Radiopharmaceuticals (4b) Flashcards
1
Q
Drugs used to enhance nuclear medicine studies
A
- Medication can interfere with nuclear medicine studies
- This can be used to advantage to enhance or extend the diagnostic capability of a NM investigation
- A specific drug may be administered before during or after administration of the radiopharmaceutical
- Alters organ function
- Gives diagnostic information as a result of changes in biodistribution, uptake or excretion
2
Q
CV system
A
- 2 categories of NM cardiac study
- Myocardial imaging to assess regional coronary blood flow and evidence of stenosed blood vessels
- Blood pool imaging to determine ventricular function
- Induction of stress used to increase the diagnostic sensitivity of MPI investigation
3
Q
Cardiac studies
A
- Patients undergo MPI in 2 parts
- Heart stressed by exercise or pharmacologically to achieve vasodilation
- Heart imaged at rest if stress test abnormal
- Comparison of 2 studies proveides the diagnosis
4
Q
Drugs used to induce cardiac stress
A
- Adenosine (vasodilator used to mimic exercise)- 140mg/Kg/min, tracer given after 4 mins infusion, adenosine continued for 2 minutes more
- Half-life 13 seconds. Unlicensed 100mL minibags used
- Can cause asthma attacks
- Dobutamine- used in asthmatic patients
- Regadenoson (Rapiscan)- 400mcg dose, no dose adjustment for weight. 10-sec bolus followed by the radiopharmaceutical
5
Q
Renal studies
A
- One aim of renal studies is to distinguish between dilated, non-obstructed urinary tracts from those with significant mechanical obstruction
- Determination is important- renal atrophy can result if obstruction is not corrected surgically
6
Q
Use of furosemide
A
- Prolonged retention of tracer seen in the dilated, non-obstructed system due to reservoir effect
- Increasing urine flow with diuretic results in a washout of the activity
- In contrast, the obstructed system will demonstrate progressive accumulation of activity with no response to diuretic
- Furosemide 40mg IV given
- Furosemide to distinguish between obstructed and non-obstructed
7
Q
Detection of renal artery stenosis
A
- RAS most common cause of secondary HTN
- Angiotensin II secretion preferentially constricts efferent arteriole to maintain perfusion pressure in the kidney
- Giving captopril causes a fall in perfusion pressure- diagnosis made by comparing a baseline study with a captopril enhanced
8
Q
Hepatobiliary studies
A
- Morphine used in the investigation of Sphincter of oddi dysfunction
- Morphine causes constriction of the sphincter of oddi
- All prescribed nacrotic/opioid analgesics must be withdrawn at least 24 hours before the investigation
- Sub-analgesic dose of morphine 2mg IV
- Phenobarbitone- used in infants prior to T-BIDA scan for biliary atresia, to enhance uptake and excretion
- CCK analogue sincalide or fatty meal - used to induce gall bladder contraction and emptying
9
Q
TBIDA- morphine
Negative scan
A
- Clinical indications:
- Ongoing symptoms after laparoscopic cholecystectomy
- Having RUQ and epigastric discomfort
Sphincter of Oddi dysfunction
10
Q
TBIDA morphine- positive scan (there is a problem with the oddi sphincter)
A
- Clinical indications
- Previous laparoscopic cholecystectomy
- MRCP shows mildly dilated ducts
- To rule out sphincter of Oddi dysfunction
11
Q
Thyroid blockade
A
- Free iodine is a problem due to
- In vivo degradation of radio-iodinated compounds, releasing free radioiodine
- Free iodine present as an impurity
- Will always get some free iodine- iradiate the thyroid
- Thyroid blockade is necessary if dose to thyroid >50mGy
- 123-I > 15MBq
- 125-I > 0.2MBq
- 131-I > 0.1MBq
- Duration of blockade depends on type of diagnostic/therapeutic radiopharmaceutical: 24 hours DaTSCAN, 48 hours mIBG, 10 days 131-I
12
Q
Thyroid blocking agent
A
- Potassium iodate85mg x 2 daily- can induce hyperthyroidism
- Lugol’s iodine 0.1-0.2mL TDS- very unpalatable
- Pottasium Iodine- can induce hyperthyroidism
- Potassium perchlorate 200mg TDS- associated with blood dyscrasias on prolonged use
