Hybrid Imaging PET/CT & PET/MRI Slide 59-76

What was the clinical context in which the PET/MRI images were obtained?

Post-chemotherapy imaging in a male patient with multiple myeloma

What is the anatomical site showing residual nodal activity?

Right supraclavicular region

Which hybrid imaging modality was used for these images?

PET/MRI

Why is PET/MRI particularly useful in this case?

It combines metabolic and soft tissue information, ideal for multiple myeloma

What radiotracer would most likely be used in these PET images for multiple myeloma?

F-18 FDG

What challenge might arise with PET/MRI scans that doesn't affect PET/CT?

MRI’s strong magnetic field interferes with certain detector electronics

What type of MRI scanner is traditionally associated with causing claustrophobia in patients?

Long Bore Scanner

Which MRI scanner design offers the best spatial resolution for optimal imaging?

Long Bore Scanner

What is a key feature of the short bore MRI scanner that improves patient comfort?

It is 50% shorter and 5% wider than traditional MRI scanners

Why might a short bore scanner be selected over a long bore scanner in clinical practice?

To reduce patient discomfort and accommodate larger body types

What is the primary advantage of long bore scanners compared to short bore scanners?

Superior spatial resolution

What is the typical field strength for a permanent magnet in MRI?

< 0.3 T

Which type of magnet requires electricity to maintain its magnetic field and operates around 0.6 T?

Resistive Magnet

What type of MRI magnet uses cryogens and provides the strongest field strength?

Superconductive Magnet

What is the common field strength range for superconductive MRI magnets?

0.5 – 7 T

What type of magnet is always on and does not require electricity?

Permanent Magnet

What’s the equivalent of 1 Tesla in Gauss?

10,000 G

What is the Earth's magnetic field range for reference?

50 µT to 0.5 G

What is the significance of the 5-Gauss line in MRI safety?

It indicates the field strength where magnetic objects can become projectiles

Why is a detailed patient history crucial before an MRI scan?

To identify any metallic implants that could cause harm during scanning

What type of objects are most dangerous in the MRI environment?

Ferromagnetic metallic objects like pacemakers or bullet fragments

What makes MRI magnets especially dangerous?

The magnetic field is invisible and can attract ferrous metals with great force

Which MRI plane divides the body into left and right halves?

Sagittal

What makes MRI unique compared to CT when it comes to imaging planes?

Coronal

True or False: MRI can produce oblique plane images for better visualization of specific organs.

True

Who first discovered the rotating magnetic field concept foundational to MRI?

Nikola Tesla

What did Felix Bloch and Edward Purcell discover that led to a Nobel Prize?

They measured magnetic resonance in bulk material like liquids and solids

Who identified the relationship between magnetic field strength and RF frequency (Larmor Frequency)?

Sir Joseph Larmor

What did Isidor Rabi observe in the 1930s?

That nuclei exposed to radio waves in a magnetic field experienced resonance

What was the original term for MRI?

Nuclear Magnetic Resonance

Who introduced gradients into the magnetic field to create 2D MRI images?

Peter Lauterbur

Which physicist demonstrated Echo Planar Imaging and mathematical analysis of MR signals?

Sir Peter Mansfield

What was the name of the first NMR scanner built by Raymond Damadian?

The Indomitable

Who received the 1991 Nobel Prize for work on High-Resolution pulsed Fourier spectroscopy?

Richard Ernst

Who received the 2002 Nobel Prize for demonstrating 3D molecular structures in solution?

Kurt Wüthrich

What is the role of the magnetic field in Nuclear Magnetic Resonance (NMR)?

It aligns the nuclei of atoms to prepare them for RF interaction

In NMR, what does the term resonance specifically refer to?

The absorption and re-emission of RF energy at a matching frequency

Why is the term "nuclear" used in NMR?

It refers to the behavior of atomic nuclei in a magnetic field

Which of the following statements is true about MR examinations?

MR exams use magnetic fields and radio waves to create images without ionizing radiation

Why must caution be exercised around MR scanners, even when they are not actively scanning?

The magnetic field is always active in a superconducting MR system

Which type of imaging is most accurate for soft tissue without using ionizing radiation?

Magnetic Resonance Imaging

What is one key characteristic of MR image acquisition?

It creates multidimensional images of the body

What is the first step in performing an MRI exam?

Place the body part in the center of the bore

Why must the patient be exposed to the magnetic field?

To align hydrogen nuclei

What do RF pulses do during MRI?

Flip hydrogen atoms out of alignment

What happens when RF pulses stop?

Atoms realign and release energy

What is detected to create the MRI image?

The energy signal released during relaxation

What causes the loud thumping sound during MRI?

Pulses being turned on/off

What causes precession in hydrogen nuclei during MRI?

Applied magnetic field

What type of motion is described by precession?

A cone-like wobbling motion of spin axis

What is FID?

A decaying signal produced by relaxing hydrogen nuclei

What tool is used to convert FID signals into usable imaging data?

Fourier Transform

What happens when the RF pulse is turned off?

Nuclei realign with the magnetic field and emit an FID

What is the purpose of MRI coils?

To transmit and receive RF signals for imaging

Why do MRI facilities purchase coils from specific manufacturers?

Because of camera compatibility

True or False: Phased array coils help increase signal-to-noise ratio (SNR).

True

What type of relaxation is also called longitudinal or spin-lattice relaxation?

T1

When does T1 relaxation occur?

After RF energy is turned off and hydrogen begins to realign with the magnetic field

What percentage of longitudinal magnetization recovery defines T1 time?

63%

What is T2 relaxation also known as?

Spin-spin

What happens during T2 relaxation?

Protons dephase in the transverse plane

At what point is T2 relaxation time measured?

37% loss of magnetization in the transverse plane

What does the 90° RF pulse do?

T1 relaxation measures:

How fast protons realign with B₀

T2 relaxation is caused by:

Spin-spin dephasing

What kind of coil is used to detect the signal in MRI?

Receiver coil

T1 and T2 processes happen:

Simultaneously

What does a voxel represent compared to a pixel?

A volume element

Which formula calculates voxel volume?

(FOV ÷ Matrix) × slice thickness

What affects geometric magnification in CT?

FDD & FOD

Pixel pitch refers to…?

Distance between centers of adjacent pixels

MRI voxel size differs from CT because...

It’s not based on geometric magnification