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Imaging Assessment of Diabetic Foot Infections

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Imaging Assessment of Diabetic Foot Infections. Regina Alivisatos, MD. Medical Officer ... 62 feet in 59 patients with suspected osteomyelitis were ... – PowerPoint PPT presentation

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Title: Imaging Assessment of Diabetic Foot Infections


1
Imaging Assessment of Diabetic Foot Infections
  • Regina Alivisatos, MD
  • Medical Officer
  • DSPIDPs

2
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

3
WHY?
  • Decreasing size of the PP populations that may be
    distributed unequally
  • Inaccurate assessment of the true efficacy for
    one or both of the treatment arms
  • Database size insufficient to draw conclusions
    about a drugs efficacy in CSST infections or in
    the diabetic foot subset

4
Applications to Date
5
Complications
  • Determination of infection complicated because of
    superimposed neuropathic osteoarthropathy and
    peripheral vascular disease
  • Neuropathic disease can lead to f/x, deformity,
    bone production, and hyperemia which can mimic
    infection on MRI and scanning increasing the
    false positives
  • Peripheral vascular disease can prevent contrast
    material or tracer from reaching site of concern
    and lead to false negatives

6
Diagnosis - osteomyelitis
  • Presence of osteomyelitis impacts on failure rate
    of soft tissue infections
  • gold standard is bone histology and culture
    through non-infected tissue

7
Procedures
  • 1) Plain films
  • 2) Radionuclide or Scintigraphic imaging
  • Triple Phase Bone Scan (TPBS)
  • Gallium Scan
  • Indium-111 Leukocyte Scan
  • 3) Magnetic Resonance Imaging (MRI)
  • 4) Probe to Bone

8
Procedures
  • 1) Plain films
  • 2) Radionuclide or Scintigraphic imaging
  • Triple Phase Bone Scan (TPBS)
  • Gallium Scan
  • Indium-111 Leukocyte Scan
  • 3) Magnetic Resonance Imaging (MRI)
  • 4) Probe to Bone

9
X-Ray
  • Initial screening tool
  • Easily obtained, relatively inexpensive and
    provides anatomical information
  • Demineralization, periosteal reaction, bony
    destruction (the classic triad)
  • Appear after 30 50 of bone destroyed and can
    take as much as 2 weeks to appear
  • Found in other conditions such as fracture or
    deformity
  • Sensitivity and specificity approximately 54 and
    80

10
Procedures
  • 1) Plain films
  • 2) Radionuclide or Scintigraphic imaging
  • Triple Phase Bone Scan (TPBS)
  • Gallium Scan
  • Indium-111 Leukocyte Scan
  • 3) Magnetic Resonance Imaging (MRI)
  • 4) Probe to Bone

11
Three-phase bone scintigraphy (TPBS)
  • Highly sensitive since positive as early as 24
    hours after onset
  • Focal hyperperfusion, hyperemia, bony uptake
  • Can also be seen in fractures, neuropathic joints
    and longstanding cellulitis decreasing
    specificity
  • Fourth phase (24 hour image) enhances specificity
  • Concurrent TPBS with IN111 scanning optimal

12
TPBS
  • Literature review of 20 reports of 1,166 patients
    (method of confirmation of osteomyelitis
    diagnosis not specified)
  • In patients w/o prior bone changes 94 sensitive
    and 85 specific for osteomyelitis
  • In patients with complicating conditions 95
    sensitive, 33 specific.
  • Schauwecker et al The scintigraphic
    diagnosis of osteomyelitis. AJR 1992 158(1)9-18

13
Gallium Scanning
  • Must be performed with a TPBS
  • Diagnostic criteria include
  • gallium uptake exceeds TPBS scan uptake
  • gallium and TPBS scan results are discordant
  • Sensitivity 81 and specificity 69
  • Cost of gallium scan AND TPBS may exceed cost of
    a single more sensitive and specific test such as
    an Indium scan or an MRI
  • Schauwecker et al. AJR 158 9 - 18,
    January 1992

14
Indium scanning
  • Best sensitivity, specificity, and cost
    compromise in patients with and without prior
    bone abnormalities
  • 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 diabetic subjects from 5 studies showed
    sensitivity of 88.6 and specificity of 84
  • Schauwecker et al. AJR 158 9 - 18, January 1992

15
Procedures
  • 1) Plain films
  • 2) Radionuclide or Scintigraphic imaging
  • Triple Phase Bone Scan (TPBS)
  • Gallium Scan
  • Indium-111 Leukocyte Scan
  • 3) Magnetic Resonance Imaging (MRI)
  • 4) Probe to Bone

16
MRI High-tech, high cost?
  • Decreased marrow signal intensity on T1-weighted
    images and increased signal intensity on
    T2-wighted images with marrow enhancement after
    injection of contrast
  • Associated findings of soft tissue mass, cortical
    destruction, sequestrum formation and sinus
    tracts with ulceration increase diagnostic
    certainty
  • Good anatomical detail
  • Sensitivity and specificity comparable to that of
    Indium scan
  • Review of 129 diabetics showed MRI sensitivity of
    86 and specificity of 84
  • American College of Radiology Imaging
    diagnosis of Osteomyelitis in patients with
    DM/Appropriateness Criteria, 1999

17
MRI continued
  • 62 feet in 59 patients with suspected
    osteomyelitis were prospectively evaluated (27
    with DM, 35 w/o)
  • In DM sensitivity 82, specificity 80
  • In non-DM sensitivity 89, specificity 94
  • Accuracy increased with contrast-enhanced studies
    (89) vs.78
  • Cost savings initially because test is more rapid
  • Competitively priced compared with combination of
    TPBS and Indium or with gallium
  • Allows good delineation of surgical field
  • Morrison, WB et al, Radiology Aug
    1995196557-64

18
TPBS with In-111-labeled WBC scintigraphy in the
examination of the feet in diabetic patients
Results of Published Reports
19
Procedures
  • 1) Plain films
  • 2) Radionuclide or Scintigraphic imaging
  • Triple Phase Bone Scan (TPBS)
  • Gallium Scan
  • Indium-111 Leukocyte Scan
  • 3) Magnetic Resonance Imaging (MRI)
  • 4) Probe to Bone

20
Probe
  • 75 subjects with 76 ulcers from one center
  • Osteomyelitis diagnosed in 50 (66), excluded in
    26
  • Confirmation based on histologic examination
  • culture data not analyzed as cultures were taken
    from base of infected ulcer
  • if bone biopsy not done, diagnosis was based on
    radiographic tests or surgeons finding of
    purulent nonviable bone
  • Bone probed in 36 of 50 with contiguous
    osteomyelitis and in 4 of 26 w/o osteomyelitis
  • Sensitivity 66, specificity 85, positive
    predictive value 89, negative 56
  • Conclusion Palpation of bone strongly correlated
    with presence osteo. Probing included in initial
    assessment of diabetics with infected ulcers.
    Specialized imaging studies not necessary if
    positive
  • Grayson et al JAMA 1995 Mar 1273(9)721-3

21
Cost
22
ConclusionWhich procedure?
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