Radiopharmaceuticals in Nuclear Medicine

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Radiopharmaceuticals in Nuclear Medicine : 

Radiopharmaceuticals in Nuclear Medicine Sian E. Iles

Technetium Radiopharmaceuticals : 

Technetium Radiopharmaceuticals Technetium found in minute quantities in nature Atomic number 43; Metallic element Multiple isotopes: most useful Tc-99m Product of decay of Molybdenum 99 Mo 99 produced by fission of Uranium 235

Technetium 99m : 

Technetium 99m Best nuclear properties for imaging T ½ 6 hours Decays by gamma decay 140 keV penetrate tissues but good high energy for camera No particulate radiation ( i.e. alpha particles or beta particles)

Technetium : 

Technetium Adsorbed onto alumina Decays to Tc 99m with a t1/2 of 67 hours Technetium eluted from generator by isotonic saline

Technetium Generator : 

Technetium Generator Molybdenum- Technetium generators “Parent” is Molybdenum 99 Decays to Technetium 99m

Generator : 

Generator Molybdenum is adsorbed onto Alumina Saline used to elute Technetium 99m

Technetium Generator : 

Technetium Generator Generators “milked” every day Mo-99 decays too Supply decreases with time Ideally eluted once every 24h Usually get one or more generators per week

Technetium : 

Technetium Technetium comes off generator as Technetium Pertechnetate: TcO4- +7 oxidation state Stable chemically Has to be made more chemically active by use of a “reducing” agent

Technetium Chemistry : 

Technetium Chemistry Reducing agent needed to make it chemically active Donates electrons to make technetium less positive valence state Stannous agent most commonly used (SnCl2)

Technetium : 

Technetium In +4 or +3 state it can be incorporated into another compound “Chelation” Shares multiple electrons with more than one other atom* Chelate means “claw”

Technetium Radiopharmaceuticals : 

Technetium Radiopharmaceuticals Substance bound to technetium alters pattern of distribution in the body (biodistribution) Tracers for skeletal,reticuloendothelial, cardiovascular,genitourinary,central nervous system, red and white cells

Technetium Radiopharmaceuticals : 

Technetium Radiopharmaceuticals Kits are available Contain all necessary reagents Made up in lab with eluted Technetium

Technetium Radiopharmaceuticals : 

Technetium Radiopharmaceuticals Tc O4- Technetium Pertechnetate Similar to iodide: used for thyroid imaging Cannot cross normal BBB: can trace blood brain barrier function Taken up by gastric mucosa: can detect ectopic gastric mucosa i.e. Meckel’s Diverticulum Used as flow agent to detect testicular torsion

Thyroid Imaging : 

Thyroid Imaging

Meckel’s Diverticulum Study: Negative : 

Meckel’s Diverticulum Study: Negative

Meckel’s Diverticulum: Ectopic Gastric Mucosa : 

Meckel’s Diverticulum: Ectopic Gastric Mucosa

Testicular Torsion : 

Testicular Torsion Delayed image of late testicular torsion

Technetium Colloids : 

Technetium Colloids Technetium forms colloid ( suspension of particles) with sulfur Taken up by Kuppfer cells in liver, phagocytic cells in bone marrow Most particles between .1 and 1 micrometers

Technetium Sulfur Colloid : 

Technetium Sulfur Colloid Used to image liver and spleen normal metastases

Technetium Sulfur Colloid : 

Technetium Sulfur Colloid Also images bone marrow Can filter sulfur colloid to get smaller particles More goes to bone marrow

Technetium Sulfur Colloid : 

Technetium Sulfur Colloid

Technetium Sulfur Colloid : 

Technetium Sulfur Colloid Mixed with scrambled eggs can trace gastric emptying

Technetium Sulfur Colloid : 

Technetium Sulfur Colloid When filtered can also be used to trace lymphatic system Used to find nodal drainage in breast and melanoma Used to diagnose lymphedema

Lymphoscintigram:Lymphedema : 

Lymphoscintigram:Lymphedema Left forearm retains activity in skin and lymphatics

Sentinel Node Breast : 

Sentinel Node Breast

Technetium Radiopharmaceuticals : 

Technetium Radiopharmaceuticals Tc 99m MAA Macro aggregated albumin Large particles that are trapped in small end arterioles in lung Allows imaging of lung perfusion

Tc 99m MAA : 

Tc 99m MAA Very small percentage of arterioles blocked Diagnosis of Pulmonary Embolus most common use Usually performed with ventilation study as well

Tc 99m MAA V/Q Scan : 

Tc 99m MAA V/Q Scan Ventilation study done first with aerosolized agent usually Tc 99m MDP Need special device to do this Droplets must be small enough to avoid trapping in large airways Patient breathes through mask Multiple images obtained

Ventilation Study : 

Ventilation Study

V/Q Scan : 

V/Q Scan Tc 99m MAA is given intravenously Patient should be lying down to minimize gravitational effects on blood flow Ventilation and Perfusion images are compared

V/Q Scan : 

V/Q Scan Normal

V/Q Scanning : 

V/Q Scanning Pulmonary Embolus: mismatch between ventilation and perfusion No mechanism to stop ventilating non- perfused area

Technetium Agents:Bone Imaging : 

Technetium Agents:Bone Imaging Chelated with a bisphosphonate Most common Methylenediphosphonate (MDP) Taken up at sites of bone turnover with calcium deposition Osteoblastic activity traced Normal skeleton has active bone turnover Look for sites with more or less activity

Tc 99m MDP: Metastases : 

Tc 99m MDP: Metastases Many causes of increased bone turnover Fracture, infection, arthritis, metastases most common

Tc-99m MDP: Occult Fracture : 

Tc-99m MDP: Occult Fracture

Tc 99m MDP: Osteoid osteoma : 

Tc 99m MDP: Osteoid osteoma

Genitourinary System : 

Genitourinary System Multiple tracers with slightly different properties Tc 99m DTPA excreted purely by glomerular filtration May be used to calculate GFR as well as image by taking blood samples

Tc 99m DTPA : 

Tc 99m DTPA Decreased uptake and excretion Patient with acute severe left renal obstruction

Genitourinary System : 

Genitourinary System Tc 99m MAG 3 Glomerular filtration and tubular secretion Better images especially when function is poor

Tc 99m MAG 3 Renal Study : 

Tc 99m MAG 3 Renal Study

Genitourinary System : 

Genitourinary System Tc 99m glucoheptonate and Tc 99m DMSA ( dimercaptosuccinic acid) Used primarily for morphology ie to demonstrate scarring DMSA binds to tubules Glucoheptonate has mixed properties

Tc 99m DMSA : 

Tc 99m DMSA normal Scarring from reflux and infection

Gastrointestinal System: Biliary Tract : 

Gastrointestinal System: Biliary Tract Tc 99m DISIDA ,HIDA, mebrofenin Iminodiacetic acid derivatives Taken up by hepatocyte and excreted into bile Assesses biliary excretion and function of gallbladder Biliary leak, obstruction and gallbladder disease

Tc 99m DISIDA : 

Tc 99m DISIDA Normal DISIDA gallbladder

Tc 99m DISIDA : 

Tc 99m DISIDA Acute cholecystitis

Technetium Labeled Cells : 

Technetium Labeled Cells Red cells most common Use stannous agent Added to blood either in patient or in test tube Enters cell Tc pertechnetate reduced in cell and binds to hemoglobin

Technetium Labeled Red Cells : 

Technetium Labeled Red Cells Blood pool Cardiac function imaging and Cardiac imaging requires dynamic acquistion and gating to heart rate via EKG Detection of GI bleeding site GI bleeding site requires continuous imaging

Wall Motion Study : 

Wall Motion Study

GI Bleeding Study : 

GI Bleeding Study 1 min per frame

GI Bleeding Study : 

GI Bleeding Study Lateral views confirm bleeding site in rectum

GI Bleeding Study : 

GI Bleeding Study

Tc Labeled Red Cells: Other uses : 

Tc Labeled Red Cells: Other uses Pool in areas of relative stasis Hemangioma of liver accumulates blood over time Scintigraphy used to confirm diagnosis of hemangioma, a benign lesion

Tomographic Imaging: Hemangioma : 

Tomographic Imaging: Hemangioma

Liver Lesion on CT : 

Liver Lesion on CT

Myocardial Perfusion : 

Myocardial Perfusion Technetium 99m Sestamibi, tetrofosmin Lipophilic Enters myocardial cells proportional to blood flow Cells must be viable

Myocardial Perfusion Studies : 

Myocardial Perfusion Studies May have severe coronary stenosis and normal blood flow to heart at rest Stress increases blood flow and hydrodynamic effects of arterial narrowing Blood flow beyond stenosis decreases Creates perfusion abnormality

Myocardial Perfusion Imaging : 

Myocardial Perfusion Imaging

Technetium 99m : 

Technetium 99m Ideal imaging properties: 6h half life,140 keV gamma ray, no particulate radiation Readily available from generator Multiple compounds allow imaging of many body processes Backbone of Nuclear Medicine!