CÁC HỆ THỐNG THIẾT BỊ & KỸ THUẬT GHI ĐO TRONG Y HỌC HẠT NHÂN - Nguyễn Văn Hoà

Automatic Multiple-Sample Systems • Automatic multiple sample systems are necessary for counting large number of samples or repeated tests • The main problem of the multiple sample wel

99m Tc eluted

99m Tc eluted

99 Mo Column

AugersAlphas

Range of 

-of maximum Energy (Emax)

in soft tissue

RADIONUCLIDE THERAPY

IN CRH NUCLREAR MEDICINE

DƯỢC CHẤT PHÓNG XẠ cho SPECT

Tc 99m MDP

Assay of Absolute Activity

• Two methods are used for the determination of absolute activity from the counting rate:

calibration table and calibration (standard) source

• Long-lived radionuclides are used as calibration (“mock”) source: 137Cs for 131I, 129I for 125I and 57Co for 99mTc

• Sample’s absolute activity X is given by X =

κA(mock)[R(sample)/R(mock)], where A is mock A(mock)[R(sample)/R(mock)], where A is mock activity and κA(mock)[R(sample)/R(mock)], where A is mock the ratio of emission frequencies

Dose Calibrators

• Dose calibrators are gas filled ionising chambers The gas

is air and sealed to avoid variations in temperature and atmospheric pressure

• Dose calibrators are used to assay large quantities of

activities where it is too large for NaI(Tl) detector

(generator, patient preparation, shipment etc).

• The activity is determined by measuring the total amount

of ionisations in the chamber with no inherent ability of energy discrimination.

Dose Calibrator

Introduction

Pulse height analyzer

Pulse-height distribution

NaI(Tl)

Nuclear Medicine Counting

• Nuclear Medicine radionuclide decay counting

follows Poisson distribution

• Nuclear Medicine question is that how good is the result N from a single measurement?

• The assumption is that Nm so that there is

68.3% chance that m is within the range NN

N is uncertainty in N

• Percentage uncertainty is defined as V= (N/N) x 100%

Coincident Summing

• Occurs when a radionuclide emits two or more γ rays from single disintegration.

• Prominent in detector system with high

geometric efficiency, such as well counter.

• Summing also occurs between x and γ rays

as well as two 511 KeV annihilation

photons

Scalers and Timers

• A device that only counts pulses is called a scaler

• An auxiliary device that controls the scaler counting time is called timer.

N N

Photocathode cathodd

Well Counter

Automatic Multiple-Sample

Systems

• Automatic multiple sample systems are

necessary for counting large number of

samples or repeated tests

• The main problem of the multiple sample well counters is the background shielding

on top of the wells

• SCA, MCA and computers are all being used for the interface with the detectors.

Multiple-Sample System

Multi-Sample Through-Hole

System

Automatic Multiple Sample Liquid

Scintillation Counters

• Automatic multiple sample liquid

scintillation counters are designed to

handle large amount samples or repeated counting.

Multi-Sample Liquid Counter

Analog Ratemeters

• A analog ratemeter is used to determine the

average number of events occurring per unit

time The average is determined continuously

rather than over discrete counting time

• Linear vs logarithmic ratemeters: V0=knQRp vs

V0=klog(nQRp) - wider range of counting rate

• Ratemeter responds to the rate change has a time constant which can be adjusted (change the

NaI(Tl) Probe System

THYROID UPTAKE MEASUREMENT

In Vivo Counting Systems

• In vivo refers to human or animals body

• Probe system is designed to detect single organ or localised parts of the body

• A typical probe system employs 5x5cm NaI(Tl) cylinder crystal plus cylindrical or conical shaped collimator (as well as PM tube etc).

Surgical Gamma Ray Probes

Gamma Ray Probe System

In Vivo Counting Systems

• Whole body counting system is designed to measure total radioactivity of whole body (not local activity).

• Most whole body counters employ large

NaI(Tl) crystal (15-30cm diam x 5-10 cm

thick) in order to detect high energy

photons and small activities.

B Cassen H.O Anger

PIONEERS

Gamma camera

Used to measure the spatial and temporal distribution of a

Gamma camera (principle of operation)

PM-tubes Detector Collimator

Position X Position Y Energy Z

Camera based SPECT systems can be one of the

configurations below:

Distances vs Positions

Step-and-Shot Acquisition

Rotational SPECT Camera

GAMMA CAMERA

SPECT cameras are used to

determine the three-dimensional

distribution of the radiotracer

It is ideal to mark the background region in such a manner as to exclude

KIDNEY FUNCTION

(Tc99m-DTPA)

Renogram

Ejection Fraction

Calculation

Segmental Wall Motion

Calculation

THYROID SCAN

Single probe Scanner Gammacamera

BONE SCAN

Whole Body Imaging

-Different Intensity

BONE SCAN

normal Alzheimers disease

CEREBRAL BLOODFLOW

First Pass Cardiac Studies

• Data acquisition technique

– List or Frame: 0.5 second per image

• Data reformat

• Ventricular function evaluation

– EF, Ventricle size, wall motion similar to multiple gated studies

• Detection of Intra-cardiac shunts

– Left to right shunt: Qs=Qp-Qsh; (Qp/Qs)>1.3

– Right to left shunt: some activity goes directly into the left

ventricle without first passing through the lung.

Gated SPECT

Phase Image

SHUNT QUANTIFICATION

ECG-GATED BLOODPOOL

SCANNING

transversal

sagittal

MYOCARDIAL PERFUSION TOMOGRAPHIC SLICES

Stress Rest

MYOCARDIAL PERFUSION

MYOCARDIAL PERFUSION

Cinematic Display

• The images to be displayed are

formatted into an area memory known as

buffer so that information can be retrieved quickly

ECG-GATED MYOCARDIAL

PERFUSION

SPECT/CT TECHNOLOGY & FACILITY

DESIGN

SPECT / CT

• Na(Tl) I works well at 140 keV, and is the most common scintillator used in SPECT cameras

Density (g/cc) Z Decay time

(ns)

Light yield (% NaI)

Atten length (mm)

BGO 7.13 75 300 15 11

LSO 7.4 66 47 75 12

GSO 6.7 59 43 22 15

SPECT / CT

SUMMARY OF SPET/CT

• SPECT cameras are scintillation cameras, also called gamma cameras, which image one gamma ray at a time, with optimum detection at 140 KeV, ideal for gamma rays emitted

Positron Emission Tomography

Overall data flow during PET acquisition and processing

+

+-

511 keV

511 keV

positron

CYCLOTRONS IN HOSPITALS

FDG Module

Beam extractor Target

Ion

Source

PET Radiopharmaceuticals

Nuclide Half-life Tracer Application

O-15 2 mins Water Cerebral blood flow

C-11 20 mins Methionine Tumour protein synthesis

N-13 10 mins Ammonia Myocardial blood flow

F-18 110 mins FDG Glucose metabolism

F18-FDG

Manufacture of FDG

• End of bombardment of the target material with the ion source beam is only 18F, NOT FDG

• Bombardment could typically be 2 hours (one half-life)

• 18F then sent to a chemistry module (synthesis module)

to react with a number of reagents to produce fluorinated deoxyglucose

• Synthesis module performs a number of steps such as heating, cooling, filtering, purifying, etc

• FDG synthesis typically adds another hour

Manufacture of 18F

• Proton is accelerated

• Strikes 18O target

• Merges with 18O

• Neutron ejected

n F

p

O 11 189 11

18

CH 2 HO

HO HO

O

OH OH

Coincidence Detection

Detector

Detector

• Anatomical detail

• Cannot differentiate between active and benign disease

• Better resolution than PET

• Good dynamic range bone to lung

PET/CT

CYCLOTRON

• Combines the functional information with the anatomical detail

• Accurate anatomical registration

• Higher diagnostic accuracy than PET or

CT alone

MULTIMODALITY IMAGING

PET

CT

biograph LSO standard protocol

FORE AWOSEM

Fused PET/CT

XẠ TRỊ NGOÀI : MÁY GIA TỐC (LINAC )

Treatment plan

RT planning and response

Case: Female with bronchial CA for RTP.

Scan protocol:

Standard whole-body PET/CT scan pre- and therapy Pre- and post-therapy PET/CT can be registered using manual syngo -fusion tool.

post-Findings:

PET

Splee n

ABDOMINAL AORTA

CẤP LIỀU 188Re-HDD-Lipiodol

Kiểm tra bằng DSA Tiêm

Re-188

Liều Re-188thám sát

(5mCi)

Liều Re-188điều trị (< MTD)

Splee n

ABDOMINAL AORTA

Tiêm liều 188Re-HDD-Lipiodol thám

sát 5mCi dùng DSA hướng dẫn

Máy DSA

Tiêm liều

Re-188thám sát (5mCi)

 Hình học cơ quan người chuẩn , trừ khối U.

 Cơ quan nguồn phân bố hoạt độ đồng nhất.

 Cơ quan bia hấp thụ năng lượng đồng nhất

Cơ quan nguồn phân bố hoạt

độ đồng nhất

Cơ quan bi a hấp thụ năng

A.3 NGUỒN XẠ Re-188

γ : 155 KeV(max)15%)

1 CT / MRI chẩn đoán, tính thể tích Gan, U gan.

2 LABO pha chế Re-188 -HDD-Lipiodol và đo

chuẩn liều

3 SPECT chụp ảnh tính hệ số chuẩn, suy giảm,tán

xạ

4 DSA hướng dẫn cấp liều Re-188 thám sát

5 SPECT chụp ảnh phân bố Re-188 thám sát

6 MIRD tính phân bố liều hấp thụ trong cơ thể

7 Excel spreadsheet tính liều xạ trị dung nạp cực

đại để liều Gan lành < 30Gy , phổi < 12 Gy, tủy xương

<1.5Gy

B.6 QUI TRÌNH LẬP KẾ HOẠCH &

TÍNH LIỀU DUNG NẠP CỰC ĐẠI Re-188

B.5 LẬP KẾ HOẠCH & TÍNH LIỀU DUNG NẠP CỰC

ĐẠI Re-188 THEO THUẬT TOÁN MIRD

PATIENT DATA

FOLLOW UP VOLUME DIAGNOSIS

CT / MRI

FPLLOW UP TREATMENT SCOUT

DSA

FOLLOW UP SCOUT FLOOD STANDARD

SPECT

TREATMENT DOSE OUTPUT DATA INPUT

EXCEL SPREAD SHEET

ALGORITHM ( MIRD )

D(Gan lành ) = D(Gan lành  Gan lành với U )

+

+

+

* Dùng các hệ số S điều chỉnh theo khối lượng

TÍNH LIỀU HẤP THỤ TẠI BIA

Thuật toán tính liều MIRD có hiệu chỉnh

XẠ HÌNH SPECT

ATTENUATION

với Re-188 liều thám sát 5 mCi

Aûnh truyền qua Phổi ,Gan

Aûnh nguồn chuẩn

Aûnh

u gan

Aûnh

Aûnh toàn thân Re-188 liều thám sát 5 mCi

Aûnh nguồn chuẩn

C.6 TÍNH LIỀU XẠ TRỊ BẰNG EXCEL

SPREADSHEET THEO THUẬT TOÁN MIRD