Blue Book: Cancer Imaging-Principles Flashcards
How can imagining be used in cancer medicine? (5 headings)
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. The RECIST system is used in clinical trials to assess response:
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 to detect BC.
Describe CT images and concerns of using this technique.
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:
Contrast is nephrotoxic and should be used with caution in patients with renal impairment.
Radiation exposure: risk of malignancy
Contraindicated in pregnancy.
Describe MRI and concerns of using this technique.
High soft tissue contrast in cross-sectional plane.
Gold standard: neurospinal, rectal, prostate and musculoskeletal tumours and in the staging for some head and neck.
The Images can be reconstructed to examine a particular organ system: MR angiography of cardiac vessels or MR cholangiopancreatograms.
Real time MR: MR over time or after contrast images: used in breast masses
Concerns:
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. Metal Foreign bodies in eye or brain are an absolute exclusion.
Describe US and the concerns of this technique.
High frequency sound waves at soft tissue interfaces and generates the ultrasound image.
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.
Concern:
-Operator dependent: less reliable for the serial measurement of lesions for response.
What is nuclear medicine?
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 IV Tc99 Isotope used for?
isotope GFR
What is PET scan used for?
Benefits?
short-lived radioisotopes can be tethered to molecules such as glucose. Glucose is taken up my metabolically active cells. Radioisotopes emit high energy photons which are dented by PET.
Functional imaging. Uptake of FDG.
b) short half life which minimises radiation exposure
What is the use of FDG-18 PET-CT scan?
To identify occult metastases e.g in non-small cell lung cancer.
