Chapter 19 Hybrid Imaging SPECT/CT & PET/CT

Which of the following statements about modern PET scanners is most accurate?

Virtually every PET scanner includes a CT component

What is increasingly true about modern SPECT imaging systems?

They often include integrated CT units

What is the primary advantage of hybrid imaging systems?

They combine functional and anatomical images in spatial alignment

Which best describes a limitation of nuclear medicine imaging (PET/SPECT) when used without hybrid systems?

It produces poor anatomic localization

What is a reason radiotracers might still show regional anatomy clearly in some cases?

The tracer uptake is predictable in certain organs (like the heart)

Compared to CT or MRI, how does the spatial resolution of PET/SPECT generally perform?

Poorer, especially in localizing structures

What challenge existed before hybrid imaging became common?

Images from separate machines were hard to align

Why did delays between scans cause problems?

Patient positioning and condition may have changed

What is a major advantage of combining CT/MRI with nuclear medicine scans?

Provides the full functional and structural story in one exam

What is one major benefit of acquiring PET or SPECT and CT scans in quick succession?

It improves spatial and temporal image registration

What does CT imaging contribute to PET/SPECT in hybrid systems?

It allows attenuation correction of PET/SPECT images

Why are hybrid imaging systems more convenient for patients?

They allow two scans to be completed in a single session

What is a key feature of x-ray CT that differentiates it from nuclear medicine techniques like PET/SPECT?

CT uses high-intensity external x-ray beams for transmission imaging

Which of the following is true about the reconstruction techniques used in CT compared to PET or SPECT?

CT uses backprojection methods similar to PET/SPECT.

Which best describes why CT achieves better spatial resolution than PET/SPECT?

CT uses a narrow, high-flux beam of x-rays

What is the purpose of the filament in the x-ray tube?

To generate electrons when heated

What is a key purpose of using a rotating anode in the x-ray tube?

To distribute heat over a larger area of the anode

What are the two main types of x-ray photons produced at the anode target?

Bremsstrahlung and characteristic radiation

What type of detectors are most commonly used in modern CT scanners?

Ceramic or CsI(Tl) scintillators coupled to silicon photodiodes

What is a limitation of older CT systems using xenon gas detectors?

They produce weaker signals and are slower than solid-state detectors

What does the output signal from CT x-ray detectors primarily represent?

The number of x-rays detected, proportional to the x-ray flux

What allows the gantry in a modern CT scanner to rotate continuously without interruption?

Slip ring technology

What component of the CT scanner is responsible for rapidly spinning around the patient during image acquisition?

Gantry

Why is high-voltage power used in a CT scanner?

To produce x-rays from the x-ray tube

What is the purpose of the conductive brushes in slip ring technology?

To allow continuous electrical connection while the gantry spins

Which of the following best describes how data is collected from a rotating CT gantry?

Via slip ring technology or wireless transmission

What is the standard range for rotational speed of a modern CT gantry?

1–3 revolutions per second

What key benefit does slip ring technology bring to CT scanning?

It allows continuous gantry rotation without cable entanglement

Before slip ring systems, what did technologists have to do between rotations?

Unwind the scanner wires to prevent entanglement

Why was the old practice of manual wire unwinding during CT scanning problematic?

It slowed down scan time significantly

What kind of path does the CT scanner follow when acquiring image data?

Helical

In CT image reconstruction, what does each projection file typically correspond to?

A single transaxial section

What is the name of the algorithm commonly used in CT and nuclear medicine to reconstruct image data from projections?

Filtered backprojection

What is the primary use of small animal SPECT/CT scanners?

Researching and evaluating new radiotracers

What advantage does SPECT/CT provide in small animal research?

Combines functional and anatomical imaging

In the provided image, which radiotracer is being used in the mouse scan?

In-111

Why was the development of SPECT/MRI technology slower than PET/CT?

MRI magnets interfere with nuclear medicine equipment

What problem arises when integrating SPECT with MRI systems?

The electromagnetic field causes detector failure

Why is PET/MRI integration more successful compared to SPECT/MRI?

PET detectors are placed on opposite sides of the MRI magnet

What is the main advantage of using PET/MRI in oncology?

It combines metabolic and soft tissue detail

Which PET imaging feature shows only the highest uptake regions?

MIP