title: CTA-enhanced perfusion CT: an original method to perform ultra-low-dose CTA-enhanced perfusion CT.
abstract: BACKGROUND
  Utilizing CT angiography enhances image quality in PCT, thereby permitting acquisition at ultra-low dose.
  
  
  METHODS
  Dynamic CT acquisitions were obtained at 80 kVp with decreasing tube current-time product [milliamperes × seconds (mAs)] in patients suspected of ischemic stroke, with concurrent CTA of the cervical and intracranial arteries. By utilizing fast Fourier transformation, high spatial frequencies of CTA were combined with low spatial frequencies of PCT to create a virtual PCT dataset. The real and virtual PCT datasets with decreasing mAs were compared by assessing contrast-to-noise ratio (CNR), signal-to-noise ratio (SNR), and noise and PCT values and by visual inspection of PCT parametric maps.
  
  
  RESULTS
  Virtual PCT attained CNR and SNR three- to sevenfold superior to real PCT and noise reduction by a factor of 4-6 (p < 0.05). At 20 mAs, virtual PCT achieved diagnostic parametric maps, while the quality of real PCT maps was inadequate. At 10 mAs, both real and virtual PCT maps were nondiagnostic. Virtual PCT (but not real PCT) maps regained diagnostic quality at 10 mAs by applying 40 % adaptive statistical iterative reconstruction (ASIR) and improved further with 80 % ASIR.
  
  
  CONCLUSIONS
  Our new method of creating virtual PCT by combining ultra-low-dose PCT with CTA information yields diagnostic perfusion parametric maps from PCT acquired at 20 or 10 mAs with 80 % ASIR. Effective dose is approximately 0.20 mSv, equivalent to two chest radiographs.
authors.affiliation: Department of Radiology, Neuroradiology Division, University of Virginia, Box 800170, Charlottesville, VA, 22908, USA.
authors.forename: Elizabeth
authors.initials: E
authors.lastname: Tong
authors.forename: Max
authors.initials: M
authors.lastname: Wintermark
mesh_terms: D002545:Brain Ischemia / Q000000981:diagnostic imaging*; D002533:Cerebral Angiography / Q000379:methods*; D005583:Fourier Analysis; D006801:Humans; D064847:Multimodal Imaging; D055420:Perfusion Imaging / Q000379:methods*; D011829:Radiation Dosage; D015203:Reproducibility of Results; D012189:Retrospective Studies; D059629:Signal-To-Noise Ratio; D020521:Stroke / Q000000981:diagnostic imaging*; D014057:Tomography, X-Ray Computed / Q000379:methods*
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