Assessment of Inter-modality Spatial Alignment Accuracy in Hybrid Single Photon Emission Computed Tomography in Patients with Hand and Wrist Pain

Abstract

Single photon emission computed tomography (SPECT) and computed tomography (CT) integrated in one system (SPECT/CT) is an effective co-registration technique that helps to localize and characterize lesions in the hand and wrist. However, patient motion may cause misalignment between the two modalities leading to potential misdiagnosis. The aim of the present study was to evaluate the hardware-based registration accuracy of multislice SPECT/CT of the hand and wrist and to determine the effect of misalignment errors on diagnostic accuracy. A total of 55 patients who had multislice SPECT/CT of the hand and wrist between July 2008 and January 2010 were included. Two reviewers independently evaluated the fused images for any misalignments with six degrees of freedom: Translation and rotation in the X, Y and Z directions. The results were tested against an automated fusion tool (Syntegra). More than half of the patients had moved during SPECT scanning (Reviewer 1: 29 patients; Reviewer 2: 30 patients) and they all originated in the Y-direction translation (vertical hand motion). Five fused images had significant misalignment errors that could have led to misdiagnosis. The Wilcoxon test indicated statistically non-significant difference (P > 0.05) between reviewers and statistically non-significant difference between the reviewers and software registration. The study also showed high inter-reviewer agreement (κ = 0.87). Hand movement during the SPECT scan was common, but significant misalignments and subsequent misdiagnosis were infrequent. Future studies should investigate the use of hand and wrist immobilization devices and reductions of scan time to minimize patient motion.

Keywords: Image fusion; registration; single photon emission computed tomography/computed tomography.

Figure 1

The “Superman” position for single photon emission computed tomography/computed tomography scanning

Figure 2

The dual-head gamma camera single photon emission computed tomography/computed tomography system – Philips Precedence 16

Figure 3a

The fusion display tool demonstrates misalignments between the single photon emission computed tomography and computed tomography images in the transverse (top left) and sagittal (bottom) planes. The re-alignment box (top right) displays the coordinates in millimeters for six degree of freedom

Figure 3b

The reviewer has re-aligned the single photon emission computed tomography image over the computed tomography image. The re-alignment box displays the misalignment distance of 5.8889 mm in the Y-direction translation

Figure 4

Left: The patient's thumb moved during the single photon emission computed tomography (SPECT) scan while all other parts were aligned. Right: The patient's third, fourth and fifth digits moved during the SPECT scan. The misalignment is most visible on the fifth digit

Figure 5a

Images before misalignment correction of patient B. Misalignment between the single photon emission computed tomography and computed tomography images had caused the area of increased focal uptake to be located at the soft-tissues overlying the trapezium

Figure 5b

Images after misalignment correction of patient B. The area of increased focal uptake is correctly positioned over a cystic lesion of the trapezium

Figure 6

Thermoplastic mesh made from lightweight plastic. It can be individually molded to fit the patient's hand providing better support and immobilization