Why does the Computed Tomography Dose Index increase with a smaller slice thickness?
470784
Because the number of slices increases while still maintaining the same coverage amount, CTDI increases.  \ne.g.) You want to scan an area of 20cm (200mm).  You decrease the slice thickness from 10mm to 5mm.  You need 40 slices instead 20, thus, increasing the dose.
130567
i think that long-time exposer to X-rays is very bad for you. i think that when a cell is struck by an X-ray it is damaged, hence the lead aprons when you get an X-ray. i think that it would hurt people that get alot of expoture to the X-rays, such as frequent flyers and aiport workers
572843
focal lenth will definitely increase. because refractive index will decrease
577466
it states that intensity of x rays at a point is inversely proportional to the square of distance of the point from the source
761199
Although there is a general trend toward an increase in the first ionization energy as we go from left to right across this row, there are two minor inversions in this pattern. The first ionization energy of boron is smaller than beryllium, and the first ionization energy of oxygen is smaller than nitrogen.\n\nTo read about why, follow the link. It's really hard to explain
36159
As mechanical engineer this is out of my normal field but felt you deserved an answer of some sort.\n\n"Because of diffraction effects caused by slits or apertures in optical measurement systems, the radiation energy which is directed towards a particular region on a sample will be spread over a larger area than desirable. By employing an apodizing filter in the radiation path in such system, diffraction tails of the system will be reduced. The apodizing filter preferably has a pattern of alternating high transmittance areas and substantially opaque areas where the locally averaged transmittance function is an apodizing function. In the preferred embodiment, the locally averaged transmittance function varies smoothly and monotonically from the periphery to the center of the filter"\n\nI see the theory here, also found on on using an apodizing mirror to stabalise images in a telescope\n\n"I built and used an apodizing screen for my 6" f/8 scope many years \nago. I made it by layering several layers of window screen, each one \nwith a circular cutout of different diameter. The result was an aperture \nmask with a step-wise approximation to a smooth apodizing function. It \nwas claimed to improve contrast for planetary viewing. Anyway, my \nexperience was that it seemed to make the image more stable but if it \nimproved contrast, I couldn't see it. If you do this on-axis, the \ndownside is that your diagonal mirror will now become more of a factor \nin the contrast equation. The bottom line is I wouldn't recommend it."\n\nAlso "An excellent reference for all sorts of technical techniques is\n>"Procedures in Experimental Physics" (also printed under the title\n>"Physical Laboratory Practice") by John Strong.  I don't recall the\n>publisher, but it came out in the 30's.  The bad news it that it's been\n>out of print for decades (and some SOB stole the copy I got from my\n>father!); the good news is that an outfit called Lindsay is reprinting it\n>in paperback.  (Don't have their name/address here in the office; I'll try\n>to remember to look it up tonight.)\n>\n>                            Dr. Kurt Hillig\n\nEvery ATM should have a copy of this great book. Lots of stuff on\nmirror making, figuring, special laps,making flats, prism ,etc.\nThere is nice modifed Draper machine ( upper disk also powered)\nand a homemade diamond cutting wheel to cut small glass blocks.\n( I would like to build this one someday ) A great section on\nkinematical mechanical construction. Yeah this a mid 30,s book but the \ninfo\nstill can be used. No I don't work for Lindsay Publications,<G>\n\nBob Pfaff\n\n\n This book, in paperback form, can be ordered from\n      http://www.amazon.com, on the Web. It can also be ordered\n      through your local bookstore. Amazon prices it at $23.95, and\n      provides the following information:\n\n      Published by Lindsey Publications\n      Publication date: June 1986\n      ISBN: 0917914562"\n\nSorry couldn't find any really decent expplanations, but at least you've got a starting point.
926622
The CT will only work on an AC circuit so I don't see where it would make any difference.  The only thing that would is to have another phase too close and the magnetic fields might cancel each other. Since the current being measured is AC the output from the CT will also be AC and shouldn't matter on the leads.
575484
A ct system doesn't generate enough radiation to change the water.  And yes, it is safe to drink.  I would make kool-aid, set up a stand and safely sell it to neighborhood school children!
943704
Increases it.  I assume you are talking common emitter configuration.
626305
Because you can read/see something better through a smaller hole. It's just like making a small circle with your index finger and thumb, if you look through it you can see a lot better!
1097585
I am a registered radiologic technologist and a registered/certified nuclear medicine tech.  I'm not exactly sure about what tools you're talking about?  For regular x-ray there is the tube; the part that looks like a camera.  Inside of the tube is a high voltage circuit that shoots electrons from a cathode to a rotating anode made of tungsten.  Due to the principles of cascading electrons in the electron shells of the tungsten, x-rays are produced. The other part is the film or receiving screen, this is always put behind the anatomy that the radiographer is evaluating.  Once the tube shoots the x-ray, the varying densities in the tissue allow different amounts of rays through to the film. This is the reason on x-ray images that bone shows up the lightest, bone is most dense, thus it allows the least rays through.  Barium, which is used in digestive tract imagine has a high density, so it can highlight anatomy when you drink it.  Lead is used to block any radiosensitive anatomy not included in the image such as gonads, thyroid, eyes, etc..
929935
variations matter greatly in interpreting data.  Something might seem like it is returning significantly different results than the control but stat evaluation may show that the variations are minimal at best
946504
Intensity varies as the square of the distance.\nThat should help
935799
because the ct scan can create 3 dimensional rotating images of structural components.  So if the person was say, laying face down, they would still have an image of the front side because the mechanism rotates taking in information from all perspectives and computers can then even generate that into a full 3 dimensional image. a good source is always wikipedia and heres a direct link to ct scans   \n\nhttp://en.wikipedia.org/wiki/Computed_axial_tomography
159581
There is a simple answer and a much longer, more complicated answer.\n\nThe simple answer is that the T1 and T2 spins show different tissues more clearly.  On T2-weighted images, water is very bright.  On T1-weighted images, fat is very bright.\n\nI won't go into the physics of WHY that is.  It's not that important, except to us who get excited about it.  ;)
281380
kVp (kilovoltage peak) is the measure of the quality of the x-ray photon.\n\nIt determines if the photon will be absorbed into the patient or pass through them and hit the x-ray film.\n\nThe higher the kVp the darker the film and generally the higher the kVp the safer it is for the patient because most of the radiation is passing through the patient instead of being absorbed.
617836
To answer this question, you will need to consult with your doctor.  A radiologist will have to review the CT scan with you doctor in order to determine the significance of the irregular density in the lower poles of your kidneys. You may require an additional CT scan with contrast or and MRI with contrast to determine what these densities are.\n\nA 'renal scan' will not be helpful in this case.  This is a 'functional' test and measures the ability of the kidneys to excrete (pass) a nuclear 'dye'.  It can be used to compare function between your kidney and is often used as a test to help determine a condition where there is decreased blood flow to one of the kidneys (a condition called renal artery stenosis).\n\nIt is important to make sure that these densities are a normal variant and not something that you have to worry about (for example kidney cancer).  Given that they are in the same location and on both sides I would think that this is highly unlikely, but this is always important to determine.  Suggested further testing, if needed, is usually part of a CT report, but I would make sure that these densities are benign.\n\nUnfortunately, you are complaining of pain.  Irregular densities, solitary cysts, and even cancers rarely cause pain.  Medical testing is designed to eliminate (rule out) causes of diseases that are harmful and usually does a good job of this.  However, the absence of any findings on the CT  to explain the pain you are experiencing does not mean that the cause of the pain can't be determined or that the pain can't be treated.  There are many causes of back pain/kidney pain that are not picked up by a CT.\n\nPlease follow up with your doctor and make sure he or she is answering your questions.  Best of luck.