Radionuclide imaging in orthopedic infections

Imaging exams of bone lesions in patients with diffuse cutaneous leishmaniasis (DCL)

We studied bone lesion alterations in three patients with diffuse cutaneous leishmaniasis (DCL) by imaging exams (radiography and scintigraphy) and histopathology. Two patients had bone lesions of distal extremities of hands and feet, and one infiltrating plaques in the skin. The study was conducted at three specialized centers (Presidente Dutra Hospital/Nucleus of Tropical Pathology, UFMA-MA; Gonçalo Moniz Research Center-FIOCRUZ-BA; Laboratory of Pathology of Infectious Diseases (LIM-50), University of São Paulo, SP). Three-phase bone scintigraphy demonstrated high sensitivity and specificity for bone lesions, showing increased uptake of the radiopharmaceutical at sites of active lesions. In contrast, radiography demonstrated lytic lesions, cortical destruction and local osteopenia of the bone extremeties in two patients. Histopathological analysis showed sequestration with presence of amastigote forms of Leishmania (osteomyelitis), mononuclear cells and macrophages containing amastigote forms of Leishmania in one patient. These preliminary data indicate that imaging exams (radiography and scintigraphy) are important in the evaluation of bone lesions in diffuse cutaneous leishmaniasis and should be included in the routine histopathological diagnosis of the disease and follow-up of bone lesions.

Musculoskeletal infection imaging: Past, present, and future

Imaging plays a key role in the evaluation of patients with known or suspected musculoskeletal infection. Although conventional radiograph still remains as the initial imaging approach, it has low sensitivity and specificity in the setting of acute infection. Magnetic resonance is highly sensitive for the detection of acute osteomyelitis and septic arthritis. Computed tomography is usually reserved for guided interventional procedures (eg, aspiration or drainage) and for evaluation of sinus tracts in chronic infections. Ultrasound is useful for fluid detection in joints and soft tissues but limited in bone assessment. Nuclear medicine, with the different radiotracers currently available, is highly sensitive for the diagnosis of acute osteomyelitis. Newer radiotracers are being developed that promise high sensitivity and specificity for the detection of these pathologies.

Diagnostic values of positron emission tomography versus triple-phase bone scan in hip arthroplasty loosening

INTRODUCTION

The most frequent complications of total hip arthroplasty are septic and aseptic wear-induced loosening. A reliable differentiation between septic and aseptic loosening with current diagnostic tools is not possible. Therefore, we examined the diagnostic valency of positron emission tomography (PET) with (18)F-fluorodeoxyglucose (FDG) in cases of septic or aseptic hip arthroplasty loosening compared with conventional triple-phase bone scan (TPBS).

MATERIALS AND METHODS

Fifty patients with 70 total hip replacements (symptomatic n=50, asymptomatic n=20) were examined by means of FDG-PET and TPBS to detect septic and aseptic loosening and differentiate between the two. A differentiated algorithm subdivided into categories I-V was developed for FDG-PET. Additionally, standardized uptake values (SUV) were calculated from the lesion with the highest FDG uptake. Interpretations of the TPBS were done according to the criteria described by Wilson. The final diagnosis was based on operative findings including microbiological and histological examinations (n=50), while the remaining asymptomatic arthroplasties (n=20) were integrated into a clinical follow-up (> or =9 months).

RESULTS

Sensitivity/specificity of FDG-PET was 91%/92% (accuracy 91%) compared with 78%/70% (accuracy 74%) for TPBS. A high correlation could be proved between FDG-PET investigation and operative histopathological findings (r(Spear)> or =0.9). No significant differences were found regarding cemented and uncemented implanted hip arthroplasties (p> or =0.05). Calculation of the SUV turned out to be inappropriate as a sole criterion for image interpretation.

CONCLUSION

FDG-PET is a promising, highly accurate examination method to detect polyethylene and metal wear-induced chronic inflammation followed by periprosthetic osteolysis. In addition, FDG-PET has a significantly higher sensitivity and specificity than TPBS for differentiating between aseptic loosening and infection.

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.

Mycobacterium marinum Infections of the Upper Extremity

A significant number of patients infected with Mycobacterium marinum have been treated at the Curtis National Hand Center in Baltimore, Maryland. The purpose of this study was to review the authors' experience with M. marinum infections of the upper extremity. Twenty-nine patients were identified and their charts were reviewed for all factors related to diagnosis and treatment. The most common presenting symptoms were swelling (n = 25) and pain (n = 14). Only 69 percent of patients could correlate their injury with aquatic activities. The mean time from injury to diagnosis was 5.2 months. Acid-fast bacilli stains were positive in only 22 percent of specimens. The mean number of procedures was 1.75, with the majority being tenosynovectomy. The mean duration of antibiotic therapy was 6 months. Clinical history, pathological evaluation, and a high clinical suspicion can lead to early diagnosis and introduction of antibiotics. The authors' patients were successfully treated with 6 months of antibiotic therapy and early surgical intervention.

The usefulness of 99mTc sulfur colloid bone marrow scintigraphy combined with 111In leucocyte scintigraphy in prosthetic joint infection

AIM

To assess the extent to which bone marrow scintigraphy (BMS) makes the interpretation of leucocyte scintigraphy (LS) easier and improves its diagnostic value.

METHODS

Seventy-three 111In LSs, 99mTc hydroxymethylene diphosphonate bone scintigraphies (BSs) and 99mTc sulfur colloid BMSs were performed in 60 patients with suspected infection related to a hip prosthesis or knee prosthesis, either in situ (+group, n = 43) or after removal for septic loosening (-group, n = 30). Bacteriological samples were obtained from all patients. LS was interpreted together with BS (LS-BS) or with BMS (LS-BMS) by three independent readers.

RESULTS

The concordance among readers, estimated by the kappa test, was average with LS-BS (kappa/kappam coefficients = 0.58, 0.58 and 0.46, respectively, for the three pairs of readers) and excellent with LS-BMS (kappa/kappam coefficients = 1.00 for the three pairs of readers). With LS-BS, 64/219 interpretations were equivocal whereas only one was equivocal with LS-BMS. Sensitivity, specificity and accuracy of LS-BMS were, respectively, 80%, 94% and 91% in the +group, and 33%, 100% and 93% in the -group.

CONCLUSION

We conclude that (1) the interpretation of the results for LS-BMS is very easy, in contrast to LS-BS; (2) the diagnostic value of LS-BMS for detecting infected joint prostheses is good; and (3) additional data are needed to assess the accuracy of LS-BMS when the prosthesis has been removed.

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.

Protocol for treatment of diabetic foot ulcers

Each year, 82,000 limb amputations are performed in patients with diabetes mellitus. The majority of these amputations could be avoided by following strict protocols. The collective experience treating patients with neuropathic diabetic foot ulcers of 4 major diabetic foot programs in the United States and Europe were analyzed. The following protocol has been developed for patients with diabetic foot ulcers: (1) measurement of the wound by planimetry; (2) optimal glucose control; (3) surgical debridement of all hyperkeratotic, infected, and nonviable tissue; (4) systemic antibiotics for deep infection, drainage, and cellulitis; (5) offloading; (6) moist-wound environment; and (7) treatment with growth factors and/or cellular therapy if the wound is not healing after 2 weeks with this protocol and a new epithelial layer is not forming. In addition, the pathogenesis of diabetic foot ulcers is discussed, as well as the associated costs and complications, including amputation. Debridement, wound-bed preparation, antibiotics, various types of dressings, biological therapies, growth factors, and offloading are described as treatment modalities for patients with diabetic foot ulcers. In diabetic foot ulcers, availability of the above modalities, in combination with early recognition and comprehensive treatment, ensure rapid healing and minimize morbidity, mortality, and costs, as well as eliminate amputation in the absence of ischemia and osteomyelitis.

A comparative study of2O1T1 scintigraphy and three-phase bone scintigraphy following therapy in patients with bone and soft-tissue tumors

OBJECTIVE

The purpose of this study was to evaluate the usefulness of 201Tl scintigraphy in comparison with three-phase bone scintigraphy in the differentiation of residual/recurrent tumors from post-therapeutic changes, in patients previously treated for bone and soft-tissue tumors.

METHODS

Thirty-five 201Tl and three-phase bone scintigraphy scans were obtained for 30 patients with a history of bone or soft-tissue tumor who had undergone chemotherapy, radiation therapy, tumor resection, or a combination of these treatments. The planar 201Tl images were acquired 10 mins (early) and 2 hrs (delayed) after the intravenous injection of 111 MBq 201Tl-chloride. Three-phase bone scintigraphy was performed using 740 MBq 99mTc-HMDP at the same lesion site as for 201Tl imaging. The blood flow images were obtained every 10 sec for 2 mins and were immediately followed by the blood pool image after 5 mins. Three to 4 hrs later, bone images were obtained. 201Tl and three-phase bone scintigraphies were correlated with the histopathologic findings and/or clinical follow-up of more than 3 months.

RESULTS

Of the 35 cases, 15 were free of disease and 20 had residual or recurrent tumors. Of the 20 residual or recurrent cases, all had true-positive 201Tl early and delayed scans, while bone scintigraphy was true-positive on the blood flow, blood pool and bone images in 16, 18 and 12 cases, respectively. 201Tl early and delayed images and 99mTc-HMDP blood flow and blood pool images were false-positive in one patient. The histology of this false-positive case showed the presence of lymph proliferative tissue.

CONCLUSIONS

Although 201Tl uptake after treatment does not always indicate recurrence, 201Tl scintigraphy may still be more useful than three-phase bone scintigraphy in the follow-up of patients with bone and soft-tissue tumors following therapy.

FDG PET for differentiation of infection and aseptic loosening in total hip replacements: comparison with conventional radiography and three-phase bone scintigraphy

PURPOSE

To compare the diagnostic efficacy of fluorine 18 fluorodeoxyglucose (FDG) positron emission tomography (PET) with that of conventional radiography and three-phase bone scintigraphy in patients suspected of having infection in their total hip replacements.

MATERIALS AND METHODS

Thirty-five patients with painful total hip replacements and possible septic prosthetic loosening were examined with FDG PET, conventional radiography, and three-phase bone scintigraphy. PET, radiographic, and scintigraphic images were each evaluated by two independent observers in a blinded fashion. For 32 of 35 patients, serial conventional radiographs were available. Results of microbiologic examinations of surgical specimens represented the standard of reference in 26 patients, and results of joint aspiration plus clinical follow-up of at least 6 months represented the standard of reference in the remaining nine patients. Sensitivity, specificity, accuracy, and interobserver variability (kappa) values were calculated. The imaging modalities were compared in terms of diagnostic confidence by using the sign test.

RESULTS

Nine patients had septic and 21 patients had aseptic loosening. In five patients, neither loosening nor infection was confirmed. For diagnosing infection with FDG PET, conventional radiography, and bone scintigraphy, respectively, sensitivity values for reader 1 and reader 2 were 33% and 22%, 89% and 78%, and 56% and 44%, while specificity values were 81% and 85%, 50% and 65%, and 88% and 92% and accuracy values were 69% for both readers, 60% and 69%, and 80% for both readers. PET was significantly more specific (P =.035) but less sensitive (P =.016) than conventional radiography for the diagnosis of infection.

CONCLUSION

In a study population of patients suspected of having infected total hip replacements, FDG PET performed similarly to three-phase bone scintigraphy. FDG PET was more specific but less sensitive than conventional radiography for the diagnosis of infection.

Role of anti-granulocyte Fab??? fragment antibody scintigraphy (LeukoScan) in evaluating bone infection: acquisition protocol, interpretation criteria and clinical results

Scintigraphy using anti-granulocyte Fab' fragment (LeukoScan) was performed in a series of 220 consecutive patients with suspected bone infection referred to our centre between September 1999 and June 2002. Two protocols were compared for interpreting scans: (1) evaluation of early 4 h imaging alone (protocol A), and (2) evaluation both of early and delayed 24 h imaging (protocol B). Protocol A and protocol B showed equal values of sensitivity (91.9% in patients with diabetic foot and 84.2% in patients with joint prosthesis/peripheral bone implants). Conversely, specificity was higher adopting protocol B than protocol A: 87.5% vs 75.0% in patients with diabetic foot, and 85.7% vs 76.2% in patients with joint prosthesis/peripheral bone implants, respectively. In particular, an improvement in specificity using protocol B was found in those patients with infection and with only a mild LeukoScan uptake in the early 4 h imaging: in these patients an increasing uptake intensity pattern observed in the delayed 24 h imaging was indicative of infection while a decreasing pattern suggested a negative result. Instead, the evidence of a high uptake intensity in the early LeukoScan imaging was a strong indicator of infection and delayed imaging in these cases did not further improve specificity. In conclusion, in our experience, LeukoScan showed high sensitivity in diagnosing bone infection in patients with diabetic foot and joint prosthesis or other peripheral bone implants. Moreover, in patients with an early high LeukoScan uptake intensity further delayed images appears unnecessary for the purpose of diagnosing infection. In contrast in patients with an early mild LeukoScan uptake intensity only, delayed imaging appears to be recommendable for improving specificity.

Charcot osteoarthropathy in a case of Klippel-Trenaunay-Weber syndrome

A case of a patient with Klippel-Trenaunay-Weber syndrome (KTW) with Charcot osteoarthropathy is presented. A medline literature review was performed using the words Klippel-Trenaunay, orthopaedic, ankle, foot, and Charcot joint. Seven articles reported orthopaedic manifestations of KTW. They included limb hypertrophy and atrophy, limb-length discrepancies, digital anomalies, ulcerations, and spine and hip abnormalities, but no mention of Charcot osteoarthropathy. After many years of chronic nonhealing ulcers and repeated incision and drainage procedures the patient developed Charcot osteoarthropathy of the ankle without evidence of osteomyelitis or peripheral neuropathy but with severe deformity that required transtibial amputation.

Imaging modalities of the diabetic foot

Charcot osteoarthropathy is a devastating process that occurs in the diabetic foot. It must be distinguished from other conditions, such as osteomyelitis, with efficiency and accuracy. The prognosis and treatment depends on it. Charcot progresses along four radiographically identifiable stages; therefore, plain films should be the first step in the evaluation. When osteomyelitis is suspected, a three-phase bone scan may allow clear enough anatomic detail to diagnosis bony involvement compared with soft tissue in the forefoot. In the midfoot, a three-phase bone scan alone is not specific enough to distinguish between Charcot and osteomyelitis. Enhancing the bone scans by adding an additional phase (four-phase) or tracer (gallium) does not appear to improve specificity significantly. Computerized bone flow studies may be more helpful in making the distinction, particularly in acute presentation. A CT scan is not indicated because the MR image will better define the anatomic extent of the process for preoperative planning. The combined WBC scans and sulfur colloid marrow scans show improved specificity and can distinguish between Charcot and osteomyelitis. Combined leukocyte scan with bone marrow imaging is superior to leukocyte and bone scan alone or in combination for detecting infection in the neuropathic foot. The combined leukocyte scan and bone marrow imaging is the current gold standard for evaluating the presence of diabetic foot infection versus osteoarthropathy, and MR imagine is the anatomic gold standard that may be used to define the extent of the process.

LeukoScan for imaging infection in different clinical settings: a retrospective evaluation and extended review of the literature

PURPOSE

The aim of the current study was to determine the overall diagnostic accuracy of Tc-99m-labeled antigranulocyte monoclonal antibody Fab' fragments (LeukoScan) for the routine detection of bone and soft tissue infections in a retrospective evaluation.

PATIENTS AND METHODS

138 patients (63 men, 75 women; mean age, 58.29 +/- 25.38 years) with fever of unknown origin and possible endocarditis (n = 59), infection of arthroplastic joints (n = 20), arthritis (n = 16), peripheral (n = 15) and central bone infections (n = 14), soft tissue infection (n = 6), appendicitis (n = 4), pericarditis (n = 2), or vascular graft infection (n = 2) underwent imaging after injection of 555 to 925 MBq (15 to 25 mCi) Tc-99m-labeled antigranulocyte monoclonal antibody Fab' fragments (LeukoScan).

RESULTS

True-positive results were found in 63 of 81 lesions. The overall sensitivity and specificity were 76% and 84%, respectively. In arthritis, seven of seven foci could be detected, whereas false-negative results were found in infections of the femoral bone in three of nine lesions and in periprosthetic infections of long bones in three of eight lesions. Good results were found in five of six soft-tissue infections, in four of six patients with endocarditis, in three of four atypical cases of appendicitis, in two of two infected vascular grafts, and in one of one patient with pericarditis. Subacute and chronic infections of the spine always showed photopenic areas in eight of eight patients. If photopenic lesions were included as diagnostic criteria, the sensitivity and specificity were 88% and 67%, respectively.

CONCLUSIONS

Tc-99m-labeled antigranulocyte monoclonal antibody Fab' fragments can be used for imaging acute infections of peripheral bones and soft tissues. False-negative results are likely in patients with chronic infections. Sensitivity can be increased while decreasing specificity by including photopenic lesions in the spine as diagnostic criteria for localizing disease.

Radionuclide bone imaging: an illustrative review

Bone scintigraphy with technetium-99m-labeled diphosphonates is one of the most frequently performed of all radionuclide procedures. Radionuclide bone imaging is not specific, but its excellent sensitivity makes it useful in screening for many pathologic conditions. Moreover, some conditions that are not clearly depicted on anatomic images can be diagnosed with bone scintigraphy. Bone metastases usually appear as multiple foci of increased activity, although they occasionally manifest as areas of decreased uptake. Traumatic processes can often be detected, even when radiographic findings are negative. Most fractures are scintigraphically detectable within 24 hours, although in elderly patients with osteopenia, further imaging at a later time is sometimes indicated. Athletic individuals are prone to musculoskeletal trauma, and radionuclide bone imaging is useful for identifying pathologic conditions such as plantar fasciitis, stress fractures, "shin splints," and spondylolysis, for which radiographs may be nondiagnostic. A combination of focal hyperperfusion, focal hyperemia, and focally increased bone uptake is virtually diagnostic for osteomyelitis in patients with nonviolated bone. Bone scintigraphy is also useful for evaluating disease extent in Paget disease and for localizing avascular necrosis in patients with negative radiographs. Radionuclide bone imaging will likely remain a popular and important imaging modality for years to come.

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.

[99mTc-labelled antigranulocyte anibody fragment Fab scintigraphy (sulesomab, leukoscan) and three-phase bone scintigraphy in the study of painful hip and knee prosthesis]

We aim to assess the diagnostic utility of the combination of a three phase bone scintigraphy (3FBS) and scintigraphy with Fab'antigranulocyte fragments-99mTc (Sulesomab, Leukoscan) in patients with painful joint replacements. We studied 29 patients (22 women and 7 men with mean age 64 years) with knee (15) and hip (14) prosthesis. Scintigraphy was performed with a Siemens Orbiter 75 gammacamera with all purpose collimator. 3FBS was performed as usual with 740 MBq of MDP-99mTc. Sulesomab images were obtained at 1 and 4 hours following injection of 740 MBq, with 300,000 cts per view (knee) and 500,000 cts per view (hip). Both scintigraphic studies were interpreted visually by two nuclear medicine physicians with a 0, 1, 2, 3 score corresponding to normal or mild, moderate or intense hyperactivity respectively. Interpretation criteria for bone infection was Sulesomab uptake grade 2 or 3 in a moderate or large sized area, with congruent hyperactivity on the bone scan. Grade 1 uptake with Sulesomab was considered nonspecific associated to nonseptic conditions. The frequent pattern of uptake in synovial femoral tissue (cap shape sign) in knee prosthesis was considered nonspecific. Diagnostic confirmation procedures were surgery and culture (9) and follow-up (20). All six septic joints were correctly identified. A false positive result was obtained in a case of mechanical loosening in the knee. Negative studies were very helpful in the exclusion of infection. Our conclusion is that sensitivity is high, 100%, and that a normal or grade 1 Sulesomab image makes the presence of infection improbable.

Osteomyelitis: diagnosis with (99m)Tc-labeled antigranulocyte antibodies compared with diagnosis with (111)In-labeled leukocytes--initial experience

PURPOSE

To compare a technetium 99m-labeled murine immunoglobulin M monoclonal antigranulocyte antibody that binds to human polymorphonuclear leukocyte CD15 antigens with indium 111 ((111)In)-labeled leukocytes in the diagnosis of appendicular skeletal osteomyelitis.

MATERIALS AND METHODS

Twenty-four patients suspected of having infected joint replacement (n = 12), diabetic pedal osteomyelitis (n = 8), or long bone osteomyelitis (n = 4) were imaged 5, 30, 60, and 120 minutes after antibody injection. Following injection, one patient experienced moderate joint pain exacerbation that resolved spontaneously. Patients underwent imaging with (111)In-labeled leukocytes and three-phase bone imaging. All studies were interpreted alone. Images obtained in antibody and (111)In-labeled leukocyte studies were also interpreted with the bone scans. One reader, without knowledge of other study results or final diagnoses, reviewed and interpreted images in a random order. Sensitivity, specificity, and accuracy were calculated for the antibody study at each time point, the (111)In-labeled leukocyte study, the three-phase bone scanning procedure, and dual-tracer studies.

RESULTS

There were 11 cases of osteomyelitis. Bone scintigraphy was sensitive (1.0) but nonspecific (0.38). Images obtained in the 120-minute antibody study were sensitive (0.91), moderately specific (0.69), and comparable to those obtained in the (111)In-labeled leukocyte study (0.91 sensitivity, 0.62 specificity). When interpreted with bone scans, images obtained in the antibody and (111)In-labeled leukocyte studies showed improved sensitivity and specificity (1.0 and 0.85 and 1.0 and 0.77, respectively).

CONCLUSION

Use of the monoclonal antigranulocyte antibody was comparable to the use of (111)In-labeled leukocytes in the diagnosis of appendicular skeletal osteomyelitis. The combined results of the monoclonal antibody study and bone scanning were more accurate (0.91) for diagnosing this entity than were the results of any of the other studies.

[Atypical findings of the combined scintigraphy of bone marrow and labeled leukocytes in osteonecrosis of the hip secondary to infection]

Avascular osteonecrosis can be associated with septic arthritis and osteomyelitis. Combined labeled leukocyte-marrow imaging scintigraphy has demonstrated excellent accuracy for the detection of infection since both tracers accumulate in the bone marrow and only leukocytes accumulate in infection. We report an unusual total absence of 99mTc HMPAO leukocytes/9mTc-sulfur colloid tracer accumulation, not only in the femoral head but also in the acetabulum and hip in hip osteonecrosis secondary to septic arthritis and osteomyelitis.

Comparison of Tc-99m methylene diphosphonate, Tc-99m human immune globulin, and Tc-99m-labeled white blood cell scintigraphy in the diabetic foot

PURPOSE

The aims of this prospective study were to evaluate the contribution of Tc-99m methylene diphosphonate (MDP), Tc-99m human immune globulin (HIG), and Tc-99m white blood cell (WBC) to the diagnosis of osteomyelitis in the diabetic foot and to evaluate the surgical or medical therapy with Tc-99m HIG and Tc-99m WBC scans.

METHODS

Twenty patients (15 men, 5 women) with suspected pedal osteomyelitis were included in the study. All patients had type II diabetics. Three- and four-phase bone scintigraphy (3P-MDP, 4P-MDP), early (e) and late (l) HIG, and WBC scans were completed within 1 week in all patients. The lesion-to-background ratios were calculated for early and late images of the feet for all scans and named as the indices. Eight weeks after the end of medical or surgical therapy, Tc-99m HIG and Tc-99m WBC scans were repeated in 10 patients. The difference in indices between 3P-MDP and 4P-MDP for osteomyelitis and indices for osteomyelitis, cellulitis, and inflammation in Tc-99m HIG and Tc-99m WBC in early and late scans were tested for significance.

RESULTS

In 20 patients, 53 lesions were investigated. Among these 53 lesions were 25 sites of proved osteomyelitis, 6 sites of cellulitis, and 22 sites of inflammation confirmed by radiography, microbiologic culture, and clinical evaluation. 4P-MDP was more specific than 3P-MDP for detecting osteomyelitis (50% and 67%, respectively). There was also a significant difference between the mean indices of 3P-MDP and 4P-MDP (P < 0.000). The index values were increased in 4P-MDP scans. There was no significant difference between the indices of early and late Tc-99m HIG scans for inflammation, cellulitis, and osteomyelitis. Early and late Tc-99m WBC scans did not show a significant difference in differentiating osteomyelitis. However, Tc-99m WBC scans could differentiate aseptic inflammation from infection (P < 0.031) in early and late scans. There was a significant difference of index values between pre- and post-treatment Tc-99m HIG and Tc-99m WBC scans. The best combination of scans for detecting osteomyelitis was 4P-MDP with WBC scans, with an accuracy rate of 92%.

CONCLUSIONS

These results show that four-phase bone scintigraphy with early Tc-99m WBC scanning is preferred for detecting osteomyelitis of the diabetic foot. To evaluate the response to therapy, Tc-99m WBC scans are the preferred method, but if this is not available, Tc-99m HIG scanning can be used.

Role of nuclear medicine in diagnosis of the infected joint replacement

Some complications of joint replacement surgery are easily diagnosed; however, differentiating infection from aseptic loosening is difficult because these entities are remarkably similar at clinical and histopathologic examination. Clinical signs and symptoms, laboratory tests, radiography, and joint aspiration are insensitive, nonspecific, or both. Cross-sectional imaging modalities are hampered by artifacts produced by the prosthetic devices themselves. Radionuclide imaging is not affected by the presence of metallic hardware and is therefore useful for evaluating the painful prosthesis. Bone scintigraphy is useful as a screening test, despite an accuracy of only 50%-70%, because normal results essentially exclude a prosthetic complication. The addition of gallium-67, a nonspecific inflammation-imaging agent, improves the accuracy of bone scintigraphy to 70%-80%. The accuracy of combined leukocyte-marrow imaging, 90%, is the highest among available radionuclide studies. Its success is due to the fact that leukocyte imaging is most sensitive for detection of neutrophil-mediated inflammation (ie, infection). The success of leukocyte-marrow imaging is tempered by the limitations of in vitro labeling. In vivo labeling has been investigated, and a murine monoclonal antigranulocyte antibody appears promising. Some investigations have focused on fluorodeoxyglucose imaging. Although this method is sensitive, specificity is a concern.

Fluorine-18 fluorodeoxyglucose-position emission tomography: a highly accurate imaging modality for the diagnosis of chronic musculoskeletal infections

BACKGROUND

The noninvasive diagnosis of chronic musculoskeletal infections remains a challenge. Recent studies have indicated that fluorine-18 fluorodeoxyglucose-positron emission tomography is a highly accurate imaging technique and is significantly more accurate than the combination of a bone scan and a white blood-cell scan for the diagnosis of chronic infection in the central skeleton (p < 0.05). However, patients who had had surgery within the previous two years were excluded from study. It was our aim to evaluate the technique in an unselected, clinically representative population.

METHODS

Sixty patients with a suspected chronic musculoskeletal infection involving the central skeleton (thirty-three patients) or the peripheral skeleton (twenty-seven patients) were studied with fluorine-18 fluorodeoxyglucose-positron emission tomography. Thirty-five patients had had surgery within the previous two years. The fluorine-18 fluorodeoxyglucose-positron emission tomography studies were read in a blinded, independent manner by two experienced readers. The final diagnosis was based on histopathological studies or microbiological culture (eighteen patients) or on clinical findings after at least six months of follow-up (forty-two patients).

RESULTS

On the final composite assessment, twenty-five patients had infection and thirty-five did not. All twenty-five infections were correctly identified by both readers. There were four false-positive findings; in two of these cases, surgery had been performed less than six months prior to the study. The sensitivity, specificity, and accuracy were 100%, 88%, and 93% for the whole group; 100%, 90%, and 94% for the subgroup of patients with a suspected infection of the central skeleton; and 100%, 86%, and 93% for the subgroup of patients with a suspected infection of the peripheral skeleton. Interobserver agreement was excellent (kappa = 0.97).

CONCLUSIONS

Fluorine-18 fluorodeoxyglucose-positron emission tomography is highly accurate as a single technique for the evaluation of chronic musculoskeletal infections. It is especially valuable in the evaluation of the central skeleton, where white blood-cell scans are less useful. Because of its simplicity and high degree of accuracy, it has the potential to become a standard technique for the diagnosis of chronic musculoskeletal infections. Further studies are needed to assess its ability to identify infections at the sites of total joint replacements and to distinguish infection from aseptic loosening of these prostheses.

Diagnosing spinal osteomyelitis: a comparison of bone and Ga-67 scintigraphy and magnetic resonance imaging

PURPOSE

The objective of this investigation was to compare the accuracies of bone and Ga-67 scintigraphy and magnetic resonance imaging (MRI) for diagnosing spinal osteomyelitis and to determine the optimal radionuclide approach to this disorder.

METHODS

Twenty-two patients, with 24 sites of possible spinal osteomyelitis, who underwent three-phase bone scintigraphy with SPECT, Ga-67 scintigraphy with SPECT, and MRI with and without contrast were included in this retrospective review. Bone scans were interpreted as three-phase studies, delayed planar images alone, delayed planar plus SPECT, and SPECT alone (to identify uptake patterns). Sequential bone/ Ga-67 images were interpreted as planar and as SPECT studies. Planar and SPECT Ga-67 images were also interpreted alone. Precontrast MRI studies were used to identify osteomyelitis, whereas postcontrast images were used to identify soft tissue infection.

RESULTS

Eleven sites of spinal osteomyelitis were identified. Tracer uptake in two contiguous vertebrae, as noted on SPECT, was the most accurate bone scan criterion for detecting spinal osteomyelitis (71 %). SPECT bone/Ga-67 was significantly more accurate (92%) than both planar bone/Ga-67 (75%) and bone SPECT (P = 0.15 and P = 0.2, respectively). SPECT Ga-67 was as accurate as SPECT bone/Ga-67 and as sensitive as MRI (91 %); the radionuclide study was slightly but not significantly more specific (92% vs. 77%) than MRI. Of 11 sites of extraosseous infection, 10 were identified on MRI, 9 on SPECT Ga-67, 7 on planar Ga-67, and none on bone scintigraphy.

CONCLUSIONS

Spinal osteomyelitis and accompanying soft tissue infection can be diagnosed accurately with a single radionuclide procedure: SPECT Ga-67. This procedure can be used as a reliable alternative when MRI cannot be performed and as an adjunct in patients in whom the diagnosis is uncertain.

Role of radionuclide imaging in the diagnosis of postoperative infection

Postoperative infections are a serious cause of morbidity and mortality and are difficult to diagnose. Signs and symptoms that are generally associated with infection may be masked by, or mistaken for, normal postoperative changes. Anatomic imaging modalities provide high-quality anatomic detail and are the procedures of choice in affected patients because of their availability, ease of performance, accuracy, and value in the selection of treatment options. However, radionuclide studies demonstrate physiologic processes, which often precede anatomic changes, and can help distinguish normal postoperative inflammation from infection. Radionuclide studies are also useful in identifying complicated orthopedic infections, in which the often extensive distortions produced by metallic hardware can confound the interpretation of anatomic images. Of the three agents (gallium-67 citrate, indium-111-labeled leukocytes, technetium-99m-labeled leukocytes) that are currently approved in the United States for imaging of infection, In-111-labeled leukocyte imaging is the procedure of choice for diagnosing postoperative infection. Gallium scintigraphy is best reserved for those situations in which leukocyte imaging is not available or there is concern that the suspected infection may not incite a neutrophil response. In general, the value of radionuclide imaging is maximized when used only in those patients for whom the results of anatomic imaging are negative, nondiagnostic, or at odds with the clinical impression.

Late correlative imaging findings of previous acute infective spondylitis

PURPOSE

To evaluate late correlative imaging findings in relation to clinical outcome in persons with previous acute infective spondylitis, the authors performed bone and leukocyte scintigraphy (planar and SPECT imaging) and magnetic resonance imaging of the spine in nine patients (two men, seven women; mean age, 66 years; age range, 57 to 84 years) 3.1 years (range, 0.9 to 6.2 years) after the acute disease.

METHODS

All images were evaluated visually. The relevant uptake on SPECT images was also quantitated using an adjacent normal vertebral body as the reference area.

RESULTS

Except for one patient, all other patients had increased uptake in the affected vertebra on bone scintigraphy [corrected]. In leukocyte scintigraphy, clearly decreased uptake was noted quantitatively in six of the seven patients who underwent SPECT. On the magnetic resonance and computed tomographic scans, the typical findings were destruction of intervertebral disks and compression deformities of vertebral bodies, but there was high interindividual variance of other findings, such as osteophytes, spondylolisthesis, increased vertebral fat content, and postoperative changes. These data show that nearly all patients with previously acute infective spondylitis have gross abnormal anatomic and functional imaging findings years after the acute disease, despite good clinical outcome [corrected].

CONCLUSIONS

The utility of bone and leukocyte scans in the diagnosis of reactivated spondylitis is limited, and incidentally observed abnormal imaging findings in asymptomatic patients with known previous spondylitis should be interpreted with caution.

The diabetic foot

Foot complications in diabetics often lead to amputation. Ulceration is the most common complication in the diabetic forefoot and underlies more than 90% of cases of pedal osteomyelitis. The diagnosis of osteomyelitis is, nevertheless, difficult, and imaging is an important part of the work-up. Plain radiographs, although useful for anatomical information, are neither sensitive nor specific. Three-phase bone scintigraphy is sensitive but not specific. Labelled leucocyte scintigraphy and MRI are both useful and are complementary to one another. Labelled leucocyte scintigraphy is valuable for diagnosis as well as follow-up of pedal osteomyelitis. MRI offers exquisite anatomical detail, which is invaluable for guiding surgical management. The principal complication in the mid and hind foot is the neuropathic or Charcot joint. Although infection of the neuropathic joint is infrequent, its diagnosis is difficult. The extensive bony changes that accompany this disorder severely diminish the value of radiography and bone scintigraphy. It is not always possible to distinguish the marrow oedema of neuropathy from that of osteomyelitis and the role of MRI in the evaluation of this entity is still uncertain. Uptake of labelled leucocytes in the absence of infection may occur and is owing, at least in part, to haematopoietically active marrow. Combined leucocyte/marrow scintigraphy holds considerable promise for identifying the infected Charcot joint.

Diagnostic value of TI-201 and three-phase bone scintigraphy for bone and soft-tissue tumors

PURPOSE

Although TI-201 is highly sensitive for detecting bone and soft-tissue tumors, its uptake is not specific for malignant lesions. This study assessed the differentiation of malignant and benign lesions and evaluated the sensitivity, specificity, and accuracy of TI-201 imaging and three-phase bone scans.

MATERIALS AND METHODS

Forty bone and soft-tissue tumors (16 malignant and 24 benign) were evaluated. TI-201 static images were acquired 10 minutes (early) and 2 hours (delayed) after injection of the radionuclide. Within 14 days, three-phase bone scintigraphy was performed using Tc-99m HMDP with the patient in the same position. The count ratio of the lesion compared with the normal contralateral or adjacent site (L:N ratio) was measured.

RESULTS

With TI-201 scintigraphy, mean (+/- SD) values of early and delayed L:N ratios were 3.36 +/- 1.25 and 2.88 +/- 1.20, respectively, in malignant lesions; and 1.88 +/- 1.14 and 1.48 +/- 0.76, respectively, in benign lesions. TI-201 accumulation in benign lesions was significantly less than that of malignancies on early and delayed images. However, an overlap of both ratios between malignant and benign lesions was seen. No such significance was detected on three-phase bone scintigraphy (L:N ratios of malignant and benign tumors were 2.57 +/- 1.22 and 2.24 +/- 2.11, respectively, for blood flow imaging; 2.41 +/- 0.78 and 2.26 +/- 1.54, respectively, for blood pool imaging; and 2.80 +/- 2.10 and 2.89 +/- 4.55, respectively, for bone imaging). When we assumed that the tumor was malignant when the delayed TI-201 L:N ratio exceeded the blood pool phase L:N ratio with bone scintigraphy, the sensitivity rate was 81%, specificity rate was 100%, and accuracy rate was 93%.

CONCLUSIONS

TI-201 imaging for bone and soft-tissue tumors was better than three-phase bone scintigraphy alone but was not good enough to clearly differentiate malignant lesions from benign ones. TI-201 scintigraphy, performed in combination with three-phase bone scintigraphy, may be superior to either one of the two imaging procedures alone for bone and soft-tissue tumor diagnosis.

Demonstration of Achilles tendon rupture by three phase bone scintigraphy and MRI

A man with complaint of soreness in the right medial ankle underwent three-phase bone scintigraphy; the results of the study suggested chronic active osteomyelitis or cellulitis, he was on antibiotics and was not experiencing any improvement. MR imaging confirmed Achilles tendon rupture. This case illustrates that a positive three-phase study is non-specific disease entity.

67Ga-citrate and 99Tcm-MDP for estimating the severity of vertebral osteomyelitis

The aim of this study was to evaluate the roles of 67Ga-citrate and 99Tcm-methylene diphosphonate (99Tcm-MDP) planar and single photon emission tomographic (SPET) imaging in patients with vertebral osteomyelitis. Thirty patients (22 females, 8 males) aged 62.7 +/- 16.4 years (mean +/- s) were enrolled prospectively between May 1995 and May 1998. The patients had been on antibiotics for 7 +/- 4 weeks prior to the study. Histology was available for all but nine patients with mild infections, who were evaluated by a combination of magnetic resonance imaging (MRI), clinical and laboratory tests. 67Ga-citrate (185 MBq) and three-phase bone (555 MBq 99Tcm-MDP) planar and SPET imaging were performed in all patients, together with MRI as a comparison. In total, 67 infectious foci were detected. Based on histology, there were four cases of severe, 13 cases of moderate and four cases of mild osteomyelitis; nine mild infections were also classified by the combination of MRI, clinical and laboratory results. Combined MRI and 67Ga-citrate SPET correctly classified all patients; MRI detected all 67 infectious foci, whereas 67Ga-citrate SPET identified 54 only. False-negative results were seen with all other modalities, especially in cases of mild and moderate infection. 67Ga-citrate SPET identified unsuspected cases of endocarditis (n = 2), paravertebral abscess (n = 1), subaxillary soft tissue abscess (n = 1) and rib osteomyelitis (n = 1). For 67Ga-citrate SPET, the target-to-background ratio was 2.24 +/- 0.31, 1.76 +/- 0.07 and 1.30 +/- 0.18 for severe, moderate and mild osteomyelitis, respectively. Significant differences were noted between severe and moderate infection (P = 0.0051) and between severe and mild infection (P < 0.0001); that between moderate and mild infection was non-significant. For 99Tcm-MDP planar and SPET imaging, and for planar 67Ga-citrate imaging, there was no correlation with severity. We conclude that 67Ga-citrate SPET is able to identify vertebral osteomyelitis and detect additional sites of infection. It can also aid in determining the severity of infection and, potentially, the response to therapy.

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.

When to use bone scintigraphy. It can reveal things other studies cannot

Despite advances in nuclear medicine, bone scintigraphy remains an important imaging technique. It is sensitive in detecting stress fractures and bone metastases and can assess suspected injury that is difficult to see on plain films (e.g., rib fracture). Scintigraphy is useful in evaluating new symptoms, response to therapy, and prognosis in patients with known malignant tumor. In patients with low back pain, the technique can determine the age of fractures to help identify osteoporosis and can uncover other causes of the pain (e.g., spondylolysis, arthritis). When Paget's disease is suggested by unexplained bone pain or an elevated serum alkaline phosphatase level, bone scintigraphy is a useful screening test. Combined with other appropriate nuclear medicine studies, it helps in early identification and localization of osteomyelitis. Scintigraphic scans can provide a general indicator of malignant versus benign disease (according to the amount of lesion activity seen) and may produce characteristic findings in certain primary tumors (e.g., osteoid osteoma) that are difficult to evaluate with other methods.