View Full Version : radiation exposure

06-09-2006, 03:31 AM
Thought this was quiet interesting, specially as it quantifies the difference in radiation exposure between conventional and digital imaging

Prospective randomized comparison of radiation exposure from full spine radiographs obtained in three different techniques
Torsten Kluba1 , Jürgen Schäfer2, Tobias Hahnfeldt1 and Thomas Niemeyer1

(1) University Tübingen, Department of Orthopaedics, Tübingen, Germany
(2) University Tübingen, Department of Radiology, Tübingen, Germany
(3) , ,

Received: 15 February 2005 Revised: 18 May 2005 Accepted: 8 July 2005 Published online: 22 April 2006

Abstract Problem: The purpose of the investigation was a comparison of two different digital X-ray techniques with conventional standing full spine films. Evaluation of dose area product, image quality and inter-observer error of Cobb-angle measurement in patients with scoliosis and kyphoscoliosis were studied.
Methods: A consecutive series of 150 patients were prospectively randomized into three groups. Patients in group 1 (n=53) received a conventional standing postero-anterior full spine radiograph. All films were evaluated on the light box. Patients in group 2 (n=48) received a X-ray using the digital storage phosphor plate system (CR). For group 3 (n=49) digital pulsed fluoroscopy was used. In groups 2 and 3 images were exported to a picture archiving and communicating system (PACS) workstation and viewed on a monitor (Siemens SMM 21140P, Germany). Dose area product measurements were performed in all three groups (Diamentor-M, PTW, Freiburg). Three experienced investigators independently reviewed all pictures. Pedicles and endplates were counted. Cobb-angles of the main curves were measured.

Results: The mean dose area product was 97.0 cGy cm⊃ (37.0–380.0 cGy cm⊃) for conventional films, 31.5 cGy cm⊃ (6.0–66.0 cGy cm⊃) for CR imaging and 5.0 cGy cm⊃ (1.0–29.0 cGy cm⊃) for digital fluoroscopy.

The differences of Cobb-angle measurements were not significantly different for the three methods. Differences in the count of pedicles and endplates between the investigators were significantly lower for the conventional film as an indicator for the best detail presentation.

Conclusion: A significant reduction in dose area product is possible with modern digital X-ray methods. The inter-observer error of Cobb-angle measurement is not significantly altered. The detail information is decreased in comparison to conventional films.

06-09-2006, 10:15 AM
I wonder why there is such a spread, for instance on CR imaging (digital) it ranges from 6.0 - 66.0 cGy cm with an average of 31.5 cGy cm ? Does anyone know ?

06-09-2006, 10:45 AM
i never noticed that spread, that is quite a large variation, somehow must have to do with "thickness" of the subject, i.e higher radiation doses must be used for more obese patients, as there is more tissue to travel through, cannot think of another reason.

06-15-2006, 07:17 PM
While on the subject of x-rays; can anyone tell me the correct way to position the patient who has a leg length difference? Megan

09-04-2006, 10:02 PM
where do I go to check my private messages?

09-05-2006, 12:16 AM

I don't know the answer to that, but you should try to verify that she actually has a leg length discrepancy. Most discrepancies are misdiagnosed. The only way to know for sure is to have special xrays taken of her legs.


11-12-2008, 08:08 PM
i never noticed that spread, that is quite a large variation, somehow must have to do with "thickness" of the subject, i.e higher radiation doses must be used for more obese patients, as there is more tissue to travel through, cannot think of another reason.

Thicker pts do require a bit higher technique then others, you're right. Those who are quite muscular and/or have an 'additive' pathology may require it too.

The reason why digital lowers dose is because within the bucky board, there are sensors (AEC). They are designed to terminate the xrays when a set amount of radiation has been reached.
With digital there is also post-processing abilities which eliminates the need for repeats (thus cutting down dose as well). For example if an image is too light or dark, the contrast/brightness can be adjusted; if a marker can't be seen, one can be annotated on etc etc

Hope this helps clear it up a bit?! ;):)

~**~ Congenital Scoliosis w associated radial clubhand/thumb aplasia ~**~
*~2 Harrington rods + fusion in 1985 (age 10) by Dr.W Bobechko, Toronto~*
:):) 23 yrs post op...have 3 kids, training to be MRT, next to nil pain! :):)

05-18-2009, 07:35 PM
That is interesting, there are even x-ray like machines that use a light and do not expose the paitent to any radiation, but they are not too commonly used yet.
The radiologist sometimes uses the lead cover ups but not always, I'm not sure why? I've had around 36 X-rays and only got the lead cover ups for like 8.

Megan- About the Leg Length X-rays, They had me lie down on a table and they positioned me right by the rulers taped to the table and took the X-ray. I'm pretty sure that is how all LLD X-rays are done.