Radionuclide Therapy Flashcards
Administration routes
- IV injection
- infusion
- oral
- intracavitary
- intra-arterial
Dose target
Aim for max 5% deviation from prescribed activity, but relation between activity and outcome not straightforward, so more leeway in prescribing than with XRT ‘target dose’
Limitations of radio-nuclide therapies
- time and cost restriction on workload
- no agent is entirely selective to the desired target
- dose calc issues: inhomo deposition, individual physiology
- radiation is not risk free
- IRMER reqs a net positive benefit
- Prescription limited by normal tissue toxicity
Ideal imaging radiopharm
- Short T1/2 eff
- No particulate emissions EC or IT
- High target / BG ratio
Ideal therapy radipharm
- Very high target/bg ratio with rapid clearance from no target tissue
- Suitable pH, Sterile, pyrogen free, non-toxic
- Practical - kit / min prep
- Imaging emissions if possible
- T1/2p and T1/2b match up
- Particulate emissions
What are the following therapies used for ?
- P32, Sr-89, Samarium-153, Y-90 + Rhenium-186, Y90
P32 - treats polycythaemia vera Sr-89 - Bone mets Samarium-153 - Bone mets Y-90 + Rhenium-186 - Inflammation of the joints + bleeding in the joints (haemophillia treatment). Y-90 hepatocellular carcinoma
Outline thyrotoxicosis therapy
- Treatment of an overactive thyroid
- Outpatient treatment
- Follow up blood test of thyroid hormone levels
- May require second treatment or hormone tablets if below normal levels after
RP advice post thyrotoxicosis therapy
See MDGN Table 15.2
3 days careful bathroom hygiene
Stay 1m away from adults for 11 days
Stay 1m away from children under the ages of 3 for 21 days
No Blood sampling for 1 month
Carry instruction card for 1 month, 3 month if travelling.
Outline the thyroid ablation therapy pathway
- Painless lump, biopsy, histology
- Thyroidectomy
- Ablation of thyroid tissue
- Post ablation whole body scan
- Diagnostic Imaging, neck u/s, Tg blood results
? Further Therapy? Other imaging
What is the purpose of thyroid ablation ?
Eliminate residual thyroid tissue
Reduce recurrence and aid monitoring
Admin activity is based on the amount of residual tissue post surgery.
What is the purpose of post ablation imaging?
- Baseline to show residual thyroid tissue at time of treatment.
- However it cannot distinguish between thyroid tissue and well differentiated tumour.
Laws relating to therapy administration
IRMER - patient dose and jusification
IRR - Dose to Staff / Members of the public
EPR - Waste accumulation, storage, disposal.
Outline the calculation of the dose to the thyroid from thyrotox therapy.
Use the MIRD method
1. Calc Te - effective half life
(tp x tb)/(tp+tb)
- Calc acumulated activity:
A = 1.44 x A0 x Te x fh - Calc Abs dose:
D = A x s = Act under curve x S-value
Thyroid therapy patient prep
- Advise patient to avoid high Iodine foods + review meds
- Pregnancy test
- Exclude breast-feeding patients unless alt arragement can be made.
- Assess continence
- Obtain written consent
RP during thyroid treatment (inpatient)
- ID check (IRMER)
- Instruct nursing personnel of the rad risk
- Periodically monitor activity of the patient’s thyroid gland
- Review measured act against the departure limit set by their risk assessment.
- Note any other med conditions/ establish contingency plans.
- Medical necessity overrides concern about rad risk.
- Instruct patient to keep hydrated and shower regularly
- Double flush the toilet
- Display visitor restriction time on the door (set by NM staff)
