Study Guide: Imaging Techniques NMPO1Y1

IMAGING TECHNIQUES NMPO1Y1

Overview of Imaging Techniques

• Before any NM imaging techniques or acquisitions can be performed, certain important preparatory steps must be completed.

NM Scan Request

• An appointment date must be scheduled.

• Important patient information to be recorded on the request form includes:   - Name of the patient.   - Gender.   - Date of birth.   - Patient’s hospital number.   - Contact details of the patient and next-of-kin.   - Full clinical history, including the indication for the scan and the requested study.   - Referring physician and their contact details.   - Referring hospital and ward/outpatient clinic information.   - Possibility of pregnancy (for females of childbearing age) and any other relevant information.

• Important Note: The request form is a medico-legal document.

Pre-Imaging Requirements

• Imaging can only occur after:   - A radiotracer has been administered.   - Peak uptake in the target organ or area of interest (AOI) is achieved.

Radionuclides in Imaging

• The most commonly used radionuclide is Technetium-99m (Tc99m), which can be injected as is or labeled with a pharmaceutical.

• Examples of formulations include:   - Tc99m-MDP: Used for bone imaging.   - Tc99m-MAA: Used for lung perfusion studies.   - Tc99m-DTPA: Used for kidney imaging.   - Bromobiliarone and DMSA: Used for other specific organ studies.

• Students should learn the full names and purposes of pharmaceuticals used with radionuclides.

Radionuclide Dosage

• Common injected doses for imaging include:   - 1 mCi in MBq   - 5 mCi in MBq   - 10 mCi in MBq   - 15 mCi in MBq   - 20 mCi in MBq

Injection Procedures

• There are two main positions for injection procedures:   - Patient in a supine position: Used for dynamic and 3-phase studies; mandatory for lung perfusion radiotracer (Tc99m-MAA) administration; not mandatory for delayed imaging investigations.   - Patient in a sitting position: Most common for planar imaging; can also be in an erect position, which is uncommon for dynamic imaging.

Injection Equipment

• Essential materials for injection include:   - Gloves (Nitrile or Latex)   - Kidney dish.   - Tourniquet.   - Cotton wool swabs and plasters.   - Alcohol swabs (Webcol).   - Jelco needle or butterfly needle.   - 3-way stopcock.   - Radiopharmaceutical to be injected (using a syringe shield).   - Lead pot/pig for shielding.

After Injection Protocol

• The injection of the radiotracer must be documented on the request form, including:   - Date and time of injection.   - Name and dose of the radiotracer.   - Anatomical site of injection (all attempts must be recorded).   - Name of the person administering the radiotracer.

Understanding Protocols

• A protocol dictates how procedures are performed and involves:   - The organ to be imaged.   - Acquisition parameters set prior to imaging.   - Acquisition steps and patient orientation relative to the gamma camera detectors.

• Patient information must be entered before selecting a protocol.

Imaging Techniques Description

• The description of imaging techniques must include:   - Selection and editing of the acquisition protocol and parameters.   - Prescribed views for the organ being studied.   - Removal of artifacts.   - Confirmation/adjustment of patient position and orientation.   - Correct gamma camera detector configuration/mode employed.

• Note: Acquisition parameters can be modified during imaging to enhance image quality.

Acquisition Protocols

• Acquisition protocols may consist of one or more of the following imaging steps:   - Dynamic/Flow/Perfusion imaging.   - Static studies.   - Blood pool (BP) imaging.   - Delayed studies.   - One day protocols.   - Two-day protocols.

Acquisition Parameters

• Key acquisition parameters include:   - Frame/matrix sizes:     - 64x64, 128x128, 256x256, 256x1024 (commonly used), 512x512, 512x1024 (not available on all gamma cameras).   - Frame times: 1 sec/frame, 2 sec/frame, 10 sec/frame, 30 sec/frame.   - Frame rates: 1 frame/sec, 2 frames/sec, 3 frames/sec, etc.   - Total acquisition time: 60 sec, 120 sec, 180 sec, 1800 sec, 3600 sec.   - Total counts: 300k, 500k, 1000k.

• The acquisition window width/energy is crucial, indicating the range of accepted photon energies for pulse height analyzers (PHA). The photon peak for Tc-99m is 140 keV, with a window width/energy of 20%.

Gamma Camera Heads

• Types of gamma camera heads include:   - Single head.   - Dual head.   - Triple head.   - The choice of one, two, or three heads for imaging depends on various factors including the specific imaging protocol required.

Patient Positioning and Orientation

• The advent of dual head gamma cameras has mitigated issues regarding patient positioning as patients can lie supine more comfortably.

• Patient orientation refers to the area of the patient’s body that is closest to the gamma camera detectors, classified as follows:   - Head first supine (HFS).   - Feet first supine (FFS).

• The angulation (in degrees) of the gamma camera detectors must be appropriate for various static and SPECT acquisitions.

Common Imaging Views

• Common views vary based on the organ of interest and include:   - Anterior   - Posterior   - Left lateral   - Right lateral   - Left anterior oblique (LAO)   - Right posterior oblique (RPO)   - Dual head pairing views depending on arrangement (students required to list these views).

Detector Angulations

• Detector angulations to note include:   - Various degree settings which affect the alignment of detectors relative to patient anatomy.     - Example angles: 0° (Anterior), 30° (RAO), 60° (Lateral), 120° (Posterior), and others.

Imaging Technique Considerations

• Before imaging, critically assess:   - Whether dynamic imaging needs to occur prior to the radiotracer administration.   - Selection of imaging protocol and acquisition parameters based on patient clinical history and other determining factors.

Patient Preparation Prior to Imaging

• Important steps include:   - Ensuring the patient has emptied their bladder.   - Providing clear explanations of the imaging technique and offering reassurance.   - Preparing the patient regarding the movements of the Nuclear Medicine Technologist (NMT).   - Assessing and ensuring patient comfort and cooperation during the procedure.   - Removal of any artifacts that may affect imaging outcomes.   - Appropriately positioning the patient in relation to the gamma camera.

Imaging Process Management

• When imaging has commenced:   - Effective communication and instructions to the patient are essential.   - Continuous reassurance during the process helps alleviate patient anxiety.   - Observation of the patient throughout the imaging procedure is vital.

Planar Imaging Techniques

• Planar imaging can involve:   - Whole body imaging or limited whole body imaging, specifically for conditions like bone imaging.   - Determining which spot views need to be acquired for effective diagnosis.

GC Detector Configuration

• Configuration for the gamma camera typically involves:   - Ant and Post (anterior and posterior configuration).   - Symmetrical positioning with patients supine on the imaging table.   - Centering the area of interest in the field of view (FOV).   - Patient comfort considerations during positioning include providing blankets, arm rests, etc.

Detector Positioning and Adjustments

• Important factors include:   - Ensuring detectors are positioned symmetrically to improve diagnostic precision.   - Specific settings for different patient orientations and examinations.   - Head and body configurations for optimized imaging.

Conclusion and Final Considerations

• Important to address post-imaging steps, confirm the effectiveness of the procedures, and maintain ethical guidelines through confidentiality regarding shared diagnostic images.

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