CORE Nucs 2 9/2014
Terms in this set (92)
Rest or stress first in single day sestamibi scan?
Dose of Sestamibi for rest?
Stress after what dose?
An additional 20-30 mCi
Imaging performed how long after injection of sestamibi and why?
30 minutes to allow liver acitivity to clear. And because there is no redistribution to worry about.
**This means that gated SPECT images show wall motion at time of imaging while perfusion images show perfusion at time of injection
**PET rest/stress imaging is better in every way compared to spect
What are agents used in PET myocardial perfusion?
Rubidium-82 and N-13 Ammonia
For quantification of myocardial blood flow, which PET agent is preferred?
N-13 ammonia- better extraction
When is imaging performed with thallium?
Immediately post exercise and 3-4 hours later after redistribution. Its uncommonly used because of its long half life and resultant high patient dose.
**At first ask if it is a good study, for example, the SNR should be much better in the stress images due to the higher dose
Right ventricular uptake on myocardial perfusion scan?
R heart disease or pulmonary hypertension
Pulmonary uptake on myocardial perfusion scan?
L ventricular dysfunction
Fixed defect differential?
Scar vs hibernating myocardium
Size of defect?
Segments. 1-2 Small. 3-4 Medium. 5 or more is large
Transient ischemic dilatation significance?
May imply three vessel disease
Total number of cardiac segments
**Review the cardiac territories in this chapter.
I-131 emits what?
Beta particles and 364 keV gamma photons
Half life and production of I-131?
8 days. Generator
Use of I-131?
Only for therapy. Treatment of thyroid cancer s/p thyroidectomy and treatment of hyperthyroidism from Graves or multinodular goiter
I-123 method of decay?
I-123 photon energy?
I-123 half life
How is I-123 administered?
**I-123 is excellent for thyroid, high detail and can obtain uptake values
Difference in thyroid uptake of pertechnetate vs iodine?
It is taken up but not trapped, it is subsequently released into the blood pool. It does still provide great images.
**Because pertechnetate doesn't specifically go to thyroid, you can get high background counts- only 1-5% is taken up by thyroid
What organs do you see with pertechnetate that you don't see with Iodine?
How is Tc-99m pertechnetate administered?
When is Tc-99m pertechnetate preferred over iodine?
When patient has received iodinated contrast because iodine blocks thyroid uptake of additional iodine. Also when a quick study is needed or when IV medication is needed isntead of oral.
Breast feeding after Iodine 123 and 131? Tc-99m?
Can resume 2-3 days after I-123, must stop for rest of pregnancy after I-131. After Tc-99 can resume 12-24 hours after administration
TSH before thyroid scan?
It must not be suppressed, so stop exogenous thyroid hormone for four weeks or give two recombinant TSH IM injections.
Retrosternal thyroid tissue?
Usually due to a substernal goiter.
What thyroid nodules are imaged?
If cytology is indeterminate
Risk of a cold nodule?
Most common cold nodule?
Benign colloid cyst (70-75%)
Warm nodule is usually what?
Cold nodule overlapping thyroid tissue
What to do with a warm nodule?
Discordant thyroid nodule?
Hot on Tc-99 and cold on I-123- Biposy.
Malignancy in a multinodular goiter?
Relatively uncommon. If there is a dominant cold nodule, investigate. Smaller cold nodules are unlikely to be malignant.
Autoimmune disorder characterized by hyperthyroidism, thyromegaly, homogenously increased thyroid activity, and often a prominent pyramidal lobe
Normal 6 and 24 hour thyroid iodine 123 uptake?
Tc-99 and I-123 in Graves?
In graves it can take Tc-99 so strong that it causes the salivary glands to not be seen...so sometimes can't tell difference
Graves treatment options?
1-131 radiotherapy. Surgery (less common). Mithimazole or propylthiouracil, may achieve remission after 1-2 years of use.
Most common inflammatory disease of thyroid?
Thyroid levels in patients with Hashimotos?
Variable depending on stage but hypo is most common
Appearance of Hashimotos?
Variable. Can range from Hashimotos appearance to patchy uptake similar to multinodular goiter. Patchiness is thought to be due to cold areas from infiltration by lymphocytes and lymphoid follicles
Clinical presentation of subacute thyroiditis?
Painful swollen gland. Some patients present with sildent hypothyroidism.
Imaging of subacute thyroiditis?
Decreased uptake and a low 24 hour uptake.
Treatment of subacute thyroiditis?
It is usually self limited. Symptom control with NSAIDS. Steroids in severe cases.
How long after thyroidectomy is I-131 administered?
1-2 months for imaging and treatment
Protocol for I-131 imaging/treatment?
After thyroidectomy, thyroid replacement therapy is withelt to allow endogenous TSH to increase, in order to increase uptake of I-131.
Dosing of I-131?
Dependent on oncologic risk. Low risk patient- Less than 30 mCi. High risk patient- 100-200 mCi I-131
**New approach is the standard dose of 30 mCi for treatment of all T1, T2, N1 cancers
**After ablation with I-131, patients with thyroid carcinoma are monitored by following thyroglobulin levels. If they rise, get an I-123 scan. If its positive, do I-131 for ablation. Note that presence of anti-thyroglobulin antibodies precludes ability to monitor the thyroglobulin levels.
Treatment of Graves?
I-131 is administered in a single oral dose to treat Graves
Contraindications to I-131 treatment of Graves?
Pregnancy. Lactation. Inability to comply with radiation safely guidelines.
Dosing of I-131 for treatment of Graves?
Varies. Many use a calculated dose based on estimated thyroid weight and 24 hour uptake. Another has shown one of three fixed doses up to 15 mCi to be equally effective.
Treatment of multinodular goiter? Dose?
I-131 can reduce goiter size...may require higher dose than Graves and may require multiple treatments. 25 mCi is typical dose.
Tc-99m sestamibi. Taken up by thyroid and parathyroid, but thyroid uptake decreases over time.
Dose for Tc-99m sestamibi in parathyroid imaging?
What can be used for intermediate cases of parathyroid adenoma?
Tc-99m pertechnetate. Parathyroid tissue does not take this up so it can be used for intermediate cases.
What takes up sulfur colloid?
Reticuloendothelial cells-Liver (Kupffer cells), Spleen. Marrow.
**Kupffer cells make up only 10% of liver mass
What percentage of sulfer colloid is taken up by the liver?
80-90%. Note that the majority of remainder is spleen. The marrow takes up a tiny amount and is not usually seen at normal windowing levels.
Biologic half life of sulfur colloid?
Most common cause of hepatic photopenic defect on sulfer colloid scan?
Most hepatic masses on sulfur colloid scan?
Decreased uptake, this includes HCC, Adenoma. Abscess.
Increased hepatic uptake on sulfur colloid scan?
FNH. Regenerating nodule in cirrhosis. Budd Chiari (Caudate)
Increased uptake in spleen and marrow on colloid scan- liver dysfunction usually due to cirrhosis
Diffuse pulmonary uptake in colloid scan?
Cirrhosis. COPD w/ superimposed infection. LCH. High serum albumin (antacids or excell aluminum)
FNH on sulfur colloid scan?
1/3 have increased. 1/3 iso. 1/3 decreased
Best scan for FNH?
HIDA scan- positive FNH and i believe negative for adenoma
Preparation of Tc99m red blood cells?
In vitro is best. 1-3 mL of anticoagulated blood mixed with stannous chloride and an oxidizing agent. Add Tc-99m. Takes about 20 minutes.
**Tc-99m sulfur colloid can be used for RBC scan but it requires a ton of prep time and has a short vascular half life
What percent of Meckel's diverticula contain gastric mucosa?
**Lateral view may be helpful in Meckel's scan to ensure activity is anterior and not associated with the ureter
What is used for Meckels?
Tc-99 pertechnetate- uptake by gastric mucosa
Main HIDA radiotracers?
Disofenin and Mebrofenin
**Both disofenin and mebrofenin are actively transported into hepatocytes but are not conjugated
Disofenin and Mebrofenin differences?
Disofenin allows visualization with bilirubin as high as 20 mg/dL and has 90% hepatic uptake. Mebrofenin allows visualization as high as 30 mg/dL and has 98% uptake.
HIDA fasting protocol?
NPO for 6 hours but must have eaten within 24. If NPO for greater than 24 hours give CCK.
.02 microg/kg as a slow infusion. Give slow or exacerbate symptoms. Wait two hours before starting exam
When to image for HIDA?
Dynamic imaging starts right after infusion.
If GB not seen in one hour?
Morphine is given (.04 mg/kg up to max dose of 4 mg). Image for 30 more minutes. Moprhine contracts the sphincter of Oddi, redirecting bile into cystic duct.
Only give morphine if what?
If tracer is seen in small bowel, otherwise there may be a common duct obstruction.
If patient has a morphine allergy?
Image for 4 hours.
Normal HIDA scan?
Liver visible by five minutes, GB by 15 minutes. Tracer seen in small bowel.
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