RADIONUCLIDE IMAGINGSEMINAR

Presented by:- Aarti Dubey

Guided by:-Dr Suvarna Dangore Dr R.R. Bhowate Dr S.S. Degwekar

“In this era of diagnostic radiology, progress lies not in enhancing what is, but in advancing towards what will be”

PURPOSE STATEMENTAt the end of the presentation learners

should be able to explain about radionuclide imaging, history,indications, contraindications, advantages ,disadvantages , describe mechanism of radionuclide imaging & various newer radionuclide imaging procedures.

S no.

Learning objectives

domain level criteria condition

1. Explain what is radionuclide imaging.

Cognitive Must know All -

2 Describe the history of radionuclide imaging.

Cognitive Must know All -

3 Enumerate indications and contraindications of radionuclide imaging.

Cognitive Must know All -

4 Enumerate its advantages and disadvantages

Cognitive Must know All -

5 Compare Conventional VS nuclear imaging

Cognitive Must know All -

6 Explain Mechanism of radionuclide production

Cognitive Must know All -

7 Explain about PET, SPECT and fusion imaging

Cognitive Must know All -

ContentsIntroductionHistoryTerminology Indications & Contraindications.Advantages Disadvantages Conventional VS nuclear radiologyRadionuclidesBasics of radionuclide productionRadiopharmaceuticalsNewer techniques (SPECT,PET, PET-CT )ApplicationsConclusion

IntroductionDiagnostic tool that utilizes a radioactive

substance to help diagnose a disease process from inside the body.

Plain radiographs, CT & MRI – Structural/ morphological alterations

Radionuclide imaging-Early physiologic changes/ metabolic alterations

Allows the function of target tissue to be examined under both static and dynamic conditions.

MILESTONES IN RADIONUCLIDE IMAGING

One of the earliest instances of nuclear medicine occurred in 1946 when radioactive iodine, via “atomic- cocktail”, was first used to treat thyroid cancer.

Gamma ray detection (1947-1948)- Coltman and MarshallScintillation camera- Anger in 1957Scintillation detector (1950’s)- Macintyre, Cassen et

al.,Widespread use of radionuclide imaging began in early 1950’s.

SPECT- (1963)- Kuhl and EdwardsIn the 1960’s and the years to follow, the growth of

radionuclide imaging as a speciality discipline was phenomenal.

Initially techniques were developed to measure blood flow to lungs and to identify cancer “hot spots”.

By the 1970’s most organs of the body could be visualized with nuclear medicine procedures including liver and spleen scanning, brain tumour localisation and studies of GIT tract.

In 1971 the American Medical Association officially recognised Radionuclide Imaging (nuclear imaging) as a medical speciality.

1980’s- radiopharmaceuticals were designed, FDG was developed.

1989- FDA approved rubidium-82 for myocardial perfusion imaging.

1990’s- PET was becoming an important diagnostic tool.2000- PET-CT( fusion imaging). The ability to detect the

exact location of the metabolic spot “hot spot” by overlaying the PET and CT images provided priceless information.

Terminologies Nuclear medicine :is a branch of medical

imaging that uses small amounts of radioactive material to diagnose or treat a variety of diseases, including many types of cancers, heart disease and certain other abnormalities within the body.

Radioisotopes: isotopes with unstable nuclei which undergo radioactive disintegration.

Half life: time interval for a specific number of unstable nuclei to decay to one half their original number.

Physical half life Biologic half life

Half-life, biological time required for the body to eliminate one-half of an administered quantity of a radioactive chemical. 

Half-life, physical time required for half of a quantity of radioactive material to undergo a nuclear transformation. The chemical resulting from the transformation may be either radioactive or non-radioactive. 

Gamma ray short wave-length electromagnetic radiation released by some nuclear transformations. It is similar to X-ray and will penetrate through the human body. Iodine 131 emits gamma rays. Both gamma and X-rays cause ionisation.

Ionisation sufficient energy is deposited or removed in a neutral molecule to displace an electron, thus replacing the neutral molecule with positive and negative ions.

Scintillation a flash of light produced in certain materials when they absorb ionizing radiation

Units of activityActivity : Number of disintegrations per

unit time.Curie : represents a radioactivity equal to

3.7x 10dps.In international system of units, activity is

represented by the becquerel.

IndicationsAssessment of site and extent of bone

metastases.Investigation of salivary gland function

particularly in Sjogren’s syndromeEvaluation of bone grafts.Assessment of continued growth in

condylar hyperplasia.Investigation of thyroid function.Brain scans and assessment of a

breakdown of blood brain barrier.

ContraindicationsPregnancy

Allergic reactions

Previous surgical, radiologic procedures.

Prior medications

AdvantagesTarget tissue function is investigated.All similar target tissue can be examined

during one investigation.Computer analysis and enhancements of

results are available.

DisadvantagesPoor image resolution.High radiation dose.Images are not disease specific.Difficult to localize exact anatomical site of

source of emission.Facilities are not widely available.

Nuclear Imaging vs Conventional radiology

The patient, rather than the machine, is source of radiation.

The detection instrument is different.The sensitivities of nuclear medicine are very

great.The specificities are very low.

Radioisotopes

RADIOISOTOPES TARGET TISSUE

Technetium(99m Tc-pertechnetate)

SG,Thyroid,bone,blood,liver,lung and heart

Gallium(67 Ga) Tumours and inflammation.

Iodine(131I) Thyroid

Krypton(81 Kr) Lung

Radiopharmaceuticals

Radionuclide that has been modified by chemically combining it with various biochemicals that may have physiologic or metabolic properties that would be beneficial in a particular study.

Incorporated into diverse and biologically important compounds

GlucoseAmino acidsAmmonia

Why Technetium(99m Tc-pertechnetate) ???Single 141ev gamma emissions which are

ideal.Short half life=6.5 hrsReadily attached to variety of different

substances that are concentrated in different organs.

Safe, Easily produced , as and when required, on site.

Nuclear Imaging Radionuclide delivered to the patient

emission of photons from within the patient.

Location of radionuclide within the structure.

This information emitted from the structure is captured by a detector.

The scintillation detector is used.

Detectors collect the emissions= IMAGE.

Anger cameraMost commonly used equipment.Developed by Hal Anger in 1957.Consist of a lead collimator and a means of

detecting the emission.Detector is made up of a scintillation

crystal coupled to a photomultiplier tube.Scintillation substance used is thallium-

activated sodium iodide.Image illustrating the amount and location

of the radioactivity that has collected inside the patient.

Gamma radiation

Detected by scintillating crystal ( ability to fluoresce on interaction with gamma rays)

Fluorescence detected by photomultiplier tube that magnifies and amplifies the signal

Amplified signal is digitized

Production of image by computer algorithm ( use of a scintillation crystal for obtaining data for image formation has led to this technique being labelled as scintigraphy.)

Imaging devicesPlanar nuclear imagingSingle-photon-emission computed

tomographyPositron emission tomographyFusion imaging

Planar imagingScintillation cameras convert detected

gamma radiation into light emissions.Image display &analysis – Photomultiplier

tube and computer systems.Commonly used to examine:Primary and secondary malignancies Inflammatory conditionsMetabolic diseaseTrauma

BONE SCANIn contrast to a radiograph, bone scan

gives no information on morphology of lesion, either internally or in areas of bone adjacent to the lesion.

The scan does demonstrate, however areas of altered bone metabolism within and around the lesion, thus allowing a reasonably accurate assessment of the growth of a lesion and extent of its borders.

Bone scan also allows to view the entire skeleton with no additional radiation burden to the patient.

Positive findings usually lead to conventional radiographs of the suspicious areas, allowing morphologic study of regions with altered metabolism.

Types of Bone scanStandard whole body scan.

Three-phase bone scan.

Three-phase bone scanDynamic vascular flow phase- imaging

every 2-3 seconds after injection of intravascular contrast medium.

Blood pool phase: images are taken after every 5 mins.

Osseous delayed static phase: occurs after 2-4 hours.

Agents usedTechnetium bone scanGallium bone scan (half life=78 hrs)

If a technetium bone scan is being contemplated, it should be performed first.

Gallium scan is mainly used in cases of osteomyelitis.

Adjunct with technetium scan.

Mechanismthe patient is injected (usually into a vein in the

arm or hand, occasionally the foot) with a small amount of radioactive material.

Binds to calcium ion in bone-

Attaches to methylene diphosphonate in bone

Scanning with gamma camera

More active the bone turnover, the more radioactive material will be seen.

A patient undergoing a SPECT bone scan. The patient lies on a table that slides through a scanner, while two gamma cameras rotate around him. Machine operators typically work remotely from another room, shielded from the radiation being emitted by the patient.

Bone scan showing multiple bone metastases from prostate cancer.

Positron Emission TomographyA nuclear medicine imaging technique which

provides high resolution tomographic images of the bio-distribution of a radiopharmaceutical or radiotracers in the body.

A PET scan measures important body functions, such as blood flow, oxygen use, and sugar (glucose) metabolism, to help doctors evaluate how well organs and tissues are functioning.

a radioactive isotope that decays by positron emission is introduced into the body.

Many different radioisotopes are there, such as Fluorine18, Oxygen15, and Carbon11.

18F is the most commonly used isotope. It replaces hydroxyl (OH) group in molecules of interest.

Within the cell, FDG is phosphorylated by enzyme “hexokinase” to 2-deoxyglucose-6-phosphate

Increased proliferation of tumor cells manifest as increased uptake of FDG in cancer cells compared to the surrounding normal tissue

Positron emitting radioisotopes are prepared by bombarding stable atomic nuclei by protons.

Protons are speeded up in a particle accelerator called cyclotron which then impinge upon the stable nuclei, and knocks out one neutron from its nucleus.

ANNIHILATION The Feynman diagram below is one of the most common

occurrences when an electron e- and a positron e+ collide and

it is called electron-positron annihilation.

The result of this collision is the transformation of the electrons

into gamma ray photons.

TRACER

EMITTS POSITRON

POSITRON THEN ANNILATES WITH ELECTRON

TWO GAMMA PROTONS EMITTED IN OPPOSITE DIRECTION

PET SCANNER DETECTS THESE EMISSION COINCIDENT IN TIME (PROVIDES RADIATION EVENT LOCALIZATION, THUS INCREASING RESOLUTION OF IMAGES THAN SPECT)

ADVANTAGESNon-invasiveLow-risk infection compared to surgeryIdentifying active diseases after therapy

completionOutcome of chemotherapy

E.g. In non-Hodgkin’s lymphoma, FDG uptake was found to decrease as early as 1 d after the initiation of chemotherapy

early assessment of response during the first treatment cycles is important to appreciate chemosensitivity and may potentially guide further risk-adapted therapeutic strategies in aggressive lymphoma

DISADVANTAGESRadiation risk: although minimal

(equivalent to 2 chest radiograph)Not indicated in pregnancy & lactationShort t1/2, limited time for completing scan

on patient (~120 mins)ExpensiveNon-availability of cyclotron (expensive)

UsesDetect nodal neck disease in OSCC.Response of tumor to treatment.Detect distant unknown metastasis. for occult or micrometastasis.Acceptable sensitivity and specificity.Can give false positive New granulation tissue Inflammation.Recently irradiated neck

Single Photon Emission Computed Tomography

Emissions of single photon from decay process.

Dynamic imaging modality where a series of images are obtained

Images obtained in three planes.Obtained from different angles.Reconstructs the layer .

RADIOISOTOPE IS DELIVERED TO THE PATIENT

ATTACHES TO SPECIFIC LIGAND IN THE BODY FORMING

RADIOLIGAND WHICH HAS CHEMICAL BINDING PROPERTIES TO CERTAIN TYPES OF TISSUES

THIS RADIOLIGAND IS CARRIED AND BOUND TO PLACE OF INTEREST

THERE IS GAMMA EMISSION OF RADIOLIGAND WHICH IS DETECTED BY GAMMA CAMERA

PRODUCTION OF IMAGE

AdvantagesNot as expensive as PET.Standard radiopharmaceuticals are used

eliminating the need for a cyclotron to produce short half life radiopharmaceuticals.

Requires less space and consumables.

Fusion imagingCombinations of two different modalities to

produce final image.CT and SPECT.CT and PET.PET and MRIStructure and function.Eliminate the mismatching of images.Imaging times are reduced.Accurate localization.

Coregistered FDG-PET and low-resolution MRI images and image fusion

Sublingual glands Tonsils Spinal cord Submandibular glands

Applications of radionuclide imagingLymphoscintigraphySalivary gland scintigraphyOral and maxillofacial inflammationTumorsTraumaBone healingTmj

Lymphoscintigraphy

Simple and non-invasive functional test for demonstrating lymphatic pathways.

Technetium 99m sulphur colloid is injected in 4-6 subcutaneous sites around neoplastic sites.

Colloid will be carried in lymphatic channels to first lymph node draining that area, so called sentinel node.

Best predictor of nodal spread of tumor.Imaged using gamma camera.Sentinel node is free, remaining nodes are

free.Sentinel nodes are positive- remove

remaining nodes.

If the node is disease free, patient is spared an elective neck dissection.If node is positive, the patient goes on to a more formal neck dissection.

Salivary Gland Studies Used for functional evaluation and evaluating

mass lesions.Te99 mimics chloride influx into the acinar

cells.Involves administrating a radioactive tracer

with affinity for tissue of interest.Recorded with scintillation camera.Study is rarely diagnostic, but is useful adjunct.Mass lesions in a gland present as areas of

decreased uptake.Patients with Sjogren’s syndrome may have

poor uptake and poor response to stimulation.

Agent used Tc99m Iodinated contrast media

Administration Intravenous Retrograde pressure of contrast media

Detector Gamma camera Fluoroscope

Structures Glandular parenchyma

Duct system

Advantages Function, sensitive High resolution of ducts.

Disadvantages Non specific Contraindications

Salivary gland scan Sialography

Inflammatory diseasesBone scintigraphy can be used to disclose

periapical lesions .Used to detect inflammatory responses of TMJ.SPECT is used to detect arthritic changes.Osteomyelitis of jaws.

Bone-graft viabilityMeans of predicting graft failure before clinical

or radiographic changes are apparent.Positive scan is correlated with a viable bone

graft.Negative bone scan corresponds to non-viable

bone graft.

Periodontal diseaseIn various studies, it has been reported that

the uptake of radionuclide Tc99m was elevated in alveolar bone with chronic destructive periodontal disease.

More sensitive method to detect bone loss than were standard intraoral radiograph.

TumorsBone scanning at three and 24 hours

following radiopharmaceutical administration has been shown to enhance differentiation of benign from malignant tumors.

Uptake increases in malignant tissue.Uptake in degenerative lesions decreases.FDG PET test has a good predictive value

for identifying recurrent malignancies in head and neck.

TraumaInitial detection of subtle bone fractures , not

apparent on standard radiographs.Evidence of stress fracture on radiographs

appear late in the healing process i.e. up to two to 12 weeks after nuclear imaging.

An interesting case report described a stress fracture detected by nuclear imaging in an ice cream scooper’s hand.

Temporomandibular jointEvaluation of bone metabolism in bony

components of TMJ.For assessment of skeletal facial growth.Presence of active hyperplastic activity in

these joints.Effectiveness of SPECT for quantitative

skeletal scintigraphy of mandibular condyle.Usefulness of Tc 99m uptake in correlation

of mandibular growth with chronological and skeletal age.

Radiation dose

CT Scan 7.6 Sv

Bone scan 4 Sv

F-18FDG PET 5.9 Sv

PET 6 Sv

If an injection of 3.7 X 10 (8) Bq of 99m Tc delivered = a whole body radiation dose of 1 mGy which is about 1/3rd the average annual effective dose resulting from natural radiation.

CONCLUSIONNuclear medicine procedures are costeffective. There are nearly 100 different nuclear medicine

imaging procedures available today. Unlike other tests/procedures, etc., nuclear

medicine provides information about the function of virtually every major organ system within the body.

Nuclear medicine procedures are painless and do not require anesthesia.

Nuclear medicine is an integral part of patient care and contributes to the well being of patients worldwide.

REFERENCESFreny R Karjodkar; Dental & Maxillofacial

Radiology; 2nd edWhite & Pharoah; Oral Radiology principles

and interpretation; 5th edGhom’s ; Oral RadiologyHenry N. Wagner.What is nuclear medicine;

Siemens Medical Solutions, USA,Inc.; Philips Medical Systems; and Digirad.

Johan Nuyts. Nuclear Medicine Technology and Techniques;