Oliver S Grosser1,2, Marcus Klutzny3, Heiko Wissel4, Dennis Kupitz4, Michael Finger4, Simone Schenke4, Jan Wuestemann4, Christoph H Lohmann3, Christoph Hoeschen5, Maciej Pech4,6, Christian Staerke3, Michael C Kreissl4,6. 1. Department of Radiology and Nuclear Medicine, University Hospital Magdeburg and Medical Faculty of Otto-von-Guericke University, Leipziger Strasse 44, 39120, Magdeburg, Germany. oliver.grosser@med.ovgu.de. 2. Research Campus STIMULATE, Otto-von-Guericke University, Magdeburg, Germany. oliver.grosser@med.ovgu.de. 3. Department of Orthopaedic Surgery, University Hospital Magdeburg and Medical Faculty of Otto-von-Guericke University, Magdeburg, Germany. 4. Department of Radiology and Nuclear Medicine, University Hospital Magdeburg and Medical Faculty of Otto-von-Guericke University, Leipziger Strasse 44, 39120, Magdeburg, Germany. 5. Chair of Medical Systems Technology, Institute of Medical Engineering, Faculty of Electrical Engineering and Information Technology, Otto-von-Guericke University, Magdeburg, Germany. 6. Research Campus STIMULATE, Otto-von-Guericke University, Magdeburg, Germany.
Abstract
BACKGROUND: SPECT-CT using radiolabeled phosphonates is considered a standard for assessing bone metabolism (e.g., in patients with osteoarthritis of knee joints). However, SPECT can be influenced by metal artifacts in CT caused by endoprostheses affecting attenuation correction. The current study examined the effects of metal artifacts in CT of a specific endoprosthesis design on quantitative hybrid SPECT-CT imaging. The implant was positioned inside a phantom homogenously filled with activity (955 MBq 99mTc). CT imaging was performed for different X-ray tube currents (I = 10, 40, 125 mA) and table pitches (p = 0.562 and 1.375). X-ray tube voltage (U = 120 kVp) and primary collimation (16 × 0.625 mm) were kept constant for all scans. The CT reconstruction was performed with five different reconstruction kernels (slice thickness, 1.25 mm and 3.75 mm, each 512 × 512 matrix). Effects from metal artifacts were analyzed for different CT scans and reconstruction protocols. ROI analysis of CT and SPECT data was performed for two slice positions/volumes representing the typical locations for target structures relative to the prosthesis (e.g., femur and tibia). A reference region (homogenous activity concentration without influence from metal artifacts) was analyzed for comparison. RESULTS: Significant effects caused by CT metal artifacts on attenuation-corrected SPECT were observed for the different slice positions, reconstructed slice thicknesses of CT data, and pitch and CT-reconstruction kernels used (all, p < 0.0001). Based on the optimization, a set of three protocols was identified minimizing the effect of CT metal artifacts on SPECT data. Regarding the reference region, the activity concentration in the anatomically correlated volume was underestimated by 8.9-10.1%. A slight inhomogeneity of the reconstructed activity concentration was detected inside the regions with a median up to 0.81% (p < 0.0001). Using an X-ray tube current of 40 mA showed the best result, balancing quantification and CT exposure. CONCLUSION: The results of this study demonstrate the need for the evaluation of SPECT-CT protocols in prosthesis imaging. Phantom experiments demonstrated the possibility for quantitative SPECT-CT of bone turnover in a specific prosthesis design. Meanwhile, a systematic bias caused by metal implants on quantitative SPECT data has to be considered.
BACKGROUND: SPECT-CT using radiolabeled phosphonates is considered a standard for assessing bone metabolism (e.g., in patients with osteoarthritis of knee joints). However, SPECT can be influenced by metal artifacts in CT caused by endoprostheses affecting attenuation correction. The current study examined the effects of metal artifacts in CT of a specific endoprosthesis design on quantitative hybrid SPECT-CT imaging. The implant was positioned inside a phantom homogenously filled with activity (955 MBq 99mTc). CT imaging was performed for different X-ray tube currents (I = 10, 40, 125 mA) and table pitches (p = 0.562 and 1.375). X-ray tube voltage (U = 120 kVp) and primary collimation (16 × 0.625 mm) were kept constant for all scans. The CT reconstruction was performed with five different reconstruction kernels (slice thickness, 1.25 mm and 3.75 mm, each 512 × 512 matrix). Effects from metal artifacts were analyzed for different CT scans and reconstruction protocols. ROI analysis of CT and SPECT data was performed for two slice positions/volumes representing the typical locations for target structures relative to the prosthesis (e.g., femur and tibia). A reference region (homogenous activity concentration without influence from metal artifacts) was analyzed for comparison. RESULTS: Significant effects caused by CT metal artifacts on attenuation-corrected SPECT were observed for the different slice positions, reconstructed slice thicknesses of CT data, and pitch and CT-reconstruction kernels used (all, p < 0.0001). Based on the optimization, a set of three protocols was identified minimizing the effect of CT metal artifacts on SPECT data. Regarding the reference region, the activity concentration in the anatomically correlated volume was underestimated by 8.9-10.1%. A slight inhomogeneity of the reconstructed activity concentration was detected inside the regions with a median up to 0.81% (p < 0.0001). Using an X-ray tube current of 40 mA showed the best result, balancing quantification and CT exposure. CONCLUSION: The results of this study demonstrate the need for the evaluation of SPECT-CT protocols in prosthesis imaging. Phantom experiments demonstrated the possibility for quantitative SPECT-CT of bone turnover in a specific prosthesis design. Meanwhile, a systematic bias caused by metal implants on quantitative SPECT data has to be considered.
Authors: Monica Abella; Adam M Alessio; David A Mankoff; Lawrence R MacDonald; Juan Jose Vaquero; Manuel Desco; Paul E Kinahan Journal: Phys Med Biol Date: 2012-04-05 Impact factor: 3.609
Authors: T Van den Wyngaert; K Strobel; W U Kampen; T Kuwert; W van der Bruggen; H K Mohan; G Gnanasegaran; R Delgado-Bolton; W A Weber; M Beheshti; W Langsteger; F Giammarile; F M Mottaghy; F Paycha Journal: Eur J Nucl Med Mol Imaging Date: 2016-06-04 Impact factor: 9.236