Introduction to Introduction to Nuclear Nuclear

MedicineMedicine

What is Nuclear What is Nuclear medicine?medicine? It is the use of radioactive materials in medicine.It is the use of radioactive materials in medicine.

It may be either diagnostic or therapeuticIt may be either diagnostic or therapeutic In the therapeutic issue we must differentiate In the therapeutic issue we must differentiate

between between Brachytherapy Brachytherapy ((internal radiotherapy) sealed internal radiotherapy) sealed

source radiotherapysource radiotherapy is a form of is a form of radiotherapy where where a a radiation source is placed inside or next to the area is placed inside or next to the area requiring treatment. Brachytherapy is commonly used requiring treatment. Brachytherapy is commonly used as an effective treatment for as an effective treatment for cervical, prostate, breast, , prostate, breast, and skin cancerand skin cancer

and and TeletherabyTeletheraby ( (External beam radiotherapy)External beam radiotherapy). . Kilovoltage ("superficial") X-rays are used for treating Kilovoltage ("superficial") X-rays are used for treating skin cancer and superficial structures. Megavoltage skin cancer and superficial structures. Megavoltage ("deep") X-rays are used to treat deep-seated tumors ("deep") X-rays are used to treat deep-seated tumors (e.g. bladder, bowel, prostate, lung, or brain).(e.g. bladder, bowel, prostate, lung, or brain).

Nuclear Medicine Nuclear Medicine ProceduresProcedures

Nuclear medicine procedures may be:Nuclear medicine procedures may be: diagnostic studies, which are tests of body diagnostic studies, which are tests of body

functionfunction

therapeutic procedures in which the radiation is therapeutic procedures in which the radiation is used to treat disease.used to treat disease.

Radionuclide therapy is used in the Radionuclide therapy is used in the treatment of both benign disease (eg treatment of both benign disease (eg hyperthyroidism and arthritis) and malignant hyperthyroidism and arthritis) and malignant disease (eg thyroid cancer, Suprarenal gland disease (eg thyroid cancer, Suprarenal gland tumors and hepatocellular carcinoma)tumors and hepatocellular carcinoma)

Nuclear Medicine Nuclear Medicine Diagnoses What?Diagnoses What?

RadiopharmaceuticalsRadiopharmaceuticals The radioactive materials administered to The radioactive materials administered to

patients are known as patients are known as radiopharmaceuticalsradiopharmaceuticals..

These consist of :These consist of : a chemical molecule which determines the a chemical molecule which determines the

behavior of the radiopharmaceutical in the bodybehavior of the radiopharmaceutical in the body a radionuclide. The radiation emitted by the a radionuclide. The radiation emitted by the

radionuclide may be detected from outside the radionuclide may be detected from outside the body by a radionuclide imaging device (a body by a radionuclide imaging device (a gamma camera) or may be detected in a sample gamma camera) or may be detected in a sample of a body fluid (eg plasma or urine)of a body fluid (eg plasma or urine)

RadiopharmaceuticalsRadiopharmaceuticals

Diagnostic radiopharmaceuticals must Diagnostic radiopharmaceuticals must deliver the minimum possible radiation deliver the minimum possible radiation dose to the patient while still obtaining dose to the patient while still obtaining the required diagnostic information.the required diagnostic information.

Therapy radiopharmaceuticals must Therapy radiopharmaceuticals must deliver the maximum radiation dose to deliver the maximum radiation dose to the diseased organ or tumor, while the diseased organ or tumor, while minimizing the radiation dose to non-minimizing the radiation dose to non-target tissues such as the bone marrow.target tissues such as the bone marrow.

The Ideal Radionuclide The Ideal Radionuclide for for

In-vivo ImagingIn-vivo Imaging It must emit photons in high abundance in It must emit photons in high abundance in

energies which can be efficiently detected energies which can be efficiently detected by the gamma camera (100 keV - 300 keV)by the gamma camera (100 keV - 300 keV)

It should not emit charged particles as It should not emit charged particles as these are absorbed within a few millimetres these are absorbed within a few millimetres of tissue. These can not be detected of tissue. These can not be detected outside of the body and greatly increase the outside of the body and greatly increase the radiation dose to the patient.radiation dose to the patient.

It should have a short half-life, again to It should have a short half-life, again to keep the radiation dose as low as possible.keep the radiation dose as low as possible.

The Ideal Radionuclide The Ideal Radionuclide for Therapyfor Therapy

Must emit energetic charged particles. Must emit energetic charged particles. These are usually beta particles but may These are usually beta particles but may be Auger electrons, internal conversion be Auger electrons, internal conversion electrons or even alpha particles.electrons or even alpha particles.

Low cost, available, safe.Low cost, available, safe.

A fairly short half-life, typically several A fairly short half-life, typically several days.days.

Targeting the Right Targeting the Right Tissue or OrganTissue or Organ

The metabolism of the radiopharmaceutical in The metabolism of the radiopharmaceutical in the body will depend on its chemical the body will depend on its chemical properties.properties.

Some are simple ions, such as Some are simple ions, such as 6767Ga citrate and Ga citrate and sodium sodium 131131IodideIodide

Some are particles or aggregates of molecules Some are particles or aggregates of molecules labelled with a radionuclidelabelled with a radionuclide

Some are radio-labelled blood cells (red cells or Some are radio-labelled blood cells (red cells or white cells)white cells)

The remainder are labelled complex molecules, The remainder are labelled complex molecules, such as phosphonates, peptides and antibodies.such as phosphonates, peptides and antibodies.

Clinical applicationsClinical applications

Bone scintigraphy:Bone scintigraphy: is a study of the is a study of the skeletal system that uses a form skeletal system that uses a form 99m99mTc Tc injected intravenously absorbed by the injected intravenously absorbed by the bone. bone.

Genitourinary studies: Genitourinary studies: provides both an provides both an anatomic and functional evaluation of the anatomic and functional evaluation of the kidneys especially after transplantation.kidneys especially after transplantation.

Brain scan: Brain scan: evaluate various neurologic evaluate various neurologic conditions as Alzheimer and Parkinson conditions as Alzheimer and Parkinson disease.disease.

Thyroid uptake study: Thyroid uptake study: to evaluate to evaluate functions of the thyroid gland using functions of the thyroid gland using sodium iodide sodium iodide 131131I.I.

Radionuclides in Radionuclides in Common UseCommon Use

Four radionuclides account for the large Four radionuclides account for the large majority of clinical procedures. These are :majority of clinical procedures. These are :

99m99mTcTc T T½½ 6 hours principal 6 hours principal energy 140 energy 140 keVkeV

131131I I T T½½ 8 days principal 8 days principal energy 360 energy 360 keVkeV

6767GaGa T T½½ 3.3 days principal 3.3 days principal energies 93 energies 93 keV, keV, 184 keV and 296 keV 184 keV and 296 keV

201201TlTl T T½½ 3 days x-ray emission at 70-80 3 days x-ray emission at 70-80 keVkeV

Nuclear Medicine TeamNuclear Medicine Team Nuclear medicine technologist:Nuclear medicine technologist:

responsible for handling, assessment, and responsible for handling, assessment, and administration of radionuclides, patient administration of radionuclides, patient safety, statistical analysis for digitally safety, statistical analysis for digitally processed images, decontaminate the processed images, decontaminate the area. area.

Nuclear medicine physician: Nuclear medicine physician: radiologist has received training in the radiologist has received training in the performance and interpretation of nuclear performance and interpretation of nuclear medicine procedures.medicine procedures.

Medical nuclear physicist: Medical nuclear physicist: received received advanced training in nuclear physics, advanced training in nuclear physics, computers, and radiation safety. computers, and radiation safety. Responsible for preparing radioactive Responsible for preparing radioactive materials and calibration and materials and calibration and maintenance of imaging equipment.maintenance of imaging equipment.

Radionuclide Imaging Radionuclide Imaging and Radiation Safety and Radiation Safety

(1)(1) Unlike Diagnostic Radiology and Unlike Diagnostic Radiology and

Radiotherapy, Nuclear Medicine imaging Radiotherapy, Nuclear Medicine imaging devices do not emit radiation. devices do not emit radiation.

The technologist may take as many The technologist may take as many images as required to provide the images as required to provide the diagnosis without changing the radiation diagnosis without changing the radiation exposure of the patient.exposure of the patient.

Radionuclide Imaging Radionuclide Imaging and Radiation Safety and Radiation Safety

(2)(2) However, a malfunctioning gamma camera may However, a malfunctioning gamma camera may

result in errors in diagnosis or an non-result in errors in diagnosis or an non-interpretive study so that the patient gets no interpretive study so that the patient gets no benefit from the radiation exposure arising from benefit from the radiation exposure arising from the administered radiopharmaceutical.the administered radiopharmaceutical.

It is therefore essential that the principles of It is therefore essential that the principles of radionuclide imaging are well understood, that radionuclide imaging are well understood, that the quality control procedures are routinely the quality control procedures are routinely performed and that the gamma camera is performed and that the gamma camera is serviced when required.serviced when required.

Advantages of Nuclear Advantages of Nuclear medicine imagingmedicine imaging

Functional Functional Sensitive, quantitative.Sensitive, quantitative. Very safe.Very safe. Low radiation.Low radiation. Screening & Follow upScreening & Follow up Whole body evaluation without Whole body evaluation without

increased radiation dose to the increased radiation dose to the patient.patient.

Very high specificity (no natural Very high specificity (no natural radioactivity from the body).radioactivity from the body).

Disadvantages of Nuclear Disadvantages of Nuclear medicine imagingmedicine imaging

Not widely available.Not widely available. Poor SNR.Poor SNR. Require NM instruments & Require NM instruments &

radiopharmaceuticals.radiopharmaceuticals. Relatively higher cost than X-ray or US.Relatively higher cost than X-ray or US. Radiation exposure to the patient.Radiation exposure to the patient. Low spatial resolution (5-10mm).Low spatial resolution (5-10mm). Slow image acquisition. Slow image acquisition.