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Rollsie
Hi, first post with a simple (ish) question
Dec 9 2011, 1:48 PM EST | Post edited: Dec 9 2011, 1:48 PM EST
Hello, I'm a student and this is my first post! Sorry if it's not very exciting.

I have been considering the clinical consequences of some quality assurance test results. In one test, the tube output was measured against a baseline. at 100kVp and 20mAs the tube's output is 50% lower than the baseline (the baseline was 0.12cGy, FFD 100cm), and this occurs on every test. This may seem like a simple question, but when using this equipment what would the clinical consequences be and how would you guys overcome this problem?

I understand that there will be underexposure and increased skin dose, am I on the right track? I feel rather humbled asking this! lol! Do you find this valuable?    
Gajaal
Gajaal
1. RE: Hi, first post with a simple (ish) question
Mar 23 2012, 10:31 PM EDT | Post edited: Mar 23 2012, 11:51 PM EDT
Great question Rollsie.

This appears to me to be a question of callibration of the Tube and Generator and very much your Chief's responsibility to have the Engineers correct the problem.

The first issue to address is the Half Value Layer. In other words is the nominal Primary Beam keV being achieved, the accurate selection of which is fundamental to correct Technique and good Radiography. I refer to the Optimum kV Technique for achieving the best image of the structures projected.

The "Hardness" of the beam is also influenced by Filtration, both Added and Inherent (ie: fixed at manufacture and governed by the materials used in construction). Some high end X-Ray systems allow the Added Filtration to be changed for different applications and examinations, whether by thickness or combination, (ie: Aluminium, Tin, Copper, Yrrbium etc.) Is the wrong Filter in place? (Yopu might like to read up on K edge absorption.)

The next question, which again will require the Engineer's input, is the callibration of the Tube Output related to Tube Current, and the accuracy of the timer, which in the modern era should in fact be the most accurate component out of kV, mA and Time.

Upshot, and most direct conclusion: Get the Engineer to re-callibrate. All the Department's Irradiating Apparatus should be within a few % of each other in terms of Output and Callibration to HVL.

Regards

Gary Allbutt Do you find this valuable?