title: Technical assessment of a prototype cone-beam CT system for imaging of acute intracranial hemorrhage.
abstract: OBJECTIVE
  A cone-beam CT scanner has been developed for detection and monitoring of traumatic brain injury and acute intracranial hemorrhage (ICH) at the point of care. This work presents a technical assessment of imaging performance and dose for the scanner in phantom and cadaver studies as a prerequisite to clinical translation.
  
  
  METHODS
  The scanner incorporates a compact, rotating-anode x-ray source and a flat-panel detector (43 × 43 cm2) on a mobile U-arm gantry with source-axis distance = 550 mm and source-detector distance = 1000 mm. Central and peripheral doses were measured in 16 cm diameter CTDI phantoms using a 0.6 cm3Farmer ionization chamber for various scan techniques and as a function of longitudinal position, including out of field. Spatial resolution, contrast, noise, and image uniformity were assessed in quantitative and anthropomorphic head phantoms. Two reconstruction protocols were evaluated, including filtered backprojection (FBP) for high-resolution bone imaging and penalized weighted least squares (PWLS) reconstruction for low-contrast soft tissue (ICH) visualization. A fresh cadaver was imaged with and without simulated ICH using the scanner as well as a diagnostic multidetector CT (MDCT) scanner using a standard head protocol. Images were interpreted by a fellowship-trained neuroradiologist for imaging tasks of ICH detection, gray-white-CSF differentiation, detection of midline shift, and fracture detection.
  
  
  RESULTS
  The nominal scan protocol involved 720 projections acquired over a 360° orbit at 100 kV and 216 mAs, giving a dose (weighted CTDI) of 22.8 mGy (∼1.2 mSv effective dose). Out-of-field dose decreased to <10% within 6 cm of the field edge (approximate to the thyroid position). Image uniformity demonstrated <1% variation between the edge of the field (near the cranium) and center of the image. The high-resolution FBP reconstruction protocol showed ∼0.9 mm point spread function (PSF) full-width at half-maximum (FWHM). The smooth PWLS reconstruction protocol yielded ∼1.2 mm PSF FWHM and contrast-to-noise ratio exceeding 5.7 in ∼50 HU spherical ICH, resulting in conspicuous depiction of ICH down to ∼2 mm (the smallest diameter investigated). Cadaver images demonstrated good differentiation of brain and CSF (sufficient, but inferior to MDCT, recognizing that the CBCT dose was one-third that of MDCT), excellent visualization of cranial sutures and fracture (potentially superior to MDCT), clear detection of midline shift, and conspicuous detection of ICH.
  
  
  CONCLUSIONS
  Technical assessment of the prototype demonstrates dose characteristics and imaging performance consistent with point-of-care detection and monitoring of head injury-most notably, conspicuous detection of ICH-and supports translation of the system to clinical studies.
authors: Department of Biomedical Engineering, Johns Hopkins University, Baltimore, Maryland 21205.
authors: Jennifer
authors: J
authors: Xu
authors: Department of Biomedical Engineering, Johns Hopkins University, Baltimore, Maryland 21205.
authors: Alejandro
authors: A
authors: Sisniega
authors: Department of Biomedical Engineering, Johns Hopkins University, Baltimore, Maryland 21205.
authors: Wojciech
authors: W
authors: Zbijewski
authors: Department of Biomedical Engineering, Johns Hopkins University, Baltimore, Maryland 21205.
authors: Hao
authors: H
authors: Dang
authors: Department of Biomedical Engineering, Johns Hopkins University, Baltimore, Maryland 21205.
authors: J Webster
authors: JW
authors: Stayman
authors: Department of Biomedical Engineering, Johns Hopkins University, Baltimore, Maryland 21205.
authors: Michael
authors: M
authors: Mow
authors: Carestream Health, Rochester, New York 14608.
authors: Xiaohui
authors: X
authors: Wang
authors: Carestream Health, Rochester, New York 14608.
authors: David H
authors: DH
authors: Foos
authors: Department of Neurology, Johns Hopkins University, Baltimore, Maryland 21205.
authors: Vassillis E
authors: VE
authors: Koliatsos
authors: Russell H. Morgan Department of Radiology, Johns Hopkins University, Baltimore, Maryland 21205.
authors: Nafi
authors: N
authors: Aygun
authors: Department of Biomedical Engineering, Johns Hopkins University, Baltimore, Maryland 21205; Russell H. Morgan Department of Radiology, Johns Hopkins University, Baltimore, Maryland 21205; Department of Computer Science, Johns Hopkins University, Baltimore, Maryland 21205; Department of Neurosurgery, Johns Hopkins University, Baltimore, Maryland 21205; and Armstrong Institute for Patient Safety and Quality, Johns Hopkins University, Baltimore, Maryland 21205.
authors: Jeffrey H
authors: JH
authors: Siewerdsen
mesh_terms: D000208:Acute Disease; D054893:Cone-Beam Computed Tomography / Q000379:methods*; D006801:Humans; D021621:Imaging, Three-Dimensional; D020300:Intracranial Hemorrhages / Q000000981:diagnostic imaging*; D019095:Point-of-Care Systems; D011829:Radiation Dosage; D059629:Signal-To-Noise Ratio