SP18:Multimodality Imaging Flashcards
Which one of the following statements is true about hybrid PET/CT or SPECT/CT imaging systems?
(a)The same detector is used for both modalities
(b) Images do not have to be checked for patient motion
(c) Daily QC takes less time than for stand-alone systems
(d) The two modalities are acquired simultaneously
(e) The CT provides anatomic correlation for the SPECT or PET
(e) In addition to providing a map of tissue attenuation values, the CT serves to localize features seen on the SPECT or PET.
Which one of the following statements is true about the CT in SPECT/CT or PET/CT?
(a)CT is slower than previous methods of performing attenuation correction
(b) CT images must be scaled and smoothed before being used for attenuation correction
(c) CT has worse spatial resolution than SPECT or PET
(d) Truncation of the body in the CT does not affect the SPECT or PET images
(e) Surgical or dental implants made from high-Z materials do not affect attenuation correction
(b) X-rays produced by the CT are lower in energy than the photons emitted by radiopharmaceuticals, so attenuation coefficients derived from CTs must be scaled to the energy of the radiopharmaceutical. Because SPECT and PET images have poorer spatial resolution than CT, the CT also must be rebinned into large pixels or blurred to avoid artifacts at tissue boundaries.
Which of the following is NOT a potential source of artifacts in PET/CT or SPECT/CT imaging?
(a)CT beam hardening
(b) Anatomic coverage
(c) CT contrast medium
(d) Respiratory motion
(e) Metal implants
(b) Anatomic coverage
Which of the following is not a barrier to combining an MRI system with either a SPECT or PET system?
(a)The duration of MRI scans makes sequential scanning lengthy
(b) PMTs do not function in high magnetic fields
(c) MRI scanners are expensive
(d) MRI scanners do not produce ionizing radiation
(d) MRI scanners also have better soft tissue contrast than CT.
If performing a CT for attenuation correction only, why would the CT parameters be significantly altered from those for a diagnostic CT scan?
(a)To save time
(b) To reduce the radiation exposure to the patient
(c) To increase patient throughput
(d) You would not alter the parameters
(e) None of the above
(b) You would modify the CT parameters in an effort to reduce the patient’s radiation dose.
A CT scan to define the area of the body to be scanned is called a:
(a)Blank scan
(b) Quick scan
(c) Scout scan
(d) Topogram
(e) None of the above
(f) Both (c) and (d)
(f) The scan to define the body area to be scanned can be called either a scout or topogram.
CT artifacts can be caused by:
(a)The operator
(b) The scanner
(c) The patient
(d) All of the above
(e) None of the above
(d) CT artifacts can be caused by the individual operating the scanner, the scanner itself, or the patient. They also can be caused by a variety of other factors such as the reconstruction algorithm, contrast medium, etc.
How often should the CT calibration be checked and a tube warm-up performed?
(a)Daily
(b) Weekly
(c) Monthly
(d) Quarterly
(a) CT calibration must be checked daily, typically by scanning a water phantom then (1) comparing the measured HUs to the permitted range of values, and (2) visually checking the images for artifacts. A tube warm-up may be necessary throughout the day depending on the scanner use.
IV contrast must always be administered during a PET/CT scan.
(a)True
(b)False
(b) IV contrast may be administered but is not routinely administered to all patients having a SPECT/CT or PET/CT scan, especially if the CT is for attenuation correction only.
Artifacts due to respiration mismatch between CT and SPECT or PET are most likely to be seen near:
(a)Lung apices
(b) Dome of the diaphragm/liver
(c) Maxillary sinuses
(d) Pulmonary artery
(b) Most commonly seen is the “banana” artifact, a curvilinear cold artifact just above the dome of the diaphragm/liver.
If a patient moves between the CT and the SPECT or PET, which two of the following corrections will be affected?
(a)Attenuation
(b) Scatter
(c) Decay
(d) Normalization
(e) Dead time
(a) and (b)
Select two reasons that metal implants in patients create problems for SPECT/CT and PET/CT systems:
(a)Additional weight of patient may exceed table’s load limit
(b) High CT numbers from metal overestimate the attenuation that photons emitted by radiopharmaceutical will experience
(c) Artifacts in CT images due to the presence of metal may propagate to attenuation maps
(d) Metal disturbs magnetic field of CT
(b) and (c)
In this fused PET/CT transaxial slice through the mandible, what is the likeliest explanation for the area of activity extending outside the boundary of the CT (shadow/ghosting/mismatch)
(a)Facial edema
(b) Patient tilted head between CT and PET
(c) Benign cyst
(d) Lupus
(b) The arrow is pointing to the outline of the patient’s jaw in the PET image, and the mismatch between the jaw position in the PET compared to the CT indicates that the patient moved his head between modalities.
