[Importance of SPECT/CT for knee and hip joint prostheses]. / Stellenwert der SPECT/CT bei Knie- und Hüftgelenkprothesen.

CLINICAL/METHODICAL ISSUE: Complications, such as loosening or infections are common problems after hip or knee arthroplasty. STANDARD RADIOLOGICAL METHODS: If conventional X-rays are equivocal bone scintigraphy is the classical second-line imaging modality. METHODICAL INNOVATIONS: Single photon emission computed tomography/computed tomography (SPECT/CT) offers metabolic and morphologic information in one imaging step and is becoming increasingly more available in larger hospitals. PERFORMANCE: The SPECT/CT procedure is a promising method and is increasingly being used in daily routine to evaluate joint arthroplasty. The additional benefit compared with classical conventional bone scintigraphy has to be evaluated in further prospective studies. ACHIEVEMENTS: In our hospital SPECT/CT regularly gives important additional information regarding prosthetic joint complications. PRACTICAL RECOMMENDATIONS: SPECT/CT is increasingly being used as the second step imaging standard modality if conventional X-rays are equivocal.

MR/CT image fusion of the spine after spondylodesis: a feasibility study.

The objective of this study is to evaluate feasibility, accuracy and time requirements of MR/CT image fusion of the lumbar spine after spondylodesis. Sagittal MR and CT images derived from standard imaging protocols (sagittal T2-weighted MR/sagittal reformatted multi-planar-reformation of the CT) of the lumbar spine with correct (n = 5) and incorrect (n = 5) implant position were fused by two readers (R1, R2) using OsiriX in two sessions placing one (session 1) or two (session 2) reference point(s) on the dorsal tip(s) of the cranial and caudal endplates from the second lumbar to the first sacral vertebra. R1 was an experienced musculoskeletal radiologist; R2 a spine surgeon, both had received a short training on the software tool. Fusion times and fusion accuracy, defined as the largest deviation between MR and CT in the median sagittal plane on the ventral tip of the cranial end plate of the most cranial vertebra visible on the CT, were measured in both sessions. Correct or incorrect implant position was evaluated upon the fused images for all patients by an experienced senior staff musculoskeletal radiologist. Mean fusion time (session 1/session 2; in seconds) was 100.4/95 (R1) and 104.2/119.8 (R2). Mean fusion deviation (session 1/session 2; in mm) was 1.24/2.20 (R1) and 0.79/1.62 (R2). The correct/incorrect implant position was identified correctly in all cases. In conclusion, MR/CT image fusion of the spine with metallic implants is feasible, fast, accurate and easy to implement in daily routine work.