Imaging

Diabetic Ulcers

Preliminary Diagnosis: Diabetic Ulcers

I. What imaging technique is first-line for this diagnosis?

After initial radiograph, magnetic resonance imaging is the imaging technique of choice.

II. Describe the advantages and disadvantages of this technique for diagnosing diabetic ulcers.

Advantages

  • MRI can rule out complications of diabetic ulcers, such as osteomyelitis, fluid collections, abscesses, and sinus tract.

  • MRI does not use ionizing radiation and may be performed in pregnant patients.

Disadvantages

  • Expensive

  • Requires a significant amount of patient cooperation due to long imaging times

III. What are the contraindications for the first-line imaging technique?

Contraindicated in patients with non-MR compatible metallic hardware or foreign bodies.

IV. What alternative imaging techniques are available?

  • Plain radiograph

  • Nuclear medicine

  • Computed tomography

  • Ultrasound

V. Describe the advantages and disadvantages of the alternative techniques for diagnosing diabetic ulcers.

Plain radiograph

Advantages

  • Relatively quick imaging procedure that requires minimal patient cooperation

  • Inexpensive

  • Recommended as the initial imaging technique to evaluate osteomyelitis associated with diabetic ulcers; radiography and MRI are complementary, and both are indicated

Disadvantages

  • Exposure to ionizing radiation

  • May be normal in early osteomyelitis

Nuclear medicine

Advantages

  • Can be used if MRI is contraindicated

  • The 3-phase bone scan has a high sensitivity for osteomyelitis

  • An alternative nuclear imaging technique is the 111In-labeled white blood cell scan

Disadvantages

  • Weak anatomic analysis

  • Relatively expensive

  • Radiation risks due to administered radionuclide

  • 3-phase scan loses specificity in the setting of recent trauma or surgery, which may mimic osteomyelitis

  • 111In-labeled white blood cell scan has a poor image resolution and often fails to distinguish whether the infection is in the bone, soft tissue, or both

Computed tomography

Advantages

May be useful in patients who have a contraindication to MRI

Disadvantages

Exposure to ionizing radiation

Ultrasound

Advantages

  • Noninvasive

  • Inexpensive technique

  • Does not use ionizing radiation

  • Can assess associated soft tissue abnormalities, such as cellulitis, soft tissue abscesses, and acute septic arthritis

Disadvantages

  • Operator dependent

  • A patient with acute tenderness at the site of suspected infection may not be able to tolerate the ultrasonic probe touching the surface

  • Limited bone evaluation

VI. What are the contraindications for the alternative imaging techniques?

Plain radiograph

Pregnancy is a relative contraindication for plain radiographs. The small risk must be weighed against the benefit

Nuclear medicine

Contraindicated in pregnant women and those who are breastfeeding.

Computed tomography

Contraindicated in pregnant women, especially within the first two trimesters

Ultrasound

None

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