VivaShit Flashcards
Caudal boundary of external iliac nodes
Contour around with a 7mm brush(like everywhere except obturators):
Transition from the inguinal area, when the vessels adopt a horizontal path above the upper edge of the iliopubic ramus.
** Should be at the very apical border of the femoral heads.
Boundaries for obturator nodes
Use 18mm brush:
Caudal edge is the apical pubic symphysis
Ant and post edges of iliac bone on axial (imagine a coronal line) define the ant and post borders.
Continue up til you hit the horizontal path of the externals.
Some technical downsides of VMAT:
VMAT: Gantry and MLCs both moving during dose delivery:
Potential for high MU
higher MLC leak/penumbra.
Anatomical boundaries of:
IMN (just the sup inf)
SCF
1) Sup aspect 1st rib, superior aspect of 4th rib.
2) Sup edge: Caudal to cricoid,
Inf edge: Caudal edge of clavicula head.
Ant: SCM
Post: Ant surface of scalenes
Medial: exclude thyroid and trachea
Lateral: in neck then lateral edge of SCM, lower junction of 1st rib and clavicle.
Relationship between heart dose and cardiotoxicity risk:
Basic interventions to minimise RISK:
7%/Gy linear w/no apparent threshold.
1) No Herceptin or acanthrocylines during/around treatment
2) Treatment techniques:
a) Position
- DIBH - typical MHD (left sided) around 1.5Gy vs 2.5Gy free breathing.
- Prone position.
- Lateral decubitis position.
b) Technique:
- conformal IMRT/VMAT
- Wide tangent in conjunction w/DIBH has been shown to reduce dose further.
- Electrons for IMN.
3) Minimise modifiable cardiac risk factors.
Benefit of hormone therapy in Br Ca:
Also give doses because the College are cunts who’ve conflated memory with intelligence.
EBCTG:
Tamoxifen:
Overall BCS improved by 10% at 10yrs.
LN -ve = 5%
LN +ve = 12%
ATAC - AI superior to tamox in post meno
SOFT-Tex:
Ovarian Suppression + AI
OS benefit even in LN-ve - but high drop out rate.
Define brachytherapy
Essential components of a HDR brachytherapy system:
Sealed source placed in (interstitial) or in contact (intravity/mould/plaque) with the tumor providing high dose to the tumor with small volumes of normal tissue irradiated.
Operating console of the remote afterloader unit,
remote afterloader unit,
radioactive source,
transfer tubes,
afterloading catheters and applicators,
treatment planning system.
Safety system - Bunker, afterlocks, emergency procedures.
QA tests for:
Mechanical, planning, radiation, safety, electrical systems
In terms of brachytherapy define LDR and HDR:
Low dose rate (LDR)
(0.4 - 2 Gy/h)
HDR
(>12 Gy/h)
The essential components of remote afterloading
machines:
- A safe to house the radioactive source
- Radioactive sources (single or multiple)
- Remote operating console
- Source control and drive mechanism
- Source transfer guide tubes and treatment applicators
- Treatment planning computer
For each of these systemic therapies give the side effects for which they are famous:
Taxanes
Cisplatin
Carboplatin
5-FU
Capecitabine
Etoposide
Ritux
Cetuxumab
Taxanes: Perif neuropathy - cardiomyopathy if used with Acanthracycline.
Cisplatin: Neuropthy, ottotoxicity, nephropathy, N&V
Carboplatin: Myleosuppression
5-FU: Mucocitis, hand foot and mouth - like rash, coronary artery spasm
Capecitabine: Is converted to 5-FU
Etoposide: Myleosuppression
Ritux: Super COVID
Cetuxumab: Skin rash - 95% of the time.
Describe a 3D breast plan:
How would you improve homogeneity (while not changing technique)?
Whole Breast/Chest wall only:
Opposing pair tangential fields, with non-divergent posterior edge.
Breast/ CW + SCF + IMC:
Mono-isocentric technique
- Breast/CW: 2 As above.
- IMN: wide tangent field crossing midline to cover IMN (or electrons)
- SCF: AP field, junction inferior edge with tangent field, angled 10deg off cord, 6MV energy
prescribed to 3cm depth
- Options to improve homogeneity
o Bilateral wedge (with thick edge anteriorly)
o Field in field/ subfields
o Hybrid IMRT
o Electronic compensation (ECOMP)
Describe a whole brain technique for multiple brain mets:
Whole brain RT 30Gy/10#s, 3Gy/# VMAT technique with hippocampal sparing. 6MV photons. Prescribed to D50. Would include down to C2 if post fossa mets.
Pre sim: dex, analgesia, anti seizure as required.
Sim: Supine, head towards gantry, knee and ankle supports. Immob with thermoplastic mask.
1mm Slice CT scalp vertex to C7. Planing MRI (T1) to help deliniate hippos.
Volumes:
CTV = whole brain.
Hippocampal Avoidance Zone = bilateral hippos +5mm.
PTV = CTV+5mm with the hippocampal avoidance zone subtracted from this volume.
Goals:
1) Hippo:
Aim max dose <16Gy
Min dose <9Gy.
Blah.
Mechanical vs Radiation isocentre (2019)
- Define
- How is it checked
- How often checked in QA
If the isocentre was off by 2-3mm, what would the problem be?
Mechanical isocentre. Point in space around which couch and gantry rotate. affected by sagging of collimator head by gravity.
Radiation isocentre: A point like volume where the beams intersect when couch, gantry or colimator is rotated. Daily QA - Radiation isocentre kept within 1mm movement within all planes. Rough guideis bunker lasers and a laser son the gantry.
Isocentre off by 2-3mm effects dosimetry and accuracy, with this effect amplified in non-coplaner plans (e.g. SABR).
Where do you place the isocentre
Eg in setting of re-irradiation or at nearby site
And other scenarios?
1) Single field either surface or at depth (no signif diff)
2) Asymmetric fields (one or both of X and Y collimator settings are not equal) have 2 benefits. 1st enable a tx plan isocentre to be located on a convenient anatomical set-up point rather than being restricted to the centre of the PTV. 2nd, enables the beam divergence of adjacent fields to be matched to one another.
E.g. posterior part of simple breast tangent pair has non divergent edge aligned posteriorly.
In incredibly simple terms - Larger linac field sizes do what
- Increased secondary electrons - higher surface dose
What is a monitor unit
The amount of charge measured in an ionisation chamber in the linac head which correlates to a dose of 1cGy measured in a water phantom on the central axis in fixed conditions. Allows direct monitoring of linac output in a dose related way (but does not reflect field size changes ect).
Benefit of using Flattening Filter Free approach:
Disadvantages
Bene: Tight control of fluence, higher dose rate (less treatment time), much less scatter from treatment head. Reduced out of field dose. Good for patient motion - preferred for SABR.
Dis: Very high dose rate can quickly deliver unintended high dose to OAR if unplanned patient movement. Not suited to larger field size SABR.
What should TSH be prior to RAI?
Advice to achieve this:
Alternative method:
Diet advice
> 30 mIU/L
Cease thyroxine 4 weeks prior. Restart day 3 post.
Recombinant human TSH (Thyrogen) - 2 injections 24 hours apart, just prior to RAI to raise TSH level rapidly
Low iodine diet to commence 2 weeks prior.
NBM for 2 hours prior to administration.
Definite indications to NOT give RAI for thyroid cancer:
Contraindications
Small tumors less than 1-2 cm confined to the thyroid gland with no evidence of spread to the lymph nodes or surrounding tissues.
Contraindications:
1) Pregnancy or desire too become preg in the next 6-12 months. Discuss role of contraceptives.
2) Unable to comply with safety guidelines.
3) Graves eyedisease
4) Currently unwell with GI upset.
Advice post RAI
1) Will have uptake scan 1 week post
Precautions:
Avoid close contact with children <5 and preg ladies for 3 weeks.
Avoid preg (or trying to make a baby if a dude) for 6-12 months.
For 7 days:
- Avoid sleeping in the same bedroom as another person
- Use your own set of crockery and cutlery and wash separately. Alternatively use disposable cutlery
- Refrain from food preparation and dishwashing
- Double wash clothes. Wash separately from clothes of others
- Continue to double flush the toilet
For 3 days:
Keep pets at arms length
Avoid visiting places of entertainment or going to work
Verbalize (in order) the list of shit you would say for a compromised PTV/CTV plan:
“I would review the plan in detail ensuring that:
- The volumes are correct
- Noting the location of hotter spots, cold spots, considering beam energies.
- OAR dose and the extent of compromise.
IMRT/VMAT:
“I would re-plan with a change of weights on more critical OARS”
3D:
“consider beam arrangements, Add beams, consider wedges, bolus, more conformal technique”
If still no love:
Consider the likie consequences of increased dose to OARS vs PTV compromise and discuss with patient with informed consent.
Steps of describing sim/pre-sim:
Pre sim:
Beta HcG if appropriate
Dental - H&N
Dex/anti seizure
Analgesia/PRNS
Specific consent - e.g. retreat H&N
Sim (they want added detail):
Position: including arm/shoulder
Organ requirements: e.g “comfortably full bladder”
Bolus
Markers - e.g prostate fiducials.
Other - I always forget this - e.g. tampon for cervix plan.
CT
almost always say would fuse relevant diagnostic imaging.
Describe Sim for a head and Neck treatment:
Pre-sim:
Dental review and necessary treatment complete
Consider dietician
PEG
Smoking cessation
Analgesia and adequate supply PRNs
Sim:
Supine head towards gantry in neutral position, shoulders low, arms by side.
Immobilisation w/thermoplastic mask, knee and ankle supports.
1mm slice contrast ct, scalp vertex to upper thorax, fused with MRI T1+C and relevant diagnostic imaging including PET.
Pathophys of acute oesophagitis:
Risk factors:
Acute inflammation of the esophageal mucosa - especially the basal layer where treatment induced cell death leads to reduced production and subsequent depletion. This leads to mucosal abrasion and ulceration
Patient: age>70, co-morbidities esp existing dysphagia, previous esophageal surgery.
Tumour: T and Nstage
Treatment: Dose, fractionation, volume, CONCURRENT CHEMO
Pathophys of late oesophagitis:
Cellular injury leads to release of ROS and increased migration of inflammatory cells, sustained relese of inflammatory markers (e.g Il-1, Il-2, TGF) and fibroblast migration/maturation and increased ECM matrix pproduction of clollagen leading to fibraosis - altering muscle function, and causing stenosis. May clinically manifest as stricture, fistula, chronic ulceration.
