x Turn on thread page Beta
 You are Here: Home >< Physics

# X-ray tube output math questions watch

1. 1. The problem statement, all variables and given/known data
(The question is in the image attached)

(c) An X-ray unit in the cardiac catheter labs has an output of 80µGy/mAs at 1 meter when the unit is set at 100 kVp. After adding 0.3mm Cu to the beam the photon intensity is reduced to a quarter and tends to vary in proportion to kV3 (i.e. kV to the power of 3). What would be the output rate at 80cm from the tube focus for a
continuous beam at 80 kV p and 5 mA ?
(d) The same unit as in c) is now used for an acquisition run. The protocol uses 15 frames per second with a 10ms pulse width at 100kV without the copper filtration and a 20 x 20cm square field. The detector distance is 1m from the tube. If the measured output rate at 1m is 900 µGy/s what is the peak tube current of each pulse? What DAP reading in cGycm2 would be measured in 10 seconds of acquisition?

2. The attempt at a solution
(c) 80 μG/mAs
(Working: 20 * (1/0.8)2 * (80/100)3 * 5)

(d)
Current = 75 mA
(Working: I need an mA of 11.25 per second but as the machine is only on for 0.15 seconds I need 11.25 * 1/0.15 = 75)

Thank you

TSR Support Team

We have a brilliant team of more than 60 Support Team members looking after discussions on The Student Room, helping to make it a fun, safe and useful place to hang out.

This forum is supported by:
Updated: April 29, 2016
Today on TSR

### Four things top students are doing

Over the Easter break

### Her parents made her dump me

Poll

The Student Room, Get Revising and Marked by Teachers are trading names of The Student Room Group Ltd.

Register Number: 04666380 (England and Wales), VAT No. 806 8067 22 Registered Office: International House, Queens Road, Brighton, BN1 3XE