Radiation Physics
Proton therapy’s sharp distal fall-off feature.
What is the Bragg peak?
The imaging method that uses sound waves instead of radiation.
What is ultrasound?
Your body’s largest organ.
What is the skin?
Approximate practical range in water for 12 MeV electrons.
What is ~6 cm (R~E/2)?
Duke University’s mascot.
What is the Blue Devil?
The heavy material in dentist vests that blocks x-rays.
What is lead?
By definition, water has this CT number.
What typical material is 0 HU?
Number of lung lobes on the right and left.
What are 3 on the right and 2 on the left?
From 8 mCi with T_1/2=6 h, activity after 18 h?
What is 1 mCi (three half-lives → 1/8)?
The iconic Gothic landmark at the heart of campus.
What is Duke Chapel?
The three classic ways (factors) to reduce radiation exposure.
What are time, distance, and shielding?
PET scanners detect pairs of photons created when this particle meets an electron.
What is a positron (annihilation)?
Counts of vertebrae in the mobile spine.
What are 7 cervical, 12 thoracic, and 5 lumbar?
In the quantum-limited regime, doubling mAs changes SNR by what factor?
What is sqrt{2} (SNR ∝ √N)?
She and her husband studied radium and polonium and popularized the term “radioactivity.”
Who are Marie and Pierre Curie?
Name the three dominant photon interactions across diagnostic/therapy energies.
What are photoelectric effect, Compton scatter, and pair production?
The three pillars of image quality often traded off in systems design.
What are contrast, spatial resolution, and noise (accept dose as a related constraint)?
The three standard planes used to view medical images.
What are axial (transverse), coronal, and sagittal?
Detector pixel size 0.25 mm. What is the Nyquist frequency?
What is 2 line pairs/mm (1/(2×0.25 mm))?
He discovered x-rays in 1895.
Who is Wilhelm Röntgen?
The narrow-beam attenuation law relating intensity and thickness.
What is I = I_0 *e^−μx?
Raising this x-ray generator setting increases beam quality (HVL) and lowers subject contrast.
What is kVp?
This retroperitoneal organ lies posterior to the stomach and produces digestive enzymes.
What is the pancreas?
This everyday fruit is slightly radioactive thanks to potassium-40.
What is a banana?
He built the first clinical CT scanner (Nobel Prize shared).
Who is Godfrey Hounsfield