ABR Part I

Today I took Part I of the ABR exam. Here are some trends I noticed:

General PHYS Section

• broken into two parts, simple (1 point) and complex (3 points)
• problems 1-52 are simple
• 53-80 are complex
• next time I'll start at problem 53 and do all the complex ones as they are weighted more and take longer, then with the remaining time I'll breeze through the simple ones

Simple Section

• rough trends and estimates based on my own personal record keeping and statistical analysis
• about 14% of the problems were based on the category of interactions
• about 13% were based on the category of imaging characteristics and parameters
• MTF
• subject contrast
• etc...
• one problem on geometric efficiency of a detector
• about 8% on basics of radioactivity, decay, etc...
• about 5% on shielding/ radiation protection
• about 3-5 questions on ultrasound
• about 3-5 questions on radiation biology

Clinical Section

• goes very quickly
• very heavy on radiological anatomy and biology
• about 39% radiation biology
• about 33% basic anatomy/physiology
• about 15% diag rad phys
• about 10% radiological images asking you to identify anatomy

W-value, or (W/e) value

Johns and Cunningham helped me understand this concept of W-value better than any other book or professor so far. They simply state that:

[W]e know that to produce 1 coulomb of charge by the ionization of air requires an energy absorption of 33.85 joules. 

There you go. You have a little pocket of air. An x-ray passes by and excites it, transferring 33.85 Joules of energy to it and poof! You have created 1 Coulomb of charge in that little pocket of air. If you have an electrometer nearby you can detect it.

See Johns and Cunningham (1983), The Physics of Radiology, 4th edition, p. 235.