title: Evaluation of the potential utility of flat panel CT for quantifying relative contrast enhancement.
abstract: OBJECTIVE
  Certain directed oncologic therapies seek to take advantage of the fact that tumors are typically more susceptible to directed therapeutic agents than normal tissue owing to their extensive networks of poorly formed, leaky vasculature. If differences between the vascularity of normal and tumor tissues could be quantified, patients could be selected for or excluded from directed treatments on the basis of this difference. However, angiographic imaging techniques such as digital subtraction angiography (DSA) yield two-dimensional data that may be inadequate for this task. As a first step, the authors evaluated the feasibility of using a commercial implementation of flat panel computed tomography (FPCT) to quantify differences in enhancement of a simulated tumor compared with normal tissue based on differences in CT number measured in precontrast and postcontrast scans.
  
  
  METHODS
  To evaluate the FPCT scanner studied, the authors scanned several phantoms containing simulated normal and tumor tissues. In the first experiment, the authors used an anthropomorphic phantom containing inclusions representing normal, tumor, and bone tissue to evaluate the constancy of CT numbers in scans repeated at clinically relevant intervals of 1 and 3 min. The authors then scanned gelatin phantoms containing dilutions of iodinated contrast to evaluate the accuracy of relative contrast enhancement measurements for a clinical FPCT system. Data were analyzed using widely available software.
  
  
  RESULTS
  CT numbers measured in identical locations were constant over both scan intervals evaluated. Measured relative contrast enhancement values were accurate compared with known relative contrast enhancement values. Care must be taken to avoid artifacts in reconstructed images when placing regions of interest.
  
  
  CONCLUSIONS
  Despite its limitations, FPCT in the interventional laboratory can be used to quantify relative contrast enhancement in phantoms. This is accomplished by measuring CT number in simulated tumor and normal tissue on precontrast and postcontrast scans. This information opens the door for refinement of technique in an effort to use such a technique to plan directed therapies.
authors: Department of Imaging Physics, University of Texas MD Anderson Cancer Center, Houston, TX 77030, USA. kyle.jones@mdanderson.org
authors: A Kyle
authors: AK
authors: Jones
authors: Armeen
authors: A
authors: Mahvash
mesh_terms: D003287:Contrast Media; D005240:Feasibility Studies; D006801:Humans; D019047:Phantoms, Imaging; D011856:Radiographic Image Enhancement / Q000295:instrumentation* / Q000379:methods; D011857:Radiographic Image Interpretation, Computer-Assisted / Q000295:instrumentation* / Q000379:methods*; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity; D014057:Tomography, X-Ray Computed / Q000295:instrumentation* / Q000379:methods*; D014963:X-Ray Intensifying Screens
chemical_list: D003287:Contrast Media