Bone Imaging HW

4, 9

Explain how 99m Tc MDP localizes in bone.

• 99m tc MDP localized in bone by action of chemisorption

• Radionuclide attaches to hydroxyapatite crystals on bones.

• Within 2-4 hours

  • ~50% of the MDP is absorbed into the bones

  • ~50% is excreted through the kidneys.

List five clinical indications for a bone scan.

SAPOC (Sad Alucard Pouncing On CillianMurphy)

• Skeletal metastatic diseases and staging

• Avascular necrosis

• Osteomyelitis

• Primary bone tumors

• Complex regional pain syndrome

Differentiate between: Three-Phase bone scan and a Whole Body bone scan.

Three phase has three phases

• Phase 1 = blood flow

  • Immediately records dynamic flow images as tracer uptakes in the bone every 2-4 seconds for 60 seconds

• Phase 2 = blood pool (statics)

  • Performed directly after flow is done

• Phase 3 = delay

  • Done 2-3 hours after initial injection

  • Wants to see how it settled in the bone

• Phase 4 (rare)

  • Necessary when there is excessive background activity

Whole body bone

• Inject through iv and take pictures 2-3 hours after injection

Why is patient hydration encouraged?

• Reduce soft tissue uptake

• Ensure problem areas are not covered by random tracer uptake

What causes increased tracer uptake?

Increased biological activity (osteoblastic activity) in the area.

Is this distribution normal or abnormal?

1. Abnormal

2. Abnormal

3. Abnormal

4. Normal

Describe the abnormal findings in this image

1. Not uniformly distributed and random black spots

2. Asymmetrical uptake in the skull, pelvis and right femur

3. Increased uptake in the feet and pelvis

4. Normal with pediatric patients

Suggest a possible differential diagnosis

1. Cancer that has metastasized to different locations

2. padgets

3. arthritis

4. Pediatric patient

If additional imaging might be beneficial? Why?

1. SPECT/CT might be beneficial to give better specificity on what is being affected

2. SPECT/CT might be beneficial as it can provide anatomic background to show what is specifically uptaking more tracer

3. Spot images might be beneficial on specific joints to provide more detailed views

4. Normal pediatric scan

A 67 year old man with prostate cancer complains about worsening lower back pain.

Why was a bone scan ordered?

A bone scan was ordered to check for potential bone metastasis coming from the prostate cancer and to evaluate any potential causes for the back pain.

A 67 year old man with prostate cancer complains about worsening lower back pain.

What findings would suggest metastatic disease?

Randomly scattered black spots known as dalmation spots across the body.

A 67 year old man with prostate cancer complains about worsening lower back pain.

Which skeletal sites are most commonly involved?

Ribs, spine, hips, and pelvis, skull

A 67 year old man with prostate cancer complains about worsening lower back pain.

What other imaging studies may complement the bone scan?

CT, MRI, SPECT

Define osteoblastic and osteoclastic

• Osteoblastic: bone growth and repair (b = build)

• Osteoclastic breaking down and absorption of bone (c = clash)

What radiopharmaceuticals are widely used for skeletal images

1. Tc-99 MDP (methylene diphosphate)

2. Tc-99m PYP/PYR

3. Tc-99m HDP (hydroxymethylene diphosphonate)

4. ¹⁸F FDG (fluorodeoxyglucose).

Name a bone radiopharmaceutical for a PET bone scan

¹⁸F FDG (fluorodeoxyglucose).

A patient walks into a nuclear medicine department for a four-phase bone scan. Explain the procedure from injection to imaging. Explain the radiopharmaceutical, side effects, contraindications, and imaging techniques.

1. Administer 20-30 mCi Tc-99 MDP.

2. Position patient on the table for blood flow images (60 seconds)

3. Blood pool images taken immediately after (3-5 minutes)

4. 2-3 hours later, delay phase images.

5. If excessive background activity, a fourth phase scan (up to 24 hours after injection)

1. Tc-99 MDP tags through chemisorption.

   1. Side effects uncommon

   2. Contraindications:

      1. Another Tc-99 study within the past 24-48 hours

      2. Recent barium contrast (causes attenuation)

Why would a patient need a four-phase study?

• If there is excessive background activity on the third phase.

• They would need to come back 24 hours later.

An incontinent patient voided on themselves prior to their whole-body imaging. What should you do as a technologist?

Clean up:

1. Put on proper PPE

2. Undress the patient

3. Wash and dry contaminated area

4. Dress patient in a new & clean gown to ensure there is no contamination in region(s) of interest.

Define the glove phenomenon in your own words

• When a technologist injects the patient with a dose into an artery

• Results in the pharmaceutical pooling in the soft tissue of the hand.

Define superscan in your own words

• When the radiotracer is almost completely absorbed into the bone.

• Other soft tissues and kidneys are not visible.

You perform a delayed spot view of the pelvic area on a 59-year old man for an indication of prostate cancer. After completing the imaging, you notice that the patient had a gigantic belt buckle.

How will this affect the images? Describe how it will look and what would you do next.

You are about to perform a delayed spot view of the pelvic area on a 90-year old male patient. The male patient tells you that he has a diaper on and has voided on the diaper.

What will you do? Explain why.

• Jewelry → artifacts, occludes image

• Ask to remove buckle

• Urine → contamination

• Escort to bathroom. If patient requires assistance, don PPE and assist removal of contamination

How many mCi do you usually inject a patient for a bone scan?

• Normal: 20-30 mCi of MDP

• Possible range:10-30 mCi

What could a patient be diagnosed with if you see a hot spot?

Depends on location. Could indicate problems such as:

• Arthritis

• Paget's

• Cancer

• Fractures

Why is it important to make sure a patient isn’t wearing a necklace during a bone scan?

Necklace can show up as an artifact and potentially block a spot that indicates a diagnosis.

What is the difference between a pediatric whole-body scan and that of an older patient?

Pediatric:

• Dose: determined by weight

• You will see hot spots on the epiphyseal plates due to bone growth

Older Patient

• Dose: 10-30 mCi

• May show problems such as less dense bones with older patients with osteoporosis.

Can a patient consume a big cheese burger before their bone scan? What about after the completion of their scan?

• No restrictions on what they eat before or after their scan.

• Encouraged to drink plenty of water as it helps with uptake.

burger allowed :D

Bones are made out of

• Collagen

• Hydroxyapatite/Bony Matrix - Crystalline inorganic bone

Bone types

LFSSI (Leon Flying Slapped Squids… Impossible)

• Long

• Flat

• Sesamoid

• Short

• Irregular

Bone mets are most commonly from what types of cancer?

• Thyroid

• Lung

• Breast

• Prostate

• Kidney

Standard dose for bone scans

• Adult: 20-30 mCi

• Pedes: 10-20 mCi (weight based)

Chemisorption via ion exchange is a chemical absorption process where

Unwanted ions are removed and replaced by equivalently charged ions

Axial Skeleton

• Skull

• Ribs

• Sternum

• Spine

What appears hot on pedes patients

Epiphyseal plate/growth plate

Increased concentration of RP is…

Commonly osteoblastic activity (more common)

Decreased concentration of RP is…

Commonly osteoclastic activity (ex. lytic lesion)

What were the first attempts radiopharmaceuticals (pure beta)? Which came after (mixed emitters)?

1. ³²P and ⁴⁵Ca

2. ⁴⁷Ca, ⁸⁵Sr, and ⁸⁷mSr

   1. 1.3 meV, 523 meV, and 388 keV, respectively

   2. Expensive, long half life

Which skeletal sites are most commonly involved for mets?

Skull, spine, ribs, pelvis, shoulders

Bone scans are useful because they have a high ______. Can cause issues because they have a low ______.

High sensitivity, low specificity