Nuclear Medicine and Radiopharmaceuticals

• Nuclear medicine images physiologic functions of organs at the molecular level.
• Administering radiopharmaceuticals introduces a radioactive substance into the body.
• Intravenous injection is the most common method to introduce the radiopharmaceutical.
• Radiopharmaceuticals can be introduced by inhaling, ingesting, or instilling.
• Radiopharmaceuticals are radioactive drugs used for diagnosis and treatment by tagging a radionuclide with a pharmaceutical.
• When injected, the pharmaceutical carries the radionuclide to the organ.
• Gamma rays emitted by the radiopharmaceutical are digitally recorded by a gamma camera.
• Images provide an anatomic view of the organ structure as well as diagnostic insights regarding the function of the organ.
• Technetium-99m (Tc 99m), at 140 keV and a physical half-life of 6 hours, is the most commonly used nuclide.
• Typical doses for most diagnostic procedures range from 200 microcuries (µCi) to 30 millicuries (mCi).
• Nuclear medicine images are very different to conventional images.
• Nuclear medicine shows spatial distribution of physiology, also called functional anatomy.
• Anatomical detail is not shown on NM images.

Comparison With Other Modalities

• PET and SPECT measure physiology, MRI measures anatomy (physiology*), and CT measures anatomy.
• PET's resolution is 3-5 mm, SPECT's is 8-10 mm, MRI's is 0.5-1 mm, and CT's is 1-1.5 mm.
• PET uses Positron annihilation, SPECT uses Gamma emission, MRI uses Nuclear magnetic resonance, and CT uses Absorption of x-rays.
• PET, SPECT and CT use radiation exposure. MRI has none known.
• PET's use is research and clinical, SPECT and CT are clinical, and MRI is Clinical (research*).
• PET has 4-12 examinations per day, SPECT 5-10, MRI 10-15, and CT 15-20.

Key Learning Outcomes

• Demonstrate the current applications of radiopharmaceuticals for diagnostic imaging.
• Evaluate nuclear medicine's clinical applications and patient management compared to conventional medical imaging.
• Understand patient preparation/aftercare, radionuclide administration, and radiation safety.
• Understand principles of imaging with gamma cameras, SPECT, PET, and hybrid modalities.
• Show understanding of nuclear medicine diagnostic information and images.
• Nuclear medicine focuses on the use of radioactive materials (radiopharmaceuticals) for diagnosis, therapy, and medical research.
• Nuclear medicine is physiologic or functional.
• Radiopharmaceuticals are introduced through injection, ingestion, or inhalation and are organ or tissue-specific.
• Gamma or scintillation cameras capture emissions into images.
• ALARA (As Low As Reasonably Achievable) is applied in nuclear medicine.
• The NM team consists of a nuclear medicine physician, technologist, physicist, and pharmacist or specially trained technologist.

Biological Tracers

• Biological tracers are sometimes known as labels and binding agents.
• Biological tracers consist of organic compounds that are metabolized in cells (molecular).
• Biological tracers selected according to the metabolic needs of the target physiological system.
• Examples of biological tracers include bone scans (phosphor), thyroid scans (iodine), and blood scans (serum albumin).
• Radiopharmaceuticals are mixed in a NM hot lab daily at 7.00am in Dubai Hospital.
• Radionuclide 'labeled' with biological tracer require clinical, with radiation safety conditions.
• Preparation requires gloves, gowns, Pb shields, masks, tools, and splash guards.
• A radionuclide is tagged to a pharmaceutical based on its gamma emission characteristics and ability to localize to a specific function.
• Radiopharmaceuticals visualize specific organ functions via radioactive emissions post-physiological incorporation.
• Radiopharmaceuticals metabolize in target tissues and emit gamma rays, appearing as "hot spots" (increased uptake) or "cold spots" (decreased/no uptake) on images.
• Conventional nuclear medicine (NM) uses radionuclides like 99mTc, 123I, 131I, 111In, 201TI, and 67Ga.
  • Conventional NM radionuclides with high atomic weight, result in labeled compounds with poor radioactive analogs for natural substances, and qualitative studies.
• PET radionuclides include 11C (carbon), 13N (nitrogen), 15O (oxygen), and 18F (fluorine).
• Radionuclides for PET are low-atomic-weight counterparts and emit positrons.
• Because they directly replace their stable isotopes, 18F is the most commonly used PET radionuclide, and can replace hydrogen in many molecules.
• The image-enhancing contrast agents used in many radiographic studies may cause a toxic reaction.
• Radiotracers are biochemically compatible with the body and minimize toxicity risks because they are administered in trace amounts to minimize alteration of homeostasis.
• X-ray dose is greater than radiation dose of NM studies
• The radiotracers in PET are similar to the body's own biochemical constituents and are administered in very small amounts.

Radiopharmaceuticals

• Radiopharmaceuticals should be sterile and pyrogen-free, with quality control measures followed.
• Common quality control measure is a radionuclide and a pharmaceutical composition:
• Radionuclide is the radioactive material used to tag the pharmaceutical, allowing for localization.
• And then a biologically active compound is selected based in preferential localization of function in an organ.
• Doses depend on radionuclide, examination type, and patient size.
• Characteristics desirable in an imaging radiopharmaceutical include easy production/availability, low cost/radiation dose, primary photon energy between 100-400 keV, and half-life greater than preparation time.
• Additional characteristics include effective half-life relative to examination time, suitable chemical forms for rapid localization, differential uptake versus surrounding tissue, low toxicity in administered form, and stability.

Nuclear Pharmacy Cont'd

• Radiopharmaceuticals used in nuclear medicine include:
  • Chromium-51: Sodium chromate, used for red blood cell volume and survival.
  • Cobalt-57: Cyanocobalamin (vitamin B12), used for vitamin B12 absorption.
  • Fluorine-18: Fluorodeoxyglucose, used in oncology and myocardial Hibernation
  • Gallium67: Gallium citrate to image inflammatory process and tumor.
  • Indium -111: DTPA, ibritumomab tiuxetan, and octreoscan are neuroendocrine tumor tests. Oxine for abscesses, prostascint for prostrate cancer.
  • Iodine 121, 131: Sodium iodide or homan albumen to test thyroid function.
  • Nitrogen 13: ammonia for Myocardial perfusion and cardiovascular imaging
• Imaging modalities in Nuclear Medicine requires minimal patient preparation.
• Contrast enhancement may cause toxic reactions when used in radiographic studies
• Biochemical compatibility of tracers minimizes patient risk because they are deemed non-toxic -Traces minimize alterations of body homeostasis

Gamma Cameras NM

• Examinations with gamma cameras includes Static imaging, Whole-body imaging, Dynamic imaging, and SPECT.

PET Scanners

• PET is similar to nuclear medicine radioisotope emission procedures and uses compounds that emit positions that during decay forms a 3D tomographic image
• Tracer distribution in the body highlights biochemical processes within different organs

Hybrid Systems Combination

• Hybrid systems combined PET or SPECT with CT with the CT being in the same scan for accurate location of PET findings

Static Imaging

• Static imaging acquires a single "snapshot" image of a particular structure like lungs, bones, and thyroids
• Is often obtained at various angles with low levels of radiation
• Images are acquired at a preset time or minimum number of counts

Whole-Body Imaging

• The detector is moved to produce an image of the entire body or a large body section. Dual detection systems are incorporated for simultaneous anterior and posterior acquisition for bone or tumor images

Dynamic (Flow) Imaging

• Dynamic imaging involves displaying a particular radiopharmaceutical over a period of time to evaluate blood perfusion in organs
• Images may be acquired at intervals as little as 1/10th second
• Hepatobiliary and Renal assessment are achieved with dynamic flow

SPECT (single photon emission computed tomography)

• Single Photon utilizes gamma cameras, 3D images and angles to acquire images.
• Information is reconstructed from image slices and gamma cameras can be built with CT systems to provide function imaging data

Positron Emission Tomography (PET)

• PET is a 3D tomographic imaging technique that that is used to demonstrate the biochemical function of the body's organs and tissue
• This is in contrast to that of organs or other imaging methods which only highlight anatomy
• Detectable disease in the early onset

SPECT vs PET

• SPECT is a convetioinal imaging using single photon emission
• It is used to assess tissue funcition employs collmators and lower energy phots
• Low sensitive over 10x5 sensitivity as PET
• PET Has better resoolution then SPECT with 2 to 10 X
• accounts for phonton losss and transmission

Hybrind Modalities

• CT and other anatomical modalities will provide the neccassary information for nuclear imaging of the PET
• All new pET imaging systems are fused with a CT scanner for attenuation and anatomical info
• SPECT imaging is used in corelation

SPECT IMAGING

• SPECT is employed in brain, liver, tumor and bone imaging
• Cardiac perfusion and liver tumor may be displayed

Overview - General Preparation

• Patient requires minmal preperation and should remove all metal from their bodies
• Patients may be fitted with normal clothes and can resume all activites after routine procedure

Positron Emission Tomography

• Patietns are injected with nuclidtiodes and Fluorodeoxyglucose a positrone emittited from collision of redioncutide wjth the substance emmited from the tissue via weblink

Clinical Applications of PET

• Study of Tumors using valuable tools to assess metabolism
• cancerious cells accelerated the process of glyclosis in turn active tumors are rapidly taken up with FBG. The increase in glycosylsis will assist in the increase in organ region

Combined Cardiac pet CT

• Cardiac arteriarty diseas begins when blood flow is obstructed
• PET can assess how cardianry disae affect heart functions which can be trused by pet and NH3 perfusion
• Ct provides anatomical structures of atheosicltic lesions

PET vs CT

• combines pets vs CT with pet molecular functions and CT anatomical information
• there is concern that CT doses may higher then the PET alone.

PET images

• PET has the capabilities to show areas of increased molecular activity
• RED = high uptake which indicates disease
• Blue = small uptake

SPECT Images

• More sensative to MRI than imaging Brain.

Brain Scan:

• For Brain assessment PET will evalue, trauma,dementia,tumore epilepsy

Assesment of Bone scan

• Osteomyelitis NM detectes 5% of bone demineralization before X-ray can at 30%
• Bone scans are employed to evaluate bone disease for primary and secondary cancers.
• fractures and healing

Bone Scitigraphy

• Aids in the dectection of metastasis from breast lung prostate of kidney. Fractures of bone can also be observed
• Bone assessment provides the evaluation of pain and or trauma. As well as the evolution of metabolic bone diseases and arthritis

Factors affecting bone scan

• It takes 15% calcium loss for NM procedure to detech otherwise X-ray must cause 30 -50% mineral loss for fractures
• Adults require a bone scan 24 hours after a fracture while ederely require more than 72 hours.
• bone will Uptake can go back to normal within a year

Bone scans

• Radionulcide scans take time in Tc-99
• bone assessment utilzes methyl diphostate metabolizes into phosphor
• A gamma camera is injected after the scan and takes images ranging between 30 and 70 minutes
• Bone structure excreted via urine.

Bone Scan Positioning Procedure

• Requires careful monitoring of patients anatomy.

Cardiac NM and stress

• Cardiolite and thallium scans show how blood flows to the heart in evalalting artery flows for cardiomyopathay

How are cardiac assessments done

• The cardiologist will review your medical history assess risk to perdict problems - the patients wil be injected with a radioactive material that can show where in your heart that there might be bloackges
• Scans are performed are and after and compared.

Indicaitons for Thyriod Assestment

• Evaluation of the anatomy. Benign Vs malignant.

Complications of Idone Assesment

• Allergies, recent contrast
• not discontuined medication food

Patient Preperaion for Assesmnet

• Preceationer Identies the patient explaines the proceedure
• Patint must disconitue medication and stop contast materials. Food containing cabbage, turnips, kelp,
• Patients are often scedulded in 4-6-24 hr intervals.
• Tc -99m and iodine are utilized to perform assays to see thyroid

The role of Nuclear Scan

• Dect tumor.

Key charcteristics of Iodide

• Idoidide. thyroid

Renal Scan indication

• stenosis, obstruction and trauma.

Contraindications for Assessment

• Idonine contrast ACE enhibitors, food

Renal Scans Key indicators

• DMSA is the tracer images are for perfuction for childrean

Images via DMSA

• Shows pediatric pathology

Assesment of DTPA images

• images aid in blood flow analysis.

Abnormailities via scanning tests

• Time for waste water discharge

Lung VENT & pERF procedures

• Vent utilizes assessement to airtflow
• Gas xenion inhaled Scan PER assesses blood low for pulmonary issues which can also assess T.C99m- MA

Nuclear medicine utilizes radiopharmaceuticals to image organ functions at a molecular level. Administered intravenously, these radioactive drugs emit gamma rays, captured by a gamma camera. This provides both anatomical and diagnostic insights, with Technetium-99m being a common nuclide.