title: 4D-SPECT/CT in orthopaedics: a new method of combined quantitative volumetric 3D analysis of SPECT/CT tracer uptake and component position measurements in patients after total knee arthroplasty.
abstract: OBJECTIVE
  The purpose was to evaluate the intra- and inter-observer reliability of combined quantitative 3D-volumetric single-photon emission computed tomography (SPECT)/CT analysis including size, intensity and localisation of tracer uptake regions and total knee arthroplasty (TKA) position.
  
  
  METHODS
  Tc-99m-HDP-SPECT/CT of 100 knees after TKA were prospectively analysed. The anatomical areas represented by a previously validated localisation scheme were 3D-volumetrically analysed. The maximum intensity was recorded for each anatomical area. Ratios between the respective value and the mid-shaft of the femur as the reference were calculated. Femoral and tibial TKA position (varus-valgus, flexion-extension, internal rotation- external rotation) were determined on 3D-CT. Two consultant radiologists/nuclear medicine physicians interpreted the SPECT/CTs twice with a 2-week interval. The inter- and intra-observer reliability was determined (ICCs). Kappa values were calculated for the area with the highest tracer uptake between the observers.
  
  
  RESULTS
  The measurements of tracer uptake intensity showed excellent inter- and intra-observer reliabilities for all regions (tibia, femur and patella). Only the tibial shaft area showed ICCs <0.89. The kappa values were almost perfect (0.856, p < 0.001; 95 % CI 0.778, 0.922). For measurements of the TKA position, there was strong agreement within and between the readings of the two observers; the ICCs for the orientation of TKA components for inter- and intra-observer reliability were nearly perfect (ICCs >0.84).
  
  
  CONCLUSIONS
  This combined 3D-volumetric standardised method of analysing the location, size and the intensity of SPECT/CT tracer uptake regions ("hotspots") and the determination of the TKA position was highly reliable and represents a novel promising approach to biomechanics.
authors.affiliation: Institute for Radiology and Nuclear Medicine, Kantonsspital Baselland, 4101 Bruderholz, Switzerland.
authors.forename: Helmut
authors.initials: H
authors.lastname: Rasch
authors.forename: Anna L
authors.initials: AL
authors.lastname: Falkowski
authors.forename: Flavio
authors.initials: F
authors.lastname: Forrer
authors.forename: Johann
authors.initials: J
authors.lastname: Henckel
authors.forename: Michael T
authors.initials: MT
authors.lastname: Hirschmann
mesh_terms: D000328:Adult; D018771:Arthralgia / Q000175:diagnosis* / Q000209:etiology / Q000378:metabolism*; D019645:Arthroplasty, Replacement, Knee / Q000009:adverse effects*; D005260:Female; D006801:Humans; D007089:Image Enhancement / Q000379:methods; D007090:Image Interpretation, Computer-Assisted / Q000379:methods; D021621:Imaging, Three-Dimensional / Q000379:methods; D007719:Knee Joint / Q000000981:diagnostic imaging / Q000378:metabolism* / Q000473:pathology; D008297:Male; D064847:Multimodal Imaging / Q000379:methods; D015588:Observer Variation; D019275:Radiopharmaceuticals / Q000493:pharmacokinetics; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity; D013669:Technetium Tc 99m Medronate / Q000031:analogs & derivatives* / Q000493:pharmacokinetics; D015899:Tomography, Emission-Computed, Single-Photon / Q000379:methods*; D014057:Tomography, X-Ray Computed / Q000379:methods*
chemical_list: D019275:Radiopharmaceuticals; C024226:technetium Tc 99m hydroxymethylene diphosphonate; D013669:Technetium Tc 99m Medronate