BONE ISOTOPE SCANBONE ISOTOPE SCANالمقبل قصي المقبل الدكتور قصي الدكتور

- والطب األشعة قسم مشارك - أستاذ والطب األشعة قسم مشارك أستاذالنوويالنووي

- والتكنولوجيا العلوم جامعة الطب - كلية والتكنولوجيا العلوم جامعة الطب كليةاألردنيةاألردنية

IntroductionIntroduction

Bone scan is one of the most commonly Bone scan is one of the most commonly performed procedures in nuclear performed procedures in nuclear medicine.medicine.

Bone scan often provides an earlier Bone scan often provides an earlier diagnosis and demonstrates more lesions diagnosis and demonstrates more lesions than are found by radiographic than are found by radiographic procedures.procedures.

Sensitivity and SpecificitySensitivity and Specificity

Bone scan is very sensitive study but it is Bone scan is very sensitive study but it is not specific. not specific.

Although findings on bone scan are non-Although findings on bone scan are non-specific, its monostotic or polyostotic specific, its monostotic or polyostotic status and anatomical distribution can status and anatomical distribution can provide important clues to the differential provide important clues to the differential diagnosis.diagnosis.

RadiopharmaceuticalsRadiopharmaceuticals

They are bone seeking agents.They are bone seeking agents. They are labeled with Tc99m.They are labeled with Tc99m. They are phosphate analogs.They are phosphate analogs. Most commonly used one is HDP Most commonly used one is HDP

(Hydroxy Methylene Diphosphonates).(Hydroxy Methylene Diphosphonates). They are given intravenously.They are given intravenously.

Mechanism of LocalizationMechanism of Localization

Phosphate groups bind to the hydroxyapatite Phosphate groups bind to the hydroxyapatite [Ca3(Po4)2] structure of bone tissue by a [Ca3(Po4)2] structure of bone tissue by a mechanism called chemisorption.mechanism called chemisorption.

The hydroxyapatite structure of the bone is The hydroxyapatite structure of the bone is exposed during bone remodeling. So, more exposed during bone remodeling. So, more radiopharmaceutical will deposit in that region radiopharmaceutical will deposit in that region giving “hot” area.giving “hot” area.

50-60% of injected dose localized on bone, 50-60% of injected dose localized on bone, remain dose is cleared by kidneys.remain dose is cleared by kidneys.

Whole body bone scanWhole body bone scan

This is the bony phase of bone scan.This is the bony phase of bone scan. Inject radiopharmaceutical and image in Inject radiopharmaceutical and image in

2-4 hours.2-4 hours. When we say bone scan, we usually When we say bone scan, we usually

mean whole body bone scan. mean whole body bone scan.

Three Phase Bone ScanThree Phase Bone Scan

It is done to see if there is soft tissue It is done to see if there is soft tissue hyperemia.hyperemia.

First phase is the perfusion phase or First phase is the perfusion phase or vascular phase.vascular phase.

Second phase is the blood pooling phase Second phase is the blood pooling phase or soft tissue phase.or soft tissue phase.

Third phase is the bony phase.Third phase is the bony phase.

First PhaseFirst Phase

30-60 dynamic images are usually 30-60 dynamic images are usually obtained over 1 minute immediately after obtained over 1 minute immediately after injection.injection.

This is radionuclide angiography and gives This is radionuclide angiography and gives an idea about the local vasculature. During an idea about the local vasculature. During the first minute after injection, injected the first minute after injection, injected dose is still intravascular. dose is still intravascular.

PerfusionPerfusion

Second PhaseSecond Phase

Static image is obtained in 5 minutes after Static image is obtained in 5 minutes after dose injection.dose injection.

Within 5 minutes post injection, Within 5 minutes post injection, radiopharmaceutical moves from radiopharmaceutical moves from intravascular space to extravascular space intravascular space to extravascular space (soft tissue). It gives idea about soft tissue (soft tissue). It gives idea about soft tissue edema. edema.

Blood PoolBlood Pool

HyperemiaHyperemia

If there is focal increased activity in If there is focal increased activity in the first and second phases, the first and second phases, hyperemia or acute inflammatory hyperemia or acute inflammatory process is presentprocess is present..

Third PhaseThird Phase

It is the bony phase image obtained in It is the bony phase image obtained in 2-4 hours post injection.2-4 hours post injection.

It is the same as whole body bone It is the same as whole body bone scan. scan.

Clinical ApplicationsClinical Applications

Malignancy Malignancy

1- Primary bone cancer1- Primary bone cancer

2- Secondary metastatic bone disease2- Secondary metastatic bone disease

Osteomyelitis Osteomyelitis Stress fractures Stress fractures

Primary Bone MalignancyPrimary Bone Malignancy(Sarcomas)(Sarcomas)

MRI provides more exact information MRI provides more exact information regarding tumor extent, particularly in soft regarding tumor extent, particularly in soft tissue. So, bone scan is not a diagnosis tissue. So, bone scan is not a diagnosis image in primary bone tumors.image in primary bone tumors.

Bone sarcomas-cont..Bone sarcomas-cont..

Bone scan is a staging and restaging Bone scan is a staging and restaging image in bone sarcomas. It is performed to image in bone sarcomas. It is performed to see if there is bone metastatic disease see if there is bone metastatic disease (bone to bone).(bone to bone).

40 – 50% of patients with either Ewing’s 40 – 50% of patients with either Ewing’s sarcoma or osteosarcoma develop sarcoma or osteosarcoma develop osseous metastases within 2 years of osseous metastases within 2 years of presentation.presentation.

Metastatic Bone DiseaseMetastatic Bone Disease

Bone scan is an extremely important tool Bone scan is an extremely important tool in decision making during management of in decision making during management of cancer patients.cancer patients.

Any cancer potentially could cause bone Any cancer potentially could cause bone metastatic disease. metastatic disease.

However, prostate, breast and lung However, prostate, breast and lung cancers have propensity to metastasize to cancers have propensity to metastasize to bone. bone.

Metastatic Bone Disease and Metastatic Bone Disease and Bone PainBone Pain

About 80% of patients with known cancer About 80% of patients with known cancer and bone pain have metastases and bone pain have metastases documented by bone scan.documented by bone scan.

30 – 50% of patients with metastatic bone 30 – 50% of patients with metastatic bone disease do not have bone pain. disease do not have bone pain.

Metastatic Bone Disease and Metastatic Bone Disease and Image FindingsImage Findings

The hallmark of metastatic bone The hallmark of metastatic bone disease is multiple foci of increased disease is multiple foci of increased osteoblastic activity in bony skeleton. osteoblastic activity in bony skeleton. However, single lesion could be also However, single lesion could be also metastatic.metastatic.

Stress FracturesStress Fractures

It is often difficult to visualized on a plain It is often difficult to visualized on a plain radiograph.radiograph.

Fractures may be identified by bone scan Fractures may be identified by bone scan as early as 24 hours after occurrence.as early as 24 hours after occurrence.

3-phase bone scan is usually done. 3-phase bone scan is usually done. There is hyperemia and osteoblastic There is hyperemia and osteoblastic

process (three phases are positive).process (three phases are positive).

Stress FractureStress Fracture

Blood PoolBlood Pool

Anterior Posterior

Anterior Posterior Left Lat Right Lat

Left Lat Right Lat

2 hour delay2 hour delay

Stress FractureStress Fracture

Acute OsteomyelitisAcute Osteomyelitis

Early plain radiography signs of Early plain radiography signs of osteomyelitis are non-specific.osteomyelitis are non-specific.

3-phase bone scan is usually the 3-phase bone scan is usually the procedure of choice to differentiate procedure of choice to differentiate between osteomyelitis and cellulitis.between osteomyelitis and cellulitis.

Acute Osteomyelitis-cont..Acute Osteomyelitis-cont..

If first and 2nd phases are positive If first and 2nd phases are positive (hyperemia) with normal third phase, (hyperemia) with normal third phase, diagnosis would be cellulitis.diagnosis would be cellulitis.

In acute osteomyelitis all 3-phases In acute osteomyelitis all 3-phases are positive (hyperemia and are positive (hyperemia and osteoblastic process in the bone).osteoblastic process in the bone).

PerfusionPerfusion

Blood PoolBlood Pool

Whole Body Whole Body Bone ScanBone Scan