A practical approach to interpretation of 18F-fluorodeoxyglucose positron emission tomography/computed tomography for postoperative spine infection.

OBJECTIVE: 18F-fluorodeoxyglucose-PET/CT is the imaging modality of choice for the diagnosis of postoperative spine infection. Published interpretation criteria are variable and often incompletely described. The objective was to develop a practical and standardized approach. MATERIALS AND METHODS: Two-hundred-twenty-seven FDG-PET/CTs performed on 140 postoperative patients over a 7-year period were reviewed retrospectively. The presence or absence of infection was determined from clinical history, microbiology, other investigations, and clinical outcome during a minimum 6-month follow-up. RESULTS: No activity attributable to normal healing was seen in the post-discectomy space or at the bone-hardware interface in the absence of a complication at any stage. Within the incision, activity from normal healing persisted for months. Wound infections were diagnosed clinically, and most had already been treated before FDG-PET/CT was done to assess deep structures. With proven infection, 95% of cases had activity in bone or soft tissue outside the surgical field. The remaining 5% had activity confined to the post-discectomy space. Sterile hardware loosening may cause elevated activity which remains confined to the bone/hardware interface. Pathogens are introduced directly at the time of surgery and may be avirulent resulting in indolent infection with low-grade activity. At the same time, activity from non-infectious causes can be intense. A semi-quantitative method using SUVmax performed poorly compared with assessment of the distribution of activity. CONCLUSION: These observations have been incorporated into a checklist which is now being used at the time of interpretation. The potential sensitivity and specificity in the diagnosis of infection are close to 100%.

Diagnostic challenges in pyogenic spinal infection: an expanded role for FDG-PET/CT.

In a preliminary investigation of FDG-PET/CT for assessment of therapy response of pyogenic spine infection, it was concluded that activity confined to the margins of a destroyed or degenerated joint with bone-on-bone contact represents nonseptic inflammation, regardless of the intensity of uptake. Only activity in bone, soft tissue, or within the epidural space represents active infection. The purpose of this investigation was to assess the performance of these pattern-based interpretation criteria in a series of problem cases of proven or suspected spine infection. Eighty-two FDG-PET/CTs were done for initial diagnosis because other imaging failed to provide a definitive diagnosis and 147 FDG-PET/CTs were done to assess treatment responses. Pattern-based interpretations were compared with the clinical diagnosis based on bacterial cultures and outcomes after cessation or withholding of antibiotic therapy. Pattern-based interpretation criteria achieved a sensitivity and specificity of 98 and 100%, respectively, for initial diagnosis and a specificity of 100% for assessment of treatment response. The same data was analyzed using intensity of activity as the primary factor. Sensitivity and specificity using the intensity-based criteria were 93 and 68%, respectively, for initial diagnosis, and the specificity of a negative interpretation for therapy response was 55%. Differences from pattern-based criteria are highly significant. Pattern-based criteria perform well in problem cases with equivocal MR and for treatment response because they correctly eliminate activity from nonspecific inflammation associated with destroyed joints with bone-on-bone contact. Response occurs within a timeframe that is useful for managing antibiotic therapy.

Common normal variants of pediatric vertebral development that mimic fractures: a pictorial review from a national longitudinal bone health study.

Children with glucocorticoid-treated illnesses are at risk for osteoporotic vertebral fractures, and growing awareness of this has led to increased monitoring for these fractures. However scant literature describes developmental changes in vertebral morphology that can mimic fractures. The goal of this paper is to aid in distinguishing between normal variants and fractures. We illustrate differences using lateral spine radiographs obtained annually from children recruited to the Canada-wide STeroid-Associated Osteoporosis in the Pediatric Population (STOPP) observational study, in which 400 children with glucocorticoid-treated leukemia, rheumatic disorders, and nephrotic syndrome were enrolled near glucocorticoid initiation and followed prospectively for 6 years. Normal variants mimicking fractures exist in all regions of the spine and fall into two groups. The first group comprises variants mimicking pathological vertebral height loss, including not-yet-ossified vertebral apophyses superiorly and inferiorly, which can lead to a vertebral shape easily over-interpreted as anterior wedge fracture, physiological beaking, or spondylolisthesis associated with shortened posterior vertebral height. The second group includes variants mimicking other radiologic signs of fractures: anterior vertebral artery groove resembling an anterior buckle fracture, Cupid's bow balloon disk morphology, Schmorl nodes mimicking concave endplate fractures, and parallax artifact resembling endplate interruption or biconcavity. If an unexpected vertebral body contour is detected, careful attention to its location, detailed morphology, and (if available) serial changes over time may clarify whether it is a fracture requiring change in management or simply a normal variant. Awareness of the variants described in this paper can improve accuracy in the diagnosis of pediatric vertebral fractures.

Fluorodeoxyglucose Positron Emission Tomography/Computed Tomography Interpretation Criteria for Assessment of Antibiotic Treatment Response in Pyogenic Spine Infection.

PURPOSE: The objective of the study was to determine if fluorodeoxyglucose positron emission tomography/computed tomography ((18)F-FDG PET/CT) can assess the response of patients with pyogenic spine infection to antibiotic treatment in a clinically useful time frame. METHODS: Twenty-eight patients with suspected pyogenic spine infection had baseline (18)F-FDG PET/CT. Patients with proven or probable infection were divided into good and poor responders to antibiotic therapy based on clinical criteria. These patients had a follow-up (18)F-FDG PET/CT 6-8 weeks later. RESULTS: Six of 28 patients were deemed negative for infection based on (18)F-FDG PET/CT. Two patients were excluded because of discrepancies in interpretation. Of the 20 patients deemed positive for infection, 13 had a pathogen isolated and all showed (18)F-FDG uptake in bone and/or soft tissue at baseline. Patients with a poor clinical response to treatment had persistent (18)F-FDG uptake in bone and/or soft tissue on follow-up. Patients with good clinical response had uptake confined to the margins of the destroyed disc. None of these patients had recurrent infection, even if antibiotics had already been discontinued at the time of the follow-up scan. CONCLUSIONS: (18)F-FDG uptake confined to the margins of a destroyed disc after antibiotic therapy of pyogenic spine infection must not be considered indicative of persistent infection and likely represents mechanically induced inflammation. (18)F-FDG uptake in bone or soft tissue does indicate active infection. Quantification of activity could not reliably differentiate patients with active infection from those without active infection and those who had had a successful response to therapy. The pattern of activity is critical to accurate interpretation.

Results of a prospective phase II trial evaluating interim positron emission tomography-guided high dose therapy for poor prognosis diffuse large B-cell lymphoma.

Patients with diffuse large B-cell lymphoma (DLBCL) with a poor prognosis based upon advanced stage and elevated serum lactate dehydrogenase achieve a 3-4-year progression-free survival (PFS) of only 55%. The role of interim fluoro-2-deoxy-d-glucose (FDG) positron emission tomography (PET) to guide use of upfront high dose chemotherapy (HDCT) and autologous stem cell transplant (ASCT) for patients with poor prognosis DLBCL is unproven. A prospective phase II clinical trial was designed to evaluate the outcomes of HDCT/ASCT for patients with poor prognosis DLBCL aged 18-65 years who had unfavorable interim restaging PET scans. Of the 70 eligible patients, 36 had unfavorable and 34 favorable interim PET responses, with 3-year PFS rates of 65.2% and 52.7%, respectively. In conclusion, favorable interim PET response as defined in this study is not associated with improved PFS rates for patients with poor prognosis DLBCL treated with RCHOP (rituximab, cyclophosphamide, doxorubicin, vincristine, prednisone). A phase III trial evaluating this PET-guided approach is not warranted.

Clinical utility of PET/CT in the evaluation of head and neck squamous cell carcinoma with an unknown primary: a prospective clinical trial.

BACKGROUND: Metastatic head and neck squamous cell carcinoma with an unknown primary is an uncommon but important problem. PET/CT, as an adjunct to diagnosis, is potentially useful but has never been studied in a prospective, single-blinded clinical trial. METHODS: In all, 20 subjects with cervical metastases from an unknown head and neck primary were enrolled in a prospective clinical trial. A standard protocol was used in both clinic and operating room (OR). Study surgeons were blinded to the PET/CT result upon completion of the standard work-up. RESULTS: PET/CT increased the detection of a primary site from 25% to 55% (5 vs 11 subjects). This difference was statistically and clinically significant (p = .03, McNemar's test). There was 1 false negative PET/CT scan. CONCLUSIONS: An unknown primary should be diagnosed only after a complete head and neck examination, flexible endoscopy, and CT or MRI. PET/CT performed prior to panendoscopy will increase the diagnostic yield in the unknown head and neck primary population, leading to more targeted, and less morbid, treatment.

Evaluation of pediatric CNS malignancies with (99m)Tc-methoxyisobutylisonitrile SPECT.

UNLABELLED: SPECT has the potential to add valuable information to the diagnosis and management of central nervous system (CNS) malignancy. Radioactive tracers including (99m)Tc-methoxyisobutylisonitrile (MIBI), or sestamibi, have been shown to be sensitive markers for brain tumors; however, their role in imaging children is poorly defined. METHODS: We undertook a pilot study of 29 pairs of (99m)Tc-MIBI and MRI images from 20 children to explore the clinical usefulness of this tracer in CNS malignancy. RESULTS: Tumor types that took up (99m)Tc-MIBI included brain stem glioma, fibrillary astrocytoma, other low-grade astrocytomas, and glioblastoma multiforme. Most tumors positive for (99m)Tc-MIBI uptake were astrocytomas, including those in the brain stem, cerebellum, and cortex. This method of nuclear imaging not only was able to identify the presence of a tumor but also could identify changes in the same tumor over time. Some correlation between histologic grade and (99m)Tc-MIBI uptake was observed. Several tumors, including craniopharyngioma, medulloblastoma, and optic glioma, were evident on MRI but not on (99m)Tc-MIBI SPECT. CONCLUSION: The results suggest that this modality is a potentially useful tool in the diagnosis and management of CNS malignancies, particularly higher-grade astrocytomas, in children.