Imaging Principles/Imaging in Oncology Lecture Notes PDF

Presented by Imaging Principles/Imaging in Gregory Fury Oncology Senior lecture Date: 30/09/24  Aims of the session To understand the principles of the different imaging techniques used To understand the role of imaging in the oncology patient pathway Nam...

Presented by Imaging Principles/Imaging in Gregory Fury Oncology Senior lecture Date: 30/09/24  Aims of the session To understand the principles of the different imaging techniques used To understand the role of imaging in the oncology patient pathway Name these types of imaging 1. 2. 3. 4. Principles of Imaging  Visualisation of internal What is medical imaging? body structures Obtaining an image or set of images Usually non-invasive Painless Structural or anatomical information Functional information.  What is an image? A representation of the distribution of some property of an object. Formed by transferring information from the object to an image domain In practice – the ordered transfer of energy from some source via the object to a detector system The detected signal is processed and can then be displayed and stored.  Technological changes Significant changes over recent decades Film based systems largely replaced by digital imaging Range of modalities to image wide ranging conditions  Imaging Modalities What imaging modalities do you think are used in oncology? – X-ray images (plane and fluoroscopy) – Computerised Tomography (CT) – Magnetic Resonance Imaging (MRI) – Ultrasound (u/s) – Radionuclide Imaging. X-rays  X-rays They can produce images which represent spatial relationships within the body X-rays are produced in an x-ray tube (25- 150kV) They travel in straight lines and they are absorbed or scattered when they interact with matter The intensity of the emerging primary beam carries information about the interactions that have occurred within the body This beam can be detected by an image intensifier X-rays Cherry P and Duxbury A (2009) Practical Radiotherapy – Physics and equipment  X-rays The amount of absorption is dependant on the atomic number of the tissues and the energy of the x-rays.  Contrast Contrast agents such as liquids containing iodine or barium can be used to make structures visible. Iodine and barium have a very different LAC to the surrounding tissues. Limitations? Ability to show features in low contrast tissue 2 dimensional. Computerised Tomography (CT) CT Imaging Uses x-rays to produce 3 dimensional images The images produced are cross-sectional in the 3 standard anatomical planes Acquisitions are helical CT video  Practical configurations Most CT scanners are third or fourth generation Multi slice CT – several detector arrays are stacked together longitudinally and irradiated simultaneously. Permits rapid collection of projection data and efficient use of x-rays from the tube. Cone beam CT - CBCT is a compact and faster version of CT. Through the use of a cone shaped X-Ray beam, the size of the scanner, radiation dosage and time needed for scanning are all dramatically reduced. Inside the CT scanner Video - Inside a CT scann er T X-ray tube D X-ray detectors X X-ray beam R Gantry rotation https://commons.wikimedia.org/wiki/ File:Ct-internals.jpg  Generation changes CT scanner CT scanners were first introduced in 1971 with a single detector for brain study under the leadership of Sir Godfrey Hounsfield, an electrical engineer at EMI (Electric and Musical Industries Ltd). Thereafter, it has undergone multiple improvements with an increase in the number of detectors and decrease in the scan time. First generation detectors: one type of beam: pencil-like x-ray beam tube-detector movements: translate-rotate duration of scan (average): 25-30 mins  2nd and 3rd generation Second generation detectors: multiple (up to 30) type of beam: fan-shaped x-ray beam tube-detector movements: translate-rotate duration of scan (average): less than 90 sec Third generation detectors: multiple, originally 288; newer ones use over 700 arranged in an arc type of beam: fan-shaped x-ray beam tube-detector movements: rotate-rotate duration of scan (average): approximately 5 sec Fourth generation detectors: multiple (more than 2000) arranged in an outer ring which is fixed type of beam: fan-shaped x-ray beam tube-detector movements: rotate-fixed duration of scan (average): few seconds Other technologies Other CT technologies have been adapted to third and fourth generation scanners, including: helical ("spiral") image acquisition used in all modern CT machines slip-ring technology made helical acquisition possible dual energy CT scanning Practical points third and fourth generation scanner technologies are both used in many health care settings the fourth generation is a fundamentally different acquisition method, but the resulting image quality is similar to the third generation for most applications 4th Generation CT Scanner CT video What am I?? CASHEW NUTS! Magnetic Resonance Imaging (MRI) http://science.howstuffworks.com/mri3.htm  MRI Imaging Uses a strong magnetic field (0.5- 3.0 Tesla) and radiofrequency (RF) pulses to produce images of the hydrogen distribution within the body. Like CT, it provides visualisation of the body in slices It uses the magnetic properties of hydrogen atoms to generate the images T1 weighted images – fat and white matter appear bright and CSF appears dark T2 weighted image – CSF is very bright  Advantages of MRI? No ionising radiation Excellent visualisation of soft tissue (low and similar density close to each other) e.g. head and neck, abdomen and pelvis Gadolineum based contrast agents can be injected IV to highlight areas of high vasculature (tumour) High grade gliomas enhance vividly with contrast Can also be used in rectal cancer despite close proximity to other organs.  AnMRI excellent Imagingtechnique for imaging soft tissue Used in diagnosis, localisation and follow up Used to plan radiotherapy treatment when fused with CT data Contrast-enhanced MRI can improve diagnosis and staging  Disadvantage of MRI patients that have any metal located within the body cannot be scanned (unless non ferromagnetic e.g. titanium) Metal in an MRI  Disadvantage of MRI patients that have any metal located within the body cannot be scanned (unless non ferromagnetic e.g. titanium)  Modern use of MRI Due to advances in technology we can now plan straight from MRI Algorithms can extract Hounsfield units from the scan data as well as produce Bony DRR Image distortion can be accounted for, less accurate when imaging more superficial targets Advantage of better soft tissue delineation MRI linac Need for image fusion is reduced CT and MRI Fusion  Ultrasound (u/s) Ultrasound image Ultrasound of post-operative breast cancer equipment  Ultrasound Uses high frequency sound waves to produce an image Frequencies in the range 1-20 MHz (well beyond human hearing) Can be used to demonstrate the internal structure of a lesion Differentiate a solid mass from a fluid-filled cyst Used in particular for; uterus, ovary, prostate, kidney and breast Often used in combination with fine needle biopsy  Ultrasound Advantages: – Relatively cheap – It’s safe – no ionising radiation – Gives real time images – Good soft tissue contrast Disadvantages – Can be subjective – Can be difficult to interpret  Radionuclide Imaging Primarily concerned with the physiological function of organs and tissues Use of unsealed radiopharmaceuticals for diagnosing (& investigations and treatment) A suitable radionuclide (unstable isotope that will spontaneously decay) is combined with a pharmaceutical which marks a particular biological function Radionuclide gamma ray emission provides the energy for the transfer from the object to the image Gamma Camera Radionuclide Imaging This radiopharmaceutical is usually injected into the body and has a known biodistribution Different radiopharmaceuticals have a distribution relating to the physiology of different tissues The behaviour of this radio-labelled compound is monitored by a gamma camera which  Positron Emission Tomography (PET) Information about physiological function PET is based on the emission of positrons from radioactive isotopes that have been administered to the patient Radioactive marker is attached to glucose which is injected into the patient Most common radiopharmaceutical is 18 FDG (fluorodeoxyglucose) a sugar that is readily taken up by metabolising cells.  PET Cancerous cells can be distinguished from healthy tissue due to higher glucose consumption PET alone lacks anatomical detail Hybrid imaging – independent imaging modalities are combined. PET/CT and PET/MR fusion Recap… CT and MRI vid eo Role of Imaging in Oncology  The patient pathway Treatme Diagnosi Treatme Treatme CT nt Follow s& nt nt Planning Verificati Up Staging Planning Delivery on  Diagnosis What is wrong? Where is it? How extensive is it? What stage is it?  Types of Imaging that might be Plain used? X-rays Fluoroscopy CT scan MRI scan Ultrasound PET – earlier diagnosis and improved staging – identification of nodal involvement and distant metastases often before evidence of structural anatomical change.  Radiotherapy Localisation What is localisation? How can we target the tumour accurately with radiotherapy? Where are the sensitive structures? Where is the tumour in relation to external skin marks? Can we use the images that have already been taken of this patient?  CT in Localisation CT has become the standard CT planning scan CT virtual simulation Other modalities can be fused (registered)with CT.  Advantages of CT in localisation Fast – important for patient comfort and reproducibility Volumetric data rather than 2D images More anatomical data than plane imaging alone Data can be transferred directly to planning software  Preparing for treatment Physics planning – All CT and MRI data is sent to physics planning to make a plan – Digitally Reconstructed Radiographs (DRR’s) are generated to provide a Beam’s Eye View (BEV) of the target volume – The patient set-up information is also sent Linear accelerator – CT-sim image is attached to the treatment sheet – The set-up information is completed  On set Verification How can we achieve this? Portal imaging (MV) KV imaging IGRT RCR guidance: On Target: ensuring geometric accuracy in radiotherapy  HowRadiotherapy can we verify that the Verification plan we have produced will accurately target the tumour? Compare images taken to the reference image Digitally Reconstructed Radiographs (DRR’s) DRR’s for verification  Online & Offline imaging Online treatment verification – Uses images immediately before treatment delivery and intervention to correct set-up before delivery Offline treatment verification – Compares the images taken with the reference images at some point after the treatment has been delivered. Any changes will be made before the next treatment is delivered.  IGRT Image Guided Radiotherapy (IGRT) is any imaging at the pre-treatment and treatment delivery stage that leads to an action that can improve or verify the accuracy of radiotherapy. IGRT encompasses a wide range of techniques ranging from simple visual field alignment checks, through to the more complex volumetric imaging that allows direct visualisation of the radiotherapy target volume and surrounding anatomy. Cone Beam CT (CBCT) Kv Arm (CBCT) Kv detector Mv detector IGRT – Image Guided Radiotherapy IGRT video Follow-up To monitor tumour response To assess the outcome of treatment Has the treatment been curative? What is the extent of the disease at this stage? Is further treatment required? Signs and symptoms of metastatic disease  Follow-up To monitor tumour response To assess the outcome of treatment Has the treatment been curative? What is the extent of the disease at this stage? Is further treatment required? Signs and symptoms of metastatic disease  Aims of the session To understand the principles of the different imaging techniques used To understand the role of imaging in the oncology patient pathway  Further reading NICE Pathways is an interactive tool for health and social care professionals providing fast access to NICE guidance and associated products http://pathways.nice.org.uk/pathways/lun g-cancer On Target 2 Radiotherapy On target document