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Introduction to Medical Imaging > imaging technology- imaging sensors, CT, nuclear medicine > Flashcards

imaging technology- imaging sensors, CT, nuclear medicine Flashcards

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USMLE® Step 1 flashcards
1
Q

What is imaging in radiotherapy often called?

A

Image-Guided Radiotherapy

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2
Q

What is Image-Guided Radiotherapy?

A

A technique used in cancer treatment that integrates imaging technologies with radiation therapy to improve the precision and accuracy of radiation delivery

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3
Q

How does IGRT help clinicians target tumors more accurately, minimize radiation exposure to healhty tissues and adapt treatment plans based o changes in tumour size or position during treatment?

A

By obtaining real-time or near-real time images of a patient’s tumour and surrounding anatomy

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4
Q

What are the common imaging modalities used in IGRT?

A

Computed tomography (CT), magnetic resonance imaging (MRI), and X-ray imaging

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5
Q

The simulation/planning CT

A

The patient is first positioned on a CT scanner table.
Immobilization devices, such as headrests, masks or body molds are used to immobilize the patient during the CT simulation
A CT scan is obtained, capturing the tumor and surrounding anatomical structures

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6
Q

Which step of the radiotherapy treatment plan does the Simulation/ CT planning take part in?

A

Planning stage

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7
Q

target delineation

A

Using the CT scans, the radiation oncologist outlines the Gross Tumor Volume and the Clinical Target volume + delineate critical organs and healthy tissues Organs at Risk, to minimize radiation exposure to these structures

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8
Q

What is the difference between the Gross Tumor Volume and the Clinical Target Volume?

A

The gross tumor volume is the target tumor volume
Clinical target volume is the areas that are at risk for microscopic disease spread

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9
Q

What are the 3 delineations taking place in target delineation?

A

gross volume target delineation
clinical volume target delineation
organs at risk delineation

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10
Q

PET Imaging

A

used for tumor delineation (gross tumor volume)

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11
Q

How can PET images help the radiation oncologists?

A

accurately define the tumor’s boundaries, Gross Tumor Volume
and identify potential areas of microscopic disease spread, Clinical target volume
and identify potential regions of high-risk within the tumor, such as hypoxic regions

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12
Q

What is a hypoxic regions?

A

regions within the tumor which are high-risk

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13
Q

How can PET imaging be used to identify hypoxic regions within tumors?

A

by employing specific radiotracers that selectively accumulate in hypoxic tissues. The treatment plan can then be designed to deliver a higher radiation dose to these hypoxic regions (regions of higher risk of microscopic disease spread within the tumor), while maintaining a standard dose for well-oxygenated regions.

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14
Q

Different imaging techniques to diagnose tumors

A

X-ray, CT, MRI, PET, Ultrasound

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15
Q

How do x-rays help in diagnostic imaging?

A

the first imaging test performed when cancer is suspected. Uses ionizing radiation to create 2D images of the body’s internal structures

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16
Q

How does CT help in diagnosis of cancer?

A

diagnose the stage of many types of cancer, and help guide biopsies and monitor the response to treatment

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17
Q

How is MRI useful for diagnosis of cancers?

A

Diagnosing and staging cancers in areas with complex anatomy, such as brain, spinal chord, prostate, and breast cancer

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18
Q

How is PET useful for diagnosis of cancer?

A

Due to the fact that cancer cells often have higher metabolic rates than normal cells, PET scans are used for diagnosing and staging various types of cancers

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19
Q

How is ultrasound helpful in diagnosing and staging cancers?

A

useful to diagnose and stage cancers in organs such as the liver, pancreas and kidneys. Can also help guide biopsies and monitor treatment response

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20
Q

What is fractionation?

A

Dividing radiation therapy into smaller doses, called fractions, which are delivered over a period of time

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21
Q

Why is fractionation an essential aspect of radiotherapy treatment planning?

A

it allows for the delivery of a high total radiation dose to the tumour while minimizing damage to surrounding healthy tissues.

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22
Q

What is the rationale behind fractionation?

A

Based on the different responses of cancer cells and normal cells to radiation, allowing for the preferential killing of cancer cells while giving normal tissues time to recover between fractions.

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23
Q

What happens in conventional fractionation?

A

The total radiation dose is divided into small fractions, typically ranging from 1.8 - 2 Gy/ fraction, delivered daily over several weeks

24
Q

What does the number of fractions and thte total treatment duration depend on?

A

The type and stage of cancer, as well as the patient’s overall health

25
Q

What is the main concept of radiotherapy delivery and related imaging?

A

Radiotherapeutic dose can be delivered via many routes, generally categorized in internal or external radiotherapy.

26
Q

What is internal radiotherapy?

A

a radioactive material is placed directly into or near the tumour

27
Q

How is interal radiotherapy useful?

A

Allows for the delivery of high radiation doses to the cancer cells while minimizing exposure to surrounding healthy tissues

28
Q

What imaging technique is typically used in internal radiotherapy/ brachytherapy?

A

ultrasound imaging

29
Q

How is ultrasound imaging used in internal radiotherapy, or brachytherapy?

A

used to guide the placement of the radioactive seeds, particularly for prostate and gynecological brachytherapy

30
Q

What is external radiotherapy?

A

a form of cancer treatment in which radiation is directed from an external machine towards the tumour within the patient

31
Q

In conventional therapy, how is the radiation in external radiotherpy generated?

A

A machine: linear accelerator, which produces high-energy X-rays or particles

32
Q

What do most LINAC come with?

A

Kilovoltage and megavoltage imaging for patient positioning

33
Q

Why is KV x-ray imaging used before treatment delivery?

A

To verify patient positioning and ensure accurate radiation targeting (part of the treatment planning)

34
Q

What does kV imaging typically involve?

A

Acquiring 2D or 3D images, such as planar radiographs or cone-beam CT scans

35
Q

What are the planar radiographs or cone-beam CT scans compared to?

A

the reference images obtained during the plannig phase

36
Q

How does kV imaging help the treatment team?

A

Make any necessary adjustments to the patient’s position or treatment plan to account for changes in tumor size or shape or patient anatom

37
Q

What is MV imaging?

A

Another modality used during external radiotherapy to verify patient positioning and monitor treatment accuracy.

38
Q

What does MV imaging use?

A

The treatment beam itself to generate images, by acquiring planar radiographs or volumetric images

39
Q

What are the images obtained in MV imaging vs those obtained in kV X-ray imaging ?

A

kV: planar radiographs or cone beam CT scans
MV: planar radiographs or volumetric images

40
Q

what is MV imaging particularly useful for?

A

monitoring the treatment of deep-seated tumors or when kV imaging is not available or sufficient for accurate patient positioning

41
Q

Advantage of MV over kV

A

MV can be used when kV imaging is not availbale or sufficient for accurate patient positioning

42
Q

Disadvantage of MV

A

Due to proton physics property at MeV, it is generally of poor quality

43
Q

What is surface guided imaging?

A

A modern external radiation therapy technique that uses non-invasive, real time surface imaging to monitor the patient’s external surface during treatment

44
Q

How is surface guided imaging useful?

A

It improves patient positioning accuracy, ensures proper alignment, and verifies motion management during radiotherapy

45
Q

What does surface guided imaging ultimately enhance?

A

The precision of radiation delivery to the target tumor, while minimizing the dose to surrounding healthy tissue

46
Q

What does surface guided imaging use?

A

3D camera systems and advanced software to capture patient’s external surface.
Camera systems use optical, non-ionizing radiation to create a 3D surface map

47
Q

What is the 3D map produced during surface guided imaging compared to ?

A

the patient’s reference surface obtained during the simulation phase, via CT, PET, Ultrasound, X-ray (all the different imaging modalities)

48
Q

What is a gamma knife?

A

A form of stereotactic radiosurgery that utilises highly focused gamma radiation to treat brain tumors

49
Q

What type of treatment option does gamma knife provide?

A

non-invasive

50
Q

What are the properties of the dose of radiation delivered by a gamma knife?

A

A high dose of radiation to a precise target within the brain while minimizing exposure to surrounding healthy tissue.

51
Q

What plays a crucial role in Gamma Knife treatment?

A

Imaging

52
Q

How does imaging play a crucial role in Gamma Knife treatment?

A

it helps define the target volume (gross target volume, clinical target volume ), plan the treatment, and ensure accurate radiation delivery

53
Q

How is in-treatment imaging avoided in Gamma-Knife stereotactic surgery?

A

through the use of a stereotactic frame attached to the patient’s head using local anesthesia.

54
Q

What does the stereotactic frame attached to the patient’s head with local anesthesia help provide?

A

A fixed reference system that allows for precise localization and targeting of the lesion during treatment.

55
Q

What happens after the stereotactic frame is placed on the patient’s head?

A

the patient undergoes imaging studies with the frame visible in the images. The images are then used for treatment planning.

Introduction to Medical Imaging (14 decks)

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