Medical Imaging in Oncology Review

Imaging fundamentals Medical imaging in oncology review

Overview Medical imaging allows clinicians to identify the exact anatomical location and extent of disease. Medical imaging also provides clinicians information on tumor response to therapies. The noninvasive nature of imaging enables continual assessment of a patient’s disease state and response to treatment with minimal discomfort to the patient. The resultant digital images facilitate quantitative measuring of endpoints, which are critical for reporting or comparing results within or across clinical trials.

Imaging biomarkers vs endpoints: DICOM image format Image orientation A biomarker is a biological Digital Imaging and Communications There are three primary orientations in which an image can be recorded: characteristic that is objectively in Medicine (DICOM) is the Axial measured and evaluated as an international standard image format Divides the body into superior and inferior positions indicator of normal or pathological for clinical data. (head and feet); also called transverse processes. An imaging biomarker Coronal • DICOM is an information is a biological characteristic that is Divides the body into dorsal and ventral (front and back) technology standard that allows detectable on an image. Sagittal devices that produce, display, send, Divides the body into left and right sides • Imaging biomarkers can be store, retrieve, or print imaging data anatomical or functional. to work together and exchange information. Sagittal plane • Imaging biomarkers can be qualitative i.e., descriptive – • DICOM allows users to produce, “a nodule is present in the lung” or manage, and distribute images quantitative i.e., objectively regardless of equipment vendor or measured parameter – “the location. longest diameter of the nodule • DICOM ensures that all images can decreased by 5mm after treatment Coronal plane be uploaded, transferred, and read, as compared with its size before independent of the model or treatment.” manufacturer of the imaging Endpoints are the outcomes of a trial equipment used to acquire the used to determine if a therapy is safe images. and effective. Once a patient reaches Axial plane an endpoint, he/she is generally removed from the trial. • Clinical endpoints are hard endpoints such as patient death. • Surrogate endpoints are substitutes for a clinical endpoint and correlate with clinical benefit. • An imaging biomarker can become a surrogate endpoint after going through a rigorous qualification and validation process.

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Image modalities

X-Ray Computer Tomography (CT) Magnetic Resonance Imaging (MRI) Positron Emission Tomography (PET) • Produces 2-dimensional images; Uses x-rays to produce a Standard MRI: anatomical imaging Nuclear imaging modality based on best for imaging the skeleton. 3-dimensional image in all three • Produces 3-dimensional images the use of radiolabeled tracers and orientations: axial, coronal, sagittal. using a magnetic field and radio tracking their distribution throughout • An x-ray machine sends out a beam waves: does not use radiation. the body. of x-rays at the patient that are captured on the other side by x-ray Tomography • Magnetic field strength measured in • Radioactive isotope is chemically film or a digital detector. The x-rays An imaging method that scans Tesla (T), typically ranging from 1.5 attached to a biologically important are either scattered or passed the body in sections. The width of to 3 Tesla. molecule. through the body depending on the each section is referred to as the • Produces images based on the spin • The radiolabeled tracer releases density of the object. slice thickness. of hydrogen nuclei (such as those energy (positrons) as it decays, CT, MRI, and PET are all Advantages found in water). which is detected and recorded to tomographic methods. Low cost; widely available; create an image. Advanced MRI: functional imaging portable • Dynamic contrast-enhanced MRI: • Radioactive decay lasts for a specific • Most widely used imaging modality: Contrast agent (e.g., gadolinium) and defined amount of time (i.e. half Disadvantages generates anatomical information Exposes patient to radiation; is added to enhance anatomical life). The half life of each and is often used to assess lesion produces 2D images; limited color structures: blood vessels (tumor radioisotope is unique to that size in oncology. spectrum (black/white) angiogenesis in prostate cancer); isotope. • X-rays are aimed at the patient and brain tumors. • Produces 2D and 3D images; are attenuated (scattered) based • Diffusion-weighted imaging (DWI): example of functional imaging. on the density of the tissue. A new measures diffusion of water in image is taken every few • Metabolic changes (using FDG-PET) tissues; useful for assessing millimeters. can be detected earlier than ischemia and vascular changes in anatomical changes such as an • The less dense the material (e.g., tumors related to malignancy or increase in tumor size. fat), the more black it appears on treatment response. the image; the more dense the • PET has limited spatial resolution, so material (e.g., bone) the lighter it Advantages it is commonly combined with CT or Lack of radiation can be better for appears; creates a black-white color MRI (PET/CT or PET/MRI) to obtain patients; superior to CT for visualizing gradient. functional and anatomical data in a soft tissue (for example, brain tumors) single imaging session. • Modern CT scanners contain many Disadvantages (up to 256) x-ray emitters and Advantages More costly and time consuming than detectors to produce ultra-fast Metabolic changes can be detected CT; patients can become image acquisition times. earlier than anatomical changes; can claustrophobic in the magnetic tube; provide simultaneous functional and • CT can also involve the use of ferromagnetic objects such as some anatomic data when combined with contrast agents: injected or pacemakers can be dislodged CT; easier detection of early-stage swallowed liquids with a specific tumors density that are used to highlight a particular organ, vascular structure, Disadvantages or anatomical region. Low spatial resolution when not combined with CT; radiation Advantages exposure; potential allergy or adverse Produces cross-sectional view; use response to radiotracer; high cost of contrast agents; rapid acquisition Median is the right imaging solution for Disadvantages your oncology clinical trials. By bringing Cost; radiation together image specialists, superior technology to automate and standardize image management and expert data & project management teams, we provide you with the most meaningful data so you can make better and quicker decisions about your cancer therapy. Median Technologies is a full service global imaging clinical research organization with experience in Phase I - III oncology trials.

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