Target Volume Determination 2015

Stejskal-Tanner sequence

Three principal axes

Second gradient: Rephasing Moving protons

www.wikipedia.de

The B-value • Expresses strength and duration of gradient field • Low B-values: – B = 0: T2-weighted image – B = 50 - 400 » Signal loss in fast moving protons (perfusion) • High B-values – B > 400 » Signal loss in slowly moving protons (diffusion)

The ADC • ADC = apparent diffusion coefficient • Slope of straight line connecting two values obtained with different B-values

Calculation of the ADC

90

67,5

Low b-value

High b-value

45

Calculation of signal loss/pixel

Signal intensity 0 22,5

(

) 3 λ + +

λ

λ

= ADC

1

2

ADC image

3

50

800

B-value