3997S1_06_Alivisatos

3997S1_06_Alivisatos - Imaging Assessment of Diabetic Foot...

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Unformatted text preview: Imaging Assessment of Diabetic Foot Infections Diabetic Regina Alivisatos, MD Medical Officer Medical DSPIDPs DSPIDPs Introduction Introduction Patients with osteomyelitis should be identified in order to ensure • the most appropriate course of treatment • a homogenous clinical trials population 7 – 14% of enrolled subjects found to have osteomyelitis • excluded from the PP populations • failures in the ITT analysis WHY? WHY? • Decreasing size of the PP populations that may be Decreasing distributed unequally • Inaccurate assessment of the true efficacy for one or both of Inaccurate the treatment arms the • Database size insufficient to draw conclusions about a Database drugs efficacy in CSST infections or in the diabetic foot subset foot Applications to Date Applications Diagnostic Diagnostic Procedure Procedure Applications *done at investigator’s discretion A B D E F G X* X/R C X* X* X X* Bone Scan X* In Scan X* MRI X* Probe X Bone biopsy Unknown X* X X Complications Complications • Determination of infection complicated because of Determination superimposed neuropathic osteoarthropathy and peripheral vascular disease peripheral • Neuropathic disease can lead to f/x, deformity, bone Neuropathic production, and hyperemia which can mimic infection on MRI and scanning increasing the false positives on • Peripheral vascular disease can prevent contrast Peripheral material or tracer from reaching site of concern and lead to false negatives lead Diagnosis - osteomyelitis osteomyelitis • Presence of osteomyelitis impacts on failure rate of Presence soft tissue infections soft • “gold standard” is bone histology and culture gold through non-infected tissue through Procedures Procedures 1) Plain films 2) Radionuclide or Scintigraphic imaging 2) Scintigraphic Triple Phase Bone Scan (TPBS) Gallium Scan Indium-111 Leukocyte Scan 3) Magnetic Resonance Imaging (MRI) 4) Probe to Bone Procedures Procedures 1) Plain films 1) Plain 2) Radionuclide or Scintigraphic imaging 2) Scintigraphic Triple Phase Bone Scan (TPBS) Gallium Scan Indium-111 Leukocyte Scan 3) Magnetic Resonance Imaging (MRI) 4) Probe to Bone X-Ray X-Ray Initial screening tool: • Easily obtained, relatively inexpensive and provides Easily anatomical information anatomical • Demineralization, periosteal reaction, bony destruction: Demineralization, (the classic triad) (the • Appear after 30 – 50% of bone destroyed and can take as Appear much as 2 weeks to appear much • Found in other conditions such as fracture or deformity • Sensitivity and specificity approximately 54% and 80% Procedures Procedures 1) Plain films 2) Radionuclide or Scintigraphic imaging 2) Scintigraphic Triple Phase Bone Scan (TPBS) Gallium Scan Indium-111 Leukocyte Scan 3) Magnetic Resonance Imaging (MRI) 4) Probe to Bone Three-phase bone scintigraphy (TPBS) (TPBS) • Highly sensitive since positive as early as 24 hours after Highly onset onset • Focal hyperperfusion, hyperemia, bony uptake • Can also be seen in fractures, neuropathic joints and Can longstanding cellulitis decreasing specificity longstanding • Fourth phase (24 hour image) enhances specificity • Concurrent TPBS with IN111 scanning optimal TPBS TPBS • Literature review of 20 reports of 1,166 patients Literature (method of confirmation of osteomyelitis diagnosis not specified) not • In patients w/o prior bone changes: 94% sensitive In and 85% specific for osteomyelitis and • In patients with complicating conditions: 95% In sensitive, 33% specific. sensitive, Schauwecker et al; The scintigraphic diagnosis of osteomyelitis. AJR 1992; 158(1):9-18 158(1):9-18 Gallium Scanning Gallium • Must be performed with a TPBS • Diagnostic criteria include • • gallium uptake exceeds TPBS scan uptake gallium gallium and TPBS scan results are discordant gallium • Sensitivity 81% and specificity 69% • Cost of gallium scan AND TPBS may exceed cost of a Cost single more sensitive and specific test such as an Indium scan or an MRI Indium Schauwecker et al. AJR 158; 9 - 18, January 1992 Schauwecker Indium scanning Indium • Best sensitivity, specificity, and cost compromise in Best patients with and without prior bone abnormalities patients • Issue of practicality of labeling WBCs and later images • Does not accumulate at sites that are not infected • Compilation of sensitivity and specificity for 142 Compilation diabetic subjects from 5 studies showed sensitivity of 88.6% and specificity of 84% 88.6% Schauwecker et al. AJR 158; 9 - 18, January 1992 Procedures Procedures 1) Plain films 2) Radionuclide or Scintigraphic imaging 2) Scintigraphic Triple Phase Bone Scan (TPBS) Gallium Scan Indium-111 Leukocyte Scan 3) Magnetic Resonance Imaging (MRI) 3) Magnetic 4) Probe to Bone • MRI: High-tech, high cost? MRI: Decreased marrow signal intensity on T1-weighted Decreased images and increased signal intensity on T2-wighted images with marrow enhancement after injection of contrast contrast • Associated findings of soft tissue mass, cortical Associated destruction, sequestrum formation and sinus tracts with ulceration increase diagnostic certainty with • Good anatomical detail • Sensitivity and specificity comparable to that of Sensitivity Indium scan Indium • Review of 129 diabetics showed MRI sensitivity of 86% Review and specificity of 84% and American College of Radiology: Imaging diagnosis of Osteomyelitis in patients with DM/Appropriateness Criteria, 1999 with MRI continued MRI • 62 feet in 59 patients with suspected osteomyelitis were 62 prospectively evaluated (27 with DM, 35 w/o) prospectively • In DM sensitivity 82%, specificity 80% • In non-DM: sensitivity 89%, specificity 94% • Accuracy increased with contrast-enhanced studies Accuracy (89%) vs.78% (89%) • Cost savings initially because test is more rapid • Competitively priced compared with combination of Competitively TPBS and Indium or with gallium TPBS • Allows good delineation of surgical field Morrison, WB et al, Radiology; Aug 1995:196:557-64 Morrison, TPBS with In-111-labeled WBC scintigraphy in the examination of the feet in diabetic patients: Results of Published Reports Published Author Sensitivity Specificity 16 80% 55% Larcos 1991 51 79% 78% Jacobson 1991 45* 73% 91% Keenan 1989 39 100% 79% Schauweker 1988 35 100% 89% Maurer 1986 MRI # patients Seabold Seabold 1993 1993 TPBS + IN-111 WBC Scan Scan Year 13 75% 89% 1999 129 86% 84% Procedures Procedures 1) Plain films 2) Radionuclide or Scintigraphic imaging 2) Scintigraphic Triple Phase Bone Scan (TPBS) Gallium Scan Indium-111 Leukocyte Scan 3) Magnetic Resonance Imaging (MRI) 4) Probe to Bone 4) Probe Probe Probe • 75 subjects with 76 ulcers from one center • Osteomyelitis diagnosed in 50 (66%), excluded in 26 Osteomyelitis • • • Confirmation based on histologic examination culture data not analyzed as cultures were taken from base of infected culture ulcer ulcer if bone biopsy not done, diagnosis was based on radiographic tests or if surgeons finding of purulent nonviable bone surgeons • Bone probed in 36 of 50 with contiguous osteomyelitis Bone and in 4 of 26 w/o osteomyelitis and • Sensitivity 66%, specificity 85%, positive predictive Sensitivity value 89%, negative 56% value • Conclusion: Palpation of bone strongly correlated with Conclusion: presence osteo. Probing included in initial assessment of diabetics with infected ulcers. Specialized imaging studies not necessary if positive studies Grayson et al JAMA 1995 Mar 1;273(9):721-3 Grayson Cost Cost Procedure Cost (1994) Plain Film $120 TPBS $550 Gallium Scan $1000 Indium Scan $1000 MRI $1000 Conclusion Conclusion Which procedure? Test Plain radiographs Sensitivity Specificity 38 - 100% 86% 84% 67 - 89% 88% 82% (55 – 91%) 92% 84% 29 - 100% Probe to bone 46% (73 – 100%) MRI 91% 45 - 100% TPBS/Indium Scan 50 - 94% 69 -95% Indium scan 80% (22 - 93%) TPBS 54% 78 - 89% 66% 85% Data obtained by varying methods and not always comparable. Dependent on the use of bone biopsy to diagnose the disease ...
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This note was uploaded on 12/24/2011 for the course STEP 1 taught by Professor Dr.aslam during the Fall '11 term at Montgomery College.

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