ABR Physics Questions And Answers With Complete Solutions

In a 1.5T MRI, if the temperature is 22C, what is the ratio of spins parallel to B₀ to those antiparallel to B₀? correct answer: 1.00001 A 10kg block of ice is at 15⁰F. How much energy must be transferred in order to heat it to a 55⁰F puddle of water? (specific heat of water is 4186 J/kg⁰C, latent heat of water is 334000 J/kg) correct answer: 4.3458×10⁶ J Charged particle equilibrium assumes which of the following: a) All indirectly ionizing particles deposit energy within the medium b) Charged particles leaving the medium are replaced by charged particles entering the medium c) Temperature of the medium fluctuates sinusoidally d) The medium is air correct answer: b Under charged particle equilibrium, which of the following relations is NOT true? a) Dose equals radiative kerma b) Dose equals collisional kerma c) Dose in air is proportional to exposure in air d) Dose equals collisional kerma multiplied by a proportionality constant correct answer: a What is the energy of the electromagnetic radiation used for a 15 T MRI? correct answer: 4.23x10⁻²⁵ J In a doppler ultrasound exam using 5MHz what is the observed frequency if the blood is flowing away at 100 m/s and the observer falls off their chair directly away from the flow of blood at 50 m/s? correct answer: 4.54 MHz Absolute 0 kelvin in farenheit is: a) -460 ⁰F b) -428 ⁰F c) -120 ⁰F d) -273 ⁰F e) 0 ⁰F correct answer: a If a radioactive source has an activity of 2 mCi and a half-life of 5 hours, how many disintegrations per second will be recorded 3 hours later? correct answer: 4.88x10⁷ dps When using a detector to measure the activity of a radioactive source what is the ratio of the measured disintegrations per second at a distance of 1m to that at 20m? a) 400:1 b) 20:1 c) 1:1 d) 1:20 e) 1:400 correct answer: a What is the mean life time for a radioactive isotope with half life of 6 hours?