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characteristics of ideal RP
- short T 1/2
- no particle emission
- metabolic suitability
- high target / non target ratio
- preferred mode of decay
mechanisms of localization
Phagocytosis, capillary blockade, active transport, simple diffusion, cell sequestration, compartmental localization, antigen antibody complex.
- removal of forgein matter by physical entrapment.
- Tc-99 S.C. RES
- mechanical obstruction of capillaries or precapillaries arterioles in lung,
- Cellular metabolism concentrates RP in organ or tissue.
- 123-I NaI for thyroid function/imaging
- movement of RP from area of higher concentration to area of lower concentraion.
- breakdown of BBB allows RP to penetrate brain in area of affected tissue.
- Removal of old or damaged RBCs from circulation by spleen; uptake of WBCs in infection sites.
- 51-Cr RBCs taken up by spleen
- 111-In WBCs sites of infection.
- introduction of RP into well-defined body compartment where it remains for and extended period.
- -99m Tc DTPA aerosol, 133Xe technegas
Antigen-Antibody complex formation;
- radiolabeled antibody binds to tumor associated antigen.
- using tumor specific labeled antibodies to detect cancer of stage therapy.
Mechanisms affecting biodistribution;
- Blood flow
- Particle size
- Protien binding
- iatrogenic alterations
For most of NM the circulatory system transports the RP via venous blood supply.
Removed from circulation ether by RES or lungs depending on size.
most RPs bind to plasma protiens ( Albumin in many cases) plasma clearance affected if bound tightly.
- causing a secondary condition arising from treatment of a primary condition.
- -undesirable-> thyroid: iodine contrast media affecting uptake. BoNE: poor uptake due to iron overload.
- -Desirable-> Renal imaging: admin of furosmide to rule out mechanical obstruction, MPI admin of persantine to dialate heart vessels.
Clinical investigation of new drugs.. steps
- Preclincal studies
- eIND ( exploratory investigational new drug)
- IND (investigational new drug) phase 1 -3
- NDA (new drug application)
performed on animals to determine biodistribution, kinetics , toxicity, dose estimitates , lethal , sublethal
- limited human exposure
- no therapeutic of diagnostic intent
- limitied duration of dose.
Phase 1 clinical study
- 20-80 people
- pharmacology studies in normal volunteers to find normal biodistributions in humans.
Phase 2 clinical study
- 100-300 people
- studies of patients with specific disease/condition
- determine additional evidence of safety and inital evidence of diagnostic or therapeutic efficacy.
Phase 3 clinical study;
- 1000-3000 people
- determine optimum dose
- establish addional uses
all commercially distributed RPs must be approved through the FDA and be assigned an NDA number.
Phase 4 clinical study
Post Market Surveillance
- cardio pulmonary decompression
- -heart failure, type A : expected , dose dependant. Type B; unexpected, hypersensitivity.
- idiosyncratic reaction; unusual individual response
organ being imaged
organ or body part receiving most of radiatin dose.
organ or body part delivering radiaiton dose to target organ (can be target organ delivering dose to self)
- absorbed dose.
- quantity of radiation enegry deposited in an absorber per gram of absorber
- 1 rad = 100 ergs/gram
- integral dose
- the total amount of energy deposited in a volume of tissue.
- g.rad = absorbed dose x tissue mass (grams)
- 1 g.rad = 100ergs of energy deposited in a vol of tissue
the fraction of energy of radiation emitted from a source organ that is absorbed in a target organ.
DOT 1 (white)
- contact .05mR/hr
- at 3ft NDR
DOT II (yellow)
- contact 50mR/hr
- 3ft 1mR/hr
DOT III (yellow)
- contact 200mR/hr
- 3ft 10mR/hr
The transport index should have the...
name of isotopes being delivered and the amount of exposure reading at 1 meter
- divide into charged particles when in a solution.
- high osmolar contrast 1300-1600 mOsm/kg
- do not divide into particles when in a solution.
- no degradation in the blood stream.
- low osmolar contrast 500 to 850 mOsm/kg
the concentration of molecular particles in the contrast agent solution.
All IV contrast has a osmolality.....
- greeater than blood plasma. 285 mOsm/kg
- so IV contrast is Hypertonic compared to blood plasma. causing movement of water from tissues into vascular space. dyhadrating the patient.
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