Chronic osteomyelitis: the relative roles of scintigrams, plain radiographs, and transmission computed tomography

We evaluated the relative contribution of transmission computed tomograms (CT), plain radiographs, and bone/gallium scans in the diagnosis of 27 patients with suspected active chronic osteomyelitis. All patients were imaged with all modalities and had surgical proof of the presence or absence of disease. At surgery, osteomyelitis was shown to be active in 20 patients, 15 of whom had sequestra, and inactive in the remaining seven. CT depicted all 15 sequestra, but was falsely positive in three patients, all of whom had bone remodeling only and had negative bone/gallium scintiscans. Plain radiographs had a limited value; they detected sequestra, which was the only findings to indicate the presence of active disease, in 5 patients out of the 15 with surgical proof thereof. The authors conclude that, considering the shortcoming of other modalities with regard to depicting sequestra, scintigraphy is helpful in confirming the presence or absence of active disease and therefore in preventing unnecessary surgery.     

Combined bone scintigraphy and indium-111 leukocyte scans in neuropathic foot disease

It is difficult to diagnose osteomyelitis in the presence of neurotrophic osteoarthropathy. We performed combined [99mTc]MDP bone scans and indium-111 (111In) leukocyte studies on 35 patients who had radiographic evidence of neuropathic foot disease and clinically suspected osteomyelitis. The [111In]leukocyte study determined if there was an infection and the bone scan provided the anatomic landmarks so that the infection could be localized to the bone or the adjacent soft tissue. Seventeen patients had osteomyelitis and all showed increased [111In]leukocyte activity localized to the bone, giving a sensitivity of 100%. Among the 18 patients without osteomyelitis, eight had no accumulation of [111In]leukocytes, seven had the [111In]leukocyte activity correctly localized to the soft tissue, two had [111In]leukocyte activity mistakenly attributed to the bone, and one had [111In]leukocyte accumulation in a proven neuroma which was mistakenly attributed to bone. These three false-positive results for osteomyelitis reduced the specificity to 83%. Considering only the 27 patients with a positive [111In]leukocyte study, the combined bone scan and [111In]leukocyte study correctly localized the infection to the soft tissues or bone in 89%. Uninfected neurotrophic osteoarthropathy does not accumulate [111In]leukocytes. We found the combined bone scan and [111In] leukocyte study useful for the detection and localization of infection to soft tissue or bone in patients with neuropathic foot disease.     

Evaluation of infectious diabetic foot complications with indium-111-labeled human nonspecific immunoglobulin G.

Osteomyelitis of the foot is a well-known complication of diabetes mellitus. In this study, the validity of 111In-labeled human nonspecific immunoglobulin G (IgG) scintigraphy was studied in 16 diabetic patients with foot ulcers, gangrene or painful Charcot joints. In all patients, plain radiographs, conventional bone scan images and 111In-IgG images were recorded. The results were verified by histologic examination of surgical specimens in patients who did not respond to antibiotic treatment within 2-3 wk (10 lesions) or long-term clinical follow-up of at least 6-mo (16 lesions). On the bone scans, all seven osteomyelitic foci were detected. However, 19 additional foci not due to osteomyelitis were seen. The absence of true-negative bone scans in this study resulted in a specificity of 0%. On the plain radiographs, four of seven osteomyelitis foci were detected; for 111In-IgG scintigraphy, six of seven (sensitivity 57% and 86%, respectively). Plain radiographs correctly ruled out osteomyelitis in 15 of 19 lesions, 111In-IgG scintigraphy in 16 of 19 (specificity 79% and 84%, respectively). All imaging procedures gave false-positive results in penetrating ulcers over the calcaneus in two patients and in one patient with a Charcot joint, most likely due to recent fractures. A false-negative 111In-IgG study was observed in a patient with severe arterial angiopathy. Accurate estimation of probable osteomyelitis was not possible from the results of soft-tissue cultures, since in only 6 of 12 positive cultures, osteomyelitic foci could be proven. Indium-111-IgG scintigraphy can contribute to adequate evaluation of osteomyelitis in diabetic foot complications because it improves specificity when compared to bone scan and radiographic findings and improves sensitivity in comparison to plain radiographs.     

Osteomyelitis of the foot in diabetic patients: evaluation with plain film, 99mTc-MDP bone scintigraphy, and MR imaging

Diagnosis of osteomyelitis of the foot in diabetic patients may be difficult because of the coexistence of chronic cellulitis, vascular insufficiency, and peripheral neuropathy. This study compared the diagnostic accuracies of plain films, bone scans, and MR imaging studies in diabetic patients with suspicion of osteomyelitis of the foot. Twenty-nine plain radiographs, 20 bone scans, and 30 MR studies were obtained in 24 patients. Twenty-nine bones from 14 patients were pathologically proved either positive (25 bones) or negative (four bones) for osteomyelitis. Another 15 bones (10 patients) studied with MR had no pathologic proof, but the bones healed with only local wound care and/or a short course of oral antibiotics. These patients had trauma, cellulitis, or unhealed ulcers. The sensitivity and specificity of plain films were both 75%. Bone scans had a very low specificity (100% false-positive rate). A negative bone scan should strongly exclude the probability of osteomyelitis. Unlike the findings in previous reports, MR had much higher sensitivity and specificity than bone scans in detecting osteomyelitis in diabetic patients. When the 10 patients without pathologic proof (those who presumably had neuroarthropathy, vascular insufficiency, and/or cellulitis) were included, the sensitivity and specificity of all three techniques decreased. Our experience with this small group of patients suggests that MR is a useful imaging technique for diagnosing osteomyelitis of the foot in diabetic patients.     

CT detection of sacral osteomyelitis associated with pelvic abscesses

In three patients the diagnosis of sacral osteomyelitis was made when CT demonstrated intraosseous (two) and intraforaminal (one) gas. Two of the three patients also had radionuclide bone scans, one of which was unremarkable. In the other case, radionuclide scintigraphy greatly underestimated the extent of the disease process when compared with CT. All three patients had contiguous pelvic abscesses as a cause of the osteomyelitis. Although there was a high clinical suspicion for an intraabdominal process, the diagnosis of superimposed osteomyelitis of the sacrum was unsuspected. The detection of intraosseous gas is a pathognomonic, albeit uncommon, manifestation of osteomyelitis. Although the radionuclide bone scan is the method of choice for detecting osteomyelitis, CT should be used as a complementary study in certain patients.     

Effect of soft-tissue pathology on detection of pedal osteomyelitis in diabetics

Three-phase bone scans were performed on 30 diabetic patients suspected of having acute pedal osteomyelitis; 23 also had a pedal ulcer, seven had coexisting cellulitis, and 14 had diminished pedal pulses. Fifteen patients were receiving antibiotics at the time of the scan. A tissue diagnosis was available in 18 patients and 12 had no clinical evidence of infection on follow-up. Focal arterial hyperemia combined with focally increased activity on blood-pool and delayed (2-3 hr) scans were interpreted as acute osteomyelitis. Scans showing venous hyperemia were interpreted as soft-tissue pathology without acute osteomyelitis. Companion radiographs were reviewed independently. The sensitivity and specificity of the scans for osteomyelitis were 0.94 and 0.79, respectively, while radiographic sensitivity was 0.93 and specificity was 0.50. The presence of soft-tissue ulcers or cellulitis, peripheral vascular disease, or recent antibiotic therapy had no significant adverse effect on the accuracy of the three-phase scan in diagnosing osteomyelitis.     

Diagnosis of osteomyelitis of the foot in diabetic patients: value of 111In-leukocyte scintigraphy

The noninvasive diagnosis of osteomyelitis of the foot in diabetic patients with currently available radiologic and radionuclide imaging techniques is often difficult. Recently, 111In-labeled leukocyte scintigraphy has been proposed as an attractive alternative. Accordingly, we retrospectively reviewed 51 111In-labeled leukocyte scans, 49 technetium-99m bone scans, and 49 plain radiographs obtained in 51 adults with diabetes in whom osteomyelitis of the foot was suspected. The sensitivity and specificity of these techniques were evaluated in all patients, as well as in a subgroup of 11 patients with neuroarthropathy. Results with 111In-labeled leukocyte scans were also examined in subsets of patients with soft-tissue ulcers (n = 35) and those receiving antibiotics during investigation (n = 20). Confirmation or exclusion of osteomyelitis was made surgically in 28 patients and clinically in 23. Fourteen patients had osteomyelitis. Bone scans were most sensitive (93%) but least specific (43%); plain radiographs were most specific (83%) but least sensitive (43%). 111In-labeled leukocyte scans were both sensitive (79%) and specific (78%), and remained useful in patients with neuroarthropathy, soft-tissue ulcers, and antibiotic treatment. Poor spatial resolution contributed to the false-negative and false-positive 111In-labeled leukocyte scans, suggesting that this technique should not be interpreted independent of other tests. 111In-labeled leukocyte scans are a valuable diagnostic tool for the diagnosis of pedal osteomyelitis in diabetic patients.     

FDG PET/CT imaging in the diagnosis of osteomyelitis in the diabetic foot

Purpose

Osteomyelitis, the most serious complication of the diabetic foot, occurs in about 20?% of patients. Early diagnosis is crucial. Appropriate treatment will avoid or decrease the likelihood of amputation. The objective of this study was to assess the value of FDG PET/CT in diabetic patients with clinically suspected osteomyelitis.

Methods

Enrolled in this prospective study were 39 consecutive diabetic patients (29 men and 10 women, mean age 57?years, range 28–71?years) with 46 suspected sites of foot infection. Of these 39 patients, 38 had type 2 and 1 type 1 diabetes for 4–25?years, and 28 were receiving treatment with insulin. FDG PET/CT was interpreted for the presence, intensity (SUVmax) and localization of increased FDG foci. Final diagnosis was based on histopathology and bacteriology of surgical samples, or clinical and imaging follow-up.

Results

Osteomyelitis was correctly diagnosed in 18 and excluded in 21 sites. Of 20 lesions with focal bone FDG uptake, 2 were false-positive with no further evidence of osteomyelitis. Five sites of diffuse FDG uptake involving more than one bone on CT were correctly diagnosed as diabetic osteoarthropathy. FDG PET/CT had a sensitivity, specificity and accuracy of 100?%, 92?% and 95?% in a patient-based analysis and 100?%, 93?% and 96?% in a lesion-based analysis, respectively, for the diagnosis of osteomyelitis in the diabetic foot.

Conclusion

FDG PET/CT was found to have high performance indices for evaluation of the diabetic foot. The PET component identified FDG-avid foci in sites of acute infection which were precisely localized on fused PET/CT images allowing correct differentiation between osteomyelitis and soft-tissue infection.     

The diabetic foot: initial experience with 18F-FDG PET/CT.

Osteomyelitis complicates up to one third of diabetic foot infections, is often due to direct contamination from a soft-tissue lesion, and represents a clinical challenge. Early diagnosis is important since antibiotic therapy can be curative and may prevent amputation. The present study assessed the role of PET/CT using 18F-FDG for the diagnosis of diabetic foot osteomyelitis. METHODS: Fourteen diabetic patients (10 men and 4 women; age range, 29-70 y) with 18 clinically suspected sites of infection underwent PET/CT after the injection of 185-370 MBq of 18F-FDG for suspected osteomyelitis complicating diabetic foot disease. PET, CT, and hybrid images were independently evaluated for the diagnosis and localization of an infectious process. Additional data provided by PET/CT for localization of infection in the bone or soft tissues were recorded. The final diagnosis was based on histopathologic findings and bacteriologic assays obtained at surgery or at clinical and imaging follow-up. RESULTS: PET detected 14 foci of increased 18F-FDG uptake suspected as infection in 10 patients. PET/CT correctly localized 8 foci in 4 patients to bone, indicating osteomyelitis. PET/CT correctly excluded osteomyelitis in 5 foci in 5 patients, with the abnormal 18F-FDG uptake limited to infected soft tissues only. One site of mildly increased focal 18F-FDG uptake was localized by PET/CT to diabetic osteoarthropathy changes demonstrated on CT. Four patients showed no abnormally increased 18F-FDG uptake and no further evidence of an infectious process on clinical and imaging follow-up. CONCLUSION: 18F-FDG PET can be used for diagnosis of diabetes-related infection. The precise anatomic localization of increased 18F-FDG uptake provided by PET/CT enables accurate differentiation between osteomyelitis and soft-tissue infection.     

Differentiation of bone and bone marrow infarcts from osteomyelitis in sickle cell disorders

To determine whether imaging techniques can differentiate osteomyelitis from bone infarction in sickle cell disorders, 39 sets of bone scans (BS) and bone marrow scans (BMS) were performed on 31 patients with sickling disorders and bone pain. In addition, three patients who had either a BS or a BMS were included. Results were analyzed according to whether scans were performed three days or less (Period 1), four to six days (Period 2), or seven or more days (Period 3) after the onset of pain. Regardless of the period, all but five BMS for 34 episodes of assumed infarction showed decreased uptake. BS findings varied depending on the time interval, with none of the ten in Period 1 showing increased uptake, but all 11 in Period 3 showing increased uptake. However, in Period 2, about half of the 13 BS showed increased uptake. All three patients with osteomyelitis in Period 3 had increased uptake on BS. The BMS done in one of these patients showed decreased uptake. Three patients with cellulitis had normal BS and BMS. One patient with septic arthritis had normal BMS, but slightly increased uptake on BS. Although typical imaging patterns are present in early and late infarction (Periods 1 and 3), the patterns for late infarction may not differ from those of advanced osteomyelitis. Therefore, imaging studies are only of value in differentiating infarction from osteomyelitis when both BS and BMS are performed soon after the appearance of symptoms.     

Diagnosis of osteomyelitis in the presence of soft-tissue infection and radiologic evidence of osseous abnormalities: value of leukocyte scintigraphy

To evaluate the usefulness of 111In-leukocyte scintigraphy for identifying osteomyelitis in the presence of soft-tissue infection, we prospectively studied 45 bone sites adjacent to soft-tissue infection in patients with abnormal findings on radiographs and 99mTc bone scans that were suggestive of osteomyelitis. 111In-leukocyte scans were analyzed in terms of the intensity of abnormal uptake and its location relative to bone. The diagnosis of osteomyelitis was established from results of percutaneous bone biopsy culture (n = 35), histologic examination of surgical specimens (n = 8), and clinical follow-up (n = 2). Osteomyelitis was present at 22 sites, including 16 of 18 sites with increased leukocyte uptake in bone, resulting in a sensitivity of 73%, specificity of 91%, and positive predictive value of 89% for this finding. Osteomyelitis was present at four of 17 sites with predominantly soft-tissue localization of leukocyte activity in the region of bone, none of seven sites with normal leukocyte scans, and two of three sites with diminished leukocyte uptake in bone. Although not helpful in distinguishing infectious from noninfectious bone abnormalities, 3- and especially 24-hr bone scans viewed in conjunction with leukocyte studies provided important correlation to aid in estimating the location of focal abnormal leukocyte uptake. The finding of soft-tissue infection with increased uptake of labeled leukocytes that extends to involve adjacent bone strongly suggests concurrent osteomyelitis. When the presence of abnormal leukocyte uptake in bone is uncertain, additional imaging and possibly biopsy may be required to establish or exclude the diagnosis of osteomyelitis.     

Chronic osteomyelitis: monitoring by 99mTc phosphate and 67Ga citrate imaging

Thirteen patients with chronic osteomyelitis, treated for 6 months with rifampin, had serial 99mTc phosphate and 67Ga scans to determine their value in assessing response to treatment. In patients who responded to treatment, gallium scans were deemed more accurate than 99mTc phosphate bone scans. The gallium scans, although still abnormal at the end of 6 months of antibiotic therapy, showed an improvement trend in all the responders except one in whom fracture recurred. Worsening or lack of improvement on gallium scans predicted active bone infection in five of six "clinical-failure" patients who had documented active bone infection. 67Ga scans eventually became normal in all patients who remained asymptomatic (excluding one with recurrent fracture). 99mTc phosphate scans became normal in only one of five clinical responders. All nonresponders had persistently abnormal scans, although after 6 months of therapy only four of seven showed worsening or no improvement on the scan. Therefore, 67Ga is preferred over 99mTc phosphate bone scans in the assessment of response to therapy in chronic bone infection. Clinical utility of the gallium scan is most significant in patients whose clinical assessment is uncertain, but routine use of this technique does not appear to be warranted. Gallium images are most valuable when obtained over a period of time, so that the trend of improvement versus nonimprovement is evident.     

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.     

Osseous lipoma: CT appearance

Characteristic radiographic and computed-tomographic (CT) features of seven cases of osseous lipoma are reported: six with medullary and one with parosteal locations. Radiological diagnosis of this lesion is discussed, with emphasis on potential pitfalls in interpretation of CT scans. Although the presence of fat-equivalent density on scans is highly suggestive of osseous lipoma, comparable attenuation is documented in cases of chronic osteomyelitis and postnecrotic subchondral excavation.     

Hematogenous pyogenic vertebral osteomyelitis: diagnostic value of radionuclide bone imaging

Hematogenous pyogenic vertebral osteomyelitis (HPVO) continues to be a diagnostic problem for clinicians due to nonspecific presentation of the disease (1,2). We reviewed our experience of the last 10 years to determine the diagnostic usefulness of radionuclide bone studies in this disease. We found 15 patients whose primary diagnosis was HPVO. Of the 15 patients, 12 had [99mTc]MDP bone scans which were all positive. Five of the 12 patients had positive [67Ga]citrate scans and one patient with chronic active HPVO had negative 67Ga and [111In]WBC bone images. At the same time, three patients' spine x-rays and one patient's CT scan of the vertebra were normal. Additionally, in three patients spine x-rays were interpreted as consistent with degenerative joint disease that contributed to the delay of the diagnosis. We conclude that when HPVO is suspected an abnormal [99mTc]MDP bone image increases the probability of the disease, even if the x-rays and CT scans of the spine are normal. An abnormal 67Ga image following an abnormal 99mTc bone image increases the specificity of the diagnosis. Normal [99mTc]MDP and [67Ga]citrate bone images of the vertebra virtually exclude the diagnosis of HPVO.     

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

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

Malignant external otitis: the role of computed tomography and radionuclides in evaluation

Nine patients with malignant external otitis (MEO) were evaluated with Tc-99m bone scans, Ga-67 citrate scans, pluridirectional tomography, and computed tomographic (CT) scans in order to assess the role of each in the diagnosis and management of MEO. The Tc-99m and Ga-67 citrate scans were the most accurate studies in the initial identification of disease activity, while the return to normal or improvement of the Ga-67 citrate scan has been shown to correlate best with clinical resolution of MEO. CT demonstrated soft-tissue disease and central skull base osteomyelitis better than pluridirectional tomography. CT is excellent for localizing and following the progression of bone disease; however, because reossification of the skull base is a very slow process, CT cannot be used to follow accurately regression or inactivity of MEO affecting this area. CT is the best modality for following soft-tissue extension of MEO.     

The "warm" sacroiliac joint. A finding in pelvic abscess

Two patients with pain referable to the low back and sacroiliac regions had bone scans with similar findings. In each, one sacroiliac joint was "warm" (uptake on that side was slightly greater than that in the contralateral area). Ga-67 imaging also demonstrated increased uptake in the same locale. Subsequent CT scanning revealed pelvic abscesses adjacent to the affected joints. Asymmetric uptake of bone imaging agent may have been related to hyperemia and "heating" of the sacroiliac joint. Rapid defervescence with antibiotics and drainage (and no CT evidence of bone involvement) suggested that osteomyelitis was not involved in these cases.     

CT findings as a significant predictive factor for the curability of mandibular osteomyelitis: multivariate analysis

OBJECTIVES: To re-evaluate computed tomographic (CT) imaging as a diagnostic tool for mandibular osteomyelitis and to assess the clinical significance of CT findings. METHODS: CT images of 78 patients with mandibular osteomyelitis were reviewed. All patients were classified as cured or non-cured. Each CT finding was investigated for frequency, correlation with duration and disease cure. RESULTS: Of the 78 patients, 49 (63%) were classified as "cured" and 29 (37%) as "non-cured". Non-cured had experienced a significantly longer duration of symptoms. The most frequent CT finding was sclerosis and defect in the trabecular bone. Changes of bone width and thickening of the cortical plate were accompanied with longer disease duration. The extent of the diseased area was linearly correlated with the duration of symptoms. The significant factors to discriminate non-cured from cured were the extent of the disease, the number of findings, changes in the bone width, osteosclerosis and thickening of the cortex. Multivariate logistic regression analysis indicated that the extent of the disease and presence of changes in bone width were significant variables correlating with the cure of osteomyelitis. CONCLUSIONS: The extent of disease and the presence of change in bone width shown on CT were significantly correlated with the curability of osteomyelitis. These results indicated the usefulness and importance of CT examination for the diagnosis of mandibular osteomyelitis.     

Value of a 24-hour image (four-phase bone scan) in assessing osteomyelitis in patients with peripheral vascular disease

The delayed images of the four-phase 99mTc phosphonate bone scan are compared with the delayed images of the three-phase study in patients with diabetes mellitus and/or peripheral vascular disease and suspected osteomyelitis. Three-phase bone imaging includes an immediate postinjection radionuclide angiogram, a blood-pool image, and delayed static images to 7 hr. The four-phase study adds a 24-hr static image. The scan is positive for osteomyelitis if images show progressively increasing lesion to background activity ratios over time. The results of analyzing 21 three- and four-phase bone scans in 17 patients were correlated with clinical course, cultures, and/or x-rays, gallium scans, and CT scans. The accuracy of four-phase bone imaging for diagnosing osteomyelitis was 85%; for three phase, 80%. Sensitivity for four phase was 80%; specificity was 87%. Sensitivity for three phase was 100%; specificity was 73%. Since overall accuracy of the four-phase study is slightly better than three phase, in these patients with diabetes mellitus and/or peripheral vascular disease, the addition of a 24-hr image, creating a four-phase bone scan, is recommended.