Bone Scan Pp

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Nuclear Medicinein Musculoskeletal system


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Introduction

Nuclear medicine is defined as a medical

speciality which uses the nuclear properties

of the matter to investigatephysiology andanatomy, diagnose diseases, and to treat

with unsealed sources of radionuclide


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Introduction

Characteristic:

Used Radiation from Nuclear desintegration

Physiologic process and change of function

from the organbiochemistric process in

celluler or moleculer levels.

Non-invasif, sensitivity >>>, specificity


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Introduction

A wide variety of musculoskeletal disorders can beinvestigated by nuclear medicine techniques,particularly through Bone scintigraphy/Bone Scan

The principal conditions that can be imaged are :

- metastatic bone disease- osteomyelitis

- variety of benign conditions (fractures,

avascular necrosis, inflammatories arthro-

pathies, metabolic bone disease, etc).


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Bone scan is commonly performed withTc99m-biphosphonates.

Bone scanning is performed with the

gamma camera.

Bone scan is more sensitive thanradiography in detecting skeletal disease.


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Pathophysiology of Biphosphonate Uptake

The bone scan provides information that reflectsskeletal metabolic activity.

The mechanism involved in biphosphonate uptakeis thought by chemiabsorption onto the calcium ofhidroxyapatite in bone, i.e. the biphosphonatemolecule is adsorbed onto the surface of bone.

The major factors which affect this adsorption :- osteoblastic activity

- skeletal vascularity.


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The bone scan therefore reflects the metabolic

reaction to a disease process.

Because its ability to detect functional

change, the bone scan can often be strongly

positive, well before the structural X-ray

changes occur.


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The Normal Bone Scan

The most important : symmetry.

There should be uniform uptake, greater activity atsites ofhighest metabolic activity (joint margins)& areas rich in trabecular bone (the spinal

vertebral bodies).

Biphosphonate not taken up by the skeleton isexcreted via the urinary tract tracer is

visualized in kidney & bladder.

Uptake of bone scanning agents can also occur insoft tissues significant abnormalities.


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Three-Phase Bone Scan

Provide additional valuable info regardingthe vascularity of a lesion.

This involves :o Initial dynamic flow study (1st phase)

o A blood pool image (2nd phase)

o Delayed static images (3rd phase) can beobtained between 2 & 4 hours.

For the diagnosis ofosteomyelitis, thethree-phase bone scan is typically used.


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Bone Scan in Malignancy

The detection ofmetastatic skeletal diseaseremains the most important indication forperforming a bone scan.

The common cancers that metastasise to the boneare those of the prostate, breast & lung.

The most characteristic feature of metastases isirregular focal lesions in a pattern that does notcorrespond to any single anatomical structure.


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Bone Scan in Malignancy

In general, metastases must generate anosteoblastic response in order to be detectedon the bone scan.

Metastases can on occasion produce an areaof decreased uptake (cold lesion) reflectingbone destruction & failure to stimulate ahealing response. This is most often seen inmyeloma or renal carcinoma.


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Important variant to recognise : Superscanof malignancyextensive focal lesions.

Therenal images are not visualizeddue to

less tracer is excreted via the renal tract.should be followed by more specific

investigation directed to the site of

abnormality.


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Bone Scanning In The Management ofMalignancy

For staging for a malignancy at presentation.

Metastases may be present in an asymptomatic

individual & even in patient with a suspectedmetastasis because of bone pain, moreextensive disease may be found when the bonescan is undertaken.


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Bone Scanning In The Management of Malignancy

The bone scan can be helpful in monitoringresponse to therapy. The use of the bonescan to assess the response to therapy is notalways straightforward.

Flare response : transient worsening of scanfindings in response to treatment in the firstfew months after therapy.


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Breast Cancer

An important part ofstaging in breast cancer patients.

In early breast cancer, the pick-up rate of metastases islow, about 3% in stage II. However, bone scan has a

useful role as a baseline study In more advances disease, at presentation the pick-up

rate of metastases is high ( 28%).

An abnormal bone scan carries a mean survival of 2-3

years, and is clearly of prognostic importance


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Prostate Cancer

Higher incidence of metastases (around 38% ) &increases in more advanced disease good case for

bone scan in all patients for staging.

Prostate-specific antigen (PSA) is used to detect

metastases. Although patients with an elevated PSA

should have bone scan.

It is common to find patients with normal PSA but

who have skeletal metastase.


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Lung Cancer

Most patients with lung cancer have a poor

prognostic at presentation. The bone scanimportant in such patients where surgery is

considered to exclude skeletal metastase.


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Primary Bone Tumours

A wide variety of benign & malignanttumours can be investigated with bone

scintigraphy.Of malignant tumours : osteosarcomas,

Ewings tumours, & giant cell tumoursusually show increased tracer uptakeon both blood pool & delayed images.


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Primary Bone Tumours

Among benign tumours, bone scan in most usefulfor detecting osteoid osteoma, as radiographs arecommonly normal & the bone scan has a

characteristic appearance

Osteoblastomas & chondroblastomas also showincreased activity on both blood pool & delayedimages but have characteristic X-ray appearances.


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Osteomyelitis

The use of bone scan for osteomyelitis has

become an established routine procedure.

Uptake in osteomyelitis is usually focal &present in all three phases.

A bone scan will often show increased

activity about 2 weeks before an X-raybecomes positive.


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Metabolic Bone Disease

Increased uptake in axial skeleton

Increased uptake in long bones

Increased uptake in periarticular area Faint or absent kidney images

Prominent calvaria and mandible

Beading of costochondral junction

Tie sternum


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Avascular Necrosis

Bony infarction complication offracture

Bone scanreduced uptake due todiminished blood supply.


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Imaging infection/inflammation

Inflammation reaction of the body to any

kind of injury

Infection simply means contaminationwith microorganism


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Radiopharmaceuticals for image infection

Non specific : Ga-67 citrate

increased blood supply, vascular

permeability and enhanced transudation

Specific : specific processes of accumulation

comprise a number of possible interaction

between the radiopharmaceuticals and thetarget


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Leucocytes : HMPAO, cytokines,

interleukin-1, 2 and 8, platelet factors 4

Antibiotics : ciprofloxacin , peptides

FDG-PET


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Imaging with Tc99m-Ciprofloxacin(Infecton)


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Introduction

Ciprofloxacin is an antibiotic with theproperty of binding to actively dividingbacteria. It binds to the DNA-gyrase

enzyme.A study showed that it binds to a widerange of bacteria, particularlystaphylococciappropriate for imaginginfection.


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Introduction

Imaging is undertaken at 1 hour & 4 hourafter injection. In particular circumstances,

a 24 hour imaging is essential.


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Normal Features

Vascular, renal & urine activity are visible becauseinfecton is renally excreted.

Decrease of liver,spleen & blood pool activity with time.

No bone marrow uptake the problem of bone marrow

interference in the interpretation of inflammatory changdoes not arrise.

Symmetrical uptake in bone epiphyses in growing

children is a normal variant.


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Clinical Advantages

The main indication : when there is a need tolocalise the site of bacterial infection, example :in patient with a fever of unknown origin.

Its particular use in distinguishing activebacterial infectionfrom inflammatory particularlyin orthopaedic conditions : osteomyelitis, septic

arthritis, evaluation of prostheses, vertebralabscess or infection in the sternum after

coronary bypass surgery.


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In the diabetic foot, is it skin & bone that is

infected or skin alone ?

In the knee, is it aseptic inflammation or septicarthritis ?

In the hip prosthesis, does it have asepticinflammation or is it infected ?

It aids the management of patients with suspectedor known bacterial infection, particularly with

regard to key issue of when to stop antibiotictherapy.


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Acute Inflammation Vs Active

Infection

In typical acute inflammatory joint due to

rheumatoid or other arthropathy, theuptake at 1 h & 4 h is visible, but at 24 h ithas fadednot infected


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Acute Inflammation Vs Active Infection

Infecton is a small molecule which rapidly

diffuses in & out of sites of inflammation.Itdiffuses in rapidly because of the extrapermeability of an inflammatory lesion. Itdiffuses out because there is no specific

binding & as the blood level of infectonfalls, so the level in the inflammation willfall.


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Acute Inflammation Vs Active Infection

If there is specific binding, then Infecton

will remain bound to that site because of thedividing bacteria.


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As well as its specificity for bacteria, there

is a dynamic specificity, which helps to

differentiate active bacterial infection fromacute or active non-bacterial inflammation.


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The key to the success of this agent is

not only that it binds to bacteria, but

that it clears quickly from sites of non-infected inflammation 24 h image is

essential.


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References

1. Maisey MN, Britton KE and Collier BD

(1998). Clinical Nuclear Medicine. 3rd

edition. Chapman & Hall Medical.London.


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