Skeletal Scintigraphy (Bone Scan) PDF

SKELETAL SCINTIGRAPHY (BONE SCAN) FS SABAYA OUTLINE INTRODUCTION -Definition ANATOMY TECHNEQUES -Radiopharmaceutical -Mechanism of uptake -Imaging techniques INTERPRETATION OF BONE SCAN CLINICAL APPLICATIONS INTRODUCTION DEFINITION – Bone scan is a test that detects areas o...

SKELETAL SCINTIGRAPHY (BONE SCAN) FS SABAYA OUTLINE INTRODUCTION -Definition ANATOMY TECHNEQUES -Radiopharmaceutical -Mechanism of uptake -Imaging techniques INTERPRETATION OF BONE SCAN CLINICAL APPLICATIONS INTRODUCTION DEFINITION – Bone scan is a test that detects areas of increased or decreased bone activity by injecting a certain radiopharmaceutical i.e. 99mTc-MDP Bone scan is one of the most commonly performed procedures in Nuclear Medicine Bone scan often provides an earlier diagnosis and demonstrates more lesions than are found in radiographic procedures It is a very sensitive study but not specific ANATOMY The skeletal system can be divided into two main divisions;  AXIAL SKELETON (HEAD AND TRUNK) -Skull -Thorax (Ribs and sternum) -Spines (includes sacrum and coccyx)  APPENDICULAR SKELETON -Shoulder girdle, clavicle& scapula -Upper extremity -Pelvic girdle -Lower extremity INDICATIONS FOR BONE SCAN ONCOLOGY ORTHOPEDICS OTHERS Oncology - Primary bone tumors -Skeletal metastasis (staging) -Extension of soft tissue neoplasm to bone -Treatment Response evaluation INDICATIONS CONT.. Orthopedics - Trauma - Fractures (Radiologic occult stress-related fractures (e.g., scaphoid, tarsals) or nonspecific symptoms) - Prothesis evaluation - Infectious bone diseases.Osteomyelitis - acute, subacute, or chronic; bacterial, mycobacterial, or fungal origin.Septic arthritis INDICATION CONT.…. Spondylodiscitis or spondylitis. Septic loosening or mechanical complication of internal fixation (long bones or spine) or arthroplasty (hip, knee, ankle, or shoulder). Others -Metabolic bone disease -Paget's disease -A-symmetric mandibular growth -Un-explain bone pain CONTRAINDICATION Pregnancy because transplacental transmission of radiopharmaceuticals is possible and Breast milk will carry isotope activity for several days after the study RADIOPHARMACEUTICALS They are bone seeking agents They are labelled with technetium-99m They are calcium and phosphate analogs The most widely used radiopharmaceuticals is Tc-99m labelled diphosphonates - 99mTc-HDP (HYDROXY DIPHOSPHONATE) - 99mTc-MDP (METHYLENE DIPHOSPHONATE) 99m Tc-MDP Used 4 hours after preparation Labelling yield: >95%, avoid injecting air into the vial…..oxidation of Tc…..oxidized Tc….poor tagging of phosphates. -Free pertechnetate in the thyroid gland and stomach They are given intravenously (I.V) High target/background ratio within 2-3 hours. With 50-60% of the injected activity localizing in bone Rapid renal clearance Renal impairment- Increased soft tissue activity, poor image quality, delayed excretion, higher radiation exposure due to retained high activity MECHANISM OF LOCALIZATION/UPTAKE Phosphate groups bind to the hydroxyapatite [Ca3(Po4)2] structure of bone tissue by a mechanism called CHEMISORPTION. The hydroxyapatite structure of bone is exposed during bone remodeling. So, more radiopharmaceutical will deposit in that region giving “hot” area. 50-60% of the injected dose localized on bone remain dose is cleared by kidneys In other word, 99mTc-MDP uptake depends on osteoblastic and osteoclastic activity TECHNIQUES Preparation: None 99mTc-MDP dose (740 – 1000)MBq or (20 – 25)mCi Good hydration afterwards and frequent voiding Wait about 2-3 hours to start imaging, avoid contamination Empty bladder prior to scanning Change the cloth and remove things likely cause artefacts e.g. metals THREE PHASE BONE SCAN It is done when there is soft tissue hyperemia Dynamic phase (Perfusion/vascular phase) (60 second immediately post injection) Blood pool phase (soft tissue phase) (5 minutes post injection) Delayed phase (Bone phase) (2-3 hours post injection) DYNAMIC PHASE 30-60 dynamic images are usually obtained over 1 minute immediately after injection This is radionuclide angiography and gives an idea about the local vasculature. During the first minute after injection, injected dose is still intravascular BLOOD POOL PHASE Static image is obtained in 5 minutes after dose injection Within 5 minutes post injection, radiopharmaceutical moves from intravascular space to extravascular space (soft tissue). It give idea about soft tissue edema DELAYED PHASE It is the bony phase image obtained in 2-3 hours post injection It is the same as whole body bone scan PROTOCOL/IMAGE ACQUISITION Instrumentation/equipment: A single- or dual-head-camera may be used. An ultra- high-resolution collimator may be used for delayed images. Collimator : A low-energy, high-resolution (LEHR) parallel-hole collimator is preferable, but a low-energy all-purpose collimator may also be used. The energy window should be centered at 140 keV with a window width of between 15% and 20%. Phase 1 images If dynamic images are acquired, the camera should be positioned over the region of interest before radiopharmaceutical injection. The acquisition computer should be programmed to acquire approximately 30–60 images at 1–3 s/frame. 64 x 64 matrix Phase 2 images Acquired for approximately 3–5 min/image immediately after the dynamic phase 128 x 128 matrix size Phase 3 images Acquired for approximately 2-3 hours post radiopharmaceutical injection 256 X 1,024 matrix size Basic views – Pelvic image (AP – PA static) - Skull (Lateral views) - Whole body sweep (15 minutes) PATIENT POSITION Supine with the feet first in the camera Arms on the sides of the body INTERPRETATION An increase in radiopharmaceutical uptake, compared with normal bone, indicates increased osteoblastic activity. A decrease in uptake intensity or number of abnormalities in comparison with a previous study often indicates improvement and may be secondary to therapy (e.g., radiation or chemotherapy). Superscan