Image Reconstruction, Processing, and Display Chapter 11

Part 1: Which of the following statements about the filtering used in reconstruction is correct

filtering is used to reduce noise and preserve signal data in the image

Part 2: Which of the following statements about the filtering used in reconstruction is correct

filtering is used to reduce artifacts created during backprojection

True or False: the frequency domain represents an image as a sum of sine waves

true

Match the following statements with either low pass filter or high pass filter

used to remove high frequency noise such as noise from statistical variation in counts

low pass filter

Match the following statements with either low pass filter or high pass filter

used to remove the blur from the backprojection artifact

high pass filter

Match the following statements with either low pass filter or high pass filter

can create grainy images but preserves detail

high pass filter

Match the following statements with either low pass filter or high pass filter

creates smoother images but image detail may be lost

low pass filter

Which of the following statements about filters is correct

1. the Nyquist frequency is 5.0cycles/pixel

2. the cutoff frequency of a filter is the minimum frequency the filter will pass

3. Nyquist filters have additional parameter called the order of the filter which controls the slope of the curve

none of the above

Which of the following statements are true about iterative reconstruction

1. images reconstructed with iterative reconstruction have less backprojection artifact than those reconstructed with filtered backprojection

2. attenuation correction can be applied during iterative reconstruction

3. owing to long computational times short cut techniques such as ordered subsets expectation maximization are often used in iterative reconstruction

4. successive iterations are performed until the projection views of the estimate closely approximate the original data or until a predefined number of iterations have been completed

all of the above

Part 1: To correct for attenuation effects in SPECT imaging with Tc-99m the correction matrix might be based upon

the transmission from a single photon emission radionuclide source

Part 2: To correct for attenuation effects in SPECT imaging with Tc-99m the correction matrix might be based upon

the known attenuation coefficient for 140keV photons in tissue

Part 3: To correct for attenuation effects in SPECT imaging with Tc-99m the correction matrix might be based upon

transmission from an x-ray beam

True or False: Measured tissue attenuation using transmission sources is generally more accurate than calculation techniques for attenuation correction for the thorax

true

True or False: MIP (maximum intensity projection) images for SPECT and PET are used to accentuate the brightest details in a study

true

Windowing is important in CT imaging because

the rage of pixel values in a CT image is much greater than the 256 level gray scale range available on a computer monitor