Intrinsic vs exogenous
Intrinsic is a signal that comes from properties naturally found in the body (tissue properties).
Extogenous is a signal that is introduced by a contrast agent or radiotracer
Intra vs Inter
Intra is a variation within the same tumor
Inter is a variation between different tumors can use histogram analysis
What are the 4 types of cancer treatments?
Chemotherapy, radiation, targeted therapy, and immunotherapy
What is neoadjuvant therapy?
Treatment given before the standard therapy (surgery)
What is adjuvant therapy?
Treatment given after standard therapy (surgery)
How does restricted diffusion look on imaging?
Bright on DWI and dark on ADC map
What is the difference between apoptosis and necrosis?
Apoptosis - programmed single cell death (caspases)
Necrosis - clustering of dead cells, inflammation, could be due to injury, no energy needed
How do you increase signal to noise?
Increase acquisition time, average the images, or increase dose (if safe)
What imaging modality uses nuclear medicine?
PET/SPECT
PERCIST is used for what?
nuclear imaging (PET/SPECT)
What are 3 applications of medical imaging?
Diagnosis, treatment, and directing surgery
What is the purpose of contrast agents?
To change the physical properties of tissues so they produce a stronger signal
What occurs first, metabolic changes or tumor size changes?
Metabolic changes
What are the units for SUV?
There are no units
How can we test repeatability of imaging metrics?
Using bland and altman plots (95% confidence interval)
What is signal to noise?
The contrast the object must overcome for the image to be seen
What is heterogeneity?
Different characteristics in the same tumor
How does cancer contribute to cell death?
Cancer cells can avoid cell death which allow them to grow abnormally and sporadically
What are the 2 types of cell death we talked about?
Apoptosis and necrosis
Entrinsic apoptosis pathways are what...
receptor mediated
Intrinsic apoptosis pathways are what...
mitochondria mediated
Chemotherapy
Systemic/ hits cells that are actively proliferating (DNA damage)/not targeted
Radiation
Not targeted/all cells in the area die (image guided)
Targeted therapy
specfically targeting a protein or receptor
Immunotherapy
Any treatment that helps activate the immune system to help kill cancer cells (ex: pembroluzimab for PD1)
Multimodel imaging can improve the assessment of treatment for what?
Cell death because necrosis, apoptosis, and more can occur in a tumor
A higher b value for DWI MRI suggest what?
Stronger diffusion effects (greater sensitivity but could show higher noise)
Can DWI tell the difference between cells?
No cells could be dead or alive
What is cell proliferation?
An increase in the number of cells as a result of cell growth and division (growth signaling pathways)
What does the compartment model show?
The bidirectional flux of tracer between blood and tissue
What is Ca and Ct in the compartment model?
radioactive concentrations
What is K1 and K2 in the compartment model?
The rate of trasnfer from one compartment to the other
What is angiogenesis?
The formation of new blood vessels
What is vasculature?
The established blood vessels
Blood flow is a rate so what imaging is needed?
dynamic imaging (contrast MRI, ultrasound, PET, SPECT)
What is tumor invasion?
Direct penetration by cancer cells into neighboring tissue
What is tumor metastasis?
The spread of cancer cells to tissues and organs beyond where they originated from
How do cancer cell circulate?
Through the lymphatic or vascular system
True or false. Cancer cells can be dormant and not actively proliferating then they can reactivate
true
FDG PET is not good for looking at what parts of the body?
brain or bone
Nonmetal vs metal probes
nonmetal - incorporates radionuclides into the structure
metal - incorporated into the targeting using antibodies
What is the best approach for looking at brain metastasis?
MRI (T1 with contrast/flair imaging) or CT
What are anatomical imaging modalities?
CT and MRI
What are functional (physiological) imaging modalities?
DWI, DCE, DSC
Blood flow is a rate so what type of imaging is needed?
dynamic imaging
What are molecular imaging modalities?
PET/SPECT
Steps for midterm
1. Identify modality
2. Identify quantifying metrics
3. Connect to underlying biology
A tumor is bright on DWI and dark on its ADC map. Which interpretation is most appropriate?
Restricted water diffusion (high cellularity)
What are some anatomic contrast agents?
bones, organs, blood vessels
What are some physiologic contrast agents?
Perfusion rates, myocardial movement, tissue metabolism
What are some molecular contrast agents?
Receptor imaging, protein targeting, drug kinetics
What is half life?
The time taken for the radioactivity of a specified isotope to fall to half its original value
What things have different types of radiodensity?
Air, fat, water, bone
Quantitative
numerical measurements (radiomics/RECIST)
Qualitative
descriptions and observations (images)
In what ways do cancer cells support angiogenesis?
immune cells, extracellular matrix, support vascularization
Metastatic disease imaging is dependent on what?
Tumor location
What is the difference between ktrans and k1?
ktrans = looks at the transfer of contrast from blood plasma to tissue and can evaluate increased vasculature and permeability
K1 = looks at active transport (cellular metabolic transport)
High grade tumors will show what kind of curve?
Steep curve with rapid and prominent washout
Low grade tumors will show what kind of curve?
Gradual uptake with a low plateau and washout
How do you calculate percent increase for RECIST?
current-baseline/baseline*100
Spatial resolution
The space between voxels
smaller voxels can reduce signal to noise
Temporal resolution
Taking images over a period of time
faster aquistion can reduce signal to noise
What are some differences between tumor and normal vessels?
Tumor - unorganized, leaky, reduced blood flow, abnormal branching
Normal - normal branching patterns, tight cell to cell junctions, no leaky parts