Clinical validation of time reduction strategy in continuous step-and-shoot mode during SPECT acquisition

Abstract

Background: The SwiftScan solution (General Electric Healthcare) combines a new low-energy high-resolution sensitivity collimator and a tomographic step-and-shoot continuous (SSC) mode acquisition. The purpose of this study is to determine whether SSC mode can be used in clinical practice with shorter examination times, while preserving image quality and ensuring accurate semi-quantification. Twenty bone scan and 10 lung scan studies were randomly selected over a period of 2 months. Three sets of image datasets were produced: step-and-shoot (SS) acquisition, simulated 25% count reduction using the Poisson resampling method (SimSS), and SimSS continuous acquisition (SimSSC), where SimSS was summed with counts acquired during detector head rotation. Visual assessment (5-point Likert scale, 2 readers) and semi-quantitative evaluation (50 focal uptake from 10 bone studies), assessed by SUV_mean, coefficient of variation (COV), and contrast-to-noise ratio (CNR), were performed using t test and Bland-Altman analysis.

Results: Intra-reader agreement was substantial for reader 1 (k = 0.71) and for reader 2 (k = 0.61). Inter-reader agreement was substantial for SS set (k = 0.93) and moderate for SimSSC (k = 0.52). Bland-Altman analysis showed a good interchangeability of SS and SimSSC SUV values. The mean CNR between SS and SimSSC was not significantly different: 42.9 ± 43.7 [23.7-62.1] vs. 43.1 ± 46 [22.9-63.3] (p = 0.46), respectively. COV values, assessing noise level, did not deviate significantly between SS and SimSSC: 0.20 ± 0.08 [0.18-0.23] vs. 0.21 ± 0.08, [0.18-0.23] (p = 0.15), respectively, whereas a significant difference was demonstrated between SS and SimSS: 0.20 ± 0.08 [0.18-0.23] vs. 0.23 ± 0.09 [0.20-0.25] (p < 0.0001), respectively.

Conclusions: SSC mode acquisition decreases examination time by approximately 25% in bone and lung SPECT/CT studies compared to SS mode (~ 2 min per single-bed SPECT), without compromising image quality and signal quantification. This SPECT sensitivity improvement also offers the prospect of more comfortable exams, with less motion artifacts, especially in painful or dyspneic patients.

Keywords: Bone; Lungs; SPECT/CT; SUV; Semi-quantification; SwiftScan.

Fig. 1

An illustration of step-and-shoot (SS) versus step-and-shoot continuous (SSC) mode acquisition, demonstrating incorporation of counts during the detector head rotation in SSC mode

Fig. 2

Bone SPECT. Comparison between SS (a) and SimSSC (b) images on a sagittal view. Images were rated as 4 for the 2 modes

Fig. 3

V/Q lung SPECT. Comparison between SS (a perfusion; b ventilation) and SimSSC (c perfusion; d ventilation) images on coronal views. Images were rated as 4 for the 2 modes

Fig. 4

Bland-Altman plot demonstrating differences in SUV as a function of average SUV between step-and-shoot (SS) and simulated step-and-shoot continuous (SimSSC) mode, pooling 50 lesions from 10 patients (5 lesions per patient)

Fig. 5

Bland-Altman plot demonstrating differences in standard deviation of SUV as a function of averaged standard deviation SUV between step-and-shoot (SS) and simulated step-and-shoot continuous mode (SimSSC), pooling 50 lesions from 10 patients

Fig. 6

Box plot on contrast-to-noise ratio for two acquisition modes (SS, step-and-shoot; SimSSC, simulated step-and-shoot continuous; SimSS, simulated step-and-shoot). The median is illustrated by the midline, first and third quartiles by the lower and upper lines of the box, and extremes by whiskers

Fig. 7

Box plot showing the coefficient-of-variation of the 50 lesions, for three acquisition modes (SS, step-and-shoot; SimSSC, simulated step-and-shoot continuous; SimSS, simulated step-and-shoot). The median is illustrated by the midline, first and third quartiles by the lower and upper lines of the box, and extremes by whiskers