final Flashcards
the initial information leaving a digital image receptor/receiver is a
electrical signal
what factor would produce a digital image with the highest spatial resolution
increased matrix size
in the context of a digital matrix, 1024 x 1024 refers to
the number of pixels in the matrix
T/F: individual pixels in digital imaging are normally invisible to the unaided eye
true
increasing the field-of-view will have what effect on the pixel size ?
increased pixel size
the total number of brightness levels that can be produced by the digital system
bit depth
will a 12-bit system or a 8-bit system have the highest contrast resolution
12 bit system
an 8 bit radiograph system is capable of displaying how many shades of gray?
256 shades
what change will increase the contrast resolution of a imaging system
increased bit depth
quantization is the process through which
detector readings are converted to specific brightness levels
the gray scale of an image is affected by the
bit depth
where does quantization take place during image processing
in the analog-to-digital converter
the smallest signal difference that can be detected and displayed by the imaging system is called
contrast resolution
image signal can be increased with what parameter changes ?
- increasing slice thickness
- decreasing echo time
- increasing repetition time
prescribing a small slice thickness causes
decreased signal to noise ratio
increasing the matrix size has what effect on signal to noise ?
decreased signal to noise
how does decreasing TR affect the SNR of an MRI image
decreased SNR
compared to a 128 x 128 matrix, a 512 x 512 matrix will result in
decreased SNR
image noise can be decreased by which parameter adjustments
- reducing bandwidth
- using surface coils
an MRI image with high spatial resolution was most likely created using which parameter
large matrix size
low signal to noise ratio can be the effect of
large matrix size
increasing the matrix size will result in what?
increased spatial resolution
decreased SNR
an MRI image demonstrating low spatial resolution might be the result of
large pixel size
modifying the imaging parameters to use an increased bandwidth has what effect on the MRI image
decreased SNR
decreasing the matrix size has what effect on SNR
increased SNR
using large slice thickness causes
decreased spatial resolution
concerning SNR, the use of a localized coil has what effect on the image
increased SNR
compared to a 1.5T, a 3T will produce
increased SNR
how does increasing voxel volume affect spatial resolution
decreases spatial resolution
image noise can be decreased by which parameter adjustments
- reducing bandwidth
- using surface coils
the difference in signal intensity compared to the background noise
SNR
the number of bits per pixel available in the system
contrast resolution
low signal to noise ratio can be the effect of
large matrix size
an increased echo time (TE) usually causes
decreased SNR
a decreased echo time (TE) usually causes
increased SNR
the MRI of the breast increases visibility of vascular structures using a process called
maximum intensity projection (MIP)
a scan is performed to evaluate the vascular supply to an acute cerebral infarct. After acquiring pre & post contrast images, what post processing technique can be used to remove non vascular structures from the images
digital subtraction
a radiologist request axial images of a stroke sequence initially acquired in the coronal plane, what post processing technique is necessary to fulfill this request?
multiplanar reconstruction (MPR)
apparent diffusion coefficient (ADC) mapping is derived from what image sequence?
diffusion weighting images (DWI)
what variables can be changed in a mulipalnar reconstruction ?
- slice gap
- slice thickness
- plane orientation
when performing a MIP which of these tissues is most likely to be displayed on the pixel
high signal tissue
