Myocardial [18F]FDG tomography using a conventional gamma camera and a seven pinhole collimator

Seven pinhole tomography (SPHT) is fast, inexpensive, and, because it relies on standard gamma cameras and computers, available everywhere. This article investigates the suitability of SPHT for the detection and localization of 511 keV gammas emitted from 18F without coincidence detection.

A standard SPH collimator and the table were additionally shielded with lead. For comparison, point sources and cardiac phantoms were imaged on SPHT and a triple head gamma camera (THC). The phantom studies were supplemented with patient examinations using a standard clinical protocol. Circumferential profiles allowed a direct comparison of perfusion under different conditions or perfusion plus metabolism.

Dedicated for cardiac workup, SPHT has a 5-10 times better sensitivity (dependent on distance) than THC and gives superior resolution for the extension of a lesion perpendicular to the long cardiac axis: The full width at half-maximum for x- and y-directions (FWHMx,y) for a 99mTc-point source was found to be 35 and 22% smaller at 130 and 220 mm distances with SPHT than with THC. The SPHT even surpasses the THC at greater distances. The resolution falls off with 18F: FWHM increases by 70 and 48%, respectively, compared to 99mTc. The in-depth resolution is worse with SPHT: The FWHM (using 99mTc) is 2-3.5 times greater with SPHT than with THC and remains within this range with 18F.

It is possible to image 18F distributions using SPHT with a very high sensitivity and good detail resolution, even in the presence of 99mTc and 201Tl. The SPHT compares well with THC for 99mTc, except in its in-depth resolution, and is unsurpassed in its sensitivity and ease of performance.