Impact of metal implants on xSPECT/CT Bone reconstruction: the “shining metal artefact”

Abstract

Background Novel reconstruction algorithms, such as xSPECT Bone, are gaining more and more importance in Nuclear Medicine. With xSPECT Bone, the reconstructed emission image is enhanced by the information obtained in the corresponding CT image. The CT defines tissue classes according to the Hounsfield units. In the iterative reconstruction, each tissue class is handled separately in the forward projection step, and all together in the back projection step. As a consequence, xSPECT Bone reconstruction generates images with improved boundary delineation and better anatomic representation of tracer activity. Applying this technique, however, showed that artefacts may occur, when no uptake regions, like metal implants, exhibit fictitious uniform tracer uptake. Due to limitations in spatial resolution in gamma cameras, the xSPECT Bone reconstructed image resulted in spill-out activity from surrounding high uptake region being uniformly distributed over the metal implants. This new technology of xSPECT Bone reconstruction in general enhances the image quality of SPECT/CT; however, the potential introduction of specific artefacts which inadvertently come along with this new technology and their frequency have not yet been addressed in the literature. Therefore, the purpose of this work was to identify and characterize these specific metal artefacts (the so-called shining metal artefact) in order to reduce false positives and avoid potentially misdiagnosing loosened or infected implants. Case presentation In this work, we report five cases imaged with bone SPECT/CT of 5 anatomical regions (foot, elbow, spine, shoulder, ribs and knee). All cases demonstrated “shining metal artefacts” in xSPECT Bone reconstruction. Conclusion While xSPECT Bone reconstruction algorithm significantly improves image quality for the diagnosis of bone and joint disorders with SPECT/CT, specific “shining metal artefacts” caused by the xSPECT Bone have to be recognized in order to avoid image misinterpretation suggesting metallic implant loosening or possible infection. The simultaneous analysis of conventionally reconstructed SPECT images (for Siemens the Flash3D reconstruction) helps to avoid misinterpretation of potential artefacts introduced by xSPECT Bone reconstruction.

Accuracy comparison of various quantitative [99mTc]Tc-DPD SPECT/CT reconstruction techniques in patients with symptomatic hip and knee joint prostheses

“…What remains is an uptake which is higher than soft tissue, yet lower than actual bone tissue. These “shining artefacts” as described in a recent case series by Lima et al [ 27 ] were not evident in our study; a reason may be the marked reduction of these artefacts with iMAR, which may lead to a more precise quantification and may have contributed to the high accuracy of the combination xSPECT bone with iMAR reconstructed CT in our study (Fig. 2 versus Fig.…”

Comparative Study of 99mTc-3PRGD2 SPECT/CT and 18F-FDG PET/CT in the Diagnosis of Metastatic Lymph Nodes from Esophageal Squamous Cell Carcinoma

“…Novel reconstruction algorithms, such as the high-de nition bone carving reconstruction technology (HD-xSPECT Bone), are gaining more and more importance in nuclear medicine. HD-xSPECT Bone reconstruction provides images with a clear boundary delineation and improved anatomical representation of tracer activity [13] . The combination of targeted integrin SPETCT imaging and HD-xSPECT Bone may achieve an accurate diagnosis of occultly metastatic LNs in ESCC.…”

Impact on Reconstruction SPECT Image Distortion by Iteration and Subset Number

“…Iterative reconstruction using Single Photon Emission Computed Tomography (SPECT) is frequently used in clinical practice and has significantly improved image quality recently. The majority of recent advancements included expanding the system model to include more variables to simulate the emission/detection process more precisely [1]. SPECT acquisitions are used to gather the photon projection from source distribution to create three-dimensional (3D) images of gamma emitter distributions [2].…”