Summary Of Evidence

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Analysis of Evidence

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A cranial computerized tomographic (CT) scan is a very useful and informative neurodiagnostic tool. Scanning of the head in successive layers by a narrow beam of x-rays enables the transmission of x-ray photons in each layer to be measured. A computer is used to process the accumulated x-ray photon data and constructs a graphic image of a tomographic slice. Normal intracranial structures and a wide variety of intracranial disorders may be demonstrated. A cranial CT scan may be ordered without contrast, with injection of standard roentgenographic contrast material or without contrast material, followed by contrast material and further sections. Contrast administration is not without risk to the patient and for some conditions adds little or no benefit to the examination.

Cranial CT scans are determined to be reasonable and necessary and are a covered service when the patient has clinical evidence of an intracranial disorder or an established intracranial disorder or disease. The general indications for use of contrast CT scanning are:

1. To assess perfusion (e.g., cerebrovascular accident [CVA])

2. To characterize a specific lesion

3. To detect defects in blood/brain barrier (e.g., infarcts, tumors, infection, vasculitis)

4. To detect neovascularity (tumors); or

5. For staging of known lung cancer, breast cancer, and lymphomas which are likely to metastasize early to the brain