High Sensitivity Collimators for Optimising Lesion Detection in SPECT Images

TL;DR

This study investigates the optimization of collimator design in SPECT imaging, demonstrating that higher sensitivity collimators significantly improve lesion detection and can reduce scan time or dose.

Contribution

The paper introduces an optimized collimator design with increased sensitivity that enhances lesion detection performance in SPECT imaging.

Findings

Optimal collimators have 6-9 times the sensitivity of conventional high-resolution collimators.

Using the optimized collimator achieves conventional image quality with one-third the scan time or dose.

Enhanced collimator sensitivity improves detection of lesions near the visibility threshold.

Abstract

Parallel hole collimators which are currently routinely used in SPECT imaging were designed a few decades ago, when filtered backprojection (FBP) was used for tomographic reconstruction. Statistical reconstruction methods with precise modeling of the projection measurement offer a different standard, and the question of optimizing resolution - sensitivity tradeoff by choosing appropriate collimator aperture needs to be revised. In this paper we search for a parallel hole collimator which offers best performance in detection of hot lesions on a uniform background. To evaluate the image quality we use standard quantitative measures like the contrast recovery coefficient, coefficient of variation, and contrast to noise ratio. We also performed signal detection by human observers followed by Receiver Operating Characteristics (ROC) analysis for a few lesions close to the limit of visibility. Our results consistently indicate that optimal performance is achieved with collimators of sensitivity 6 - 9 times that of the conventional high resolution (HR) collimator. When the optimized collimator is applied, the image quality of the conventional image obtained with the HR can be achieved at scanning time or activity dose reduced by factor of 3.