Comprehensive Notes on Nuclear Medicine

Nuclear Medicine Overview

What is Nuclear Medicine?

• Nuclear Medicine (NM) involves imaging the physiological functions of organs at the molecular level.

• This is achieved by introducing a radiopharmaceutical into the body through:

  • Intravenous injection (most common).

  • Inhalation (e.g., ventilation lung scan).

  • Ingestion (e.g., gastric emptying study).

  • Instillation (e.g., cystogram).

• Radiopharmaceuticals are radioactive drugs used for:

  • Diagnosis.

  • Treatment of diseases.

• They consist of a radionuclide (radioactive atom) tagged with a pharmaceutical (biologically active compound).

How it Works:

1. The radiopharmaceutical is administered to the patient.

2. The pharmaceutical carries the radionuclide to the target organ.

3. The radionuclide emits gamma rays.

4. A gamma camera detects these gamma rays and creates a digital image.

5. These images provide:

   • Anatomic view of the organ structure.

   • Diagnostic insights into organ function.

Common Nuclide:

• Technetium-99m (Tc 99m) is frequently used.

  • Gamma energy: $140 keV$

  • Physical half-life: 6 hours

• Typical doses range from $200 \mu Ci$ (microcuries) to $30 mCi$ (millicuries).

Image Characteristics

• NM images differ significantly from conventional images.

• NM displays the spatial distribution of physiology, also known as functional anatomy.

• Anatomical detail is less pronounced compared to other modalities.

Comparison with Other Modalities

*Secondary function.

Learning Objectives (CLO 1)

• Demonstrate clinical applications of common Nuclear Medicine imaging procedures (Week 1-4).

• Show understanding of nuclear medicine diagnostic information and images.

• Understand the clinical and basic principles underlying imaging methods of gamma camera, SPECT, PET, and Hybrid Imaging modalities.

• Understanding of nuclear medicine patient preparation and after care, radionuclide preparation and administration, and patient and staff radiation safety.

• Evaluate the role of nuclear medicine in terms of clinical applications and patient management compared to conventional medical imaging procedures.

• Demonstrate the current use of radiopharmaceuticals for diagnostic imaging.

Principles of Nuclear Medicine

• A medical specialty using radioactive materials (radiopharmaceuticals) for diagnosis, therapy, and medical research.

• Focuses on physiologic or functional information.

• Radiopharmaceuticals (or radiotracers) are introduced via injection, ingestion, or inhalation.

• Radiopharmaceuticals are organ or tissue specific.

• Radioactive decay leads to gamma-ray emissions.

• Gamma or scintillation cameras convert emissions into images.

• ALARA (As Low As Reasonably Achievable) principle is applied for radiation safety.

• The NM team includes:

  • Nuclear medicine physician.

  • Nuclear medicine technologist.

  • Physicist.

  • Pharmacist or specially trained technologist.

Biological Tracers

• Also known as labels and binding agents.

• Organic compounds that are metabolized in cells (molecular level).

• Selected based on metabolic needs of the target physiological system.

• Examples:

  • Bone scans: use phosphate compounds.

  • Thyroid scans: use iodine.

  • Blood scans: use serum albumin.

Radiopharmaceutical Preparation

• Radiopharmaceuticals are prepared in a NM hot lab.

• In Dubai Hospital, this occurs at 7:00 AM daily.

• The process involves a radionuclide being ‘labeled’ with a biological tracer.

• Prepared under strict clinical and radiation safety conditions, including:

  • Gloves, gown, Pb (lead) shields.

  • Masks, tools, splash guards.

Radiopharmaceutical Uptake and Image Interpretation

• Radiopharmaceuticals are metabolized by the target tissues.

• This metabolic process is called uptake.

• Gamma rays emitted by the tissues are detected.

• On images, this appears as:

  • Hot spots: Areas of increased/high uptake (indicating high activity).

  • Cold spots or photopenia spots: Areas of decreased/low/no uptake (indicating low or no activity).

Hot Labs, Hot Spots, and Cold Spots

• Hot labs are specially designed rooms in a nuclear medicine department for the delivery, storage, and preparation of radiopharmaceuticals.

• Hot spot indicates high uptake; the organ is very active.

• Cold spot indicates low uptake; the organ is not functioning or has low activity.

Radiopharmaceuticals: Conventional NM vs PET

• Radionuclides for Conventional NM:

  • Include $^{99m}Tc$ (technetium), $^{123}I$ (iodine), $^{131}I$ (iodine), $^{111}In$ (indium), $^{201}Tl$ (thallium), and $^{67}Ga$ (gallium).

  • These radionuclides have high atomic weight.

  • Labeled compounds with these radionuclides are poor radioactive analogs for natural substances.

  • Studies are often qualitative.

• Radionuclides for PET:

  • Include $^{11}C$ (carbon), $^{13}N$ (nitrogen), $^{15}O$ (oxygen), $^{18}F$ (fluorine).

  • Low-atomic-weight radioactive counterparts of naturally occurring body elements.

  • Emit positrons.

  • Can directly replace their stable isotopes.

  • $^{18}F$, the most commonly used PET radionuclide, can replace hydrogen in many molecules.

Toxicity and Radiation Dose: NM vs. Other Modalities

• Toxicity:

  • Contrast agents in radiographic studies can cause toxic reactions.

  • Tracers in NM are biochemically compatible, minimizing risks.

  • Trace amounts minimize alteration of the body’s homeostasis.

• Radiation dose:

  • X-ray doses in radiographic studies are generally greater than in nuclear imaging studies.

  • Radiotracers in PET are similar to the body’s own biochemical constituents and are used in very small amounts.

Radiopharmaceutical Requirements

• Radiopharmaceuticals need to be:

  • Sterile.

  • Pyrogen-free.

  • Undergo all quality control measures required of conventional drugs.

• They generally consist of a radionuclide and a pharmaceutical.

  • Radionuclide: The radioactive material used to tag the pharmaceutical for localization.

  • Pharmaceutical: A biologically active compound chosen for its preferential localization or participation in the physiologic function of a given organ.

• Doses vary depending on:

  1. Radionuclide used.

  2. The examination to be performed.

  3. The size of the patient.

Desirable Characteristics of Imaging Radiopharmaceuticals:

• Ease of production and ready availability

• Low cost

• Lowest possible radiation dose to the patient

• Primary photon energy between $100 keV$ and $400 keV$

• Physical half-life greater than the time required to prepare the material for injection

• Effective half-life longer than the examination time

• Suitable chemical forms for rapid localization

• Different uptake in the structure to be detected than in the surrounding tissue

• Low toxicity in the chemical form administered to the patient

• Stability or near-stability

Radiopharmaceuticals Used in Nuclear Medicine

The table from the transcript comprehensively lists various radionuclides, their physical half-lives, chemical forms, and diagnostic uses. Please refer to the original transcript (Page 18, Table 32-2) for this detailed information.

Image Interpretation: Photopenia

• A void or clear area in an image is often described as photopenia or a cold spot.

• Example: Absent perfusion in the right lung and subsegmental defects in the left lung.

Evaluate the Role of Nuclear Medicine

• in terms of clinical applications and patient management compared to conventional medical imaging procedures.

Overview of Imaging Methods

• Examinations are described based on computer setup imaging method used:

  1. Static.

  2. Whole-body.

  3. Dynamic.

  4. SPECT (Single Photon Emission Computed Tomography).

• Gamma Cameras NM

• PET scanners

• Hybrid PET- SPECT/CT

• PET is similar to nuclear medicine radioisotope emission procedures.

• PET uses radioactive compounds that emit positrons during radioactive decay.

  • A 3D tomographic image of the distribution of a radioactive tracer in the body is produced that reflects the biochemical processes occurring in different organs and tissues.

• acquire functional PET and anatomic CT images during a single imaging session.

  • These two image datasets can be displayed as a single volume

  • Direct, accurate localization of pathology found on a PET scan is permitted.

Static Imaging

• Static imaging is the acquisition of a single image (snapshot) of a particular structure.

• Examples: lung scans, spot bone scan images, and thyroid images.

• Usually obtained in various orientations (anterior, posterior, and oblique images).

• Low radiopharmaceutical activity levels are used.

• Images are acquired for:

  • a preset time (few secs to several mins [generally, 30 sec-5 mins ]) or

  • a minimum number of counts (100K- >1M counts)

Whole-Body Imaging

• The detector is moved to produce an image of the entire body or a large body section.

• Nearly all camera systems used for whole-body imaging incorporate a dual-head design for simultaneous anterior and posterior acquisition.

• Examples: Whole-body bone or whole-body tumor imaging and other clinical and research applications.

Dynamic (Flow) Imaging

• Display the distribution of a particular radiopharmaceutical over a specific period.

• Generally used to evaluate blood perfusion to the tissue.

• Images may be acquired and displayed in time sequences of 1/10th sec to > 10 min per image.

• Examples: Hepatobiliary studies and renal studies.

SPECT (Single Photon Emission Computed Tomography)

• camera heads or detectors rotate around the patient while acquiring the images in a process called SPECT (single photon emission computed tomography).

• SPECT provides 3D views of anatomy.

• SPECT uses one to three gamma camera detectors that can rotate at angles up to 360° around the patient to collect a series of images.

• information is reconstructed slice images of the anatomy.

• Some gamma cameras have CT systems built into them to provide fusion imaging by overlaying the anatomy of the CT with the function image of the gamma camera

Positron Emission Tomography (PET)

• PET is a 3D tomographic imaging technique that demonstrates the biochemical function of the body’s organs and tissue.

• PET is different from other imaging methods (x-ray, CT, ultrasound, MRI), which biochemical metabolism and function of organs and tissues can reveal whether they are diseased or healthy.

• can detect disease in the early stages before the onset of symptoms and to measure responses to therapy during treatment

• COMPARISON WITH NUCLEAR MEDICINE

• PET is similar to nuclear medicine radioisotope emission procedures. Both methods produce images that represent the distribution of the radiotracer throughout the body. In both modalities, radioactive compounds or “tracers” are administered to a patient by injection or inhalation. When these tracers are inside the body,

• the PET scanner detects the radiation emitted from the tracer within

• the patient’s anatomy. With the use of special computers, a 3D

• tomographic image of the distribution of a radioactive tracer in the

• body is produced that reflects the biochemical processes occurring

• in different organs and tissues.

• In contrast to nuclear medicine, PET uses radioactive compounds that emit positrons during the radioactive decay process.

SPECT vs PET

• Single-photon emission computed tomography (SPECT)

  • A conventional nuclear imaging technique.

  • Used to determine tissue function.

  • Employs collimators and lower energy photons.

  • Less sensitive (by $10^1$ to $10^5$) and less accurate than PET.

• Positron emission tomography (PET)

  • Has a resolution better than SPECT 2-10x.

  • Easily accounts for photon loss through attenuation by performing a transmission scan.

    • This is now possible in SPECT through the coupling with low-output x-ray CT, and software advancements.

Hybrid Modalities

• CT, MRI, and other anatomic imaging modalities provide complementary information to nuclear medicine imaging and PET.

• Image coregistration.

• Pinpoint physiologic function from precise anatomic locations.

• Greater emphasis is being placed on brain research and for tumor localization throughout the body.

• All new PET imaging systems are fused with a CT scanner for attenuation and anatomic positioning information.

• Many SPECT imaging systems incorporate CT technology for the same purposes.

SPECT IMAGING

• Examples: Cardiac perfusion, brain, liver, tumor, and bone studies.

Cardiac perfusion

• Cardiac perfusion: the amount of the blood circulation in the body heart

Examples of fusion in SPECT/CT

• These images demonstrate how anatomical and physiological data are combined for accurate diagnostics, especially in identifying metastases.

Patient Preparation and Aftercare

• Patient preparation is minimal, with most tests requiring no special preparation.

• Patients usually remain in their own clothing.

• All metal objects outside or inside the clothing must be removed.

• The waiting time between dose administration and imaging varies with each study.

• After a routine procedure, patients may resume all normal activities.

Positron Emission Tomography (PET) details

• Patients are injected with positron emitting radionuclide

• Fluorodeoxyglucose ($^{18}F$) commonly known as FDG

• PET detects gamma rays given off at the site where a positron emitted from the radioactive substance collides with an electron in the tissue

PET Clinical Applications

• ONCOLOGY (STUDY OF TUMORS)

  • PET is a valuable tool for assessing the metabolism of tumors.

  • malignant cells have an accelerated glucose metabolism

  • FDG, is taken up readily by active tumors.

  • An increase in glycolysis (increased use of sugar by the cells) in a specific organ or region “breaking down of glucose ” of the body is an indicator of malignancy.

  • PET may be used for the initial diagnosis, for staging of a malignancy, and as a follow-up technique for determining response to treatment.

• To how much the cancer spread in the patient body

HYBRID PET/ CT IMAGING

• CARDIOLOGY (heart study)

  • Coronary artery disease begins when blood flow to the heart is obstructed. (decrease the blood flow/ low oxygen in the body)

  • PET can assess how coronary artery disease affects the normal functioning of the heart. (the calculation of blood and oxygen)

  • A PET perfusion tracer “a radiotracer that contains a safe amount of a radioactive drug.” such as $^{13}N$-ammonia used to investigate whether certain areas of the heart are receiving insufficient blood flow

  • PET/CT permits CT angiography or calcium scoring and PET perfusion scanning at the same time

  • CT can provide anatomic information regarding the location of an atherosclerotic lesion, and PET can demonstrate its functional impact on perfusion.

PET/CT : combining PET and CT together

• Advantage of combining PET molecular function information with CT anatomical information

• Disadvantage that the CT doses are higher than PET alone

PET Images

• Cross-sectional images (capture detailed 'slices' of the body's)

• Shows areas of uptake

• Increased uptake = increased molecular thought pattern activity

• Red = high uptake hot spot (proper of blood flow ) high activity

• Blue = low activity cold spot (not active)

• Brain PET shows active versus non-active areas

• Charts brain thought patterns of activity

Single-photon emission computed tomography SPECT

• Mainly used to image brain perfusion (looking for blood flow in the brain)

• Amount of blood in tissues

• More sensitive to brain injury than either MRI or CT

• Good to show reduced blood flow

• Good for stroke, seizures and tumors ¨ Stress fractures in spine

• Shows areas of altered blood flow “not normal blood flow”

Brain scans PET: PET/CT

• Trauma = CT scan --> because it faster

• Follow up brain trauma

• Dementia

• Alzheimers = PET/ CT

• Stroke = CT scan -->

• Tumours = PET/CT

• Perfusion ”looking for blood flow”

• Epilepsy (seizures) & psychiatric symptoms

• Blood flow and brain thought activity patterns

Bone scans

• Osteomyelitis inflammation or swelling that occurs in the bone or bone marrow

• NM more sensitive than X-ray (detect earlier)

• NM detects 5% bone demineralization ‘the industry of the bone increased’

• X-ray can only detect if 30% bone demineralization

• Primary and secondary bone cancers

• Arthritis

• Fractures and fracture healing

Bone Scintigraphy (Scan)Indications (e.g.,)

• Detection of primary and staging metastatic (The spread of cancer cells from the place where they first formed to another part of the body.)disease.

  • Most commonly from breast, lung, prostate, and kidney.

• Detection of occult “hidden” (obscure, difficult to find) fractures and known or suspected fractures.

• Evaluation of bone pain and/or trauma.

• Detection and evaluation of metabolic bone diseases such as Paget’s disease (bone inflammation and resorption replaced by soft bone), osteoporosis, and osteomalacia (vitamin D deficiency = softening of the bones) and other osteopathies.

• Detection and evaluation of arthritis and degenerative disk “vertebrae disk breaking down”and/or joint (osteoarthrosis) disease.

Bone Scintigraphy (Scan)

• It takes 15% loss of calcium mineral to be detected NM procedure; 30–50% loss of calcium mineral to be detected by x-ray.

• Positive bone scan for fractures need:

  • Adult; 24 hrs.

  • Elderly: 72 hrs.

• After fracture, bone uptake returns to normal:

  • Within 1 year for ribs.

  • 3 years for elderly and long bones.

• Contraindications

  • Patient who has recently ingested contrast medium (particularly barium).

  • Patient who has recently (24– 48 hrs) had a $^{99m}Tc$-based NM scan performed.

Bone scans specifics

• Radionuclide $Tc-99m$

• Organic label phosphor based

• Methyl diphosphonate (MDP)

• Phosphor metabolized in bone

• Uptake in osteoblast cells

• Images bone growth/repair

• $Tc-99m$ MDP injected

• Gamma camera images taken after injection

• Imaging sequence 30-70minutes

• Three-phase scan images 20mins: 3hrs: 24hrs:

• $Tc-99m$ MDP excreted in urine

Advantages of bone scan

• Able to detect pathologies not seen on plain X- ray

• Identifies occult fractures

• Sports # on right not seen on X-ray

• Shows early signs of bone healing

• Can identify source of pain

• Evaluates osteoplastic activity around joint prostheses

• Can identify early cancer changes

Cardiac NM

• Thallium & Cardiolite stress test

• Shows blood flow to heart muscle to evaluate coronary artery blood flow and myocardial perfusion

• Coronary artery disease

• Cardiomyopathy

• Myocardial infarct

• Patients injected with $Tc-99m$-Sestamibi and cardiac drugs before and after working on a treadmill

• Images taken before, during and after ‘stress’ and ‘rest’ to compare blood flow and myocardial perfusion

Thyroid scan: Indications

• Evaluation of thyroid anatomy, e.g., position, goiter (enlarged gland due to inadequate iodine supply), surgery, cold or hot nodule(s).

• Differentiation of benign from malignant nodules.

• Detection, localization, and evaluation of independent functioning nodule(s).

• Evaluation of heterogeneity of function within a hyperthyroid gland.

Thyroid scan: Contraindications for Iodine

• Allergy to iodine.

• Interfering recent contrast studies.

• Patient has not discontinued thyroid or interfering medication, vitamins, or iodinated food products.

Thyroid scan: Patient Preparation

• Identify the patient. Verify doctor’s order. Explain the procedure.

• $^{99m}Tc$: None other.

• Patient to discontinue thyroid medications and avoid contrast material, Betadine®, or amiodarone.

• Refrain from eating foods containing iodine such as cabbage, turnips, greens, seafood, kelp, or large amounts of table salt.

• $^{123}I$: Patient will be returning at 4-6 hrs and 24 hrs for scan.

Thyroid scan specifics

• $Tc-99m$ with iodine tracer:

  • Cancer

  • Hyper-hypothyroidism

  • Goiter

• Patient swallows capsule

• Scans taken at:

  • 3-4hrs

  • 24hrs

  • 72hrs

• Images show level of iodine thyroid uptake:

  • High = hyperthyroidism

  • Low = hypothyroidism

Renal scans indications

• Evaluation for renal artery stenosis” abnormal narrowing ”, obstruction” blockage.”, and/or trauma.

• Evaluation of renal function. “filtering urine ”

• Evaluation of renal obstructive nephropathy “condition characterized by kidney damage resulting from impaired urine flow,” and/or hydronephrosis “medical condition characterized by the swelling of one or both kidneys due to the accumulation of urine.” (study with furosemide “A medication used to treat high blood pressure and body swelling”).

• Evaluation for renal (renovascular) hypertension (captopril study” treatment of hypertension and heart failure”).

Renal scans Contraindications

• Iodine IV contrast study on same day.

• Patient still on ACE inhibitors” medicines that help relax the veins and arteries to lower blood pressure” or ARB “treat high blood pressure and heart failure”.

• If the test is ordered as a captopril study and the patient has taken an ACE inhibitor or ARB within hrs before, some suggest taking a blood pressure.

  • Normal or high: Give the captopril ”drug To lower high blood pressure” and continue with the test.

  • Low: The test may be rescheduled.

• Food intake too close to a captopril study will decrease the sensitivity of the test and slow the absorption of the ACE inhibitor.(if the patient take any food that have the same concepts as the captopril )

Renal Scans – two main types

• DTPA tracer + $Tc-99m$

  • Diethylene triamine pentaacetic acid

  • IV administration

  • Images renal blood supply

  • Assesses renal transplant

  • Looking for blood flow

• DMSA tracer + $Tc-99m$

  • Dimercaptosuccinic acid

  • IV administration

  • Images renal perfusion and excretion rates (Gfr)

  • Often used for children

  • Looking for renal function

DMSA images

• Often used to show pediatric pathologies

• Reflux “back flow if urine” due to chronic infection and ureteric obstruction

• Low radiation dose compared to fluoroscopy

• Less invasive “ cut throw a patient body / entering the patient body ”

Abnormal Results of Renal Scans

• Slow up slope and/or down slope in one or both kidneys. dilated

• Lasix® (furosemide) to treat high blood pressure:

  • $t_{1/2}$ washout time $≥ 20$ mins. If takes more than 20 m there is a problem with kidney functions

  • Curves decline after diuretic removing urine injection: benign dilated system there is no obstraction .

  • Curves rise and continue after diuretic injection: Mechanical obstruction there is an obtraction.

• Captopril: drug To lower high blood pressure

  • Corrected slopes after captopril: Renal artery stenosis “narrowing of one or more spaces ”. Helps to check the Renal artery stenosis

  • Uncorrected slopes after captopril: Obstruction or problems other than but perhaps as well as stenosis. Or kidney stone “any stactioral disease”

  • Renal uptake @ 2-3 mins by one kidney < 40% of total. If it take more than 40% there is aproblem with the kidney

  • RCA “ Renal citrate activity” @ 20 mins differing from contralateral kidney > 20% or increase from baseline of 15%.

  • $t_{max}$ in affected kidney > 2 mins compared to baseline or nonaffected kidney. If it more than 2 min there is dilate of the kidney “function”

Lung ventilation & perfusion (VQ) scans

• Ventilation scans

  • To assess airways “breathing”

  • Xenon gas inhaled

• Perfusion scans

  • To assess blood flow

  • $Tc-99m$-MAA injected

  • Pulmonary embolism & chronic obstructive airway disease (COAD) Inhlation

Indications can do for …. VQ scans

• Evaluation for pulmonary embolism (PE). The main cause being deep vein thromboses (DVTs), clots from recent surgery, or trauma.

  • Defects match: Chronic obstructive pulmonary disease (COPD).

  • Defects mismatch: PE.

  • Reverse mismatch: Atelectasis (collapsed lung).

• Evaluation of pulmonary perfusion.

• Evaluation and management of carcinoma “cancers”of the bronchus.

• Contraindications can’t do

  • Patients with pulmonary hypertension.

  • Known active pneumonia.

  • Hypersensitivity to human serum albumin.

Abnormal Results of VQ Scans

• Ventilation/perfusion mismatch:

  • Pulmonary embolism

  • Pleural effusion “fluid in the lung”

• Ventilation/perfusion matching defects:

  • Localized hypoxia due to asthma or COPD

  • Surgery (e.g., pneumonectomy)

• Decreased perfusion to one lung:

  • Pulmonary agenesis or stenosis

  • Large PE (Pulmonary embolism)

Hepatobiliary scan

• Hepatobiliary scan ” is derived from two components: "hepato-" which refers to the liver, and "-biliary" which relates to the bile ducts and gallbladder."

• To assess biliary function

• Liver hepatic ducts: gallbladder: cystic duct & ampulla ¨ $Tc-99m$DISIDA injected – uptake in bile

• Imaged at 1min and 15min intervals to 1hour

Radiation Protection in Nuclear Medicine

• ALARA (As Low As Reasonably Achievable)

  • Reduce the probability of stochastic effects “things may happened/ not garntee” of low-level ionizing radiation.

  • In workers must minimize radiation exposure to themselves, their colleagues, patients, and public.

  • Time, distance, and shielding play an important role to this end.

  • Be mindful of dosages:

    • Where they are.

    • Who is exposed to the radiation.

    • How can the exposure be minimized.

Protection from External Exposure

A. Time:

• Reduce time spent near radioactive sources, e.g., patients, loaded syringes, generators, hot lab, therapy doses, PET doses.

• Total exposure is directly and linearly related.

B. Distance:

• Step back from any hot source, the more distance, the less exposure.

• Inverse Square Law

C. Shielding:

• Use syringe shields, lead-lined carry cases, leaded glass shields, etc., when manipulating or transporting radiopharmaceuticals.

• Exposure rate is an exponential function of shield thickness.

Protection from Internal Exposure

A. Ingestion:

• Do not permit food products, drinks, cosmetics, etc. anywhere in the area, particularly those areas where radiopharmacy is worked with and/or stored.

B. Inhalation:

• Departments that work with gaseous substances must provide a fume hood in the hot lab and a “negative pressure” closed system.

C. Percutaneous:

• Gloves, lab coats, scrubs, leather shoes, etc., are suggested to limit this type of contamination.

• Any contamination of this type requires the person to remove the clothing that may also be contaminated and the area washed.

D. Injection:

• Accidental injection into a vein is a low probability.
  There is more risk involved with inadvertent piercing of the skin with a needle that has radioactivity.

Pediatric Doses

• Clark’s Rule (Body Weight)

  • $Pediatric dose = \frac{Weight : of : child}{Weight : of : adult} \times Adult : dose$

• Modified Talbot’s Nomogram (Body Surface Area)

  • $Body : Surface : Area : (BSA, m^2) = \frac{Weight : (kg) \times Height : (cm)}{3600}$

  • $BSA_{adult} = 1.779 m^2$

  • $Pediatric : Dose =$\

• Metabolic Rule (Mass of Target Organ)

  • $Pediatric : Dose = \frac{Mass : of : target : organ : (child)}{Mass : of : target : organ : (adult)} \times Adult : Dose$

Radiation Safety

• ALARA (As Low As Reasonably Achievable)

  • Reduce the probability of stochastic effects of low-level ionizing radiation.

  • Workers must minimize radiation exposure to themselves, their colleagues, patients, and the public.

  • Time, distance, and shielding are crucial.

  • Be aware of dosages, locations, who is exposed, and how to minimize exposure.