Design guide for nuclear substance laboratories and nuclear medicine rooms

Question 1

for license to use unsealed nuc, what must applicatants submit in addition to license application?

Answer 1

DAF
Design assessment form
DAF should be done for any new construction or major reno. If you just change out gamma camera, don’t need DAF as long as it doesn’t affect other rooms etc

Question 2

do you need multiple DAFs if constructing multiple rooms of similar design?

Answer 2

No, just 1 DAF

Question 3

7 categories in DAF

Answer 3

• general info
• finishing and fixtures
• plumbing
• security
• ventilation
• shielding/dose control
• miscellaneous (ex. dedicated bathroom for nuc med patients)

Question 4

5 steps for dose estimate for convention diagnostic nuc med

Answer 4

1. architectural drawings
2. Key location where nuclear substances and nuclear medicine patients will be present for significant periods of time. Also decide on typical # procedures per year and typical activity per procedure (be conservation and plan for future expansion!)
3. occupancy factors of surrounding areas
   4.estimate radiation doses produced in each area
   o 5. Extrapolate dose rates to annual doses for the persons who may occupy each area: D = NTRS
   N is # of procedures/yr
   T is occupancy
   R is radiation dose
   S is duration of time that the source or injected patient is present at the designated source location in hours

o Add up contributions from all key locations and all types of tests done to get total dose to the maximally exposed person at the location of interest. Repeat calculations for other maximally exposed people at different locations of interest. Should do calculation for maximally exposed NEW and member of the public (since dose limits are different for these two groups).

Question 5

equation for estimating radiation doses produced in each area

Answer 5

-approximate patient as pt source
R = TAU * activity * (10^(-t/TVL))/d^2

TAU is dose rate constant (the dose rate per unit activity at 1 m from source; in units of μSv m2 MBq-1 h-1)

o If you have air kerma rate constant instead of dose rate constant, then must convert from air kerma to dose to water using mass energy absorption coefficient for water to air.
o If you have exposure rate constant, then must first convert to air kerma in air using W/e = 33.97 J/C (or use 0.876 cGy/R).
 The product of 0.876 cGy/R and mass energy absorption coefficient for water to air is commonly referred to as the roentgen to cGy conversion factor fmed.

-t is shielding thickness

• For Tc-99m, decay is not taken into account and the initial activity administered to the patient is used in the equation above.
• Patient attenuation is also not taken into account for Tc-99m.

Question 6

considerations when determining annual dose for therapist

Answer 6

o When determining annual dose for therapist, must account for the fact that the therapist moves around and is sometimes very close to patient. This is unlike e.g., receptionist who is assumed to be stationary.
o Assume that one therapist does all treatments, then divide this annual dose estimate by the number of therapists.

Question 7

shielding thickness for nuc med

Answer 7

have to take into account energies of decay products