Skeletal Flashcards by Andrew Cibulas

Workhorse radiotracer?

Methylene diphosphonate (MDP) tagged with Tc-99m

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How do you make MDP - Tc99m?

MDP + Stannous (tin) ion in a kid, add pertechnetate and stannous ion reduces it to bind MDP.

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What happens if there isn’t enough stannous ion in the kid to prepare MDP - Tc99m? (or air gets in the vial causing oxidation?) Where will this product accumulate in your study?

Results in free Tc that can accumulate in the salivary glands, thyroid gland, and stomach.

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How long do you wait to image after injection of MDP - Tc99m to image? Why?

2-4 hours to clear the soft tissues and visualize bones

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What is the mechanism of uptake of MDP - Tc99m?

Chemisorption - phosphonate binding to bone

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What is distribution of MDP - Tc99m based off of?

Osteoblastic activity and blood flow

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Study is blurry, fuzzy, with bone and kidney uptake, what tracer?

MDP - Tc99m

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Study is “high-res” and looks like a MIP-PET, what tracer?

F-18

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Study looks similar to F-18 but has brain uptake, what tracer?

FDG-PET with bone stimulation

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What organ receives the highest dose with MDP-Tc99m? F-18? Overall dose higher with?

Bone
Bladder
overall dose > with F-18

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Why can pyre lytic lesions be cold with MDP - Tc99m?

Uptake based off of blastic activity

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Where is MDP - Tc99m uptake normal?

Bone, Kidney (not seen or very faint = Super Scan), Bladder, Breasts (young women), soft tissues (low levels), epiphyses of kids

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Marked uptake in skull sutures?

Renal Ostreodystrophy

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Focal breast uptake? (asymmetric breast uptake)

can be cancer, diffuse normal in young women

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Renal cortex activity?

If hotter than lumbar spine, think hemochromatosis

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Diffuse renal uptake?

Setting of chemotherapy +/- urinary obstruction

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Liver Uptake? 4 reasons

Too much Al+3 contamination of Tc
Cancer - Hepatoma or mets
Amyloidosis
Liver Necrosis

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Spleen uptake?

Auto-infarcted spleen (sickle cell) - will have scattered hot and cold bone from multiple bone infarcts

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Lung uptake?

Most cases - heterotopic calcification
Classic MDP hot lung met = osteosarcoma
Ultimately not specific

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Single lesion is usually a false positive bone met except where?

Single sternal lesion in breast cancer patient

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Sacral insufficiency fracture sign?

Honda sign

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Diffusely decreased skeletal uptake?

Free Tc or bisphos therapy

Wait how long before dx fracture in elderly?

1 week

Horizontal linear vertebral body fracture? What happens on follow up images?

osteoporotic fracture, f/u imaging shows decreasing tracer uptake

Extension of vertebral body fracture into posterior elements or involves pedicles?

Cancer - malignant fracture

What is the flair phenomenon and how do you tell if it is the flair phenomenon?

Good response to therapy looks like bad response and increased radiotracer uptake (size and #) is seen 2wks - 3 mo after therapy On plain films lesions get more sclerotic and improve after 3 months for flair

What radiotracers are superior for detection of neuroblastoma bone mets? Where does NB like to met to in the bones?

I-123 and 131 MIBG, metaphysis

6 Cold Lesions on bone scans?

``` Radiation therapy Early osteonecrosis Infarct (early or late) Anaplastic tumor ( renal, thyroid, Neuroblastoma, myeloma) Artifact from prosthetic, pacemaker Hemangioma ```

4 characteristics of Bone Island and prostate Met?

BOTH Sclerotic Prostate met should be VERY hot Bone Island should be COLD Osteopoikilosis should be COLD

Bone scan better for lytic/blastic mets? | Skeletal survey better for lytic/blastic mets?

Bone scan better for blastic | Skeletal survery better for lytic - think MM

Why image Heterotopic Ossification?

To see if it's active/mature. If active has a higher rate of recurrence after resection.

Characteristic finding: Tramline along the periosteum of long bones. What is this process associated with? What do you need to think of and recommend?

Heterotrophic Osteoarthropathy Ass. with chronic hypoxia (COPD, Cyanotic Hrt Dz, Mesotheliomia, Pneumoconiosis) Need to think lung cancer - 10% of the time - Get CXR/CT

5 Ways Paget's is classically shown?

1) Super hot enlarged femur 2) Super hot enlarged pelvis 3) Super hot skull 4) Expanded hot entire vertebral body 5) metabolic superscan (however, if shown a metabolic superscan think Hyper PTH)

Imaging findings of AVN?

Early - Cold Middle - Hot Late - Cold

Ewings and Osteosarcoma will be? Why scan?

Hot, see extent of dz

Double density sign (central hotter nidus within a hot area) seen with?

Osteoid Osteoma

Super hot mandible?

Fibrous dysplasia - can also be leg that looks similar to paget

Benign HOT Bone scan lesions? (5)

``` Fibrous Dysplasia Giant Cell Tumor ABC Osteoblastoma Osteoid Osteoma ```

Benign COLD Bone scan lesions? (1)

Bone cyst without fracture

Variable benign lesions? (2)

Hemangioma | Multiple hereditary exostosis

Two types of super scans? How can you tell them apart?

Diffuse Mets - breast and prostate most common - and Metabolic - hyper Parathyroid, renal OD, peget, thyrotoxicosis (no kidneys seen on super scans). Skull is asymmetrically hot on metabolic.

Any uptake from bone with MIBG, I131, or octreotide should mean what?

METS!

Equivocal bone lesion next steps?

Recommend plain film, if plain film shows no corresponding lesion it is MORE concerning for mets --> get MRI at that point

3 phases of a 3 phase bone scan?

Flow, Pool, Delayed; lots can be hot on all 3 phases

Difference between cellulitis and osteomyelitis on 3 phase scan?

Cellulitis hot during flow and pool, not delayed | Osteomyelitis hot during all 3

How to use 3 phase to evaluate treatment response?

Blood flow and blood pool stay abnormal for 2 months, and delay persists for 2 years. Use Ga67 and I111 WBC for monitoring response.

Where do you see uptake in RSD? (Complex Regional Pain Syndrome)

Increased uptake on flow and blood pool, with periarticular uptake on delayed phase.

Tc tagged with what to localize bone marrow? What is the major utility?

Sulfur colloid, use in sickle cell. Major utility is to use with tagged WBC or Gallium to evaluate active infection.

When is a combined Tc-Sulfur Colloid + WBC study positive for infection?

Activity on WBC image, without corrresponding Tc-Sulfur colloid activity on bone marrow image.(except in spine!!)

What is special about imaging infection within the spine?

WBC fails to migrate showing a photopenic area, use gallium instead.

How to evaluate a prosthetic?

Look for loosening/infection, more helpful when negative - scan with combined Tc-sulfur colloid + WBC

How to evaluate a neuropathic foot?

Use combined marrow + WBC because difficult to distinguish arthritis vs infection with Tc MDP

What is the "fourth phase" of diabetic foot evaluation?

24 hour scan due to reduced peripheral blood flow

2 reasons to consider T99 HMPAO instead of In-WBC for infection? Why not all the time?

Kids - lower absorbed dose and imaging time Small parts - better in hands and feet Short halkf life and normal GI and gallbladder activity