Radiopharmaceuticals

Question 1

What does SPECT stand for?

Answer 1

Single photon emission computed tomography; it is 3D gamma ray immaging

Question 2

PET - how does it work?

Answer 2

• Positron forms and annhylates with an electron - the mass gets converted to energy and 2 photons result at 180 degree angles
• PET is a 3D imaging of photons given off when a positron annihilates with an electron

Question 3

Why is PET better than SPECT and planar scintagraphy?

Answer 3

1. immage gamma radiation of much higher energies
2. Improved quantification of data and of counting statistics - making lesions more detectable and more reliable
3. Radiopharmaceuticals used with PET have shorter half lives - meaning patients get to go home sooner

Question 4

Radiopharmaceuticals have no pharmacologic effect. Why?

Answer 4

They are used in tracer quantities

Question 5

Name 3 radionuclide production devices

Answer 5

1. Nuclear reactors
2. Charged particle accelererators
3. Radionuclide generators

Question 6

How is ^99mTcO₄^- radiopharamceutical made?

Answer 6

• Made using generator column chromatography
• Parent isotope, Mycobonium-99, decays to Technetium-99
• Tc-99 gets eluded with saline to become ^99mTcO₄^- which is in solution
• To make other RaPh that use Tc99m in label - use drug as a powder and add to the 99mTcO4- solution and it will combine to make RaPh

Question 7

Which has the shorter half life:

• Mycobonium - 99 (parent)
• Technetium -99m (daughter)

Answer 7

• Tc-99m

Question 8

Two other names for the Gamma Camera

Answer 8

• Scintillation camera
• Anger camera

Question 9

^99mTcO₄^- ⇒Thyroid Scintigraphy

Answer 9

• RaPh that acts like Iodine goes to the zygomatic salivary gland and the thyroid
• Hyperthyroid, euthyroid, and hypothyroid is based on the thyroid/salivary ratio
• Can also detect:
  
  • Hyperplasia - usually more one side than the other
  • Multinodular Adenoma - looks like string of pearls
  • Carcinoma - bilateral, metastasis can be seen

Question 10

^99mTc Sulfur Colloid - Liver Scintigraphy

Answer 10

• Normal = well demarcated liver shape, sometimes more color on one side than the other
• Liver metastasis - 4 hallmakrs of cancer:
  
  • Irregular borders
  • Abnormal morphology
  • Heterogenous uptake of pharmaceutical
  • Photopenic void = no radioactivity = lesions
• Pseudotumor pattern of cirrhosis
  
  • Looks just like cancer - need to take a biopsy to confirm dx

Question 11

Advantages of dynamic renal scintigraphy

Answer 11

• can quantify individual kidney function
• Can detect renal dysfunction before an increase in BUN can be detected

Question 12

^99mTc - DTPA Renal Scintigraphy

Answer 12

• Provides a series of images of kidneys over a period of time to detect GFR - GFR scan
• Normal GFR is >3.0 mL/min/kig
• In renal failure, there is poor renal uptake of the RaPh and prolonged blood pool activity

Question 13

^99mTc - DMSA Renal Morphology Imaging

Answer 13

• Used to evaluate size, shape, and location of kidneys
• Used to evaluate for acute pyelonephritis
• Used to determine the distribution of functional renal mass
• Uptake of the RaPh by the renal cortex

Question 14

^99mTc - MDP (methylene diphosphate) Canine Bone Scan

Answer 14

• bone is dynamic, constantly remodelling
• Normally in equilirbium between osteoclastic and osteoblastic activity - cacner can disrupt this equilibrium
• Normal to see action at the ends ofl ong bones

Question 15

QuadraMet^TM =

Answer 15

¹⁵³Sm - EDTMP

Question 16

Story of QuadraMet^TM

Answer 16

• ¹⁵³Sm identified useful nuclide for radiotherapy by MU researches
• Development began in early 1980s at MU in collaberation with teh Dow Chemical Company [phosphate ligand complexes; ¹⁵³Sm - EDTMP
  
  • ¹⁵³Sm - good agent for bone therapy because can track it in vivo
• Clinical trials for human began in late 1980s with doses supplied by MURR for phase I staudes
  
  • 80% efficacy with ~25% obtaining full pain remission
• Approved in US for pain palliation of metastatic bone cancer in March, 1997

Question 17

In ¹⁵³Sm-EDTMP; what is EDTMP?

Answer 17

Phosphonate compound that targets bone cancer

Question 18

What is planar scintigraphy?

Answer 18

2D gamma ray imaging; whole body images are usually acquired with scintigraphy

Question 19

Why do you see photopenic voids in liver scintigraphy?

Answer 19

Tc-99m sulfur colloid images reticuloendothelial system (RES), of which the liver is a major organ. Liver tumors generally lack Kupffer cells, which mediate RES. Thus, liver tumors have defective RES function, they do not take up sulfur colloid, and the lesions are visible as cold spots

Question 20

Nuclear Reactors - Give Example

Answer 20

• Nuclear reactors are a type of radionuclide prodcution device
• Example is the MURR Reactor Core
• Fast neutrons have a low probability of interaction with other nuclei. They are thermalized or slowed down to interact with other nuclei. Moderators (low MW materials like heavy water, beryllium, or graphite) are distributed in speces between fuel rods.

Question 21

Charged Particle Accelerators

Answer 21

• Charged particle accelerators are a type of radionuclide production device
• Example - positive ion cyclotron operation
  
  • Proton betwen two magnets
  • Magnets alternate in strength to cause the proton to move in a circular path. The proton eventually hits the deflection plate and goes out into the target.

Question 22

An example of a radionuclide generator

Answer 22

Mo-99/Tc-99m Generator Column Chromatography

Question 23

Fluorodeoxyglucose (FDG) metabolism

Answer 23

• FDG is taken up by hypermetabolic cells
  
  • Physiologic hypermetabolic areas - brain, muscle, salivary glands, heart, large vessels, renal pelvis, bladder, liver
  • Neoplastic cells
• FDG gets taken up by a glucose transporter and a negativley charged phopsphate gets added - this makes it unavailable for glucose metabolism and FDG is metabolically trapped inside the cell because negatively charged molecules can’t diffuse back through the negatively charged lipid membrane

Question 24

¹⁸F - FDG is used to treat _____

Answer 24

Neoplasms with hypermetabolic cells. Most neopastlic cells pick up a lot of glucose.

Question 25

¹⁸F - NaF is used in:

Answer 25

* Detection of PRIMARY bone tumors * Detection of osseous metastases * Generally considered more sensitive than ^99mTc - MDP bone scans * Often combined with ¹⁸F-FDG to show soft tissue and bone cancers

Question 26

What radiopharmaceutical is considered more sensitive in bone scans? ^99mTc-MDP or ¹⁸F-NaF

Answer 26

¹⁸F-NaF

Question 27

Why would you do a combined PET/CT or PET/MRI?

Answer 27

* aid in lesion localization * Functional information of a PET and spatial resolution of a CT * Helps to also distinguish spots on MRI that may seem concerning, but are NOT metaboically active as illustrated with the PET, and are therefore of no concern.

Question 28

Triamcinolone Acetonide * Synthesis * Treats? * Works best with what kind of administration?

Answer 28

* Industrial process - dissolve triamcinolone in acetone, acid-catalysed reaction is rapid and complete * Treats asthma * Spacer (moutpiece to inhalers) works better - gets distribtuted throughout bronchi to the lungs

Question 29

Azmacort is a \_\_\_\_

Answer 29

triamcinolone inhaler

Question 30

What RaPh is used in thyroid scintigraphy?

Answer 30

^99mTcO₄^- (acts like iodine and goes to thyroid and zyogmatic salivary glands)

Question 31

What RaPh is used in liver scintigraphy?

Answer 31

^99mTc Sulfur Colloid

Question 32

What RaPh is used in renal scintigraphy that can measure GFR?

Answer 32

^99mTc-DTPA

Question 33

Which RaPh is used in renal morphology imaging?

Answer 33

^99mTc - DMSA

Question 34

What RaPh are used in bone scans?

Answer 34

* ^99mTc- MDP * ¹⁸F - NaF

Question 35

Which RaPh is used to treat pain of metastatic bone cancer?

Answer 35

* ¹⁵³Sm - EDTMP = QuadraMet^TM

Question 36

Which RaPh is used to treat hypermetabolic neoplasms?

Answer 36

¹⁸F - FDG