Lung NM Flashcards
FDG in lung
Sarcoidosis
TB
Occult infection
Autoimmune fibrosis
Pneumonia
Cystic fibrosis
Acute lung injury
Acute RDS
Ga67-citrate
Cells with increased metabolic rate
Fe analog - - binds to transferrin receptor
Highly sensitive for FUO, sarcoidosis, idiopathic pulmonary fibrosis, Pneumocystis carinii/jirovecii pneumonia, drug induced pulmonary toxicity
Lung perfusion imaging
TC-MAA 15-100 microm - - microembolization - - lung perfusion
95% bound to MAA - - free Tc pert in stomach, thyroid
Shake vial, repeatedly invert syringe
Withdraw blood back into syringe - - microemboli - - hot spots
Lung perfusion dose
Adult - - 2-5 mCi - - 200-700k particles
Pulmonary hypertension or right-to-left shunt - - 100-200k particles
Inhomogenous distribution <100k particles
Children - - 1.11 MBq/kg (min 14.8 MBq) without ventilation or 2.59 MBq/kg with ventilation - - <0.3% of capillary bed (particles)
Pulmonary hypertension diagnostic criterion
Physiologic gradient of lung perfusion from base to apex in upright position and from back to front in supine position is altered
Tc-MAA injection
Patient keeps position for 4-5 min before administration
Cough - - several deep breaths before injection
Inject slowly 30s during 3-5 respiratory cycles
Not distal port of Swan-Ganz catheter or indwelling line or port with filter
Large matrix
Min 500k counts per view
Lung perfusion pregnant
2 days protocol
First perfusion with reduced activity
If normal - - avoid ventilation
Upright better
Increase chest cavity size
Minimize diaphragmatic motion
Low dose CT
Data for attenuation correction
Not during deep breath holding but tidal breathing
Lung ventilation with radioaerosol tracers
Tc-DTPA (highest dose), Tc-colloid, Tc-technegas (superior quality than DTPA and Xe)
Through mouth piece, nose occluded - - tidal breathing
COPD - - prefer Technegas
Upright while inhaling, supine acceptable
Ventilation before perfusion - - smaller amounts 20-40 MBq
Lung ventilation with radioaerosol
Disadvantage
Substantial airway disease - - turbulent airflow in central airways - - central deposition - - aerosol in major bronchi - - limit evaluation of alveoli
Ventilation with Xe133
Advantage
T1/2 5.3 days, gamma, some beta, 10-20 mCi
Single breath, wash-in or equilibrium and washout images
More complete characterization
More sensitive for COPD
Liver uptake because it is fat soluble - - fatty liver
Lung ventilation with Xe133
Room should be equipped with appropriate exhaust/trapping system for radioactive gas
Patient upright or supine, facemask or mouthpiece connected via bacterial filter to Xe delivery system
Breath in closed system for 3-4 min - - equilibrium phase
Usually before perfusion
After perfusion - - background activity from down scatter of 140 keV Tc with energy window 80 keV
Washout phase - - posterior oblique
High radiation burden - - not recommended
Ventilation with Kr81m
Advantage
All view without interference from prior perfusion due to gamma 190 keV - - better quality
Ventilation with Kr81m
Disadvantage
Short T1/2 of parent Rb81 4.5h - - breath continously from generator - - T1/2 13s
Low availability, high overall cost
Collimator with low septal penetration
Ga67 citrate scintigraphy
WBS - - 1.5-2 mln counts or 25-35 min
Min scan speed 6-8 cm/min
Spot views of chest - - 250k-1 mln counts or 5-20 min
At 48h remain in liver, spleen, bone, bone marrow, nasopharynx, lacrimal glands, thymus, breast
Acute PE ECG
Inversion of T waves in V1-V4
QR pattern in V1
S1Q3T3 pattern
RBBB
40% sinus tachycardia - in mild cases
Normal perfusion scan
Excludes PE
Focal perfusion defect
Tumor
Granuloma
Emphysema
Interstitial fibrosis
Bronchiectasis
Pneumonia consolidation
Atelectasis
Perfusion defect in PE
Wedge-shaped
Base facing pleura
Apex toward hilum
Around - forced perfusion due to redistribution of blood flow
PIOPED 2 criteria
Normal or not segmental match - - no acute PE
High probability - - >2 segmental perfusion defects with mismatch
Non diagnostic - - not typical multiple abnormalities
Match pattern
Reduced oxygen - - reduced blood flow
Preexisting parenchymal condition affecting both perfusion and ventilation - - PE unlikely
Mismatch pattern
Ventilation preserved area of reduced perfusion
Acute PE
Untreated or poorly treated acute PE
Chronic thromboembolic pulmonary hypertension
Recurring PE
> 30% death within 2 years
PE time line
Baseline scan - immediately (within 24h)
Soon after - at 1 and 4 weeks
At 3, 6, 12 months
Diffuse non segmental mismatch
Perfusion redistribution towards upper lung regions (ventilation less)
Left heart failure
Reverse mismatch
Ventilation worse than perfusion
Stripe sign
Pneumonia
Obstructive lung disease
inhomogenous
Ventilation more informative, but poor compliance
Convective ventilation from upper airways to bronchioles
Diffuse ventilation - - all remaining lung
Obstruction - - both components of ventilation are impaired
Asthma
Central deposition
Chronic bronchitis and Emphysema
Inhomogenous deposition
Spotty distribution
Central deposition
Asthma
Spotty deposition
Emphysema
Inhomogenous deposition
Normal
Mixed deposition
COPD
Chronic PE or interstitial lung disease
Ventricular septal defect
Tumor
תסנין דלקתי
Chronic PE
Interstitial lung disease
Inflammation, scarring, edema - - thickening of interstitium
Sarcoidosis - - bilateral pulmonary hilar and mediastinal lymphadenopathy
Ga67 citrate - - lambda sign, panda sign (lacrimal and parotid glands)
Ga67 citrate limitations
Time consuming - - 48-72h after IV
Variability of image interpretation
Sensitivity and specificity variable
High radiation exposure
Ga67 citrate vs FDG
Sarcoidosis
Lambda sign
Panda sign
Solitary pulmonary nodule
Round
diameter <3 cm
No lymphadenopathy
No Atelectasis
No Pleural effusion
Benign pulmonary nodule
Mass stable for 2 years
Peripheral subpleural
Polygonal, smooth margins
Diffuse, central, laminated, popcorn calcification
Pure solid or ground glass
<15 HU
Malignant pulmonary nodule
> 3 cm, growing mass
Lobulated margin
Corona radiata = thin spiculated edge
Any other calcification
Mixed solid and ground glass
Air bronchogram sign
15 HU
Granulomatous disease
TB
Aspergillosis
Histoplasmosis
Sarcoidosis
Benign tumor
Hamartoma
Pulmonary pseudotumor
Malignant tumor
Peripheral bronchial carcinoma
Bronchoalveolar carcinoma
Multiple MTS
Carcinoid
Kaposi sarcoma
Lymphoma
Other conditions. Solitary Pulmonary nodule
Septic embolism
Intra pulmonary LN
Arteriovenous malformation
Round atelectasis
Air bronchogram
Bacterial pneumonia
Central calcification
1 - Pleural lesion
2 - pulmonary lesion
3 - Pleural effusion
4 - extrapleural lesion
5 - Pleural and chest wall involvement
Anterior mediastinum 54%
5 Ts
Thymic mass
Thyroid or parathyroid
Terrible lymphoma
Teratoma
Thoracic aneurism
Thymic mass
Thymoma 50%
Max transverse diameter 15 mm
Benign - - well define round mass with soft tissue enhancement
Invasive
Thymic cysts after chemo or radio - - from - 15 to +80 HU due to bleeding
Lymphoma
Hodgkins - - single enlarged LN or large conglomerated mass, calcification after treatment
Non Hodgkin - - advanced disease
Extra gonadal germ cell tumor
Dermoid cysts - round, capsule, hydric or cystic density
Teratoma - - calcification of ossification foci
Seminoma
Thoracic aneurism
Ascending aorta >4 cm
Descending aorta >3 cm
Middle mediastinum 20%
Lymphadenopathy - - normal size <10 mm in short transverse diameter - - subcarinal <15 mm
Vascular malformations
Congenital mediastinal cysts
Congenital mediastinal cysts
Bronchogenic - - paratracheal or carinal location
Enteric
Esophageal duplication cyst - - not communicate with esophagus lumen
Pericardial cyst - - right cardiophrenic angle, water density
Posterior mediastinum 26%
Neurogenic tumor - - schwannoma, neurofibroma paravertebral - - neuroblastoma, benign ganglioneuroma next to aortic arch or posterior pericardium
Foregut duplication cyst
Lymphoma
Lymphadenopathy
Extramedullary hematopoesis - - thalassemia, sickle cell anemia paravertebral, ass with splenomegaly
Lymphoma
Interstitial pneumonia
Uptake in spleen and kidney, no stomach - - right-to-left shunt
Next step - - planar of brain
Acute PE
Within minutes to few hours - - local bronchoconstriction + hypocapnia
Within 18-24h - - reduced production of surfactant distal to embolization - - shrinkage of alveolar space
40% normal saturation
20% normal alveolar-arterial oxygen gradient
Modified PIOPED II
Acute PE
Perfusion defect persist 3 months
Less likely to resolve
Count rate of second imaging
3-4 times count rate of first imaging
DTPA vs Xe
Better photon flux
Acquisition of multiple projections
Xe is more sensitive in COPD
How many capillaries blocked when perfusion scan with Tc MAA
<0.1%
1 in 1000 capillaries