HMPAO SPECT or SPECT/CT Brain Although SPECT is used clinically with a wide variety of radiopharmaceuticals, brain SPECT most commonly refers to cerebral perfusion or blood flow imaging using either Tc-99m-hexamethylpropyleneamine oxime or Tc- 99m-ethyl cysteinate dimer. Measurement of regional cerebral blood flow is also an indicator of metabolic or neuronal activity; therefore, SPECT is utilized in epilepsy or neurodegenerative disorders in addition to cerebrovascular diseases. Other radiopharmaceuticals (eg, imaging of benzodiazepine or dopamine receptors) are generally confined to research studies. Perfusion SPECT is potentially a complementary tool to conventional CT/MRI and has been applied in research studies on mild, moderate, and severe TBI to identify additional lesions (eg, regional cerebral blood flow deficits) beyond anatomic imaging [18]. A study using early subacute SPECT in patients with mild to moderate TBI found that severe hypoperfusion was an independent predictor of unfavorable outcomes at 3 months; conversely, a normal initial SPECT has been shown to have high negative predictive value for persistent clinical deficits at 12 months [46]. Despite the promise of perfusion imaging (whether employing SPECT or CT/MRI-based techniques) for the detection of functional injury that may be occult on structural imaging, there is insufficient evidence to support the routine clinical use of SPECT at the individual patient level [45]. MR Spectroscopy Head MRS measures very small differences in the precessional frequencies of proton nuclei in order to differentiate their molecular environments (chemical shift effect). Single-voxel versus multi-voxel spectroscopy offers different strengths and weaknesses in signal-to-noise ratio versus spatial coverage; both have lower spatial resolution than other MRI-based techniques.
Head Trauma PCAs. HMPAO SPECT or SPECT/CT Brain Although SPECT is used clinically with a wide variety of radiopharmaceuticals, brain SPECT most commonly refers to cerebral perfusion or blood flow imaging using either Tc-99m-hexamethylpropyleneamine oxime or Tc- 99m-ethyl cysteinate dimer. Measurement of regional cerebral blood flow is also an indicator of metabolic or neuronal activity; therefore, SPECT is utilized in epilepsy or neurodegenerative disorders in addition to cerebrovascular diseases. Other radiopharmaceuticals (eg, imaging of benzodiazepine or dopamine receptors) are generally confined to research studies. Perfusion SPECT is potentially a complementary tool to conventional CT/MRI and has been applied in research studies on mild, moderate, and severe TBI to identify additional lesions (eg, regional cerebral blood flow deficits) beyond anatomic imaging [18]. A study using early subacute SPECT in patients with mild to moderate TBI found that severe hypoperfusion was an independent predictor of unfavorable outcomes at 3 months; conversely, a normal initial SPECT has been shown to have high negative predictive value for persistent clinical deficits at 12 months [46]. Despite the promise of perfusion imaging (whether employing SPECT or CT/MRI-based techniques) for the detection of functional injury that may be occult on structural imaging, there is insufficient evidence to support the routine clinical use of SPECT at the individual patient level [45]. MR Spectroscopy Head MRS measures very small differences in the precessional frequencies of proton nuclei in order to differentiate their molecular environments (chemical shift effect). Single-voxel versus multi-voxel spectroscopy offers different strengths and weaknesses in signal-to-noise ratio versus spatial coverage; both have lower spatial resolution than other MRI-based techniques.