Clinical application of dual-phase F-18 sodium-fluoride bone PET/CT for diagnosing surgical site infection following orthopedic surgery

Abstract

F-18 sodium-fluoride (NaF) bone positron emission tomography (PET/CT) has been used for diagnosing various bone and joint diseases, and, with using dual-phase scan protocol, it could give the same information obtained by the 3-phase bone scintigraphy. The present study aimed to evaluate the diagnostic ability of dual-phase F-18 NaF bone PET/CT in detecting surgical site infection after orthopedic surgery.Twenty-three patients who underwent dual-phase F-18 NaF bone PET/CT under clinical suspicion of surgical site infection of the bone following orthopedic surgery were enrolled in this study. Dual-phase bone PET/CT consisted of an early phase scan performed immediately after radiotracer injection and a conventional bone-phase scan. All dual-phase PET/CT images were visually assessed, and, for quantitative analysis, 6 parameters of dual-phase PET/CT (lesion-to-blood pool uptake ratio, lesion-to-bone uptake ratio, and lesion-to-muscle uptake ratio on both early phase and bone-phase scans) were measured.Surgical site infection was diagnosed in 14 patients of the 23 patients. The sensitivity, specificity, and accuracy of visual analysis of dual-phase F-18 NaF bone PET/CT for diagnosing surgical site infection of the bone were 92.9%, 100.0%, and 95.7%, respectively. Among the 6 parameters, the lesion-to-blood pool uptake ratio on early phase scan showed the highest area under the receiver operating characteristic curve value (0.857, 95% confidence interval, 0.649-0.966), with the cut-off value of 0.88 showing sensitivity, specificity, and accuracy of 85.7%, 88.9%, and 87.0%, respectively.Our study showed the high diagnostic ability of dual-phase F-18 NaF bone PET/CT for detecting surgical site infection following orthopedic surgery. Further studies are needed to compare the diagnostic ability of dual-phase bone PET/CT with other imaging modalities.

Figure 1

A maximal intensity projection image (A) and transaxial PET (B) and fused PET/CT (C) images from the early-phase scan and a maximal intensity projection image (D) and transaxial PET (E) and fused PET/CT (F) images from the bone-phase scan in F-18 NaF bone PET/CT of a 34-year-old man. Both early-phase and bone-phase scan images showed focally increased radiotracer uptake at the surgical site of the T12 spine (arrows in A–F). The patient underwent a revision operation and was diagnosed with surgical site infection of the spine. PET/CT = positron emission tomography/computed tomography.

Figure 2

A maximal intensity projection image (A) and coronal PET (B) and fused PET/CT (C) images from the early-phase scan and a maximal intensity projection image (D) and coronal PET (E) and fused PET/CT (F) images from the bone-phase scan in F-18 NaF bone PET/CT of a 68-year-old man. Intensely increased radiotracer uptake around the prosthesis in the right femur and knee joint is shown on both early-phase and bone-phase scan images (arrows in A–F). The patient underwent a revision operation and was diagnosed with surgical site infection of the right femur and knee joint. PET/CT = positron emission tomography/computed tomography.

Figure 3

Distribution of the lesion-to-blood pool uptake ratio on early-phase scans in F-18 NaF bone PET/CT in patients with (positive) and without (negative) surgical site infection. PET/CT = positron emission tomography/computed tomography.

Figure 4

(A) Comparison of ROC curves for the lesion-to-blood pool uptake ratio on the early-phase scan, and the lesion-to-blood pool uptake ratio, lesion-to-bone uptake ratio, and lesion-to-muscle uptake ratio on the bone-phase scan. (B) Comparison of ROC curves for the lesion-to-blood pool uptake ratio, lesion-to-bone uptake ratio, and lesion-to-muscle uptake ratio on the early-phase scan. ROC = receiver operating characteristic.