Recorded Detail

lucky_yooh07 · Joined: 26 Jan 2009 Posts: 12

We just learned about recorded detail today in class and i was wondering if anyone could explain it to me, or give me some exaples that would be easier for me to understand?
THANKS! Smile

wvaio · Joined: 22 Sep 2007 Posts: 85

Recorded detail is the ability of an IR(Image receptor) to record the information within the patient. While the term is loosely used in many textbooks the real terms are Spatial resolution and Contrast resolution. Both of them together equal recorded detail.

Spatial resolution is the ability of the IR to record pairs of lines. Imagine a screen matrix. Lets say you have a one inch box containing rows and columns. If every square in the matrix has the ability to be black or white then every other square could possess a line. If the boxes are big within the inch box you will have less ability to create pairs of lines.

XOXOXOXOXOXO
XOXOXOXOXOXO
XOXOXOXOXOXO
XOXOXOXOXOXO
XOXOXOXOXOXO

If the squares are samller you can have more pairs of lines.

xoxoxoxoxoxoxoxoxoxoxoxoxoxo
xoxoxoxoxoxoxoxoxoxoxoxoxoxo
xoxoxoxoxoxoxoxoxoxoxoxoxoxo
xoxoxoxoxoxoxoxoxoxoxoxoxoxo
xoxoxoxoxoxoxoxoxoxoxoxoxoxo
xoxoxoxoxoxoxoxoxoxoxoxoxoxo
xoxoxoxoxoxoxoxoxoxoxoxoxoxo
xoxoxoxoxoxoxoxoxoxoxoxoxoxo
xoxoxoxoxoxoxoxoxoxoxoxoxoxo
xoxoxoxoxoxoxoxoxoxoxoxoxoxo

Like when you zoom in on a digital photo. At some point the pixels are so large that you can't tell what the picture is.

Contrast resolution is the ability of the IR to record different shades of gray in each square.

If each square could only record 2 colors black and white the contrast between them would very high. If each square were able to record 10 different shades of whites, grays, and black, you could draw a much more detailed picture. Like shading with a pencil on a white sheet of paper. The more you draw on the paper the darker it gets. So the more shades of gray you produce, the better the image looks.

I'm not sure how far you are into the subject so this may be all you need for now. If not, here's the rest...

***takes a deep breath***

There are 7 technical factors that affect recorded detail.
1.Object to image distance(OID)-
2.Source to object distance-(SID)
3.Focal spot size-
4. Film screen combinations-
5. Patient motion
6.Patient factors(size, pathology, and etc.)
7.Angles(tube, part or IR)

The divergence of the beam is responsible for 1 and 2. The shorter the OID the greater the resolution because the further the information has to travel the bigger it gets by beam divergence. The longer the SID the less magnification because the center of the Xray beam has less divergence the outer edges of the collimator. When you increase your SID you will collimate to only use the less divergent rays.

No information can be recorded that is smaller than the effective focal spot. Its kinda like a pencil, it can't make a like smaller than the point of the pencil.

Differences in film-screen combinations can have an effect on resolution because of the size of the crystals in the screen and the H&D curve of the film. On digital images you have the earlier described situation. The spatial resolution of a film-screen combination is controlled by the SCREEN not the film. The phosphors in the screen are bigger than those in the film therefore like the pencil the size of what is making the image controls the smallest possible mark.

Motion will alter the resolution also because it will cause an image that does not diagnostically represent the actual patient.

Patients factors affect the resolution because of patient size( larger =more OID), pathology(metal will obscure anything that is above or below it.), and etc.

Finally, angling the tube, the part, or the receptor can cause the image to not correctly record the information of the patient. They can cause magnification, shape distortion, and size distortion.

I think that should just about cover it. Hope that helps you. If you have any more questions feel free to ask.

wvaio

hjhogle · Posted: Tue Feb 03, 2009 8:13 pm Post subject:

Wow.

I'm saving this one.

hjh, RT

wvaio · Joined: 22 Sep 2007 Posts: 85

I had the best teacher in the world for image production and evaluation I and II, physics, and etc.. She drilled that information into our heads backwards and forwards. Doubt I will ever forget it. Thanks Dr. Cheryl Burtle D.O., Fenton, MO.

wvaio Very Happy

lucky_yooh07 · Joined: 26 Jan 2009 Posts: 12

Yeah WOW! Thats alot to take in at once but it breaks it down for me so thanks alot! My teacher talks about 783495279034275 words a minute and i have trouble with the class because of that! But thanks for your little tutorial, it is much appreciated! Very Happy

papa · Posted: Fri Feb 06, 2009 12:38 pm Post subject:

ok, so what if i wanted to be the only person to post like this?

wvaio, you are on your way to being a wonderful technologist.
_________________
Mr. Green

papa RT(R)(CT) Mr. Green

Delusional Radiology
never meddle in the affairs of a dragon, for you are crunchy, and taste good with ketchup