Posted: Wed Feb 08, 2006 4:21 am Post subject: calulations
Please help me I just can't seem to understand magification and the 15% rule not even the screen changes whats wrong with me is there a book out there that can break it down to me thank you forever you can help me with
rufus1900
Joined: 28 Feb 2007 Posts: 8 Location: sarasota,fl
Posted: Fri Mar 02, 2007 10:16 pm Post subject: Re: calulations
bakerlady1@msn.com wrote:
Please help me I just can't seem to understand magification and the 15% rule not even the screen changes whats wrong with me is there a book out there that can break it down to me thank you forever you can help me with
Hi I hope this doesn't come too late...ok :
1)-magnification of an object occurs either at short SIDs or long OIDs. I understood it in class because our teacher brought a flash light to explain the concept. Turn the lights of and the flash light on and put your hand against a wall and the flash light against your hand. Than move the flash light either furter away or closer to your hand to understand the SID concept. To understand the OID keep the flash light at a set point and keep moving your hand either closer or further away from the wall. Same thing that happends with the shadow of your hand on the wall happends with any object that is between the tube and image receptor.
2)- the 15% rule reffers to the kVp increaseing mAs by 50% because when you increase your Voltage by 15% what happends in the tube is that more x-ray photons are produced (50% more). Basicaly the electrons on the filament are flying over at higher speeds because the potential difference between filament and anode is increased with the increase in Voltage.
Hope this helps and is not too late
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