Dual Energy CT
Describe Temporal Coherence.
In which tumor volume is there all the estimated tumor cells? (For a non-moving tumor)
The Clinical Target Volume
What type of scan needs to made BEFORE stereotactic neurosurgery?
MRI
How do you measure the Standardized Uptake Value?
What is different about the IVIM model compared to ADC?
IVIM is a bi-exponential model
Describe the spatial resolution of fast kV switching.
Degraded spatial resolution due to an extra large focal spot and a limited number of projections.
With Dual Energy CT (DECT)
Name four conditions where DBS can be used as therapy.
Parkinsons Disease (PD)
Dystonia
Essential Tremor (ET)
OCD
Depression
Tourettes
The Region of Interest is based on what two things?
Uptake & Anatomy
What does lower ADC about the chronic/acuteness of a brain mass?
Name each technical approach to Dual Energy CT.
- Sequential acquisition
- Rapid voltage switching
- Dual Source
- Layer detectors
- Photon counting detectors
How can you reduce variation in contouring Organs at Risk (OARs)?
- Make a clear definiton of the OARs
- Methods for automatic contouring; atlas based or deep-learning
How can a surgeon process DTI data?
With fiber tracking.
Describe FDG, and why a patient needs to be fasted before a PET scan.
FDG is a radioactive glucose analog used as tracer in PET scans.
Patients must fast to control the plasma glucose concentration and focus on only tracer uptake.What is the b-factor?
Why are photon counting detectors not currently available?
Cross-talk: when a single photon is registered as a count
Pile-up: the detector is not fast enough to count individual photons
How do you determine the electron density of tissue?
Calibrate the CT to determine the relation between the HU in CT and the electron density. You can do this with phantoms.
How can the location of activity in brain be seen in fMRI?
The imaging modality repeatedly looks at a particular brain area and measures how long the signal stays. The longer it stays, the more neuron activity there is in this region.
The activity in tissue depends on many factors. Name four.
- The injected dose
- Patient body weight
- Type of tracer used
- Characteristic of tissue
If tissue has low ADC, how will this manifest on an ADC image and what does it mean?
It will be a dark spot, which means the tissue is dense, indicating that it is a tumor
Name all of the quality criteria for the Dual Layer detector.
SS: Inferior to Dual Spiral, energy separation is on the detector level.
TC: Perfect!
SR: Full system capabilities available.
DE: Tube current modulation & iterative reconstruction available.
Name the five imaging techniques for position verification.
- Electron Portal Imaging (EPI)
- Cone Beam CT (CBCT)
- ExacTrac
- Surface Scanning
- MRI
Name the three steps that need to be done in order to carry out neuronavigation.
Step 1: MRI Scan
Step 2: Registration (of markers)
Step 3: Navigate to find tumor
Step 4: Confirm Tumor Removal (optional)
If perfusion goes from 3 to 1, and K1 stays the same, what can you say about the uptake of the tumor?
Tumor uptake is independent of the perfusion
Name 4 factors that affect diffusion.
Variation in number of cells
Variation in volume of cells
Variation in volume of extracellular space
Variation in temperature