Questions and Answers
What is the primary purpose of the filter in an x-ray tube used in CT imaging?
To shape the x-ray beam
What type of image looks very different from non-attenuation corrected images in PET?
Attenuation corrected image
What are the approximate CT number ranges for air, soft tissue, and bone?
Air: -1000, Soft tissue: -200 - +200, Bone: +300 - +1000
What is the biggest contributor to dead time in PET/CT imaging?
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What does pitch change the amount of radiation a patient is exposed to in CT imaging?
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What uses a 2D projection to make a 3D image in nuclear medicine imaging?
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What is the purpose of detecting annihilation photons in coincidence imaging?
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What happens to the annihilation photons if they are not determined to be in coincidence during a PET scan?
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Which radionuclide is NOT cyclotron produced and is used for Myocardial perfusion imaging?
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What is the energy of the annihilation photons emitted from positron-emitting radionuclides?
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What is the role of the Pulse Height Analyzer in coincidence imaging?
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Why is it necessary for the annihilation photons to be detected by both detectors on each side during coincidence imaging?
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What component is used in 2D PET imaging to absorb cross plane annihilation photons and improve image quality?
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In PET imaging, what is the purpose of time of flight (TOF) technology?
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What is the main advantage of MRI over CT in terms of imaging?
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What type of x-rays are selectively removed by the filter in an x-ray tube used in CT imaging?
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What does pitch change the amount of radiation a patient is exposed to in CT imaging?
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What refers to the ability of an imaging system to detect and accurately measure the gamma rays emitted by radioactive tracers administered to a patient?
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What is the purpose of time of flight (TOF) technology in PET imaging?
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What distinguishes 2D PET imaging from 3D PET imaging in terms of sensitivity to random and scatter coincidences?
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What component is used in 2D PET imaging to absorb cross plane annihilation photons and improve image quality?
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How are randoms corrected in PET imaging using the delayed coincidence sinogram method?
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What is the main purpose of a sinogram in PET imaging?
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What characteristic contributes to noise in PET images from a per-voxel viewpoint?
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What is the essential requirement for the detection of annihilation photons in coincidence imaging?
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What happens to the annihilation photons if they are not determined to be in coincidence during a PET scan?
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What is the main limitation of annihilation photon imaging in PET?
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What is the range of units of attenuation in a CT study, expressed relative to the attenuation of water?
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What are the approximate CT number ranges for air, soft tissue, and bone?
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What does the term 'scatter incidents' refer to in nuclear medicine imaging?
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What is the main purpose of shimming coils in an MRI scanner?
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What refers to the ability of an imaging system to detect and accurately measure the gamma rays emitted by radioactive tracers administered to a patient?
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How does pitch change the amount of radiation a patient is exposed to in CT imaging?
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What uses a 2D projection to make a 3D image in nuclear medicine imaging?
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In PET imaging, what is the purpose of time of flight (TOF) technology?
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What distinguishes 2D PET imaging from 3D PET imaging in terms of sensitivity to random and scatter coincidences?
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What characteristic contributes to noise in PET images from a per-voxel viewpoint?
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In coincidence imaging, what is the essential requirement for the detection of annihilation photons?
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What happens to the annihilation photons if they are not determined to be in coincidence during a PET scan?
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Study Notes
X-ray Tubes in CT Imaging
- The primary purpose of the filter in an x-ray tube is to remove low-energy x-rays that are selectively absorbed by soft tissue.
CT Number Ranges
- Approximate CT number ranges are:
- Air: -1000 to -900
- Soft tissue: 0 to 100
- Bone: 400 to 1000
PET Imaging
- Dead time is primarily caused by detector saturation.
- PET images that are not attenuation corrected look very different from corrected images.
- The biggest contributor to dead time is detector saturation.
Coincidence Imaging
- The purpose of detecting annihilation photons is to localize the source of the positron-emitting radionuclide.
- If annihilation photons are not determined to be in coincidence, they are discarded.
- The Pulse Height Analyzer ensures that only photons within a specific energy range are detected.
Nuclear Medicine Imaging
- SPECT uses a 2D projection to create a 3D image.
- The septa in 2D PET imaging absorb cross-plane annihilation photons and improve image quality.
- Time of Flight (TOF) technology improves image resolution by providing information on the time of arrival of annihilation photons.
MRI vs. CT
- The main advantage of MRI over CT is its superior soft tissue contrast.
X-ray Filters
- The filter in an x-ray tube selectively removes low-energy x-rays.
Pitch and Radiation Exposure in CT
- Pitch changes the amount of radiation a patient is exposed to in CT imaging by adjusting the table speed and x-ray beam width.
Sensitivity and Coincidences
- 2D PET imaging is less sensitive to random and scatter coincidences compared to 3D PET imaging.
Random Correction
- Randoms are corrected in PET imaging using the delayed coincidence sinogram method.
Sinograms
- The main purpose of a sinogram is to correct for random and scatter coincidences.
Noise in PET Images
- Noise in PET images is primarily caused by statistical fluctuations in photon detection.
Essential Requirements
- The essential requirement for the detection of annihilation photons is that they must be detected in coincidence by both detectors on each side.
Limitations of Annihilation Photon Imaging
- The main limitation of annihilation photon imaging is the low detection efficiency of annihilation photons.
Attenuation Units
- The range of units of attenuation in a CT study is expressed relative to the attenuation of water.
Scatter Incidents
- Scatter incidents refer to the detection of photons that have undergone Compton scattering.
Shimming Coils
- The main purpose of shimming coils in an MRI scanner is to improve the homogeneity of the magnetic field.
Sensitivity and Detection
- Sensitivity refers to the ability of an imaging system to detect and accurately measure the gamma rays emitted by radioactive tracers administered to a patient.
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