The interesting thing about the radiography profession is that 75% of qualified practitioners don't understand the geometry of projections. They assume that changing the tube angle will also change the geometry of what is shown. This is not the case because tube angulation does not change the position of the focus, only the angle of the tube and the centring point. Here is my video on the subject. th-cam.com/video/QRT7wpOZmko/w-d-xo.html One of the crimes in the history of radiography was The Townes Projection which required needless dose to the face if the directions were followed, whereas a slight reduction in angle would cause collimation to the brow line.
There is an additional important consideration when doing dental radiography. When doing skull imaging, the source-receptor distance is typically 100 cm. In contrast, the source-object distance is typically 8 inches to 12 inches, and very infrequently, 16-inches. This distance is set by the length of the extension collimator used by the manufacturer and model of the x-ray unit. The collimator may be round (no more than 7cm diameter) or rectangular (approximately 3.5 cm x 4.5 cm). At this short distance, achieving beam parallelism is challenging and angulation of the beam will cause distortion. Practically, this is demonstrated when improper angulation results in foreshortening or elongation of the tooth and can impact management decisions.
@@sanjaymallya4667 I spent a few months doing dental radiography but 3 years of orthodontic work. I claim to have taken 10,000 OPGs and 8,000 lat ceph. I am retired now.
Nice! Lateral ceph are standardized projections with a 5 foot source-to-midsagittal plane distance. Panoramic images are formed differently than standard projection imaging. The speed of the receptor across the collimator influences horizontal distortion. m.th-cam.com/video/5uRBGRh47lY/w-d-xo.html Thanks for your comments and hope you are enjoying retirement!
@@sanjaymallya4667 Thanks. I am. I look at all tutor TH-cam and critique what they do. The population dose seems to be about 30% higher than required though digital technology prevents radiographers from opening the collimation beyond what is required. When I did my lat cephs for orthodontists, using a Siemens machine, I added lead rubber masking to the tube to ensure the thyroid didn't get primary beam.
Amazing video sir!
sir u explained so nicely. thank you so much.
Very interesting 👌
thank you for your video
The interesting thing about the radiography profession is that 75% of qualified practitioners don't understand the geometry of projections. They assume that changing the tube angle will also change the geometry of what is shown. This is not the case because tube angulation does not change the position of the focus, only the angle of the tube and the centring point. Here is my video on the subject. th-cam.com/video/QRT7wpOZmko/w-d-xo.html One of the crimes in the history of radiography was The Townes Projection which required needless dose to the face if the directions were followed, whereas a slight reduction in angle would cause collimation to the brow line.
There is an additional important consideration when doing dental radiography. When doing skull imaging, the source-receptor distance is typically 100 cm. In contrast, the source-object distance is typically 8 inches to 12 inches, and very infrequently, 16-inches. This distance is set by the length of the extension collimator used by the manufacturer and model of the x-ray unit. The collimator may be round (no more than 7cm diameter) or rectangular (approximately 3.5 cm x 4.5 cm). At this short distance, achieving beam parallelism is challenging and angulation of the beam will cause distortion. Practically, this is demonstrated when improper angulation results in foreshortening or elongation of the tooth and can impact management decisions.
@@sanjaymallya4667 I spent a few months doing dental radiography but 3 years of orthodontic work. I claim to have taken 10,000 OPGs and 8,000 lat ceph. I am retired now.
Nice! Lateral ceph are standardized projections with a 5 foot source-to-midsagittal plane distance. Panoramic images are formed differently than standard projection imaging. The speed of the receptor across the collimator influences horizontal distortion. m.th-cam.com/video/5uRBGRh47lY/w-d-xo.html
Thanks for your comments and hope you are enjoying retirement!
@@sanjaymallya4667 Thanks. I am. I look at all tutor TH-cam and critique what they do. The population dose seems to be about 30% higher than required though digital technology prevents radiographers from opening the collimation beyond what is required.
When I did my lat cephs for orthodontists, using a Siemens machine, I added lead rubber masking to the tube to ensure the thyroid didn't get primary beam.