Question

4285HU

(a) CT = 571.4285HU, X – Ray = 2.304HU

(b) CT = 2.304HU, ΔX-Ray  = 2.304

(c) CT = 2.304HU, X – Ray = 571.4285HU

The question was posed to me in exam.

This intriguing question originated from Computerized Axial Tomography topic in division Diagnostic Investigation via Imaging Techniques of Clinical Science

Answer 1

The correct option is (b) CT = 2.304HU, ΔX-Ray  = 2.304

Easy explanation: To solve the above,

For CT

 ΔCT = l1 – l2

     = 63 – 35

     = 28

HU for CT = (l1 – l2)X 1000/(l1 + l2)/2

                  = (63 – 35)X 1000/(63 + 35)/2

                  = 571.4285HU

For X – Ray

ΔX-Ray = Σl1 – Σl2

              = 1738 – 1734

              = 4

HU for X – Ray  = (Σl1 – Σl2)X1000/(Σl1 + Σl2)/2

= (1738 – 1734)X1000/(1738 + 1734)/2

              = 2.304HU.