Abstract
BackgroundThis study attempted to compare the radiopharmaceutical uptake findings of planar bone scintigraphy (BS) and single photon emission computed tomography (SPECT)/computed tomography (CT) performed on knee joints.MethodsWe retrospectively included 104 patients who underwent bone SPECT/CT and BS 4 h after the intravenous administration of technetium-99m-hydroxymethylene diphosphonate (99mTc-HDP) for pain in the knee joint. The uptake degree of each of the knee regions (medial femoral, lateral femoral, medial tibial, lateral tibial, and patellar area) in planar images and SPECT/CT were evaluated by visual (grades 0 to 2) and quantitative analyses (uptake counts for planar image and standardized uptake values [SUVs] for SPECT/CT).ResultsThe uptake grades assessed visually on the planar images differed significantly from the uptake grades on SPECT/CT images in all areas of the knee (all p < 0.001), and SPECT/CT imaging revealed a larger number of uptake lesions than those noted in planar imaging for each patient (3.3 ± 2.0 vs 2.4 ± 2.3, p < 0.0001). In all regions of the knee, all of the quantitative values, including uptake counts obtained from the planar image as well as the maximum SUV (SUVmax) and mean SUV (SUVmean) obtained from SPECT/CT, showed statistically higher values as their visual grades increased (all p < 0.001). However, when analyzed for each area, only the SUVmax showed a significant difference by grade in all knee regions. Quantitative uptake values obtained from planar images were moderately correlated with SUVs of SPECT/CT images (r = 0.58 for SUVmean and r = 0.53 for SUVmax, all p < 0.001) in the total knee regions. Looking at each area, there was a significant but low correlation between the uptake counts of the planar images and the SUVs on SPECT/CT in the right lateral tibial region (r = 0.45 for SUVmean, r = 0.31 for SUVmax, all p < 0.001).ConclusionsIn assessing knee joints, the findings of planar images and SPECT/CT images differ both visually and quantitatively, and more lesions can be found in SPECT/CT than in the planar images. The SUVmax could be a reliable value to evaluate knee joint uptake activity.
Highlights
This study attempted to compare the radiopharmaceutical uptake findings of planar bone scintigraphy (BS) and single photon emission computed tomography (SPECT)/computed tomography (CT) performed on knee joints
There are a few previous studies that quantitatively analyzed the uptake of radiopharmaceuticals in knee SPECT/CT [5, 9], as it is possible to measure the uptake of radiopharmaceuticals as in positron emission tomography (PET) using standardized uptake values (SUVs) [10]
The SUVmean values of both patellae and the right medial tibial region showed significant differences between all grades, but there was no significant difference in SUVmean between grade 0 and grade 1 in either the medial femur or left tibia, or between grade 1 and grade 2 in either the lateral femur or the right lateral tibial region (Fig. 4b)
Summary
This study attempted to compare the radiopharmaceutical uptake findings of planar bone scintigraphy (BS) and single photon emission computed tomography (SPECT)/computed tomography (CT) performed on knee joints. BS can only obtain planar images, which have shown limitations in evaluating the deep part of the knee joint or determining the specific anatomical location of the abnormal uptake site of the radiopharmaceutical [2]. This study is an attempt to compensate for this limitation of BS using hybrid single photon emission computed tomography (SPECT)/computed tomography (CT) combined with functional SPECT imaging and anatomic CT imaging [3]. There are a few previous studies that quantitatively analyzed the uptake of radiopharmaceuticals in knee SPECT/CT [5, 9], as it is possible to measure the uptake of radiopharmaceuticals as in positron emission tomography (PET) using standardized uptake values (SUVs) [10]. BS can be quantified using the traditional method in the form of counts per second, this is fundamentally different from SUVs [11]
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