Quantitative assessment of colorectal cancer tumor vascular parameters by using perfusion CT: influence of tumor region of interest.
OBJECTIVE
To prospectively determine whether position and size of tumor region of interest (ROI) influence estimates of colorectal cancer vascular parameters at computed tomography (CT).


METHODS
After institutional review board approval and informed consent, 25 men and 22 women (mean age, 65.8 years) with colorectal adenocarcinoma underwent 65-second CT perfusion study. Blood volume, blood flow, and permeability-surface area product were determined for 40- or 120-mm(2) circular ROIs placed at the tumor edge and center and around (outlining) visible tumor. ROI analysis was repeated by two observers in different subsets of patients to assess intra- and interobserver variation. Measurements were compared by using analysis of variance; a difference with P = .002 was significant.


RESULTS
Blood volume, blood flow, and permeability-surface area product measurements were substantially higher at the edge than at the center for both 40- and 120-mm(2) ROIs. For 40-mm(2) ROI, means of the three measurements were 6.9 mL/100 g (standard deviation [SD], 1.4), 108.7 mL/100 g per minute (SD, 39.2), and 16.9 mL/100 g per minute (SD, 4.2), respectively, at the edge versus 5.1 mL/100 g (SD, 1.5), 56.3 mL/100 g per minute (SD, 33.1), and 13.9 mL/100 g per minute (SD, 4.6), respectively, at the center. For 120-mm(2) ROI, means of the three measurements were 6.6 mL/100 g (SD, 1.3), 96.7 mL/100 g per minute (SD, 42.5), and 16.3 mL/100 g per minute (SD, 5.6), respectively, at the edge versus 5.1 mL/100 g (SD, 1.4), 58.3 mL/100 g per minute (SD, 32.5), and 13.4 mL/100 g per minute (SD, 4.3) at the center (P < .0001). Measurements varied substantially depending on the ROI size; values for the ROI for outlined tumor were intermediate between those at the tumor edge and center. Inter- and intraobserver agreement was poor for both 40- and 120-mm(2) ROIs.


CONCLUSIONS
Position and size of tumor ROI and observer variation substantially influence ultimate perfusion values. ROI for outlined entire tumor is more reliable for perfusion measurements and more appropriate clinically than use of arbitrarily determined smaller ROIs.
Goh
Vicky
V
Paul Strickland Scanner Centre, Mount Vernon Hospital, Northwood, Middlesex, England.
Halligan
Steve
S
Gharpuray
Anita
A
Wellsted
David
D
Sundin
Josefin
J
Bartram
Clive I
CI
D000230:Adenocarcinoma / Q000098:blood supply / Q000000981:diagnostic imaging* / Q000473:pathology; D000368:Aged; D000704:Analysis of Variance; D001783:Blood Flow Velocity; D001810:Blood Volume; D002199:Capillary Permeability; D015179:Colorectal Neoplasms / Q000098:blood supply / Q000000981:diagnostic imaging* / Q000473:pathology; D003287:Contrast Media / Q000008:administration & dosage; D003974:Diatrizoate Meglumine / Q000008:administration & dosage; D005260:Female; D006801:Humans; D007479:Iopamidol / Q000008:administration & dosage; D008297:Male; D015588:Observer Variation; D011446:Prospective Studies; D011857:Radiographic Image Interpretation, Computer-Assisted; D014057:Tomography, X-Ray Computed / Q000379:methods*
D003287:Contrast Media; D003974:Diatrizoate Meglumine; D007479:Iopamidol