Unsealed sources Flashcards
osteoclasts =
clear away
osteoblasts =
build up
Batson Venous System (BVS)
diffusion through this system is the principle of spinal mets, spread is possible through arterial, lymphatic or locality
describe the communication between the external and iliac veins
there is abundant communications through the pelvic venous plexus which provides various collateral routes between the external and iliac veins. The venous drainage passes through the vertebrae destroying the body from the inside
where is VBS found
near the spine, blood borne spread causes lumbar mets during prostatic disease
where are osteoclasts derived from
monocytes in the bone marrow
what do osteoclasts do
wok on the outer layer, destroying the bone lining
what work as a team
osteoclasts and oesteoblasts
where are osteoblasts from
cells associated with blood vessels, once these are active they produce osteoid which is mainly made up of collagen.
what does mineral crystallise around the collagen scaffold form
hydroxyapatite crystal which contains calcium phosphate
what do osteoblasts form
new bone which becomes embedded within the matrix and differentiates into osteocytes
what does the bone composition allow for
calcium reservoir which provides support and locomotion
the role of osteoclasts
liberate minerals and molecules which are stored in the matrix, anchor the surface of the bone and create a microenvironment underneath - sealed zone. Creates an acidic environment, therefore bone is broken down dissolving the bone mineral content. Enzymes released from the oestoclasts remove the remaining collagen
bone mets
occur frequently in prostate, breast, lung patients
disruption in the osteoclasts and osteoblast balance causing pathological fractures and cord compression
associated with continuous pain or arises during movement
anti-inflammatory
EBRT local or more locally extensive
what happens once cancer arise in the bone
produce growth factors which stimulate osteoblastic or osetolytic activity which results in bone remodelling, the release of other growth factors leads to a cycle of bone destruction and growth of local tumour resulting in numerous sclerotic [hole] mets
nuclear medicine function
diagnosis, staging, follow up
determine tumour location, size and extent
staging: treatment options will differ dependent on the outcome
standard follow up is 5 years, the duration is dependent on the risk
MDP
a compound which attaches to the crystal (chemiabsorption) due to being attracted to the crystal. Tc-99m is the radioactive label which works alongside (half life of 6 hours). It emits gamma rays.
The m stands for metastable therefore once these rays are emitted it becomes Tc-99. A gamma camera is used to visualise the gamma rays. During primary excretion the amount of radionuclide within soft tissue decreases to 50% with 50% in the urinary system and 50% in bone
what is the degree of uptake dependent on
blood flow and rate of new bone formation
patient prep for a bone scan
drink plenty of water: flushes the system
all metal objects to be removed: blocks the gamma rays, creating a hole in the scan
if the radionuclide is transmitted to another area it will create a photon increased area
empty bladder: gamma rays block everything else
what is the RP and route of administration at a bone scan
500MBq Tc-99m MDP injected into the median cubital chin
what are the three phase images
flow phase
blood pool phase
delayed phase
flow phase
in the first 2-5 seconds, images are obtained for 60 seconds demonstrates blood flow, circulation and perfusion
blood pool phase
5 minutes after the injection a image is taken to look at the difference between interstitial fluid and plasma
delayed phase
obtain2-4 hours after injection, about 50% is absorbed into the bone at approximately 2-6 hours.
you can see photon deficient areas
what is a super scan
it is where there is no kidney visualisation more than 50% has been uptaken into bone
what does Tc-99m MDP detect
osseous mets
what does PET use
glucose, tumours use it as an energy source
F-18 FDG PET
used for PSMA negative patients, which have aggressive cancer or to assess recurrence
F-18 FDG PSMA PET and Ga-68 PSMA PET
used in diagnosis, staging, restating and evaluation of therapy response
fluorinated tracers have a longer half life so are more practical than gallium tracers
F = 110 minutes
Superior for patients with low PSA at detecting prostate cancer mets
Radionuclide itself
administered by IV
radionuclide travels to or near the disease sites
damages the cancer cells whilst limiting the dose to normal tissues
offers a personalised treat,ent as it is tailored ro the molecular properties of a specific timeout
why has P-32 been stopped in its use
it would enter the BM destroying RBC, WBC creating more symptoms
higher rates of myelosuppression and pancytopenia
what is wide spread mets being treated with
Radium-223 dichloride
targets area with increased bone turnover which is directly injected into the blood stream
what type of emitter is Ra-223
alpha
Alpha
low penetration
<5cm range in air
5-10 cell diameters range in tissue
HIGH LET
5-8MeV emission energy
11.43 days = half life
how does radium work
it mimics calcium, so it is rapidly taken up to form new bone. Osteoblasts want calcium, so selectively targets bone mets
Alpha particles break DSB
Before treatment a FBC is taken, any calcium supplements are stopped 2 weeks prior to treatment.
an IV injection occurs over a minute into 2 or 3 way adapter, it is flushed before and after to make sure the vein won’t collapse.
cleared by the urinary system which is then excreted as faeces
what is the standard prescription for Ra-223
6 cycles of 55kBq at intervals of 6 weeks
what are the restrictions for radium
monitor blood cell counts
report SOB, bleeding, bruising, fever (due to infection)
avoid dehydration (dry mouth and increased thirst) or urinary/kidney function (cystitis)
no restrictions via contact
gloves whilst handling urine, faeces, vomit and wash hands
follow good hygiene fro a week after injection, to mimimise with others
radium-223 side effects
haematological abnormalities: anaemia, lymphocytopaenia, leukopenia, thrombocytopenia, neutropenia
nausea
diarrhoea
vomiting
peripheral oedema
- 3.6 month increase survival
- avoid concomitant chemo - myelosupression
- patients have died due to BM failure
role of strontium-89 chloride
targets increased bone turn over which is directly injected into the blood steam, it mimics calcium attaches to the crystal
BETA EMITTER
strontium beta properties
found in aq
half life = 50.5 days
daughter product of Yttrium-89
pure beta emitter 1.463 MeV max
beta range is 7-8mm
easy to produce sterile product
non pyrogenic
beta have what type of LET
,medium with up to serval 100KeV emission energy
what does strontium do
imitates calcium, which localises in areas of remineralisation and high osteoblastic mets, and washed out of healthy bone. greatest dose is to the coticol and trabecular bone
can travel 7-8mm away from the site of active uptake
absorbs at a rate 10 fold higher in prostatic bone mets compared to healthy bone
retained in met lesions enabling a larger rad dose to mets for up to 6 months
preparation for strontium
2 weeks prior to treatment calcium supplements must be stopped, with strontium chloride being administered intravenously
syringe has a acrylic casing with a thing layer of lead encapsulated
if it was metal bremsstrahlung would take place
what is the administered dose for strontium
4mCi
it may suppress the tumour growth and has a cytotoxic effect which reduces the release of pain producing enzymes
strontium hazards
radiation: patient, staff etc
bone flat: brief pain for patients a few days (36-72 hour period)
not suitable if they have a short life expectancy
haematological depression
outcome for strontium
75-80% response rate, 32% experience no pain
when its used on its own there is 20% complete pain relief, when used alongside EBRT it has 60% complete pain relief
PSA levels have seen a decrease
cost disadvantage
samarium
combined with a molecules which targets bone prior to being injected into the blood stream
what emitter is samarium
beta
Lu-177 + PSMA targeting molecule
combined with molecules which target bone prior to being injected into the blood stream
what emitter is Lu-177 + PSMA targeting molecule
beta and gamma
what happens during the internal conversion and Lu-177
the excess energy Lu-177 interacts with electrons of other atoms
Lu-177
half life = 6.7 days
combined with PSMA target
targets cancer cells allowing targeted delivery to bony and extended disease
PSMA is expressed in nearly all prostate cancers - as its a biomarker (especially castrate cancers and prostate resistent)
what is the affinity of those who target PSMA
high
procedure of Lu-177
treatment: avg 7.5GBq per cycle up to 4 cycles
IV
anti nausea meds
IV hydration (normal saline before and after)
60 minutes later LU-177 + PSMA will commence
takes place for around 30 minutes
radiation levels monitored
overall 6-8 hour procedure
approx 24 hours post infusion a full body scan is performed
SE for Lu-177
nausea and headache
vomiting (rare)
oral rehydration needed for at least 2 days after to keep body hydrated
excreted through urine
normal activities can begin after full body scan
must avoid prolonged contact with pregnant women and young children for at least a week after
what do strontium and radium target
osteoblastic bone cells rather than met cancer cells
