instrumentation exam 2

what would the approximate pixel size be if your camera FOV was 70cm x 40cm and you were acquiring the image on 64x64 matrix?

10.9mm

If the camera diameter is 500 mm and the camera special resolution is 4mm, what matrix size would be most effective if enough counts were collected?

256x256 (formula)

If you are imaging a patient using I-131, how thick should the crystal be?

3/8-1/2 inch

how many bytes of memory would be required for a study that was collected for 120 images on 128x128 matrix in word mode?

3932160

what is the minimum matrix length in pixels that can be used for a whole-body scan imaging

512

I word mode, if you are acquiring 60 one-sec images of a kidney perfusion study, what matrix would you use?

64x64

In what substance is the gamma camera crystal housed?

Al

having a larger diameter PMT will improve the spatial resolution of a camera

FALSE

the longer the collimator holes in a parallel hole collimator, the greater the collimator sensitivity

FALSE

the organ of interest being imaged must always be centered when using a parallel hole collimator

FALSE

lower energy parallel hole collimator need, thicker septa between the hole than higher energy collimator

FALSE (is the other way around)

the images from a MUGA study are collected from wave to wave

R:R

In order to have the computer generate a tome activity curve, you must 1st draw __ over that you want to study

ROIs

Circular PMT's increase the dead space between th PMTs for getting light from the crystal to the PMTs

TRUE

humans are not able to visualize below 5% variation in count densities in a image

TRUE

the best spatial resolution for a parallel diverging and converging multi-hole collimator is best at the surface of those collimator

TRUE

the more holes a parallel hole collimator has, the better the collimator spatial resolution

TRUE

which signal is used to normalize the position signal of the events recorded?

Z

which pulse is analyzed by the detector and either accepted or rejected during energy determination

Z pulse

how os the spatial resolution of a scintillation camera semi-quantitively measured?

by imaging a bar pattern

___ occurs when a high count pixel counts is selected and counts in the pixels are increased

count addition

___ occurs when counts in each pixel in the image matrix are compared and lowest count pixel is used as a reference and the counts in the higher counts pixel are lowered

counts skimming

activity when doing planar imaging, cannot be resolved in the ___ dimension

dept

which mode would allow you to reformat a flow study by shortening the acquisition times of the individual frames that might have been collected over too long of time intervals?

list **

The ____ method of assigning a gray scale to the pixel display suppresses the number of gray scales assigned to the high count pixels while increasing the number of shades of gray to the lower count pixels

logarithmic

statistical variation in the number of counts in the pixel that create the image is called?

noise

___ is used in BKG subtraction when BKG ROI draw is smaller than the ROI draw around the organ of interest..

normalization

in order to maintain uniformity in a camera display when imaging a uniform source of radioactivity, the ___ mist be centered in the window

photo peak

when imaging a lady with large breast the upper portion of her liver image may have false low counts due to

photon attenuation

this method of increasing the cameras sensitivity includes stopping the signal collection at the PMT anode after most of the scintillation photons have been registered

pulse clipping

when using byte mode, after 255 counts are accumulated in a pixel 3 things could occur. which one will not occur?

regions of interest are generated by the camera computer to reduce the count collection

___ is the camera ability to stop gamma rays and collect counts

sensitivity

the ticker the crystal the better the camera

sensitivity

___ correction is done by creating a linearity correction map by imaging micrometrical precise linear phantoms and measuring the amount of displacement to produce straight lines in the images (a correction matrix is stored)

spatial distortion

non-uniformity in the camera display mostly comes from___

spatial distortion and energy variation

the thinner the crystal the better the camera

spatial resolution

the main loss of contrast in planar nuclear medicine imaging is due to

superimposed activity

___is used with dynamic (perfusion) image sets; weighted averaging occurs by looking at the frame before and after the frame to be altered, and the frame being smoothed is giving twice the weight

temporal smoothing

___ allows for only the PMTs in the immediate vicinity of the event to contribute to the position location

thresholding

an example of an organ that is imaged using digital zoom to improve the spatial resolution of the organs images is (are) the____

thyroid

when using a pinhole collimator, the smaller the pinhole, the better the collimators spatial resolution

true