Katrin D. M. Stumpe

Whole-body positron emission tomography using fluorodeoxyglucose for staging of lymphoma: effectiveness and comparison with computed tomography

Abstract. The purpose of this study was to evaluate whole-body positron emission tomography (WB-PET) as a staging modality in Hodgkin’s disease (HD) and non-Hodgkin lymphoma (NHL) and to compare it with computed tomography (CT) in a retrospective study. Seventy-one WB-PET studies using fluorodeoxyglucose (FDG) and 49 CT examinations were performed in 19 women and 31 men. Transaxial images were acquired and reformatted coronally and sagittally in PET. CT sections were obtained from the skull base to the pelvic floor. The written reports of the imaging data were compared with a reference standard constructed on the basis of all the data on the individual patients, including clinical follow-up of at least 6 months. The sensitivity and specificity of PET were, respectively, 86% and 96% for HD (n=53), and 89% and 100% for NHL (n=18). For CT sensitivity and specificity were 81% and 41% for HD (n=33) and 86% and 67% for NHL (n=16). Differences between PET and CT sensitivities were not significant, while in HD there was a significant difference in the specificity of PET and CT examinations, mainly because CT was unable to distinguish between active or recurrent disease and residual scar tissue after therapy. FDG tumour uptake was found in high- as well as low-grade NHL patients. In conclusion, PET appears to be highly sensitive and specific for staging of lymphoma. It is at least as sensitive as CT, and more specific, particularly in patients undergoing restaging, where a well-recognized diagnostic dilemma in CT is the presence of a post-therapeutic residual mass.

Infection imaging using whole-body FDG-PET

Abstract.The purpose of this study was to evaluate fluorine-18 fluorodeoxyglucose positron emission tomography (FDG-PET) for the detection of soft tissue and bone infections. Forty-five PET examinations in 39 patients (26 male, 13 female, age range 27–86 years) with suspected infectious foci were examined with whole- or partial-body PET scans using FDG. Twenty-seven scans were done in patients with soft tissue and 18 in patients with bone infections. Corrected and uncorrected transaxial PET images were acquired. Seven hundred and twelve body regions in these 45 PET scans were evaluated. Pathological findings were graded using a confidence scale from A to E (A, definitive infection; E, no infection). Disease status was defined in all patients by culture, biopsy or surgery and clinical follow-up. In 45 PET scans there were 40 true-positive, four false-positive and one false-negative findings. Twelve foci suspected to be infectious in nature on the basis of other imaging examinations were identified as negative by PET, thus representing true-negative findings. Sensitivities for the patients with soft tissue (STI) and bone infections (BI) and for the pooled data were 96%, 100% and 98%, respectively. As the calculation of specificity is not straightforward, it was calculated on a per lesion as well as on a per body region basis to permit estimation of an upper and a lower limit. On a per lesion basis, specificities were 70% (STI), 83% (BI) and 75% for the pooled data and on a per body region basis (dividing the body into 22 regions) they were 99% (STI), 99% (BI) and 99% for the pooled data. One false-negative result was found in a patient with cholangitis. It is concluded that PET appears to be a highly sensitive method to detect infectious foci. Specificity is more difficult to estimate, but is probably in the range from 70% to above 90%.

Diagnostic value of 18F-FDG PET/CT in trauma patients with suspected chronic osteomyelitis

PurposeTo retrospectively evaluate the diagnostic value of 18F-FDG PET/CT in trauma patients with suspected chronic osteomyelitis.MethodsThirty-three partial body 18F-FDG PET/CT scans were performed in 33 patients with trauma suspected of having chronic osteomyelitis. In 10 and 23 patients, infection was suspected in the axial and appendicular skeleton, respectively. In 18 patients, PET/CT was performed in the presence of metallic implants. Histopathology or bacteriological culture was used as the standard of reference. For statistical analysis, sensitivity, specificity and accuracy were calculated in relation to findings of the reference standard.ResultsOf 33 PET/CT scans, 17 were true positive, 13 true negative, two false positive and one false negative. Eighteen patients had chronic osteomyelitis and 15 had no osseous infection according to the reference standard. Sensitivity, specificity and accuracy for 18F-FDG PET/CT was 94%, 87% and 91% for the whole group, 88%, 100% and 90% for the axial skeleton and 100%, 85% and 91% for the appendicular skeleton, respectively.Conclusion18F-FDG PET/CT is a highly sensitive and specific method for the evaluation of chronic infection in the axial and appendicular skeleton in patients with trauma. PET/CT allows precise anatomical localisation and characterisation of the infectious focus and demonstrates the extent of chronic osteomyelitis with a high degree of accuracy.

PET/CT in musculoskeletal infection.

Early diagnosis of musculoskeletal infections is the key to successful therapy and prevention of complications. Fluorine-18 (F-18) fluorodeoxyglucose-positron emission tomography (FDG-PET) is a promising modality for imaging musculoskeletal infection and might play an important role in the evaluation of chronic osteomyelitis and spinal infection. FDG-PET has shown promising results for diagnosing both acute and chronic infection of the axial and appendicular skeletons. PET imaging will have increased importance in patients with metallic implants because FDG uptake, in contrast to magnetic resonance imaging (MRI) and computed tomography (CT), is not hampered by metallic artifacts. In patients with suspected prosthetic joint infection, results of PET are controversial, and combined indium-111-labeled leukocyte and technetium-99m-sulfur colloid marrow scintigraphy still remains the gold standard. PET/CT with the combination of PET and a low-dose or full-dose diagnostic CT provides exact anatomical correlation of bone and joint lesions and increases the accuracy of the test compared with PET alone. The question of in which situations PET/CT becomes the preferred imaging method in suspected musculoskeletal infection depends on several factors, including cost and availability. This article reviews the currently available literature and addresses the use of FDG-PET/CT in the diagnosis of musculoskeletal infections.

Unsuspected osteomyelitis is frequent in persistent diabetic foot ulcer and better diagnosed by MRI than by 18F-FDG PET or 99mTc-MOAB

Aim.  Prevalence, optimal diagnostic approach and consequences of clinically unsuspected osteomyelitis in diabetic foot ulcers are unclear. Early diagnosis of this infection may be crucial to ensure correct management.

18F-Fluoride PET/CT for detection of sacroiliitis in ankylosing spondylitis

PurposeThe aim of this study was to evaluate the performance of 18F-fluoride-PET/CT (PET/CT) for the diagnosis of sacroiliac joint (SIJ) arthritis in patients with active ankylosing spondylitis (AS).MethodsIncluded in the study were 15 patients with AS according to the modified New York criteria (AS group) and with active disease and 13 patients with mechanical low back pain (MLBP; control group) who were investigated with whole-body 18F-fluoride PET/CT. The ratio of the uptake in the SIJ and that in the sacrum (SIJ/S) was calculated for every joint.ResultsThe mean SIJ/S ratio of 30 quantified joints in the AS group was 1.66 (range 1.10–3.07) with PET/CT, and the mean SIJ/S ratio of 26 quantified joints in the MLBP group was 1.12 (range 0.71–1.52). The area under the receiver operating characteristic curve for SIJ arthritis was 0.84. With plain radiography as a the gold standard and taking an SIJ/S ratio of >1.3 as the threshold, the sensitivity, specificity and accuracy on a per patient basis were 80%, 77% and 79%, respectively. On a per SIJ basis, the greatest sensitivity (94%) was found in grade 3 sacroiliitis (n = 16).ConclusionOur results suggest that quantitative 18F-fluoride PET/CT may play a role in the diagnosis of sacroiliitis in active AS and is an alternative to conventional bone scintigraphy in times of molybdenum shortage.

Expanding role of 18F-fluoro-d-deoxyglucose PET and PET/CT in spinal infections

Abstract18F-fluoro-d-deoxyglucose positron emission tomography ([18F]-FDG PET) is successfully employed as a molecular imaging technique in oncology, and has become a promising imaging modality in the field of infection. The non-invasive diagnosis of spinal infections (SI) has been a challenge for physicians for many years. Morphological imaging modalities such as conventional radiography, computed tomography (CT), and magnetic resonance imaging (MRI) are techniques frequently used in patients with SI. However, these methods are sometimes non-specific, and difficulties in differentiating infectious from degenerative end-plate abnormalities or postoperative changes can occur. Moreover, in contrast to CT and MRI, FDG uptake in PET is not hampered by metallic implant-associated artifacts. Conventional radionuclide imaging tests, such as bone scintigraphy, labeled leukocyte, and gallium scanning, suffer from relatively poor spatial resolution and lack sensitivity, specificity, or both. Initial data show that [18F]-FDG PET is an emerging imaging technique for diagnosing SI. [18F]-FDG PET appears to be especially helpful in those cases in which MRI cannot be performed or is non-diagnostic, and as an adjunct in patients in whom the diagnosis is inconclusive. The article reviews the currently available literature on [18F]-FDG PET and PET/CT in the diagnosis of SI.

Chronic osteomyelitis of the femur: value of PET imaging.

Abstract. The purpose of this report is to discuss FDG-PET as a potentially new imaging tool in the diagnosis of infections of osteosynthetic material. We present a patient with a poly-trauma who developed a chronic osteomyelitis and ostitis after repeated osteosynthesis in a fibular transplant to the left femur. Work up included MRI, antigranulocyte antibody scintigraphy and positron emission tomography (PET) with F-18 fluorodeoxyglucose (FDG). Infection of the fibular transplant was demonstrated clearly by PET but not by the other methods. Positron emission tomography may become an important indication in the diagnosis and follow-up of bone infection.

The additional value of CT images interpretation in the differential diagnosis of benign vs. malignant primary bone lesions with 18F-FDG-PET/CT

ObjectiveTo evaluate the value of a dedicated interpretation of the CT images in the differential diagnosis of benign vs. malignant primary bone lesions with 18fluorodeoxyglucose-positron emission tomography/computed tomography (18F-FDG-PET/CT).Materials and methodsIn 50 consecutive patients (21 women, 29 men, mean age 36.9, age range 11–72) with suspected primary bone neoplasm conventional radiographs and 18F-FDG-PET/CT were performed. Differentiation of benign and malignant lesions was separately performed on conventional radiographs, PET alone (PET), and PET/CT with specific evaluation of the CT part. Histology served as the standard of reference in 46 cases, clinical, and imaging follow-up in four cases.ResultsAccording to the standard of reference, conventional 17 lesions were benign and 33 malignant. Sensitivity, specificity, and accuracy in assessment of malignancy was 85%, 65% and 78% for conventional radiographs, 85%, 35% and 68% for PET alone and 91%, 77% and 86% for combined PET/CT. Median SUVmax was 3.5 for benign lesions (range 1.6–8.0) and 5.7 (range 0.8–41.7) for malignant lesions.In eight patients with bone lesions with high FDG-uptake (SUVmax ≥ 2.5) dedicated CT interpretation led to the correct diagnosis of a benign lesion (three fibrous dysplasias, two osteomyelitis, one aneurysmatic bone cyst, one fibrous cortical defect, 1 phosphaturic mesenchymal tumor). In four patients with lesions with low FDG-uptake (SUVmax < 2.5) dedicated CT interpretation led to the correct diagnosis of a malignant lesion (three chondrosarcomas and one leiomyosarcoma). Combined PET/CT was significantly more accurate in the differentiation of benign and malignant lesions than PET alone (p = .039). There was no significant difference between PET/CT and conventional radiographs (p = .625).ConclusionDedicated interpretation of the CT part significantly improved the performance of FDG-PET/CT in differentiation of benign and malignant primary bone lesions compared to PET alone. PET/CT more commonly differentiated benign from malignant primary bone lesions compared with conventional radiographs, but this difference was not significant.

Osteomyelitis and Arthritis

Infections of bone and the joints can represent major diagnostic and therapeutic challenges to all clinicians. Together with osteomyelitis and septic arthritis, soft-tissue infections like cellulites/fasciitis and abscess formation can occur, which have to be treated appropriately. Bone scintigraphy is a sensitive method that can be used to search for bone and joint infections. Labeled leukocytes often are used as the gold standard to identify infectious foci in the musculoskeletal system, but major drawbacks of this method are the imaging of chronic infections and imaging of the axial skeleton. Like (111)In-labeled leukocyte imaging, (99m)Tc-labeled antigranulocyte antibody scintigraphy has a role in the imaging of osteomyelitis of the peripheral skeleton. Magnetic resonance imaging is widely used to evaluate musculoskeletal infections and is excellent in identifying abscess formation, but the extent and spread of infection is sometimes difficult to delineate because hyperemia and infection are not congruent.