timothy mcknight do spring 2014 stunning- decreased uptake of the therapy dose of i131 by residual...
TRANSCRIPT
Timothy McKnight DO
Spring 2014
What am I looking at? Tracer: Tc99m, I131, I123, In111, F18, Xe133 Agent: pertechnetate, sestamibi, MIBG, pentatreotide, FDG, WBC, SC,
DTPA, MAG3 Whole body or small field of view Multiple phases–
3phase bone Renal exam Delayed images for parathyroid, hemangioma, or whole body In111 and I131
exams
Need to understand the physiology of each tracer. Know a few physics properties
Tc99m 140keV gamma emissions (88%) and internal conversion (12%) 6.02 h half-life
F18-FDG 110 min half life
I131 8.02 d half life
Best PIOPED Interpretation assuming a normal ventilation scan?
A – Very low probability
B – Low probability
C – Indeterminate
D - High Probability
SNM modified PIOPED 2011 High Probability of PE (>80%)
>= 2 Large (>75%) V/Q Mismatched Segmental Perfusion Defects 2 moderate defects (25-75%) equal one 1 large defect
Intermediate Everything Else
Very Low Probability of PE (<10%) Stripe Sign (perfused lung between defect and lung surface) DDx:emphysema, PulmHTN,
resolving PE Non-segmental defects Q defect < CXR abnormality Solitary Large pleural effusion(>1/3 pleural cavity) corresponding to apparent Q defect (no
other Q defects) 1-3 small (<25%) segmental defects Solitary Triple Match Defect (V:Q:CXR) in Mid or Upper Lung (divided in rough thirds of
lung height not by segmental anatomy.) >= 2 Matched (V:Q) defects with Nml CXR
PISAPED for Perfusion only with CXR. >= 1 wedge shaped large perfusion defect and no explanation on CXR.(High Prob) Cannot determine PE+ or PE- Normal 2008 Sostman et al. PISAPED vs mod PIOPED roughly equivalent outcomes
Stripe Sign
Tc99m DTPA aerosol and 1-4mCi Tc99m MAA
Key Finding
Single large V/Q match in Superior segment of RLL
Perfusion defect is equal in size to radiographic abnormality
You must always ask for the CXR
You must be familiar with modified PIOPED II criteria.
Be ready for either Tc99m aerosol(this case) or Xe133 gas vent images!
Tc99m-MAA
Avg 10-30microns
200k-600k particles(3-5mCi)
Lower does in children, pregnancy, R-L shunts (100-200K) usually require 100k for Dx exam
Vent
10-20mCi of Xe133
30mCi DTPA in 2cc nebulizer only 1-2mCi reaches patient.
Let’s Review
Which of the following are not in the differential?
A- Thyroid adenoma
B- Parathyroid adenoma
C- Parathyroid hyperplasia
D- Medullary thyroid CA
E –All of the above are in the differential.
20mCi Tc99m-Sesatimibi Key Findings:
Focal activity just below left thyroid lobe on initial and delayed Tc99m sestamibi images
SPECT images show more specific location of sestamibi activity to facilitate planning of surgical removal
DDX: PTH adenoma, Thyroid adenoma, Met lymph node, Thyroid CA
Primary Hyperparathyroidism 80-85% single or multiple parathyroid adenomas 12-15% parathyroid hyperplasia 1-3% parathyroid carcinoma
~15% of parathyroid adenomas are ectopic
Tc99m sestamibi – mitochondrial localization. Uptake in parathyroid, thyroid, salivary, cardiac, hepatobiliary, bowel, renal tissues Utility of sestamibi is based on earlier washout of thyroid activity
compared with parathyroid adenomas Thyroid adenomas and parathyroid hyperplasia typically are more
intense than normal thyroid on initial images but usually washout by delayed images but occasionally may retain acitivty greater than washed out thyroid background
Tc99m pertechnetate images can be subtracted from sestamibi images to increase sensitivity. If a nodule has increased activity on both sestamibi and pertechnetate this is usually a follicular thyroid adenoma.
Sestamibi is a nonspecific tumor localization agent and may show increased activity in metastatic lymph nodes from: Thyroid carcinoma Breast Cancer Head/Neck Carcinomas
ECTOPIC PARATHYROID ADENOMA
Best Diagnosis? A – Breast CA Mets
B – Paget’s Dz
C – Myelofibrosis
D – Renal Osteodystrophy
E – Hypertrophic Pulmonary Osteoarthropathy (HPOA)
Tc99m MDP / HDP
Key Finding- SUPERSCAN Intense activity throughout skeleton / Minimal or no
perceivable renal activity
DDx
Mets – prostate, lung, breast, lymphoma
Look for patchy distribution and focal distant extremity mets
Metabolic – Renal Osteodystrophy, hyperthyroidism, osteomalacia
Look for uniform distribution, pseduofractures, bowed femurs, prominent costochondral junction activity, disproportionately intense calvarium
Myeloproliferative Dz / Marrow Dz
Lymphoma, myelofibrosis, mastocystosis, leukemia
Uniform Axial and Appendicular activity
Prostate Mets
Renal Osteodystrophy
Best Diagnosis?
A – Brain Death
B – NPH
C – Alzheimer’s
D – Acute Seizure
E – Obstructed VP shunt
500 microcuries In111-DTPA injected by LP
Clinical triad of Wet (incontinence), Wobbly (abnormal gait), Wacky (altered mentation)
Initial images at 2-4 hours and 24 hours post-injection
Normal activity in basal cisterns by 2-4 hours
Activity climbs up over convexities by 24 hours
Activity clears basal cisterns and fills interhemisphereic fissuse, sylvian fissures
Transient reflux in ventricles may occur at 4 hours but should clear at 24 hours
Ventricular activity at 24 hours indicates NPH
Clear ventricles but failure of activity to ascend over ventricles should prompt 48-72hr images.
Best Diagnosis? A –Parathyroid Adenoma
B – Left Colloid Cyst
C – Prior Left Thyroid Lobectomy
D – Right Autonomously Function Nodule
E – Left Thyroid Cancer
Tc99m Pertechnetate scan / I-123 uptakes
Key findings: decreased thyroid uptake / right thyroid lobe nodule with increased activity.
Autonomously functioning nodule results in suppression of normal background thyroid activity by secreting large amounts of thyroid hormone and suppressing the pituitary axis.
More common in younger adults
50% of hyperfunctioning adenomas are autonomously functioning
Tx: I-131 therapy , Surgical excision, Surveillance
Very low risk of cancer (<1%).
2hr 24hr
Increased activity on Tc99m Pertechnetate Thyroid scan
Preserved trapping consistent with solid thyroid nodule
Decreased activity on I-123 scan
Reduced organification
Treat this as a COLD nodule
DDx
Thyroid cancer
Follicular adenoma
Follicular hyperplasia
Nearly all >99% of hot nodules on I-123 are hyperfunctioning benign adenomas and do not requiring further imaging workup
Hot nodule on Tc99m pertechnetate scans require that an I-123 scan be obtained to exclude a discordant nodules which have an increased risk of carcinoma
Discordant nodule should be Biopsied!
Remember only 10-20% of cold nodules represent cancer.
Tc99m TcO4-
I-123
Which of the following is true about this scan? A- This is for preoperative initial
staging
B – Normal scan
C – Findings are suspicious for distant metastasis
D – Findings are suspicious for local recurrence in the neck
E – C and D
Bronchial Atresia
5 years previous
1-5mCi
Many preferring a range of 1–2 mCi
Decreased stunning- decreased uptake of the therapy dose of I131 by residual functioning thyroid tissue or tumor due to cell death or dysfunction caused by the activity administered for diagnostic imaging
Normal Biodistribution: salivary glands, stomach, kidneys, and bowel.
Used to diagnose and treat metastatic thyroid cancer
Used to treat hyperthyroid Multinodular goiter/Graves Typically do pre-ablation scan, post-ablation scan 4-10days post treatment. Then f/u scans at 6 and 12 months post treatment and then intermittently either yearly or every 3-5 years depending on recurrence risk.
Beta-emissions (606keV) treat disease (travel 0.8mm)
Gamma emissions (364keV) are used for imaging.
Half life 8.02 days
Locoregional disease
Single dose of I-131: ~ 65% effective in eradicating disease
Distant metastatic disease
Single dose of I-131
33% effective for lung metastases
7% effective for bone metastases
Star Artifact from septal penetration caused by intense activity in thyroid tissue. Common on initial post-TX scan. Abnormal on follow-ups.
Locally Recurrent Thyroid Cancer Total Thyroidectomy 4 years ago
Initial Post-Tx Scan w/ Star Artifact
Best Diagnosis?
A - Loosening
B - Infection
C - Pagets
D - Stress Fracture
E - Metastasis
Three phase bone scan (20 mCi) Differentiating loosening from infection in a painful joint
w/ arthroplasty is difficult. A normal scan has a high negative predictive value. A positive scan is nonspecific
Typically loosening has focal increased activity on delays at the bone/prosthesis interface especially at the tips of prosthesis stems and variable on dynamic and blood pool phases. Infection is often more diffuse and abnormal on all three phases.
Sulfur colloid combined with indium WBC scans may be helpful. Normal postsurgical activity persists for several months
20% persist up to 1 yr Aspiration and Culture is often necessary.
In111 WBC and Tc99m SC Key findings: Non-spatially congruent
activity around left knee joint. (increased areas on In111WBC that are decreased on Tc99m sulfur colloid)
DDX: Infection Loosening
Post op infections 6mo(1/3), <=1yr(1/3), >1yr (1/3)
Normal postoperative activity on Bone Scan: Hip – up to 1 yr, some minimal activity in
acetabulum, greater trochanter and at fem tip up to 2 yrs but uncommon
Knee-variable, but tends to be less than normal bone activity after first 2 yrs. Any intense activity is suspicious
Infection
Loosening
In111 WBC Tc99m SC
Best Diagnosis?
A – Pagets
B – Neoplasm
C – Stress Fracture
D – Osteomyelitis
E – Fibrous Dysplasia
Focal Bone Lesion
Key findings on Bone scan. Right knee expansile lesion from femoral epiphysis to distal femoral shaft.
Secondary involvment at right shoulder/axilla.
Stepoff suggesting pathologic fracture. Leukemia/Lymphoma
Ewing Sarcoma
Metastasis
Osteosarcoma
Infection
Plain film and cross secitonal imaging necessary in real life but not be provided at boards.
Differential is more important than final diagnosis in this case.
Don’t forget to address if there are skip lesions if you are included osteosarcoma in your differential!
1 yr prior
4 Hours 24 Hours
Type of Scan, Differential and Diagnosis?
In -111 Octreoscan (pentatreotide) Octreotide analog binding select somatostatin receptors
Biodistribution Liver, Spleen(intense), Kidneys/bladder(intense), gallbladder,
blood pool, faint thyroid,
Main route of excretion: Kidneys/Bladder
Neuroendocrine tumors ( carcinoid, panc neuroendocrine, pheochromocytoma, medullary thyroid CA)
Also: pituitary adenoma, meningioma, and others
In 111-Octreoscan with incidental activity in a large goiter.
DDX: Medullar Thyroid CA or Metastatic Disease
No other evidence of cancer. Patient was being w/u for insulinoma which was never found.
Stable US over next 1 year. Biopsy is appropriate given differential.
Many different thyroid pathologies have been reported as false positive on Octreoscan. The most important to r/o is medullary thyroid cancer.
Things other than malignant neuroendocrine tumors can be postive on Octreoscan.
Meningioma, Pituitary adenoma, Goiter, Astrocytoma, Lymphoma, Breast Cancer, small cell Lung CA, Paraganglioma
Type of Scan, Differential and Diagnosis?
PET-CT
Malignant GIST, Pheochromocytoma/Paraganglioma, Pulmonary Chondroma
I123-MIBG Focal increased activity in right adrenal mass (Malignant Pheochromocytoma)
PET-CT Hypermetabolic right adrenal mass (Pheochromocytoma) Multiple hypermetabolic liver lesions (Metastatic GIST) Right parahilar partially calcified mass (chondroma) – no activity on PET (not
shown)
I-131 or I-123 MIBG (meta-iodo-benzyl-guanidine) Guanethdine analog similar to Norepinephrine Pheochromocytomas ( MEN 2A/2B, NF, VHL, Carney, Familial) 90% sensitive Neuroblastoma 90% sensitive Lower sensitivity w/ Carcinoid, Medullary thyroid cancer, Paraganglioma Imaging at 24, 48, 72 hours Biodistribution
Typical: salivary, liver, faint cardiac, thyroid,renal/bladder Rarely: faint nasal, neck muscle, or diffuse lung activity.
Main route of excretion is kidney/bladder
Type of Scan, Differential (Best 3) and Diagnosis? Would you biopsy this?
F18- FDG PET-CT Key finding
Hypermetabolic nodule highly suspicious for Lung CA, no distant mets, lung resection demonstrated adenocarcinoma
ACCP recommends that FDG-PET be used in any for any pulmonary nodule measuring at least >8-10mm that is indeterminate on diagnostic Chest CT and is in a low-to-moderate risk category for lung CA.
DDx for SPN is vast but a few to put in your list of common things are Lung CA Inflammatory (sarcoid/rheumatoid) Infection(granulomas) Hamartoma Carcinoid Met
False-Negatives for PET include: BAC(adenocarcinoma in-situ), carcinoid, mucinous neoplasms
What constitutes a positive PET-CT for SPN is somewhat controversial
Traditional teaching was SUV max <2.5 benign and >=2.5 malignant, no longer favored (too many false negative)
Some report any activity in a nodule above lung background as suspicious. Others use activity equal or greater than mediastinal blood pool as suspicious.
Fletcher et al JNM 2007 study of 532 SPNs
No PET activity (“definitely benign” NPV 97%)
Minimal activity SUV >0.6-0.8 but <1.5-2.0 (“probably benign” NPV 87%)
Activity greater than lung background but less than blood pool.
Activity similar to mediastinal blood pool >1.5-2.0 but <2.5 (“indeterminate” NPV 78%)
F18-FDG PET
Key Finding
Classic locations of symmetric bilateral supraclavicular and paraspinal increased metabolic activity. Does no conform to any abnormality on CT only nml appearing fat
Other common areas or intercostal, perinephric and mediastinum
SUV values are highly variable
Related to adrenergic stimulation of brown adipose tissue for heat production
Winter-months or cold air-conditioned room
Pretreat with benzodiazipines or propranolol
Type of Scan, Differential and Diagnosis?
Tc99m Mebrofenin (Choletec) Key findings: Photopenic area in Right hepatic lobe.
Hyperechoic mass on US. Heteogenous mass on CT. Delayed GB filling by 120 minutes.
Normal gallbladder filling and biliary to bowel transit by 60 minutes.
Nearly all hepatic masses will be cold on hepatobiliary scan.
If no GB filling by 60 minutes can give morphine, otherwise may need delayed images up to 4hrs to exclude cystic duct obstruction.
Delayed biliary to bowel transit very nonspecific. Nml, spinchter of oddi dysfunction/spasm, common duct obstruction (stone, scar, tumor).
Acute Cystic Duct Obstruction
24 yo male with RUQ pain and jaundice
Key findings
Persistent hepatic activity to 24 hours
No biliary excretion
Persistent Cardiac activity
High specific for hepatocellular dysfunction / decreased uptake
Identify what type of radiotracer/exam
Know Tc99m properties in detail
Remember nuclear medicine is more about physiology than anatomy
Don’t forget SPECT
Thank you and Good Luck!