Blue Book: Cancer Imaging-Principles Flashcards
What are the uses of imaging in cancer medicine?
Diagnosis:
Radiological intervention forms part of the initial assessment. Histology is required for accurate diagnosis. CT or US sounds are used to guide biopsies, under local anaesthesia for histological diagnosis
Staging:
Requires definition of anatomical extent of disease.
CT for chest and abdomen
MRI for bone and soft tissues lesions and regions where the bone causes artefact in CT e.g. pelvis or posterior fossa of the brain
Response assessment:
CT/MRI reproducible techniques. CXR sometimes used.
Complete response (CR): No disease detectable radiologically
Partial response (PR): All lesions have shrunk by at least 30%, but disease still present
Stable response (SD): Less than 20% increase in size or less than 30% decrease in size
Progressive disease (PD): New lesions or lesions that have increased in size more than 20%
Follow-up:
When detection of asymptomatic relapse has shown to affect clinical outcome (eg testicular tumours)
Screening: screening mammography for BC.
What are CT images?
Rotating X-ray rube and opposing detectors: computed reconstruction of axial cross-sectional images.
Oral contrast medium can be added to out GI tract: this can demonstrate intra-luminal pathology or bowel obstruction.
Intravenous contrast medium is used to delineate vascular structures and to demonstrate tumour enhancement.
Concerns when using CT?
Contrast is nephrotoxic and should be used with caution in patients with renal impairment.
Radiation exposure: risk of malignancy
Contraindicated in pregnancy.
What is MRI?
High soft tissue contrast in cross-sectional plane.
MRI is gold standard for what conditions?
Gold standard: neurospinal, rectal, prostate and musculoskeletal tumours and in the staging for some head and neck.
Can MRI be used to examine particular organs?
The Images can be reconstructed to examine a particular organ system: MR angiography of cardiac vessels or MR cholangiopancreatograms.
What is real time MRI?
Real time MR: MR over time or after contact images.
Concerns when using MRI
Use strong magnets. Few patient killed if heavy metallic objects in range of magnetic field.
Pacemakers and implantable cardiac defibrillators are electronically vulnerable to the effects and must not enter the MRI unit. Metallic foreign bodies can be a contraindication.
What is ultra-sound?
High frequency sound waves at soft tissue interfaces and generates the ultrasound image.
Benefits and uses of US
Requires no radiations, is safe, widely available and is inexpensive.
- detect metastasis in solid abdominal organs
- specialist duplex/doppler ultrasound used to assess blood flow.
- Real-time guidance of biopsy and therapeutic interventional procedures.
Concerns of ultrasound?
-Operator dependent: less reliable for the serial measurement of lesions for respone.
What is nuclear medicine?
What can be used for skeletal metastasis?
Radioisotope-labelled pharmaceutical are administered and their distribution measured by gamma-camera detection of emitted photons. Bone scintigraphy (bone scan) remain the principle investigation for the detection of skeletal metastases.
What is PET scanning?
Positron emission tomography detects high energy photons emitted by short lived radioisotopes, which can be chemically tethered to molecules such as glucose or somatostatin to form a tracer e.g. FDG-18, a radioactive form of glucose.
What are the functions of PET scanning?
Functions:
Functional images
Differentiate between malignant from benign pathologies
Merged with CT in order to map functional images to detailed anatomy.
Can help identify occult metastases: used in situations where radical treatment seems possible but has high mortality/morbidity.
