3.2 Anatomical Imaging/Diagnostic Imaging of Cancer

What are the three goals of diagnosis?

1. is it a tumor?

2. is it malignant?

3. What is extent and grade of cancer?

Which goal of diagnosis impact’s treatment choice?

What is extent and grade of cancer?

What does sensitivity tell us?

How well a positive test detects disease

Define sensitivity

the fraction of the diseased how test positive

What is the complement of sensitivity?

false negative rate

define false negative rate

the fraction of diseased who test negative

Sensitivity and false negative add up to __

1

What does specificity tell us?

how well a negative test detects non-disease

define specificity

the fraction of the non-diseased who test negative

what is the complement of specificity

false positive rate

define false negative rate

fraction of non-diseased who test positive

specificity and false positive rate add up to __

1

What are Receiver Operating Characteristic (ROC) Curves

shows a cutoff value where above or below the line indicates either disease or normal

What is positive predictive value

the proportion of all people with positive tests who have the disease

What is negative predictive value

the proportion of all people with negative tests who do not have the disease

Name 5 main imaging modalities

ultrasound, x-rays, CT, MRI, nuclear medicine

what is another name for ultrasound

sonography

in an ultrasound, what does the acoustic impedance describe

tissue stiffness and the brightness in the image

What are the benefits of ultrasound

few contradictions, no ionizing radiation, quick, small and cheap machines, readily available, can see tumors, lumps, and bumps

what is the most common form of image guided biopsy?

ultrasound guided biopsy

what are the limitations of ultrasound

image quality is poor, sound waves can’t penetrate bone or pockets of air, sound waves have depth limit, can’t distinguish benign from malignant tumors

In X-Rays and CT, contrast is due to either ___ or ___

tissue density (air vs tissue) or presence of heavier atoms (calcium in bone

X-ray absorption is proportional to ___

electron density

What is the biggest difference between X-Ray and CT

X-Ray is planar 2D image, CT is 3D reconstruction of multiple X-ray images

Do X-rays or CT scans use more radiation

CT

Are CT or X-ray images better quality

CT

Who is suggested to get a mammogram (x-ray) and how often

yearly after 40 and every 2 years after 55

where do osteosarcomas arise from

bone-producing cells

what is the most common location for osteosarcomas

knee

osteosarcomas can produce ___ bone

ectopic

What is the limitation of CT

doesn’t work well for soft tissue

what is the limitation of x-rays

form of ionizing radiation and therefore a carcinogen

Why are MRIs safer than X-rays

they use non-ionizing radiation & magnets

What do basic contrast mechanisms in MRIs focus on?

water and fat

what is T1 in MRI contrast

fat bright, water dark

What is T2 in MRI contrast?

water bright, fat dark

Why should cancer show up on an MRI

abnormal soft tissue can change MRI signal due to changes in chemical composition and most solid tumors have higher-than-normal water content

What is a problem with T2 MRI for brain cancer

CSF is also bright

what are the limitations of MRI

slow, claustrophobia, poor signal in lungs and bone, basic sequence cannot distinguish cancer cells from surrounding edema

what is diffusion

the random motion of molecules usually along a concentration gradient

more cells = __ diffusion

less