Surveillance
Computerized Axial Tomography (CAT) scans produce a computer generated "slice" through the body using X-rays.  This CAT scan shows a large tumor in the right abdomen (left side of picture)
Ultrasound studies are very good at differentiating solid from cystic (fluid filled) masses.  The triangular black area on the right side of this study is the urine filled bladder.  To the left of the bladder is a mass with both solid and cystic components (the "speckled" area).   This is a large ovarian tumor.
FDG (fluoro-deoxy-glucose) studies utilize a polysaccharide molecule tagged with a radioactive tracer and injected into a vein.   The molecule concentrates in various tissues in the body including sites of cancers.  This study is a side view of a patient (head at top of picture) showing normal activity in the brain and bladder.  There are two suspicious dark areas in the front and back of the abdomen (left and right side of the picture).
MRI (Magnetic Resonance Imaging) studies utilize a magnetic field to computer generate slices of the body.  This study is a sagittal section through the lower spine and buttocks (spine at top of picture).   Just below the 3 black circles in the middle of the picture you can see an asymmetric dark area representing a vaginal cancer invading muscles on the side of the pelvis.