Radiotherapy Planning

Summary

In this informative script, physicist Chris from the Beacon Center explains the process of creating personalized treatment plans using CT scans. He demonstrates how to contour structures to avoid and treat, such as the prostate and bladder, in male patients. Chris illustrates the evolution from single to multiple beams, culminating in Volume Modulated Arc Therapy (VMAT) for precise dose delivery. The script also touches on breast cancer treatment, emphasizing the importance of minimizing dose to the heart and lungs. The presentation aims to educate and demystify the complexities of radiation therapy planning.

Takeaways

• 🔬 The speaker, Chris, is a physicist at the Beacon Center, responsible for creating personalized treatment plans based on CT scans.
• 📚 The process involves analyzing sagittal slices of a patient's anatomy, identifying and contouring structures to avoid and those to be treated.
• 🟢 The bladder is contoured in green, while the prostate and seminal vesicles are highlighted in another color to distinguish them for treatment planning.
• 🔴 The target for treatment is indicated in red, and the goal is to focus radiation beams on this area while minimizing exposure to surrounding tissues.
• 📉 Initially, a single beam is used, but this results in a high dose gradient that is not ideal for treatment as it exposes too much of the surrounding healthy tissue.
• 🤖 Adding more beams, such as a second from the opposite side, helps create a more uniform dose over the target but also increases exposure to other organs like the rectum and bladder.
• 🔄 To address this, additional beams from different angles are introduced, conforming the radiation to the target more closely and reducing dose to nearby organs.
• 💊 The introduction of a margin accounts for movement within the patient's body during treatment, ensuring the target is covered even with internal shifts.
• 🌐 Volume Modulated Arc Therapy (VMAT) is a newer technique that uses 90 beams rotating around the patient for a more precise and conformal dose distribution.
• 🛡️ VMAT significantly spares more of the bladder and rectum by tightly wrapping the dose around the planning target volume, improving treatment efficacy and safety.
• 👥 The script also mentions different treatment approaches for different patient anatomies, such as using only two beams for breast cancer to avoid lung and heart exposure.
• 💌 The speaker invites further questions, indicating an openness to patient education and engagement in the treatment process.

Q & A

What is the role of the Beacon Center's physicists in the treatment planning process?

The physicists at the Beacon Center are responsible for converting CT scans into detailed, personalized treatment plans for patients.

What is a sagittal slice in the context of CT scans?

A sagittal slice is a vertical anatomical section that divides the body into left and right parts, as shown in the script with a sample male patient.

What structures are identified in the pelvic region during the treatment planning?

The structures identified include the bladder, the head of the femurs, the prostate, seminal vesicles, and the rectum.

Why is it important to contour these structures during treatment planning?

Contouring is important to define areas to avoid (like the bladder and rectum) and areas to treat (like the prostate and seminal vesicles), ensuring precise targeting during therapy.

What is the target area during treatment planning, and how is it represented?

The target area is the region that requires treatment, represented in red in the script, and includes the prostate and seminal vesicles.

How does the use of a single beam affect the distribution of the dose in the patient's body?

A single beam results in a high dose at the entry point, a gradient of dose across the target, and less ideal coverage without fully sparing surrounding organs.

What is the purpose of adding more beams to the treatment plan?

Adding more beams helps to create a more uniform dose over the target area while minimizing the dose to surrounding healthy tissues and organs.

What is the significance of the pink structure introduced in the script?

The pink structure represents a margin added to account for movement within the patient's body during treatment, such as changes due to bladder filling or gas in the bowel.

What advancement in treatment technique has been mentioned in the script, and how does it improve treatment?

Volume Modulated Arc Therapy (VMAT) has been mentioned, which uses 90 beams rotating around the patient to tightly wrap the dose around the target, sparing more of the bladder and rectum.

How does the treatment planning for a breast patient differ from that of a male pelvis patient?

For a breast patient, the treatment focuses on the area close to the skin, using only two opposing beams to avoid dose to the lung and heart, unlike the male pelvis where multiple rotating beams are used.

What is the importance of considering the patient's position and potential body changes during treatment planning?

The patient's position and potential body changes, such as gas in the bowel or bladder filling, can affect the accuracy of treatment delivery, hence the need to account for these variations by drawing a margin around the target.

Outlines

00:00

🔬 Personalized Treatment Planning with CT Scans

Chris, a physicist at the Beacon Center, explains the process of converting CT scans into personalized treatment plans. He demonstrates the use of a sagittal slice from a male patient's CT scan to identify and contour critical structures such as the bladder, femur heads, rectum, and the target area for treatment. The goal is to focus radiation beams on the target while minimizing exposure to surrounding tissues. Initially, a single beam is used, but this results in a non-uniform dose distribution. To improve this, additional beams are added from different angles to create a more uniform dose over the target area, while also addressing the challenge of overlapping beams that could affect healthy tissues.

05:00

🌐 Advanced Radiation Therapy Techniques

The script transitions from the traditional method of using a few beams for radiation therapy to the modern technique of Volume Modulated Arc Therapy (VMAT), which employs up to 90 beams. This advanced approach allows for a more precise dose distribution around the planning target volume (PTV), significantly reducing the exposure to nearby organs such as the bladder and rectum. The script also includes a comparison of treatment planning for different patient types, such as a male pelvis and a female breast cancer patient, highlighting the adjustments made to the number of beams and their positioning to protect sensitive organs and optimize treatment efficacy. The summary concludes with an invitation for further questions, emphasizing the educational and informative nature of the video script.

Keywords

💡CT Scans

CT Scans, or Computed Tomography Scans, are a type of medical imaging that helps physicians and physicists visualize internal structures of the body in cross-sectional images. In the context of the video, CT Scans are the initial step in creating a personalized treatment plan, providing detailed images of the patient's anatomy that are essential for accurate targeting during radiation therapy.

💡Physicist

A physicist in the medical field, particularly in the context of the video, is a professional who applies principles of physics to the development and application of radiation therapy treatments. They are responsible for ensuring the accuracy and safety of these treatments, as well as optimizing the delivery of radiation to target areas within the patient's body.

💡Treatment Plan

A treatment plan in the video refers to a personalized strategy for administering radiation therapy to a patient. It involves the use of imaging data, such as CT Scans, to identify target areas for treatment and to plan the delivery of radiation in a way that maximizes effectiveness while minimizing damage to surrounding healthy tissues.

💡Sagittal Slice

A sagittal slice is a type of cross-sectional image that is obtained from a CT Scan or MRI, dividing the body into left and right parts. In the video, the sagittal slice is used to illustrate the anatomical structures in the pelvic region of a sample patient, which is crucial for planning the direction and intensity of radiation beams in treatment.

💡Contouring

Contouring in the context of radiation therapy is the process of delineating the structures within the patient's body that need to be targeted for treatment or avoided to prevent damage. The video describes how physicists use imaging data to draw these contours, which include the target area for treatment and organs at risk, such as the bladder and rectum.

💡Beams

In radiation therapy, beams refer to the directed streams of radiation used to treat cancerous tissues. The video explains how physicists plan the number and direction of these beams to focus on the target area while minimizing exposure to surrounding healthy tissues, starting with a single beam and progressing to multiple beams for a more uniform dose distribution.

💡Dose Gradient

Dose gradient refers to the variation in the intensity of radiation dose across different parts of the patient's body. The video script discusses the importance of managing the dose gradient to ensure that the target area receives the full dose while minimizing the dose to nearby healthy tissues, such as the bladder and rectum.

💡Volume Modulated Arc Therapy (VMAT)

Volume Modulated Arc Therapy, or VMAT, is an advanced radiation therapy technique that delivers radiation in a highly conformal manner by using multiple beams that rotate around the patient. The video highlights VMAT as a modern treatment technique that allows for more precise targeting and sparing of healthy tissues compared to traditional methods.

💡Planning Target Volume (PTV)

The Planning Target Volume is the region that includes the target volume, which requires treatment, plus a margin to account for potential movement or changes in the patient's body during treatment. In the video, the PTV is the pink structure that represents the area that needs to be covered by the radiation beams, ensuring that any movement of the target is still within the treated area.

💡Breast Patient

The term 'breast patient' in the video refers to a patient who is undergoing radiation therapy for breast cancer. The script contrasts the planning for pelvic treatment with that for breast cancer, emphasizing the need for different techniques and considerations, such as the use of fewer beams to avoid exposing the heart and lungs to unnecessary radiation.

💡Opposing Beams

Opposing beams in the context of the video are two radiation beams that enter the patient's body from opposite directions, meeting at the target area. This technique is used to deliver a high dose to the target while minimizing the exposure to surrounding tissues, as illustrated in the treatment planning for a breast patient.

Highlights

Introduction to the role of physicists in creating personalized treatment plans from CT scans.

Explanation of the process of turning CT scans into a detailed treatment plan for patients.

Demonstration of a sagittal slice through a sample male patient's pelvic region.

Identification of anatomical structures such as the bladder, head of the femurs, and rectum in the CT scan.

Importance of contouring structures to avoid and those to be treated in a treatment plan.

Use of color coding to differentiate between various anatomical structures in the treatment plan.

Description of the initial step in treatment planning: focusing beams on the target area.

Illustration of the dose gradient created by a single beam entering and exiting the patient.

Introduction of the concept of adding more beams to improve dose uniformity over the target.

Discussion on the trade-off between uniform dose over the target and the risk to surrounding organs.

Technique of adding multiple beams from different directions to conform to the target area.

Inclusion of a margin for patient movement and anatomical variation during treatment.

Introduction of Volume Modulated Arc Therapy (VMAT) as an advanced treatment technique.

Explanation of how VMAT uses 90 beams rotating around the patient for precise dose delivery.

Demonstration of dose sparing for organs at risk, such as the bladder and rectum, with VMAT.

Transition to breast cancer treatment planning and the differences in technique.

Use of fewer beams in breast treatment to minimize dose to the lung and heart.

Importance of opposing beams in breast cancer treatment to focus on the target area.

Closing remarks inviting further questions and providing an email address for inquiries.

Transcripts

hello my name is chris i'm one of the

physicists here in the beacon center

and our job is to take the ct scans that

you had

taken earlier and turn those into your

detailed

personalized treatment plan and now i'm

going to show you what that means

and here we have a sagittal slice

through

a sample male patient

and here we have a slice through the

pelvic region

this area here is the bladder

here we have the head of the femurs

where people sometimes have hips

um replaced this is the bit that gets

replaced

down here is the rectum and the first

job

is to contour draw all these structures

that we want to avoid

and draw the structures that we want to

treat

we've drawn them already so i'll just

turn them on

we will have the bladder

on that's the green one

we will turn on the

prostate and seminal vesicles and then

underneath that

we have the rectum in the blue

and you can just make it out abutting

the back side

of the target so what we're trying to do

when we're planning treatment

is to have beams focusing on the target

so the target is in red

have beams focusing on the target and

giving the full dose to the target

so we might start with one beam

and let's see what that looks like

so we'll add one beam coming in from the

front

of the patient so this pointing at the

patient's belly

and exiting through the back of the

patient the patient is lying on their

back on the couch

so this is the back of the patient this

is the patient's left side

this is the patient's right side so

we're looking from the patient's

feet upwards

so if we have one beam here

and then we turn the dose on

we can see we have quite a gradient of

dose so it starts off high and it

decreases as we move through the patient

so think of this

as contours on a map if you like so this

might be

the top of the quantock hills and it's

rolling down towards

hinckley so we have a nice high dose

where the beam first enters the patient

a nice high dose over most of the

bladder but when it comes to the

target we have quite a d quite a

gradient of dose across the target which

is not ideal

so an obvious thing to do would be to

add more beam so let's add a second beam

coming from

behind the patient so now we have a beam

focusing

through the couch at the back of the

patient

now we have a nice uniform dose

over the target which is good but it's

also

a nice high uniform dose over the rectum

which is a bad thing

and also over the bladder which is also

bad

so the easiest way to deal with that is

to add

more beams so if we add a third and a

fourth beam

so as well as one from the front and the

back we'll have one coming from the

patient's left and the patient's right

and these are now overlapping on the

target

and they are conforming fairly well

i will add another structure in here

okay so now we can see this pink

structure is a margin we allow for

movement

within the patient's body during the

treatment

so as the bladder fills and empties

it will push things around if the

patient's had a large meal

or has had i know baked beans on toast

or lots of cauliflower you will have

varying amounts of

of gas in the bowel here and that will

move things around a little bit plus

there'll be

minor variations in how how the patient

lies down on the couch

so we allow for all of that by drawing

this margin so that's from the red

structure of the prostate and the

seminal vesicles out

to the planning target volume and we can

see how we have wrapped

as tightly as we can around that pink

shape

but we are still over treating these

corners here

and a little bit into the rectum and we

would rather

not do that so we saw how things

improved by going from one beam to two

beams to four beams

what we this would have been the normal

treatment technique

in the 90s

but over the last 10 15 years we have

added

a new treatment technique called

volume 8 volume modulated arc therapy

which basically means 90 beams

coming in in a circle so the machine

will rotate around the patient

firing a little bit of dose from each

each step as it rotates

so now we can see that the dose is

much more tightly wrapped around the

pink shape around the planning target

volume

we are sparing a lot more of the bladder

and also we are dipping in and sparing

more dose around the rectum

if we look at these other views this is

a sagittal cut

here so here i've blown up that sagittal

view

and we can see that here the red

structure is our

target that we wanted to treat the pink

shape around it

is the planning target volume that we

want to cover

and the blue shape at the back

is the rectum and the green shape is the

bladder

by using 90 individual fields

which rotate around the patient we can

really shrink wrap

where the dose is going to wrap very

nicely around the pink shape and really

pull in and spare dose to the rectum

and reduce the dose to the bladder so

that's

it for pelvic planning certainly the

male pelvis

okay here we have moved to a

breast patient so we've changed we've

moved away

from the male pelvis into a female

breast here we have the lungs

and the heart that's drawn

in this case we have two beams we don't

need to have 90

rotating around the patient when we're

only trying to treat

this structure this area here that's

close to the skin

so we can scroll up and down and see

what we've

got in there we can see how things move

how the heart and the lungs change shape

and the beams are focusing on the area

that we want to treat

right so here here we can see

that we have two beams overlapping on

this area

uh we only use two beams because we want

to avoid

dose to the lung and to the heart

so that's why we just have the two and

they are

opposing each other so we're just

treating this

segment between the yellow

back border of the field

and this red sharp structure that's

drawn on

on the front that we sometimes use to

modify the patient's treatment

i hope you found this very useful and

hopefully

interesting if you have any further

questions please send them in to the

email address provided

thank you

you