Photopenic defects in marrow-containing skeleton on indium-111 leucocyte scintigraphy: prevalence at sites suspected of osteomyelitis and as an incidental finding

Joint EANM/ESNR and ESCMID-endorsed consensus document for the diagnosis of spine infection (spondylodiscitis) in adults

PURPOSE

Diagnosis of spondylodiscitis (SD) may be challenging due to the nonspecific clinical and laboratory findings and the need to perform various diagnostic tests including serologic, imaging, and microbiological examinations. Homogeneous management of SD diagnosis through international, multidisciplinary guidance would improve the sensitivity of diagnosis and lead to better patient outcome.

METHODS

An expert specialist team, comprising nuclear medicine physicians appointed by the European Association of Nuclear Medicine (EANM), neuroradiologists appointed by the European Society of Neuroradiology (ESNR), and infectious diseases specialists appointed by the European Society of Clinical Microbiology and Infectious Diseases (ESCMID), reviewed the literature from January 2006 to December 2015 and proposed 20 consensus statements in answer to clinical questions regarding SD diagnosis. The statements were graded by level of evidence level according to the 2011 Oxford Centre for Evidence-based Medicine criteria and included in this consensus document for the diagnosis of SD in adults. The consensus statements are the result of literature review according to PICO (P:population/patients, I:intervention/indicator, C:comparator/control, O:outcome) criteria. Evidence-based recommendations on the management of adult patients with SD, with particular attention to radiologic and nuclear medicine diagnosis, were proposed after a systematic review of the literature in the areas of nuclear medicine, radiology, infectious diseases, and microbiology.

RESULTS

A diagnostic flow chart was developed based on the 20 consensus statements, scored by level of evidence according to the Oxford Centre for Evidence-based Medicine criteria.

CONCLUSIONS

This consensus document was developed with a final diagnostic flow chart for SD diagnosis as an aid for professionals in many fields, especially nuclear medicine physicians, radiologists, and orthopaedic and infectious diseases specialists.

Nuclear medicine imaging of bone infections

The inflammation and infection of bone include a wide range of processes that can result in a reduction of function or in the complete inability of patients. Apart from the inflammation, infection is sustained by pyogenic microorganisms and results mostly in massive destruction of bones and joints. The treatment of osteomyelitis requires long and expensive medical therapies and, sometimes, surgical resection for debridement of necrotic bone or to consolidate or substitute the compromised bones and joints. Radiographs and bone cultures are the mainstays for the diagnosis but often are useless in the diagnosis of activity or relapse of infection in the lengthy management of these patients. Imaging with radiopharmaceuticals, computed tomography and magnetic resonance are also used to study secondary and chronic infections and their diffusion to soft or deep tissues. The diagnosis is quite easy in acute osteomyelitis of long bones when the structure of bone is still intact. But most cases of osteomyelitis are subacute or chronic at the onset or become chronic during their evolution because of the frequent resistance to antibiotics. In chronic osteomyelitis the structure of bones is altered by fractures, surgical interventions and as a result of bone reabsorption produced by the infection. Metallic implants and prostheses produce artefacts both in computed tomography and magnetic resonance images, and radionuclide studies should be essential in these cases. Vertebral osteomyelitis is a specific entity that can be correctly diagnosed by computed tomography or magnetic resonance imaging at the onset of symptoms but only with radionuclide imaging is it possible to assess the activity of the disease after surgical stabilization or medical therapy. The lack of comparative studies showing the accuracy of each radiopharmaceutical for the study of bone infection does not allow the best nuclear medicine techniques to be chosen in an evidence-based manner. To this end we performed a meta-analysis of peer reviewed articles published between 1984 and 2004 describing the use of nuclear medicine imaging for the study of the most frequent causes of bone infections, including prosthetic joint, peripheric post-traumatic bone infections, vertebral and sternal infections. Guidelines for the choice of the optimal radiopharmaceuticals to be used in each clinical condition and for different aims is provided.

Evolving role of positron emission tomography in the management of patients with inflammatory and other benign disorders

Fluoro-2-deoxyglucose (FDG) positron emission tomography (PET) has evolved from a research imaging modality assessing brain function in physiologic and pathologic states to a pure clinical necessity. It has been successfully used for diagnosing, staging, and monitoring a variety of malignancies. FDG-PET imaging also is evolving into a powerful imaging modality that can be effectively used for the diagnosis and monitoring of a certain nononcological diseases. PET has been shown to be very useful in the diagnosis of osteomyelitis, painful prostheses, sarcoidosis, fever of unknown etiology, and acquired immunodeficiency syndrome. Based on recent observations, several other disorders, such as environment-induced lung diseases, atherosclerosis, vasculitis, back pain, transplantation, and blood clot, can be successfully assessed with this technique. With the development and the introduction of several new PET radiotracers, it is expected that PET will secure a major role in the management of patients with inflammatory and other benign disorders.

Clinical feasibility of two-step streptavidin/111In-biotin scintigraphy in patients with suspected vertebral osteomyelitis

PURPOSE

Streptavidin accumulates at sites of inflammation and infection as a result of increased capillary permeability. In addition to being utilised by bacteria for their own growth, biotin forms a stable, high-affinity non-covalent complex with avidin. The objective of this investigation was to determine the diagnostic performance of two-step streptavidin/111In-biotin imaging for evaluating patients with suspected vertebral osteomyelitis.

METHODS

We evaluated 55 consecutive patients with suspected vertebral osteomyelitis (34 women and 21 men aged 27-86 years), within 2 weeks after the onset of clinical symptoms. Thirty-two of the patients underwent magnetic resonance imaging (MRI) and 24, computed tomography (CT). DTPA-conjugated biotin was radiolabelled by incubating 500 microg of DTPA-biotin with 111 MBq of 111In-chloride. Two-step scintigraphy was performed by first infusing 3 mg streptavidin intravenously, followed 4 h later by 111In-biotin. Imaging was begun 60 min later.

RESULTS

Streptavidin/111In-biotin scintigraphy was positive in 32/34 patients with spinal infection (94.12% sensitivity). The study was negative in 19/21 patients without infection (95.24% specificity). The corresponding results for MRI and CT were 54.17% and 35.29% (sensitivity), and 75% and 57.14% (specificity), respectively. All statistical parameters of diagnostic performance (Youden's J index, kappa measure of agreement with correct classification, accuracy, sensitivity, specificity, positive likelihood and negative likelihood) were clearly better for streptavidin/111In-biotin scintigraphy than for either MRI or CT.

CONCLUSION

Streptavidin/111In-biotin scintigraphy is highly sensitive and specific for detecting vertebral osteomyelitis in the first 2 weeks after the onset of clinical symptoms, and is potentially very useful for guiding clinical decisions on instituting appropriate therapy.

Applications of fluorodeoxyglucose positron emission tomography in the diagnosis of infection

The purpose of this study was to assess the accuracy of fluorodeoxyglucose positron emission tomography (FDG PET) in diagnosing infection in a large population of patients and in a variety of clinical circumstances where the performance of conventional imaging modalities has been questioned. We retrospectively analysed 167 FDG PET scans obtained to evaluate 175 anatomical sites for the presence of infection. The major indications for the scans were (1) complicated orthopaedic hardware (n=97), (2) chronic osteomyelitis (n=56), and (3) other (n=14: six fever of unknown origin, three vascular grafts, and five soft tissue). We assessed the overall diagnostic accuracy of FDG PET for each of these indications. In addition, we further analysed this modality's effectiveness by grouping the scans into specific clinical situations. A final diagnosis was made on the basis of surgical pathology and clinical follow-up for a minimum of 6 months. The overall accuracy of FDG PET in evaluating orthopaedic hardware was 96.2% for hip prosthesis, 81% for knee prosthesis, and 100% in 15 patients with other orthopaedic devices. Among the patients in our sample suspected of having chronic osteomyelitis, the accuracy was 91.2%. FDG PET was inaccurate in three cases of fever of unknown origin and accurate in all vascular graft and soft tissue infections. In 49 patients with a clinically apparent soft-tissue infection, FDG PET was able to detect or exclude underlying osteomyelitis with an accuracy of 92.3%. Among the 23 patients who had recent orthopaedic procedures, FDG PET imaging was accurate in 87% of cases. It is concluded that FDG PET is a highly effective imaging modality in the assessment of patients with suspected infection.

Detection of metallic implant-associated infections with FDG PET in patients with trauma: correlation with microbiologic results

PURPOSE

To prospectively evaluate the value of positron emission tomography (PET) with fluorine 18 fluorodeoxyglucose (FDG) in the detection of metallic implant-associated infections in patients with trauma.

MATERIALS AND METHODS

Twenty-nine partial-body FDG PET scans in 22 patients suspected of having metallic implant-associated infections were obtained prior to surgery. In two of the 22 patients, data were acquired with a combined PET-CT in-line system. Soft-tissue and bone infections were evaluated. PET scans were analyzed by two experienced nuclear medicine physicians first separately and then in consensus. Disease status was defined on the basis of the results of microbiologic evaluation of surgical specimens together with intraoperative findings. Sensitivities, specificities, accuracies, interobserver variability (determination of kappa values), and receiver operating characteristic curves were obtained.

RESULTS

Of 29 PET scans, 14 were true-positive, 14 were true-negative, and one was false-positive. Sensitivity, specificity, and accuracy were 100%, 93.3%, and 97%, respectively, for all PET data; 100%, 100%, and 100%, respectively, for the central skeleton; and 100%, 87.5%, and 95%, respectively, for the peripheral skeleton. The degree of overall interobserver concordance was high (kappa = 0.96).

CONCLUSION

FDG PET appears to be a sensitive and specific method for the detection of infectious foci due to metallic implants in patients with trauma.

Localization and diagnosis of septic endoprosthesis infection by using 99mTc-HMPAO labelled leucocytes

The aim of this study was to evaluate, retrospectively, the diagnostic value of Tc hexamethylpropylene amine oxime (99mTc-HMPAO) labelled autologous leucocytes for the preferred septic localizations of the infection of the endoprosthesis. We retrospectively reviewed 67 patients with implanted endoprostheses. Diagnosis was found in 42/67 patients. In 25/67 patients we were able to negate an acute pathological process of infection of the endoprosthesis. Our patients were divided into three groups according to the type of endoprosthesis (hip joint, knee joint, shoulder joint). The localizations of the endoprosthesis disorders are shown. The preferred localizations of the acute infection of the hip endoprosthesis are the regio intertrochanterica and the middle part of the shaft of the prosthesis. The preferred localization of the acute infection of the knee endoprosthesis is the proximal shaft of the tibia. The preferred localization of the acute infection of the shoulder endoprosthesis is the distal end of the prosthesis in the proximal humerus. It is hoped that the knowledge of these preferred localizations of infection of endoprosthesis will help patients and doctors in diagnosis and treatment in the future.

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.

Diagnosis of bone infection using 99m Tc-HMPAO labelled leukocytes

In order to evaluate the importance of 99mTc-hexamethylpropylene amine oxime (99mTc-HMPAO) leukocyte scintigraphy in the diagnosis of bone infection, we retrospectively reviewed 324 patients. Abnormal findings were seen in 221 patients. In the other 103 cases acute pathological inflammation could be ruled out. The patients with pathological findings were divided into four groups according to the location of the infection. This method showed the localizations of skeletal disorders and its differences to other diagnostic imaging modalities. The underlying abnormalities causing the inflammation were determined. In conclusion, 99mTc-HMPAO leukocyte scintigraphy is still a very sensitive method for either whole body screening or local detection of acute or exacerbated chronic osteomyelitis. The advantages of this method over other diagnostic imaging methods are shown.

Cold-hot mismatch between Tc-99m HMPAO-labeled leukocytes and Tc-99m ciprofloxacin in axial skeleton infections: a report of three cases

Radiolabeled leukocyte scintigraphy is a well-established technique for the diagnosis of inflammation and infection with a typical presentation of a hot spot within the abnormal areas. However, in some cases of osteomyelitis of the axial skeleton, a cold defect pattern has been described. Tc-99m ciprofloxacin is a new agent claimed to be specific for imaging sites containing viable bacteria. In this report, we present three cases of proved bacterial infection of the axial skeleton with a mismatch pattern between Tc-99m ciprofloxin and tagged leukocytes. Although Tc-99m-labeled leukocyte scanning showed a cold defect, probably caused by bone marrow replacement, the Tc-99m ciprofloxacin consecutively revealed a hot spot at the site of infection. These data suggest that Tc-99m ciprofloxacin should be a better agent than radiolabeled leukocytes for detecting osteomyelitis of the axial skeleton.

Isotope imaging

Patients with a wide variety of rheumatological conditions can be usefully investigated by nuclear medicine techniques and particularly by bone scintigraphy. This aspect of nuclear medicine work is increasing and the trend can be expected to continue. The principal conditions that can be imaged are sports medicine injuries, osteomyelitis, avascular necrosis, reflex sympathetic dystrophy syndrome, enthesopathies and bio-mechanical stress lesions, inflammatory arthropathies, metabolic bone disease and miscellaneous bone conditions such as costo-chondritis. Single photon emission tomography (SPECT) has provided new indications for bone scintigraphy such as the evaluation of spondylolysis and facet syndrome in the spine and of meniscal tears and ligamental lesions.