Nuclear medicine Basic principles

Nuclear Medicine Imaging  - rays

The Nuclear Medicine Department Imaging rooms Gamma cameras Radiopharmacy Hot Lab Dose calibrators Generators Waste storage areas Reading room

What is Radioactivity? Emitted energy from the nucleus of an atom “U”nstable, “D”ecays by “E”mitting “B”etas, “A”lphas, and “G”ammas

Concept of Activity rate of decay. Radioactivity measured in Curies (Ci) 1 Ci = 3.7 x 1010 disintegrations per second Also measured in Becquerels (Bq) 1 Bq = 1 disintegration per second

Concept of Half-Life (T1/2) Physical half life (Tp): the time necessary for a radionuclide to be reduced to half of it existing activity. Charachterstic value for each radionuclide . Biological half life (Tb): time is taken to eliminate half of administrated chemical by biological transport or elimination from specific site (elimination from body with urine). effective half life (Te) : incoperates both physical and biological T 1/2 e = T 1 p X T b / T p + T b

Mo-99 / Tc-99m Generator Evacuated Vial Sodium pertecnetate (Na TcO4) Saline Charge Alumina Column 99Mo (1-16Ci) (67 hrs half life) M99 give Tc99m + Beta particles (B absorbed by generator shielding) Tc99m give Tc99 + Gamma ray Direction of Saline Flow

Radiopharmaceuticals Technetium -99m Non particulate emission 6 hrs physical half life Predominate (98%) 140 KeV photon energy Small amount of internal conversion (10%) Low toxicity

Radiopharmaceuticals After IV injection : Tc 99m concentrate in salivary gland , choroid plexus ,thyroid gland and gastric mucosa . Excretion by GI and renal routes .

Gamma Cameras Dual head

Four Main Collimator Types Parallel hole Low Energy Medium Energy High Energy Diverging hole Converging hole Pinhole Multi-Energy

Scintillation Detectors Light Gamma Ray NaI crystal Thalium activated sodium iodine

Photo-multiplier Tube (PMT) Light into Electricity

Bone scan ( whole body bone scan ) Indications : Detection/Staging of Metastatic bone disease Benign bone disease Primary neoplasm Infectious processes Joint diseases Avascular bone disease Osteoporosis Trauma; Stress fractures, scaphoid fracture Metabolic disorders Pain with normal x ray

Pt prepration No special preparation Hydrate patient as much as possible and void frequently to reduce dose and background. Ask pt to empty bladder before the scan immediately . Remove any metallic object from all over the body.

Radiopharmaceuticals Tc-99m – MDP or HDP Adult dosage: 20-25mCi Route of administration IV Delay time post injection 2-3 hrs Camera any, dual heads are recommended for WB Collimators LEAP LEHR Peak 140 kv Window 15% Views : Anterior and posterior for whole bone .

Normal 99mTc-MDP Bone Scan

Metastatic

3- phase bone scan Mainly to determine osteomylities versus cellulities . Also primary bone tumor and stresss fracture Specifec area of skeleton imaged : 1- blood flow (vascularity)for 1-2 min. 2- blood pool immediate post perfusion to 5 min 3- delayed image phase .after 2 hrs

3- phased bone scan Peak at Tc 99m , 15% window LEAP collimators Immediate after IV injection Frame time : frame per 10 sec for 5 min. Delayed imaged 2-3 hrs post injection whole or limited bone scan .

3- phase bone scan Blood pool Delay image