Detection of osteomyelitis using FDG and positron emission tomography

Diagnostic Role of FDG PET/CT in Pediatric Patients With Chronic Recurrent Multifocal Osteomyelitis

PURPOSE

Chronic recurrent multifocal osteomyelitis (CRMO), or chronic nonbacterial osteomyelitis, is difficult to diagnose. The accurate diagnosis of CRMO relies on comprehensive imaging examinations because of its multifocal nature. In this regard, 18 F-FDG PET/CT has demonstrated significant utility in inflammatory diseases. This study tries to determine the value of FDG PET/CT in the evaluation of CRMO.

PATIENTS AND METHODS

We retrospectively collected imaging data from pediatric CRMO patients who underwent FDG PET/CT scans. Lesions exhibiting abnormal metabolism with/without structural abnormalities on FDG PET/CT were identified as CRMO lesions, and their location and SUV max were recorded.

RESULTS

A total of 21 pediatric patients with CRMO were included in this study. The median age at diagnosis was 9.4 years. Total 131 foci of abnormal activity were identified using FDG PET/CT imaging. The distribution pattern showed a higher prevalence of lower limbs and pelvis involvement. Among all identified lesions, abnormalities were detected on both PET and CT images of 93 lesions, whereas exclusively positive findings on 18 F-FDG PET alone were observed for 38 of them.

CONCLUSIONS

Our study findings suggest a higher prevalence of lesions in the bones of the lower limbs and pelvis among children with CRMO. Compared with CT scans, FDG PET exhibits superior sensitivity in detecting these lesions.

(18)F-FDG microPET imaging differentiates between septic and aseptic wound healing after orthopedic implant placement: a longitudinal study of an implant osteomyelitis in the rabbit tibia

BACKGROUND AND PURPOSE

(18)F-FDG PET is a widely used tool for molecular imaging of oncological, cardiovascular, and neurological disorders. We evaluated (18)F-FDG microPET as an implant osteomyelitis imaging tool using a Staphylococcus aureus-induced peroperative implant infection in rabbits.

METHODS

Intramedullary titanium nails were implanted in contaminated and uncontaminated (control) proximal right tibiae of rabbits. Tibiae were quantitatively assessed with microPET for (18)F-FDG uptake before and sequentially at 1, 3, and 6 weeks after surgery. Tracer uptake was assessed in soft tissue and bone in both treatment groups with an additional comparison between the operated and unoperated limb. MicroPET analysis was combined with radiographic assessment and complementary histology of the tibiae.

RESULTS

At the first postoperative week, the (18)F-FDG uptake in the contaminated implant group was significantly higher than the preoperative measurement, without a significant difference between the contaminated and uncontaminated tibiae. From the third postoperative week onward, (18)F-FDG uptake allowed discrimination between osteomyelitis and postoperative aseptic bone healing, as well as quantification of the infection at distinct locations around the implant.

INTERPRETATION

(18)F-FDG-based microPET imaging allows differentiation between deep infection and undisturbed wound healing after implantation of a titanium intramedullary nail in this rabbit model. Furthermore, our results indicate that (18)F-FDG PET may provide a tool in human clinical diagnostics and for the evaluation of antimicrobial strategies in animal models of orthopedic implant infection.

Critical role of 18F-labeled fluorodeoxyglucose PET in the management of patients with arthroplasty

The most frequent complications after arthroplasty are aseptic loosening and infection. It is often difficult to differentiate aseptic loosening from infection. The management of these two distinct clinical identities is quite different, however. Treatment of aseptic loosening usually requires one-step revision surgery, whereas treatment of infection requires antimicrobial therapy for an extended period before inserting a new prosthesis. Infection associated with arthroplasty is a serious complication and should be treated adequately before proceeding with a surgical intervention. PET with 18F-labeled fluorodeoxyglucose (FDG) has been proposed as an accurate technique for evaluating painful arthroplasty. This review addresses the applications of FDG-PET in such clinical settings. In addition, the potential of PET in the assessing the viability of bone grafts in revision arthroplasty is discussed.

Potential role of FDG PET in the setting of diabetic neuro-osteoarthropathy: can it differentiate uncomplicated Charcot's neuroarthropathy from osteomyelitis and soft-tissue infection?

BACKGROUND

This paper is based on the results from an ongoing prospective trial designed to investigate the usefulness of FDG PET in the complicated diabetic foot.

AIM

To investigate the potential utility of FDG PET imaging in the setting of acute neuropathic osteoarthropathy (Charcot's foot).

PATIENTS AND METHODS

A total of 63 patients, in four groups, were evaluated. The groups were: (A) 17 patients with a clinical diagnosis of Charcot's neuroarthropathy (11 men, six women; mean age: 59.4+/-8.6 years); (B) 21 patients with uncomplicated diabetic foot (16 men, five women; mean age: 63+/-10 years); (C) 20 non-diabetic patients with normal lower extremities (12 men, eight women; mean age 54+/-19 years); and (D) five patients with proven osteomyelitis secondary to complicated diabetic foot (three men, two women; mean age: 61.2+/-13.9 years). Five patients in group A had foot ulcer and intermediate to high degree of suspicion for superimposed osteomyelitis. Each subject underwent FDG PET imaging of the lower extremities in addition to MRI and the findings were compared with the final diagnostic outcome based on histopathology and clinical follow-up. The images were examined visually for focal abnormalities. Regions of interest were assigned to the sites of abnormal FDG uptake for calculating maximum standardized uptake value (SUVmax). Two important clinical decision-making issues were explored: (1) whether FDG PET shows a definitive uptake pattern in Charcot's neuroarthropathy and if so whether that could be utilized to differentiate it from other complicated forms of diabetic foot like osteomyelitis and cellulitis, which is frequently a diagnostic challenge in this clinical setting; and (2) how accurate FDG PET is in detection soft tissue infection in patients with Charcot's foot. These issues were examined by utilizing FDG PET findings along with MRI results in the same patient.

RESULTS

We observed a low degree of diffuse FDG uptake in the Charcot's joints. This was clearly distinguishable from the normal joints. The SUVmax in the Charcot's lesions varied from 0.7 to 2.4 (mean, 1.3+/-0.4) while those of midfoot of the normal control subjects and the uncomplicated diabetic foot ranged from 0.2 to 0.7 (mean 0.42+/-0.12) and from 0.2 to 0.8 (mean 0.5+/-0.16), respectively. The only patient with Charcot's foot with superimposed osteomyelitis had an SUVmax of 6.5. The SUVmax of the sites of osteomyelitis as a complication of diabetic foot was 2.9-6.2 (mean: 4.38+/-1.39). Unifactorial analysis of variance test yielded a statistical significance in the SUVmax between the four groups (P<0.01). The SUVmax between the normal control groups and the uncomplicated diabetic foot was not statistically significant by the Student's t-test (P>0.05). In the setting of concomitant foot ulcer FDG PET accurately ruled out osteomyelitis. Overall sensitivity and accuracy of FDG PET in the diagnosis of Charcot's foot was 100 and 93.8%, respectively; and for MRI were 76.9 and 75%, respectively. FDG PET showed foci of abnormally enhanced uptake in the soft tissue which was suggestive of inflammation in seven cases (43.75%) which were proven pathologically to be secondary to infection. In only two of these cases the features of soft tissue infection were noted on the magnetic resonance images.

CONCLUSION

The results support a valuable role of FDG PET in the setting of Charcot's neuroarthropathy by reliably differentiating it from osteomyelitis both in general and when foot ulcer is present.

PET/CT of a brodie abscess

Brodie abscess is a rare, localized type of subacute or chronic pyogenic osteomyelitis, usually of staphylococcal origin. Imaging with standard radiographs, bone scintigraphy, and MRI has been described in the literature. We present the case of a 28-year-old patient with pain in the right knee. Whole-body FDG-PET/CT scan showed a solitary FDG-active (SUV max 5.2) intracortical lesion in the meta-/epiphysis of the proximal tibia. CT demonstrated a sclerotic rim around the lesion. A Brodie abscess was considered a possible diagnosis. Multifocality could be excluded. CT-guided transosseous biopsy and curettage was performed and the diagnosis of a Brodie abscess was confirmed.

Bone infection in patients suspected of complicating osteomyelitis: the diagnostic value of dual isotope bone-granulocyte scintigraphy

AIM

The purpose of this study was to evaluate the diagnostic value of dual isotope bone-granulocyte scintigraphy in patients with known bone pathology clinically suspected of osteomyelitis, i.e. complicating osteomyelitis, using per-operative bacterial culture from bone as reference.

METHODS

Simultaneous dual isotope bone-granulocyte scintigraphic images were obtained in 42 consecutive patients in whom conventional X-ray, erythrocyte sedimentation rate, and C-reactive protein were also available. 99mTc MDP bone and 111In labelled granulocyte imaging was obtained simultaneously. The images were interpreted as positive for osteomyelitis if regions of interests of pathologic 111In granulocyte accumulation included 99mTc MDP activity on the bone images (except in the spine).

RESULTS

The sensitivity, specificity, and accuracy were 84, 71 and 79%, respectively, for simultaneous, dual isotope bone-granulocyte scintigraphy, higher than the other diagnostic parameters.

CONCLUSION

Simultaneous bone-granulocyte scintigraphy is a valuable diagnostic tool in diagnosing osteomyelitis complicating other bone pathology with or without soft-tissue infection.

Backgrounds of antibiotic-loaded bone cement and prosthesis-related infection

Antibiotic-loaded bone cement has been in use for over 30 years for the fixation of total joint arthroplasties, although its mechanism of action is still poorly understood. This review presents the backgrounds of bone cements, prosthesis-related infection and antibiotic-loaded bone cements. It is shown that antibiotic-loaded bone cement has a significant effect on bacteria, particularly in animal and clinical studies. However, recently, antimicrobial resistance among bacteria has been ascribed to the antibiotic-loaded bone cement. The unresolved issues both regarding the action of antibiotic-loaded bone cement and the nature of the antimicrobial resistance necessitate further research into the interaction of antibiotic-loaded bone cement and bacteria.

Positron emission tomography imaging in nonmalignant thoracic disorders

The role of the fluorodeoxyglucose (FDG) technique positron emission tomography (PET) is well established in the management of patients with lung cancer. Increasingly, it is becoming evident that FDG-PET can be effectively employed to diagnose a variety of benign pulmonary disorders. Knowledge of such applications further expands the domain of this powerful modality and further improves the ability to differentiate benign from malignant diseases of the chest. We describe pertinent technical factors that substantially contribute to optimal imaging of the thoracic structures. Particularly, the complementary role of attenuation correction (AC) to that of non-AC images is emphasized. We further outline the need for and the state of the art for co-registration of PET and anatomic images for diagnostic and therapeutic purposes. We then review patterns of physiologic uptake of FDG in thoracic structures, including the lung, the heart, the aorta and large arteries, esophagus, thymus, trachea, thoracic muscles, bone marrow, and joints and alterations following radiation therapy to the thorax. A great deal of information is provided with regard to differentiating benign from malignant nodules and in particular, we emphasize the role of dual time point imaging and partial volume correction for accurate assessment of such lesions. Following a brief review of the diagnostic issues related to the assessment of mediastinal adenopathies, the role of FDG-PET imaging in environment-induced lung diseases, including pneumoconiosis, smoking, and asthma are described. A large body of information is provided about the role of this technology in the management of patients with suspected infection and inflammation of the lungs such as acquired immunodeficiency syndrome, fever of unknown origin, sarcoidosis, chronic granulomatous disease and monitoring the disease process and response to therapy. Finally, the value of FDG-PET in differentiating benign from malignant diseases of the pleura including asbestosis-related disorders is described at the conclusion of this comprehensive review.

The importance of the location of fluorodeoxyglucose uptake in periprosthetic infection in painful hip prostheses

Ten per cent of patients with hip replacement will eventually complain of significant pain after surgery, often requiring a revision arthroplasty. The majority of these patients experience aseptic loosening rather than infection. Despite significant advances made in diagnostic imaging, distinguishing infection from aseptic loosening remains a significant challenge. Imaging using fluorodeoxyglucose (FDG) positron emission tomography (PET) has been reported to have excellent sensitivity in detecting infections associated with hip prostheses. However, in some studies, a high rate of false positive results has been reported, especially when increased tracer uptake adjacent to the prosthesis (which is not surrounded by bone) is used as the sole criterion for diagnosing infection. The objective of this investigation was to determine the optimal criteria for diagnosing periprosthetic infection, thereby avoiding false positive results in this setting. A total of 41 total hip arthroplasties from 32 patients and for whom complete clinical follow-up was available were included in this analysis. The location and intensity of FDG uptake were determined for each scan. Final diagnosis was made by microbiology, histopathology, surgical findings and clinical follow-up. Patients who did not undergo surgery were followed up to at least 9 months. Twelve patients were proven eventually to have periprosthetic infection. Images from 11 of these patients displayed increased tracer uptake along the interface between bone and prosthesis. The intensity of the increased tracer uptake varied from mild to moderate, with standardized uptake values less than 2. In contrast, images from uninfected, loose hip prostheses revealed very intense uptake around the head or neck of the prosthesis with standardized uptake values as high as 7. It is concluded that the intensity of increased FDG uptake is less important than the location of increased FDG uptake when FDG PET is used to diagnose periprosthetic infection in patients with hip arthroplasty. Using increased uptake as the sole criterion for diagnosing infection will result in false positive results in this setting.

18-fluorodeoxyglucose positron emission tomographic imaging in the detection and monitoring of infection and inflammation

During the past decade, 18-fluorodeoxyglucose (FDG) positron emission tomography (PET) has rapidly evolved from a pure research modality to a clinical necessity. FDG-PET was introduced to determine the state of brain function in physiologic and pathologic states. Its use as a powerful tool to diagnose, stage, and monitor patients with a variety of malignancies has been truly revolutionary. However, FDG is a nonspecific tracer and it has been found to accumulate at sites of infection and inflammation. It is becoming evident that PET imaging will play a major role in the treatement of patients with suspected infection and inflammation. PET has been shown to be particularly valuable in the evaluation of chronic osteomyelitis, infected prostheses, sarcoidosis, fever of unknown origin, and acquired immunodeficiency syndrome. Because of its ability to quantitate the rate of FDG uptake, PET may prove to be a powerful modality for the monitoring of disease activity and response to therapy. Novel PET tracers are being tested for imaging infection and inflammation that may further enhance the role of this technique in the appropriate clinical setting. PET imaging to detect and characterize infection and inflammation may become a major clinical indication in the day-to-day practice of medicine.