd-153 transmission window leading to suboptimal attenuation correction. A DS compensation algorithm we previously described and evaluated in phantoms was evaluated in 20 individuals (10M,10F) with less than 5% pretest likelihood of coronary artery disease. Stress MIBI studies acquired with SC were reconstructed with FBP only, Maximum Likelihood (ML) with AC (Vantage TM, ADAC Labs Milpitas, CA) and ML with AC and DS correction (DSC). Anterior/inferior (A/l), septal/lateral (S/L)wall ratios and % maximal nonuniformity between regions (NU) were extracted from a 9 region segmentation of the LV polar map.

Males Females Method %NU A/I S/L %NU A/I S/L

FBP 34 1.22 0.81 22 1.08 0.93 AC 24 1.07 0.84 16 1.07 0.93

ACw/DSC 15 1 .01 0.94 12 1.02 0.98 Downscatter compensation provides additional

improvement in the uniformity of MIBI distributions in both male and female low-likelihood patients. Further evaluation is ongoing to establish the diagnostic accuracy of this method and the validity of gender-independent normal files.