Nuclear imaging 

Few absolute contraindications for nuclear imaging: 

-renal fxn irrelevant, allergic reactions don't happen, metal OK 

-Pregnancy is a relative CI for all ionizing imaging modalities, absolute CI with I-131 as it crosses the placenta, irradiates fetal thyroid, causes cretinism 

Nuclear medicine: 

- Diagnostic (gamma rays) imaging - cardiac scan, bone scan, PET scan, (real GFR, RBC mass/volume, Schillings test), radioiodine, V/Q, HIDA, tagged RBC, tagged WBC, relative organ perfusion (how many counts are in R vs L kidney, etc), organ emptying-- GB/heart (EF)/stomach comparing counts within and outside. 

- Minor procedures: lymphoscintillagraphy (inject breast, watch tracer drain with the lymphatics; drops in eyes to see whether tear ducts are patent 

- Therapeutic: beta/alpha particles: medium dose I-131 (hyperthyroid), thyroid CA (high dose I-131), theraspheres (inject radioactive spheres into hepatic artery to get liver), radioactive seeds (bexxar, zevalin), painful bone mets (radium 223, strontium)

Bone scan: 

- Advantages: can scan whole body, great for blastic lesions, better for following evolution of bone mets over time (i.e. s/p chemo) because CT scans see the scarring/sclerosis of bone, which will stay the same even after chemo, but bone scan will see the osteoblastic activity which reflects the true act

- Disadvantages: not specific (also lights up osteo, fractures, DJD), takes hours, not sensitive for lytic lesions (renal cell CA) because can only see blastic/remodeling activity, marrow processes (MM) 

- Bone mets don't really go to bone-- they go to red marrow. When you're young, you have red marrow everywhere, but most of it is replaced by yellow marrow starting from the fingertips/toes out. Cancer goes to the red marrow first, then it goes to the adjacent bone-- once you have osteoblast activity, then and only then will the bone scan see it. 

- Kids: neuroblastoma will metastasize to the ends of the bones.