exam 2 Flashcards
whats is deoxyglucose
analog to glucose
what happens when you label deoxyglucose with F-18 and how is it used
you create F-18 fluorodeoxyglucose (FDG) and it is utilized as glucose would be in the body
what and how does f-18 decay
97% positron emission into O-18
normal f-18 fdg distrinution
brain, heart, thyroid, liver/spleen, stomach, intestines, bladder, kidneys, salivary glands
physiology of tumor cells and why fdg goes there
cx cells have an 10 times incr metabolic rate compared to that of normal cells
how is f-18 fdg trapped and what does it phosphorolate into
f-18 is phosphorylated into 2-FDG-6-phosphate by the enzyme hexokinase and phosphorylated into FDG
define phosphorylation
attachment of a phosphate group to a molecule or ion
what do cancer cells overexpress
hexokinase
what does hexokinase do
converts glucose into next step for the citric acid cycle
whats the reverse enzyme
glucose-6-phosphate and it allows it to leave the cx cells and cx cells will have no glucose-6-phosphate
what is is f-18 fdg not the best for brain tumors
brains main food source is glucose so less differentiaiton of normal cells vs abnormal cells
f-18 fdg prep
-npo 4-6 hours
-bg less than 200 (no lower limit but be cautious of too low)
-froedter bg standard= 70-210
-low carb, high protein diet
-no exercise
if a pt is below 70 but not diabetic and feeling well what do we do
proceed and just give a snack after
why no exercise for prep
glucose will preferentially move to the muscles
why low carb, high protein diet
if no carbs, cells are starving, so they will take in FDG exceptionally well and will help with less cardiac uptake
if a diabetic pt is less than 70 what do we do
give glucose pill po and send home
can f-18 fdg be given orally
no very rarely
why does low carb diet and high protein help lower cardiac uptake
bc forcing heart to be in amino acid metabolism
admin steps for fdg
-inject via IV and make sure pt is warm and still
-wait 60 min to circulate b4 imaging
why is it important to keep pt warm
brown fat keeps us warm and will eat sugar is it has to work aka if pt is cold
what is scout image for
to look for keys, metal objects, jewelery
what is a little round circle that is metal in chest area
port
fdg false positives
-inflammation: hematomas, granulomatous proccess, thyroiditis
-infection
whats granulotamous process
-bodies way of containing bacterial, fungal, or viral inf to keep from spreading
-form when immune cells clump together and create tiny nodules at inf or inflammation sites
if pt had chemo in past 6 weeks, what will happen
fdg will show up in bone marrow
why does infection pick up more fdg
neutrophils and activated macrophages which are present in infections have increased fdg uptake
what is bursitis
inflammation and irritation of the jelly like pads distributed at the areas where bone meets tissue (hips are common)
what factors affect bio-distribution of fdg
serum insulin and glucose levels
how does serum insulin affect bio disribution
-insulin released to reduce glucose levels by pushing glucose into muscles> no insulin 4 hours prior to examh
how does glucose levels affect bio-distribution
increase in glucose levels means cells are already full of glucose and won’t take p any f-18 fdg
if pt comes in with too high glucose
reschedule and if above 300 call doc and send to ER
if all muscles show up on scan then this is due to
insulin if its all over
what happens to pic if BG is 190
not much PET shown
what happens if choccy milk 2 hr prior to exam and bg is 103
upatkes in intestines
how does exercise affect bio distribution
muscles need sugar to repair themselves and will take it all up (can see for 24 hours)
what does it look like if a pt gardenened day before
hands and quads lit up
texting shows
in forearms and hands
will a pulled muscle show
yes
chewing gum and ate
uptake in salivary galnds and tummy
how does chemo affect biodisrtibution
chemo damages bone marrow
-bm uses sugar to repair
-wait 6 weeks from chemo b4 PET
why is a pet ordered day after chemo
to see if chemo is working a destroying bm and if not working siwtch chemo asapw
what happens if pt has splenomegaly
chemos causes this and then goes to bone then
how does radiation therapy affect bio distribution
xray converge on a tumor which create tumor inflammation on and around tumor site
what does rad tp look like on pet
homogenous incr in activity where xray converges
how does surgery and biopsy affect biodistribution
cellular repair at incision site bc inflammatoin
how do hemopoietins affect biodistribution
class of drug that incr production of bone marrow (usually cx patients) “colony stimulating drugs”
what does hemopoeitn look like on pet scan
highlights all Bones
how does muscle tension affect biodistribution
sitting upright activates muscles that need repair so lie pt back a bit
how does hydration affect biodistribution
the circulatory system moves/ flows better when hydrated
what muscles are often affected
tongue, vocalis, scalneus, laryngeal, sternocleidomastoid, esophogeal, heart, paraspinal, trapezius, rhomboid, colon, psoas, glutes, arms, legs, hands
if a pt has sever lymphadema what will scan show
poor blood circulation so poor circulation of tracer
what does a higher and lower suv mean
that higher suv is more metabolically active and lower is lower metabolic activity
what do we compare SUV’s for
to tell if treatment is workinh (in 2 weeks) and if suv doesm’t decr enough then switch therapies
what does suv tell us
how metabolically active an area is
need to see a suv of what percent if treatment working
25% or greater
-calculated by taking mean activity in ROI over injected dose/wt (lean body mass vs weight)
metabollically active MBq??
2.5 MBq/ml/mg or above
is it better to use weight or lean body mass when calculating suv
weight because more reproducable than lean body mass
pov: lump in breast, LT breast bx was normal–> 2 wks later PET shows activity on outside of lump. why?
bc this tumor is necrotic and cut off blood flow to the inside of tumor so we need to re-bx and pt has invasive breast cx RIP
how to differentiate radiation necrosis vs tumor
overlay ct and pet and show exact location
what happens in mesothelioma
lining of lung affected and spread to other organs= incurable
radiation causes inflammation but is less…
bright on scan compared to new tumor
what is thymus important for in kids
growth of several organs and sleep patterns
-normal to see active on PET in kids
in brain tumor imaging why would we wait longer
more time allows washout of tracer from normal tissue and can try looking at pic without attenuation correction applied
what can also be named as “false positives”
artifcats
where does brown fat store
around neck, chest, axilla, perinephric, intercostal, periaortic
what will a scan look like if pt is not warm enoigh
uptake in brown fat bc it feeds off of glucose, spots not warm on inj so shows on spine
