frank p. dawry physx.home.comcast.net ventilation/perfusion (v/q) imaging

Frank P. DawryFrank P. DawryPhysx.home.comcast.netPhysx.home.comcast.net

Ventilation/Perfusion Ventilation/Perfusion (V/Q) (V/Q)

ImagingImaging


Ventilation ImagingVentilation Imaging

Bronchi

Bronchioles

Alveoli

Air flow through the bronchial system


Perfusion ImagingPerfusion ImagingBlood flow through the pulmonary arterial system

•Based upon the trapping of large (>10 µm) particles in the capillary bed of the lungs.


Ventilation-Perfusion ImagingVentilation-Perfusion Imaging

VentilationVentilationAirway patencyAirway patency

Airway obstructionAirway obstruction

EmphysemaEmphysema

BronchitisBronchitis

PerfusionPerfusionPulmonary embolismPulmonary embolism

TumorTumor

TuberculosisTuberculosis

FibrosisFibrosis

infectioninfection


VentilationVentilation / Perfusion / Perfusion

VentilationVentilation – – usually performed prior to perfusionusually performed prior to perfusionXenon-133Xenon-133

T1/2 = 5.3 daysT1/2 = 5.3 days80 keV80 keVPosterior – seatedPosterior – seated10 to 20 mCi in re-breathing apparatus10 to 20 mCi in re-breathing apparatusEquilibrium image followed by a washout – one viewEquilibrium image followed by a washout – one view

Krypton-81mKrypton-81mT1/2 = 13 secondsT1/2 = 13 seconds190 keV190 keVConstant inhalationConstant inhalationWash in onlyWash in only

Tc99m-labeled aerosolTc99m-labeled aerosolT1/2 = 6.0 hoursT1/2 = 6.0 hours140 keV140 keV~35 mCi in nebulizer – 10% actual lung dose delivered~35 mCi in nebulizer – 10% actual lung dose deliveredThe aerosol is administered through a mouthpiece with the nose occluded and the The aerosol is administered through a mouthpiece with the nose occluded and the patient performing tidal breathing. patient performing tidal breathing. Perfusion appearancePerfusion appearance

Technegas / PertechnegasTechnegas / PertechnegasNot yet available in the United StatesNot yet available in the United StatesFullerenes (Bucky Balls)Fullerenes (Bucky Balls)


Ventilation / Ventilation / PerfusionPerfusion

PerfusionPerfusion – – follows ventilationfollows ventilation

Tc-99m MAA (Macro aggregated albumin) 2-6 mCiTc-99m MAA (Macro aggregated albumin) 2-6 mCi

larger activity than used in Aerosol imaginglarger activity than used in Aerosol imaging

4 x greater count rate compared to ventilation because both use Tc-99m4 x greater count rate compared to ventilation because both use Tc-99m

Patient usually injected slowly in supine position, taking deep breaths / Patient usually injected slowly in supine position, taking deep breaths /

imaged uprightimaged upright

500k – 1000k counts/view500k – 1000k counts/view

particles administered particles administered – Adults 200,000–700,000 particlesAdults 200,000–700,000 particles

– PediatricsPediatrics

Neonates – 10,000 particlesNeonates – 10,000 particles

< 5 years old – 50,000 to 150,000 particles< 5 years old – 50,000 to 150,000 particles

– Patients with pneumonectomy and severe hypertension – 100,000 to 250,000 particlesPatients with pneumonectomy and severe hypertension – 100,000 to 250,000 particles



Pulmonary artery progressively narrows through Pulmonary artery progressively narrows through about 22 branchings until the terminal about 22 branchings until the terminal pulmonary arteriole branches into many (~35 pulmonary arteriole branches into many (~35 micron) pre-capillary units. micron) pre-capillary units.

There are almost 3E11 units in the lung and the There are almost 3E11 units in the lung and the usual scan dose will block about one in every usual scan dose will block about one in every 10,000.10,000.



Incredibly safe – but dose should be injected Incredibly safe – but dose should be injected slowly to be sure – patient may have impaired slowly to be sure – patient may have impaired vascular tree due to extensive disease, e.g. vascular tree due to extensive disease, e.g. adenocarcinoma occluding large amounts of the adenocarcinoma occluding large amounts of the vascular tree, or profound vascular disease.vascular tree, or profound vascular disease.


When using 99mTc for both the Ventilation (aerosol) and the Perfusion (MAA), it is extremely important that the count rate of the second study is at least three to four times the count rate ofthe first study.

Ventilation count rate ≈ 2,000-counts/second

Perfusion count rate ≈ 11,000-counts/second


The number of particles available per dose of Tc-99m MAA The number of particles available per dose of Tc-99m MAA will vary depending on the physical decay that has occurred.will vary depending on the physical decay that has occurred.

The number of particles in any dose and volume to be administered may be calculated as The number of particles in any dose and volume to be administered may be calculated as follows:follows:

Assume the average number of particles per vial = 6.0 x 10Assume the average number of particles per vial = 6.0 x 1066. .

If:If:VVA = volume to be administered in ml = volume to be administered in ml D = desired dose to be administered (mCi)D = desired dose to be administered (mCi)C = concentration of Tc-99m to be added to the reaction vial. (mCi/ml) C = concentration of Tc-99m to be added to the reaction vial. (mCi/ml) Fr = fraction of Tc-99m remaining after the time of calibration – taken from decay factor chartFr = fraction of Tc-99m remaining after the time of calibration – taken from decay factor chart

P = number of particles in dose to be administered P = number of particles in dose to be administered VVTC = volume of solution added to reaction vial = volume of solution added to reaction vial

Then:Then:

VVA = __ = __D __D __ and and P = P = __Va_Va_ x 6.0 x 10 x 6.0 x 1066

C X FrC X Fr V VTCTC


Lung Perfusion particle Lung Perfusion particle calculationscalculations

1. Determine the volume dose to be administered to the patient:

specific concentration = activity/volume

required volume = activity desired/specific concentration or ml = mCi/mCi/ml

2. Calculate the particle concentration of the reconstituted kit:

total particles in kit/ml added to kit = particles/ml

3. Calculate the particles per dose:

particles/1.0 ml = particles in patient dose/ml of patient dose

(particle concentration in particles/ml)(ml dose volume) = particles in patient dose

Particle number determinationParticle number determination

Time = 12:00 (T=0)Time = 12:00 (T=0)Add 1.3 mlAdd 1.3 ml 99m99mTc Tc (30 mCi (30 mCi ) to ) to vialvialAdd Add 3.73.7 ml of saline ml of saline

=30 mCi/5.0 ml=30 mCi/5.0 ml=6 mCi/ml=6 mCi/ml

Inject 0.7 ml = 4 mCi = Inject 0.7 ml = 4 mCi = 840,000 particles840,000 particles!!

6,000,000/5ml = x/0.7ml6,000,000/5ml = x/0.7mlX = 840,000X = 840,000

Inject 0.5 ml = 3 mCi = Inject 0.5 ml = 3 mCi = 600,000 particles600,000 particles

6,000,000/5ml = x/0.5ml6,000,000/5ml = x/0.5mlX = 600,000X = 600,000

Have:Have: 30 mCi 30 mCi 99m99mTc in 1.3 mlTc in 1.3 ml

Calibration time = Calibration time = 12:0012:00

Wanted Dose:Wanted Dose:200, 000 – 700,000 200, 000 – 700,000 particlesparticles

3 – 5 millicuries3 – 5 millicuries

Given:Given:MAA Vial contains MAA Vial contains 6 x 10 6 x 1066 particles particles (6 million) (6 million)


Particle number determinationParticle number determinationmore dilutemore dilute

Have:Have: 30 mCi 30 mCi 99m99mTc in 1.3 mlTc in 1.3 ml

Calibration time = Calibration time = 12:0012:00

Wanted Dose:Wanted Dose:200, 000 – 700,000 200, 000 – 700,000 particlesparticles

3 – 5 millicuries3 – 5 millicuries


Time = 12:00 (T=0)Time = 12:00 (T=0)Add 1.3 mlAdd 1.3 ml 99m99mTc Tc (30 mCi (30 mCi ) ) to vialto vial

Add Add 5.75.7 ml of saline ml of saline

=30 mCi/7.0 ml=30 mCi/7.0 ml

=4.3 mCi/ml=4.3 mCi/ml

Inject 0.9 ml = 3.9 mCi = Inject 0.9 ml = 3.9 mCi =

1,080,000 particles1,080,000 particles!!!!6,000,000/7ml = x/0.9ml X = 1,080,0006,000,000/7ml = x/0.9ml X = 1,080,000

more dilute = more particles injectedmore dilute = more particles injected


Particle number determination Particle number determination more concentratedmore concentrated

Have:Have: 30 mCi 30 mCi 99m99mTc in 1.3 mlTc in 1.3 mlCalibration time = Calibration time = 12:0012:00

Wanted Dose:Wanted Dose:200, 000 – 700,000 200, 000 – 700,000 particlesparticles3 – 5 millicuries3 – 5 millicuries


Time = 12:00 (T=0)Time = 12:00 (T=0)Add 1.3 mlAdd 1.3 ml 99m99mTc Tc (30 mCi (30 mCi ) ) to vialto vialAdd Add 2.72.7 ml of saline ml of saline

=30 mCi/4.0 ml=30 mCi/4.0 ml=7.5 mCi/ml=7.5 mCi/ml


400,000 particles400,000 particles☺☺6,000,000/7.5ml = x/0.5ml X = 400,0006,000,000/7.5ml = x/0.5ml X = 400,000

more concentrated = less particles more concentrated = less particles injectedinjected


Particle number determination Particle number determination High specific activity High specific activity




Time = 06:00 (T= 6 Time = 06:00 (T= 6 hours early) hours early)

Add 1.3 mlAdd 1.3 ml 99m99mTc Tc (60 mCi (60 mCi ) ) to vialto vialAdd Add 3.73.7 ml of saline ml of saline



360,000 particles 360,000 particles ☺☺6,000,000/5ml = x/0.3ml X = 360,0006,000,000/5ml = x/0.3ml X = 360,000

more concentrated = less particles more concentrated = less particles injectedinjectedFrank P. DawryFrank P. Dawry

Physx.home.comcast.netPhysx.home.comcast.net

Particle number determination Particle number determination Low specific activity Low specific activity




Time = 18:00 (T= 6 Time = 18:00 (T= 6 hours later) hours later)

Add 1.3 mlAdd 1.3 ml 99m99mTc Tc (15 mCi (15 mCi ) ) to vialto vialAdd Add 3.73.7 ml of saline ml of saline


Inject 1.3 ml = 3.9 mCi = Inject 1.3 ml = 3.9 mCi = 1,560,000 particles 1,560,000 particles !!!!

6,000,000/5ml = x/1.3ml X = 1,560,0006,000,000/5ml = x/1.3ml X = 1,560,000

more dilute = more particles injectedmore dilute = more particles injectedFrank P. DawryFrank P. DawryPhysx.home.comcast.netPhysx.home.comcast.net

Particle number determination Particle number determination Rule of ThumbRule of Thumb

Never draw greater than 1.0 ml into injection Never draw greater than 1.0 ml into injection syringe. syringe.

Prepare a fresh vial of MAA instead.Prepare a fresh vial of MAA instead.

Consider reconstituting vial with 5.0 ml saline and discarding 2.5 ml, Consider reconstituting vial with 5.0 ml saline and discarding 2.5 ml, then add the low specific activity 99mTcthen add the low specific activity 99mTc

Calculations now based upon 3,000,000 particles in the vial of MAACalculations now based upon 3,000,000 particles in the vial of MAA


Frank P. DawryFrank P. DawryPhysx.home.comcast.netPhysx.home.comcast.net Perfusion segments

Frank P. DawryFrank P. DawryPhysx.home.comcast.netPhysx.home.comcast.net Ventilation segments

Frank P. DawryFrank P. DawryPhysx.home.comcast.netPhysx.home.comcast.net Quantitation of Perfusion

frank p. dawry physx.home.comcast.net ventilation/perfusion (v/q) imaging

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