This set of Clinical Science Multiple Choice Questions & Answers (MCQs) focuses on “PET & SPECT”.
1. What does the ‘P’ in PET stand for?
a) Positron
b) Photon
c) Proton
d) P – orbital
View Answer
Explanation: PET stands for Positron Emission Tomography. In a PET process, there is a nuclear reaction causing emission of a positron. This positron comes in contact with an electron, undergoes annihilation and gives out two gamma rays which are detected by the detector. On the gamma rays that are detected at the opposite ends are used to form an image. Rest are discarded as noise.
2. What does the ‘P’ in SPECT stand for?
a) Positron
b) Photon
c) Proton
d) P – orbital
View Answer
Explanation: SPECT stands for Single Emission Photon Tomography. In this process, the radioactive dyes give out photons which are detected by the detector and forms an image. The photon detector usually has Photo Multiplier Tubes (PMTs) that can amplify the received impulses from the photon and form an image.
3. What makes PET and SPECT so unique when it comes to nuclear imaging?
a) Do not require dyes
b) Do not require X – Rays
c) They show the metabolic functions
d) They give more details about the imaged organ/tissue
View Answer
Explanation: The dyes used in PET and SPECT are such that they become a part of the metabolic pathways and the transmitted radiations can help visualize the metabolic pathways. The machine that does the same work as PET and SPECT, i.e. visualizing the metabolic pathways is fMRI. However, since it does not use any dyes, it does not fall under nuclear imaging.
4. SPECT includes a ___________ for imaging.
a) Gamma Camera
b) Silver Halide Film
c) Phosphorus Sheet
d) Lead Sheet
View Answer
Explanation: A gamma camera had detectors made of PMTs to help form an image. Since PET produces 2 photons/gamma rays, correlation of the image formed at the two ends is used to form a proper image. However, SPECT produces only 1 photon so if they need to be collected properly to form an image. Thus, a gamma camera, a camera specializing in capturing images by taking the impulses from the photons in used in SPECT.
5. The detector of PET is made of _________
a) Silver
b) Gadolinium
c) Tungsten
d) Lead
View Answer
Explanation: Bismuth germinate oxide (BGO), gadolinium oxyorthosilicate (GSO) or lutetium oxyorthosilicate detectors (LSO) are three materials that can be used to form the detectors for PET. They can record impulses from the gamma rays and convert them into electrical signals which are finally processed to form images.
6. As compared to PET, SPECT isotopes have _________ half life.
a) longer
b) shorter
c) equivalent
d) unstable
View Answer
Explanation: Since PET has 2 gamma rays, it uses the correlation of the images to form the final image. The process is also faster. However, with SPECT, there is only 1 gamma ray produced. The process is longer. Thus, for better imaging and allowing multiple imaging with a single shot of dye, SPECT radioisotopes need to have a longer half life.
7. The most preferred radioisotope element for SPECT is
a) Mo
b) W
c) Tc
d) Ba
View Answer
Explanation: Tc – 99m is activated Technetium which can be produced from Molybdenum. Tc – 99m has a half life of around 6hrs, is relatively easy to produce and can be flushed out of the body without causing much harm. It is also relatively stable and thus makes a good choice for SPECT scanning.
8. Which of the following radiations are used for imaging purposes?
a) alpha
b) beta
c) gamma
d) delta
View Answer
Explanation: Gamma rays are energy rays or photon rays and do not have a mass. Thus, they do not destroy the cancerous cells or provide any relief in therapies. However, since they have a greater penetration power, they can be used for imaging. If the body is exposed to these penetrating radiations for a long time, the body may have burn and a prolonged and continuous exposure will result in damaged DNA. Increasing the intensity of the radiations also causes harm to the body.
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