Section 35.63 - Determination of dosages of unsealed byproduct material for medical use(a) A licensee shall determine and record the activity of each dosage before medical use.(b) For a unit dosage, this determination must be made by-(1) Direct measurement of radioactivity; or(2) A decay correction, based on the activity or activity concentration determined by-(i) A manufacturer or preparer licensed under § 32.72 of this chapter or equivalent Agreement State requirements; or(ii) An NRC or Agreement State licensee for use in research in accordance with a Radioactive Drug Research Committee-approved protocol or an Investigational New Drug (IND) protocol accepted by FDA; or(iii) A PET radioactive drug producer licensed under § 30.32(j) of this chapter or equivalent Agreement State requirements.(c) For other than unit dosages, this determination must be made by-(1) Direct measurement of radioactivity;(2) Combination of measurement of radioactivity and mathematical calculations; or(3) Combination of volumetric measurements and mathematical calculations, based on the measurement made by:(i) A manufacturer or preparer licensed under § 32.72 of this chapter or equivalent Agreement State requirements; or(ii) A PET radioactive drug producer licensed under § 30.32(j) of this chapter or equivalent Agreement State requirements.(d) Unless otherwise directed by the authorized user, a licensee may not use a dosage if the dosage does not fall within the prescribed dosage range or if the dosage differs from the prescribed dosage by more than 20 percent.(e) A licensee shall retain a record of the dosage determination required by this section in accordance with § 35.2063 .67 FR 20370, Apr. 24, 2002, as amended at 72 FR 55931, Oct. 1, 2007