1) Dose calibrators are gas-filled ionization chambers used to measure the radioactivity of radionuclides by detecting the ionization current produced when radiation interacts with the gas.
2) They operate in the ionization chamber region where a constant voltage collects all ion pairs produced, allowing measurement of high activity levels without dead time effects.
3) Dose calibrators measure the total ionization current rather than individual energy events, so they cannot distinguish between radionuclides in mixed samples like solid scintillation counters can.
this power-point slide presentation includes lots of information like how MRI coil works. what is shimming, magnet, fringe, and design of mri coil and also magnet. this will help a lot for radiologist and technician radiographers.. thanks.
Quality Assurance Programme in Computed TomographyRamzee Small
Introduction to Computed Tomography
Basic description of the components of a CT System
Introduction to Quality Assurance
Quality Assurance and Quality Control Tests in Computed Tomography base on frequency
Objective of QA/QC Test
this power-point slide presentation includes lots of information like how MRI coil works. what is shimming, magnet, fringe, and design of mri coil and also magnet. this will help a lot for radiologist and technician radiographers.. thanks.
Quality Assurance Programme in Computed TomographyRamzee Small
Introduction to Computed Tomography
Basic description of the components of a CT System
Introduction to Quality Assurance
Quality Assurance and Quality Control Tests in Computed Tomography base on frequency
Objective of QA/QC Test
A quality control for new equipment should start with an acceptance test to verify the equipment meets the specifications given by the vendor. The acceptance test should be performed according to accepted international standards and may require the use of instruments and phantoms not available in the department. The acceptance test forms the basis of the reference tests routinely performed in the department during the life-time of the equipment according to a schedule worked out by the medical physicist in cooperation with the nuclear medicine department. Certain parameters should be tested daily, others on weekly, monthly and yearly basis.
A quality control for new equipment should start with an acceptance test to verify the equipment meets the specifications given by the vendor. The acceptance test should be performed according to accepted international standards and may require the use of instruments and phantoms not available in the department. The acceptance test forms the basis of the reference tests routinely performed in the department during the life-time of the equipment according to a schedule worked out by the medical physicist in cooperation with the nuclear medicine department. Certain parameters should be tested daily, others on weekly, monthly and yearly basis.
Complete detail about the Radiopharmaceutical, General Introduction, Radioactive substance, Radioactive rays like alpha, beta and gamma rays. All the Measurement method to determine the radioactivity of any element and widely used instrument Geiger Muller Counter. And some Radiopharmaceutical product used in many diagnosis , treatment such like sodium iodide solution & capsule, Rose Bengal I 131 and Application of Radiopharmaceuticals.
Pharmaceutical Inorganic chemistry UNIT-V Radiopharmaceutical.pptx
Isotopes Types of decay
Alpha rays, which could barely penetrate a piece of paper
Beta rays, which could penetrate 3 mm of aluminium
Gamma rays, which could penetrate several centimetres of lead
Units of Radioactivity:
Measurement of Radioactivity
The measurement of nuclear radiation and detection is an important aspect in the identification of type of radiations (, , ) and to assay the radionuclide emitting the radiation, suitable detectors are required. The radiations are identified on the basis of their properties.
e.g. Ionization effect is measured in Ionization Chamber, Proportional Counter and Geiger Muller Counter.
The scintillation effect of radiation is measured using scintillation detector and the photographic effect is measured by Autoradiography.
Gas Filled Detectors:
Ionization Chamber:
Proportional Counters:
Geiger-Muller Counter
Properties of α, β, γ radiations
Half –life of Radioelement
Sodium Iodide (I131)
Handling and Storage of Radioactive Material:
Storage of Radioactive Substances –
Precautions For Handling Radioactive Substances
Labelling of Radioactive Substances
Pharmaceutical Application Of Radioactive Substances
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- Video recording of this lecture in Arabic language: https://youtu.be/Ve4P0COk9OI
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Preoperative Management of Patients on GLP-1 Receptor Agonists like Ozempic and Semiglutide
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These lecture slides, by Dr Sidra Arshad, offer a quick overview of physiological basis of a normal electrocardiogram.
Learning objectives:
1. Define an electrocardiogram (ECG) and electrocardiography
2. Describe how dipoles generated by the heart produce the waveforms of the ECG
3. Describe the components of a normal electrocardiogram of a typical bipolar leads (limb II)
4. Differentiate between intervals and segments
5. Enlist some common indications for obtaining an ECG
Study Resources:
1. Chapter 11, Guyton and Hall Textbook of Medical Physiology, 14th edition
2. Chapter 9, Human Physiology - From Cells to Systems, Lauralee Sherwood, 9th edition
3. Chapter 29, Ganong’s Review of Medical Physiology, 26th edition
4. Electrocardiogram, StatPearls - https://www.ncbi.nlm.nih.gov/books/NBK549803/
5. ECG in Medical Practice by ABM Abdullah, 4th edition
6. ECG Basics, http://www.nataliescasebook.com/tag/e-c-g-basics
Title: Sense of Smell
Presenter: Dr. Faiza, Assistant Professor of Physiology
Qualifications:
MBBS (Best Graduate, AIMC Lahore)
FCPS Physiology
ICMT, CHPE, DHPE (STMU)
MPH (GC University, Faisalabad)
MBA (Virtual University of Pakistan)
Learning Objectives:
Describe the primary categories of smells and the concept of odor blindness.
Explain the structure and location of the olfactory membrane and mucosa, including the types and roles of cells involved in olfaction.
Describe the pathway and mechanisms of olfactory signal transmission from the olfactory receptors to the brain.
Illustrate the biochemical cascade triggered by odorant binding to olfactory receptors, including the role of G-proteins and second messengers in generating an action potential.
Identify different types of olfactory disorders such as anosmia, hyposmia, hyperosmia, and dysosmia, including their potential causes.
Key Topics:
Olfactory Genes:
3% of the human genome accounts for olfactory genes.
400 genes for odorant receptors.
Olfactory Membrane:
Located in the superior part of the nasal cavity.
Medially: Folds downward along the superior septum.
Laterally: Folds over the superior turbinate and upper surface of the middle turbinate.
Total surface area: 5-10 square centimeters.
Olfactory Mucosa:
Olfactory Cells: Bipolar nerve cells derived from the CNS (100 million), with 4-25 olfactory cilia per cell.
Sustentacular Cells: Produce mucus and maintain ionic and molecular environment.
Basal Cells: Replace worn-out olfactory cells with an average lifespan of 1-2 months.
Bowman’s Gland: Secretes mucus.
Stimulation of Olfactory Cells:
Odorant dissolves in mucus and attaches to receptors on olfactory cilia.
Involves a cascade effect through G-proteins and second messengers, leading to depolarization and action potential generation in the olfactory nerve.
Quality of a Good Odorant:
Small (3-20 Carbon atoms), volatile, water-soluble, and lipid-soluble.
Facilitated by odorant-binding proteins in mucus.
Membrane Potential and Action Potential:
Resting membrane potential: -55mV.
Action potential frequency in the olfactory nerve increases with odorant strength.
Adaptation Towards the Sense of Smell:
Rapid adaptation within the first second, with further slow adaptation.
Psychological adaptation greater than receptor adaptation, involving feedback inhibition from the central nervous system.
Primary Sensations of Smell:
Camphoraceous, Musky, Floral, Pepperminty, Ethereal, Pungent, Putrid.
Odor Detection Threshold:
Examples: Hydrogen sulfide (0.0005 ppm), Methyl-mercaptan (0.002 ppm).
Some toxic substances are odorless at lethal concentrations.
Characteristics of Smell:
Odor blindness for single substances due to lack of appropriate receptor protein.
Behavioral and emotional influences of smell.
Transmission of Olfactory Signals:
From olfactory cells to glomeruli in the olfactory bulb, involving lateral inhibition.
Primitive, less old, and new olfactory systems with different path
Pulmonary Thromboembolism - etilogy, types, medical- Surgical and nursing man...VarunMahajani
Disruption of blood supply to lung alveoli due to blockage of one or more pulmonary blood vessels is called as Pulmonary thromboembolism. In this presentation we will discuss its causes, types and its management in depth.
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Couples presenting to the infertility clinic- Do they really have infertility...Sujoy Dasgupta
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2. 2
Definition of Radiation
“Radiation is an energy in the form of
electro-magnetic waves or particulate
matter, traveling in the air.”
or X-ray
neutron
3. 3
Types of radiation detectors
Gas field detectors.
• Radionuclide dose calibrator
Scintillation detector
• Gamma well counter
• The thyroid uptake probe
• Liquid scintillation detector
4. 4
Gas Filled Detector
Used every where because : Simple to make and portable .
Operate by utilizing the ionization produced by radiation as it passes
through a gas.
All gas-filled detectors detect radiation with different characteristics
based on the relative applied voltage between the anode and the
cathode.
8. The most widely used radiation detectors are devices that respond to
ionizing radiation by producing electrical pulses.
Ion chambers are the simplest of all gas filled detectors
An electric field is used to collect all the ionizations (positive and negative
charged particles) produced by the incident radiation in the gas volume.
Electrical collection of ions
Used to measure dose
rate
Sensitive to environmental
changes.
IONIZATION CHAMBER
9. 9
IONIZATION CHAMBERS: to measure exposure rates
detector used for the measurement of exposure rate
differ greatly from all other types of gas-filled detectors (e.g., G-M
and proportional detectors).
radiation causes a current to flow in an ion chamber detector.
Rather than detecting a series of pulses or counts .
13. 13
Geiger Mueller Counter
Most common type of detector
Gas amplification : multiplication of electrons.
Multiplication factor 108-1010
Long dead time
Used for:
– Count rate
– Dose/Dose rate
– Surface activity
Battery or High
Voltage
Resistor
(-) Cathode
+ -
(+) Anode
e
-
+
14. 1414
Types of radiation detectors
Gas field detectors.
• Radionuclide dose calibrator
Scintillation detector
• Gamma well counter
• The thyroid uptake probe
• Liquid scintillation detector
15. Dose calibrator
A gas-filled ionization chamber.
Why do we need dose calibrators?
– Used to measure the ionizing radiation exposure of a given
radioisotope.
– Used in NM to measure the amount of radioactivity of a
radionuclide before injection into a patient
Calibrators are generally gas-filled cylinders with a
well in the center of the ionization chamber into which
the radioactivity is placed.
Known as:
radioisotope calibrators.
radionuclide calibrators.
curie meters.
activity meters.
Co-57, Ba-133, Cs-137, Co-60,…….
15
16. Dose calibrator
These ionization chamber radiation
detectors are typically filled with highly
pressurized Argon [18-Ar] gas, compressed
to around 20 atmospheres.
able to measure activities anywhere from
1μCi-20Ci (3.7kBq – 740MBq).
The highly compressed gas creates an ionic
environment that favors the possibility of
ionizing events.
There is a direct relation between the
increased gas pressure and detector
efficiency.
16
17. Dose Calibrators designed to verify clinically
administered radioactivity are just one type of
radiation detector.
17
20. Why do we need to know the
activity?
We can estimate radiation absorbed
doses to the organs and whole
body.
Doses depend on the :
activity
patient size,
Bio distribution of the specific radio
labeled drug.
For a specific radio labeled drug
Activity (Bq) → Radiation dose
(Gy) to organs.
20
21. How It Works
HEP interact in 3 direct ways:
– photoelectric effect,
– Compton scattering
– pair production.
In all of these interactions between photons and
matter (argon gas), energy is transferred, leaving
ion pairs behind.
To collect the ion pairs created from these
interactions, the detector has an applied voltage
with the negative cathode as the chamber wall and
a positive anode within the ionization chamber.
After ionization, positively charged ions drift
toward the cathode and the negatively charged ions
drift toward the anode.
The positive and negative charge is supplied by a
high-voltage supply, or a battery acting as a
capacitor, within the dose calibrator.
This battery keeps the voltage on the cathode and
anode constant and functions as a backup if there
is ever a power outage to keep the calibration
factors stored in memory.
21
22. DC operates in the “ionization chamber”
region of the voltage response curve
where the ion pairs created by the
radiation are collected.
An increase in the voltage does not
significantly increase the number of ion
pairs collected.
number of collected ion pairs is
constant
current that is generated and
measured is also constant.
ionization chamber plateau:
there is no increase in measured
current because all ion pairs are
collected and there is no
recombination of pairs taking
place .
If a volume of gas is irradiated at a
constant rate, a constant amount of ion
pairs are formed, and a constant current
is generated.
22
PULSEHEIGHT
VOLTAGE APPLIED
I
ION CHAMBER
REGION
II
PROPORTIONAL
REGION
III
LIMITED
PROPOR-
TIONAL
REGION
IV
G-M
REGION
V
CONTINUOUS
DISCHARGE
REGION
(100 X B)
a
(100 X Y)
a
B
Y
VS VP VL VG VD
23. Dose calibrator
Advantage
measuring the charge
generated within the
volume is that the current
generated can be directly
correlated to the radiation
exposure.
The activity of the source
correlates with the
characteristic radiation
exposure of each
radionuclide.
Disadvantage
a lack of information
about individual
ionization events or the
energy(s) generating the
current.
This makes it impossible
for the dose calibrator to
identify or distinguish
radionuclide's in mixed or
contaminated samples.
23
24. Dose calibrator Verses solid-crystal well
counter
Dose calibrator
Gas-filled detector measures
ionizations created by photons
(radiation).
The ionization plateau collects
all ionization events avoiding
dead time effects seen with
well counters.
Able to measure high levels of
activity because it operates in
current mode, which avoids
dead-time effects.
well counter
A solid sodium iodide NaI(Tl)
crystal directly detects discrete
decay events (radioactivity).
Used for counting swipes from
around the work area to detect
small traces of contamination.
Allows for energy discrimination
and presentation of energy
spectra of samples.
24
25. Dead time effects
occur when operating in pulse mode.
NaI(Tl) crystal, used in well counters, operates in pulse mode
to capture ionization events.
Each energy event creates a voltage pulse.
If the pulses are too frequent as from a high activity source, the
detector is unable to count the pulses quickly enough and they
begin to blend into one another.
This is problematic because information is lost and the resultant
measurement isn’t a true representation of the activity of the
source.
The dose calibrator does not directly measure the energy of a
radionuclide only the current generated from ionization events,
and the measurement is not affected by this problem.
25
26. Dose calibrators
The activity of the material is measured in term of the ionization current produced by
the emitted radiations which interact in the gas.
The chamber is sealed, usually under pressure, and has two co-axial
cylindrical electrodes maintained at a voltage difference derived from a
suitable supply, the axial space constituting the well.
In the electrometer, the ionization current is converted to a voltage signal,
which is amplified, processed and finally displayed, commonly in digital form
in units of activity – Becquerel's (Bq) or curies (Ci).
26
27. Dose calibrator
The response of the detector will depend
on:
• Radionuclide ( energy of photons).
• Geometry of the detector.
• Geometry of the source.
• The condition of instrument (QC).
27
28. Geometric efficiency=
number of photons reaching the detector / the number of
photons emitted from the sample
Increasing geometric efficiency
28