To get things in perspective, not having an x-ray equates to you being exposed to 1 days background radiation.
1 chest x-ray equates to 3 days backround radiation.
Lumbar spine aprox 5 months backround radiation.
CT (Abdomen) aprox 4.5 years.
Which is why we are unkeen to send patients for x-ray unless the benfits outweigh the risks.
Bottom line, if your back aches, and your quack rules out "red flags," take up swimming and avoid hospitals.
Depending on who you belive, CT scans spark off about 1 cancer in every 2000 performed, and medical x-rays cause about 200 cancer deaths per year (UK).
Making the Best Use of a Department of Clinical Radiology , bit dated, but usfull.