Nuclear Medicine 101

What is nuclear medicine

imaging modality that visualizes the function of anatomy using radionuclides and molecules to create a tracer (radiopharmaceutical) that is inserted into the body, which emits gamma rays that the camera captures

Clinical Procedure Steps of a Nuclear Medicine Scan

1. Inject, swallow, or inhale a radiopharmaceutical into patient

2. Wait for the distribution within the body to occur

3. Once gamma radioactivity is being emitted, the NM camera takes a diagnostic image of an organ or tissue

Principles of Radioactivity

a radioactive substance consists of atoms that have special properties, and a radioactive atom has an unstable nucleus

Gamma Radiation

Photon-based radiation that is more penetrating and less harmful to patients

Half-life measurement

The time it takes for half of the atoms in a radioactive sample to decay

Radiopharmaceutical

A radioactive chemical that is injected, ingested, or inhaled during a clinical procedure (consists of a radioisotope paired with a biochemical agent)

Tagging

pairing a radioactive atom with a carrier (a biochemical molecule that is chemically bound to the radioactive element) that will facilitate the absorption of the radiopharmaceutical

How to create a radiopharmaceutical

1. Cyclotron

2. Generator

Cyclotron

radioisotopes are created by bombarding stable elements with high energy particles in a cyclotron or nuclear reactor

Generator

radioisotopes are created by monitoring radioisotope decay in a generator until they can be used to create radiopharmaceuticals

Hot Labs

a restricted room that contains lead shielding and quality control equipment to protect staff and patients

where hospitals produce “ready-to-use” radiopharmaceutical kits containing tagged and measured chemical doses

Nuclear Medicine Camera aka

Gamma Camera

Nuclear Medicine Camera Overview

1. Detects gamma photons emitted by the radiopharmaceutical into the body

2. Converts the radioactive energy into a signal that can be recieved by an electronic system

3. Accurately locates the point in the body that each gamma photon originates by measuring the energy level and position of each signal

Parts of a NM Camera

Collimator

Scintillator

Photomultiplier Tubes

Computer

Collimator

A device that shapes and directs gamma rays as they enter the camera, improving image quality and resolution by allowing only certain gamma photons to reach the scintillator.

• less collimation = higher sensitivity (speed)

• more collimation = higher resolution (detail)

Crystal

The scintillator material in the nuclear medicine camera that converts gamma photons into visible light (after passing through the collimator).This light is then detected by photomultiplier tubes to create an image

• made of sodium iodide crystal (most common)

• Thin crystal = better resolution (low energy)

• Thick crystal = better sensitivity (high energy)

Resolution

detail

Sensitivity

speed = throughput

the ability to obtain the maximum number of counts per minute, per unit of activity

Photomultiplier Tubes

Once light is emitted from the crystal (scintillator), it is detected by an array of photomultiplier tubes (PMTs) which are positioned directly behind the crystal

• PMTs are the most serviced component of nuc med cameras

Electronic System

detector components work together to produce uniform image quality

Gantry

Ring designs allow the detectors to rotate on a mechanical ring for imaging at many angles

C-arm designs have detectors mounted on a pivoting arm attached to the base of the unit

Table

Shaped like a cradle

Carbon Fiber - allows for radioactive energy to travel through the table

CZT Crystals

Cadmium Zinc Telluride

Lightweight detectors

Single Detectors

Suited for general applications of NM customers who don’t want to perform high volume of studies

Predominately for cardiac or small organs (small FOV)

Dual Detectors

Increase patient throughput, large caseload

Configured in two ways:

• fixed 90-degree angle v-shaped for cardiac studies

• variable angle: two detectors that can be adjusted in many different positions (large FOV)

Spatial Resolution

the ability to detect two objects close together

• the smaller the resolution number, the better the detail in an image

• the closer to the patient, the better IQ and spatial resolution you will have

Energy Resolution

the measurement of the camera’s ability to accurately measure the energy of incoming radiation

• good energy resolution reduces scatter and improves spatial resolution in a scatter environment

• the smaller the number, the more precisely the camera can discern different incoming energy levels

Count Rate

the camera’s ability to accurately function near the maximum rate of gamma pick-up or sensitivity

• measurement of the camera’s ability to function accurately at “max speed”

• higher the value, the better the max speed

Linearity

The measurement of the camera’s ability to reproduce straight-line sources of radioactivity as straight lines on an image

• linearity tests focus on how a specific crystal interacts with the other components in the camera

• Linearity = improves image accuracy

Uniformity

measurement of whether the detector has a homogenous response across the entire detector

• uniformity correction helps to eliminate false negatives or false positives

Reading NM Images

Don’t provide information about the anatomical structure (unless it is a SPECT/CT)

Explains HOW the patient’s body is functioning

• healthy tissues are shown in a medium color shade, while abnormal tissues are shown in hot spots or cold spots

  • Hot spot is an overactive area of cells

  • cold spot is an area of little to no cell activity

Static/Planar Imaging

involves collecting data from one area of the body at one point in time

• no motion, snapshot, static

Whole Body

collecting static data of the entire body from two-planes

• used for bone scans and the lymphatic system

Dynamic

used to evaluate blood flow through an organ or body tissues

• evaluates bodily function over a period of time

• takes multiple different snapshots usually of one organ

Gated

examines heart function

• looks at blood flow through the chambers or ventricles of the heart and the motion of the muscles in the heart walls

SPECT

Results in images that are similar to CT and MR (3D) just don’t have the anatomical mapping

Gated SPECT

the most complect acquisition available in NM

combines gated imaging acqusition with a SPECT acquistion to produce multiple cardiac slice images that can be viewed in motion

800 Series

NM 830

Nm/CT 850

NM/CT 860

NM/CT 870DR

NM/CT 870 CZT

• value prop: 800 series offers a wide range of systems and solutions to meet virtually any requirement

Benefits of CZT

GEHC is the only vendor to offer a fully digital dual-detector (870)

CZT allows for:

• 75% reduction in imaging time or injected does

• 40% improvement in SPECT contrast-to-noise ratio

• Improved spatial resolution

• Improved energy resolution

Direct conversion technology

Because there is no photon loss, the scans are completed in less time

SPECT/CT

Combination of 3D NM images with the anatomical mapping (CT)

• Increased specificity associated with greater diagnostic confidence

• Enable change in patient management

• prepare for challenging surgeries

• evaluate predicted function

StarGuide

General Purpose, all digital NM system

3D SPECT scanning using 12 individual detectors in a ring design that rotate around the patient

Optical Scout - optical body contouring for automatic patient and detector positioning

Swift Plan Workflow

SmartConsole

CZT —> allows for 3 minute FOV for lutecium imaging (theranostics)

MyoSPECT

Fully digital, cardiac-only NM system

3D SPECT imaging using a stationary, cardiac focused detector

Doesn’t perform CT imaging

Compact System

Extended FOV

Smart Positioning

2 different attenuation compensation solutions (*attenuation: the reduction in signal quality caused by the absorption and scattering of photons as they pass through the body's tissues)

SPECT Flow

CZT detectors

Aroura

A general-purpose dual-headed SPECT/CT (Ascend is on back)

128 slice CT, 40 mm coverage

Truly Hybrid System

AI for the first time in NM

Theranostics

The combination of therapeudics and diagnostics

“Lock and key” - drug companies (Novartis) create a key (Pluvicto or Lutecium 177) that can attach toa specific lock (prostate cancer)

Step 1: Image the patient with a PET/CT (Omni) to determine if a candidate for theranostics

Step 2: Do treatment cycles with Pluvicto (Lu 177)

Step 3: Post-treatment scans done on StarGuide to assess how well the treatment is working

Step 4: re-image anatomical mapping of cancer and treatment progress