MEDRADSC 3K03 Lecture Notes - Lecture 7: Mediastinum, Grayscale, Wwwl

• School: McMaster University
• Department: Medical Radiation Sciences
• Course: MEDRADSC 3K03
• Professor: Lyndsay Simmons

Document Summary

Ct numbers: calculation of ct numbers*, each pixel is assigned a ct number which corresponds to a brightness value/signal intensity, each ct# is assigned a corresponding grayscale range. In an acquired ct image, the ct number of the muscle was measured to be 53. What is the lac for this tissue given an lac at the beam energy of 0. 280. Why use a high kvp technique: 120 to 140 kvp, more common practice to manipulate the mas, rather than the kvp, when modifying the radiation dose. Why: choice of ma is more flexible, with available settings typically ranging from 20-800 ma. Question: earlier in table 4-1 we saw that the head has a different window width and level for the posterior fossa (150/40) vs the brain (100/30). Why: different densities in the bone, beam hardening: low energy photons get absorbed, we get a lot of artifact due to this, open windows in postfossa so we can clean up the artifact.