Computed Tomography Dose Index, Includes various CTDI parameters and the way of calculating effective dose from various Computed Tomography procedures along with their conversion factor.
Patient Positioning and Immobilization Devices In Radiotherapy PlanningSubhash Thakur
This is a overview of the devices used in the radiotherapy planning. These are specifically designed for patient proper positioning, reproducibility and immobilization of patient during radiotherapy treatment.
CT is one of the highest contributor for medical radiation exposure to patients. Some common CT dose descriptors and dose optimizations methods are briefly described in this presentation.
CT Dose Issues.pptx on the factors to be considered on radiation protectionsanyengere
summary, mobile radiography allows for the diagnostic imaging of patients who are unable to be seen in the X-ray examination room. Therefore, mobile X-ray equipment is useful for patients who have difficulty with movement. However, staff are exposed to scattered radiation from the patient, and can receive potentially harmful radiation doses during radiography. The protection of staff is of utmost importance; therefore, we investigated the occupational radiation doses received by RTs, particularly eye doses, using phantom measurements. RTs can be located close to a patient (i.e., the source of scattered radiation) during mobile radiography. As eye doses can be significant, protective measures are essential for RTs. Protective aprons are important for protecting RTs, as is increasing the distance from the radiation source (i.e., the patient). Lead glasses may also be necessary for protecting the eyes of RTs. To reduce RT radiation exposure, RTs should remain distant from the patient if possible. However, because this distance may hinder verification of the patient’s condition, RTs sometimes work in close proximity to patients. This is a patient phantom study. In future, the data may need validation by comparison with personal RT dosimeter records. It is important to evaluate the radiation doses delivered to RTs during mobile radiography, as well as the scattered radiation distribution, to ensure adequate protection. Further comparison studies may be needed using the Monte Carlo method.
radiographers and nurses have a responsibility to ensure that no one is within the radiation field during the X-ray exposure of the patient. This is achieved by informing all persons in the immediate area that an X-ray exposure is about to be made and asking them to stand a safe distance from the radiation field area.
Shielding
Placing a barrier of lead or concrete between the radiation source and an individual provides protection from X-radiation (Jones and Taylor, 2006; Ehrlich and Coakes, 2017). During mobile radiography, anyone assisting in an examination and staying in the radiation field should wear a lead-rubber apron or stand behind a mobile lead screen. Generally, walls in special care units where ionising radiation is used are designed to contain the radiation produced by the mobile X-ray tube within a set of criteria and limits determined by relevant legislation (Hart et al, 2002).
Radiation protection during mobile radiography
Nurses' understanding and adherence to radiation protection control measures during mobile radiography is of paramount importance in protecting patients, themselves and members of the public visiting the ward/unit. However, some research studies have found limited awareness and non-adherence to radiation protection control measures among nurses during mobile radiography (Anim-Sampong et al, 2015; Luntsi et al, 2016; Azimi et al, 2018). This can be attributed to a lack of radiation protection awareness programmes for nurses working
Patient Positioning and Immobilization Devices In Radiotherapy PlanningSubhash Thakur
This is a overview of the devices used in the radiotherapy planning. These are specifically designed for patient proper positioning, reproducibility and immobilization of patient during radiotherapy treatment.
CT is one of the highest contributor for medical radiation exposure to patients. Some common CT dose descriptors and dose optimizations methods are briefly described in this presentation.
CT Dose Issues.pptx on the factors to be considered on radiation protectionsanyengere
summary, mobile radiography allows for the diagnostic imaging of patients who are unable to be seen in the X-ray examination room. Therefore, mobile X-ray equipment is useful for patients who have difficulty with movement. However, staff are exposed to scattered radiation from the patient, and can receive potentially harmful radiation doses during radiography. The protection of staff is of utmost importance; therefore, we investigated the occupational radiation doses received by RTs, particularly eye doses, using phantom measurements. RTs can be located close to a patient (i.e., the source of scattered radiation) during mobile radiography. As eye doses can be significant, protective measures are essential for RTs. Protective aprons are important for protecting RTs, as is increasing the distance from the radiation source (i.e., the patient). Lead glasses may also be necessary for protecting the eyes of RTs. To reduce RT radiation exposure, RTs should remain distant from the patient if possible. However, because this distance may hinder verification of the patient’s condition, RTs sometimes work in close proximity to patients. This is a patient phantom study. In future, the data may need validation by comparison with personal RT dosimeter records. It is important to evaluate the radiation doses delivered to RTs during mobile radiography, as well as the scattered radiation distribution, to ensure adequate protection. Further comparison studies may be needed using the Monte Carlo method.
radiographers and nurses have a responsibility to ensure that no one is within the radiation field during the X-ray exposure of the patient. This is achieved by informing all persons in the immediate area that an X-ray exposure is about to be made and asking them to stand a safe distance from the radiation field area.
Shielding
Placing a barrier of lead or concrete between the radiation source and an individual provides protection from X-radiation (Jones and Taylor, 2006; Ehrlich and Coakes, 2017). During mobile radiography, anyone assisting in an examination and staying in the radiation field should wear a lead-rubber apron or stand behind a mobile lead screen. Generally, walls in special care units where ionising radiation is used are designed to contain the radiation produced by the mobile X-ray tube within a set of criteria and limits determined by relevant legislation (Hart et al, 2002).
Radiation protection during mobile radiography
Nurses' understanding and adherence to radiation protection control measures during mobile radiography is of paramount importance in protecting patients, themselves and members of the public visiting the ward/unit. However, some research studies have found limited awareness and non-adherence to radiation protection control measures among nurses during mobile radiography (Anim-Sampong et al, 2015; Luntsi et al, 2016; Azimi et al, 2018). This can be attributed to a lack of radiation protection awareness programmes for nurses working
The Computed Tomography (CT) dose output of some selected hospitals in the Federal capital Territory, Abuja, Nigeria have been determined by calculating the Effective doses of CT Chest and Abdomen-Pelvis of selected hospitals and compared its average with the Mean Reference Dose of CT Chest and Abdomen-Pelvis from four hospitals in the Federal Capital Territory, Abuja, Nigeria. Effective Dose and Scan type were extracted from the CT Chest and Abdomen-Pelvis examinations recorded. The Effective Dose of each patient undergoing the Chest and Abdomen-Pelvis examinations were calculated using the coefficient factor and the DLP values. Patients’ CT dose data from the ages of 18 to 60years from each of the 4 centres for each study type from January, 2013 to December, 2014 was extracted. A total of 112 patients’ CT dose data was extracted. Chest CT Effective Dose ranged from 9.0 to 34.0mSv, while Abdomen-Pelvis CT Effective Dose ranged from 15.9 to 61.0 for all the Centres in Federal Capital Territory, Abuja. This is higher than the recommended Reference Effective Dose range for CT Chest which is from 5 – 7mSv. and for CT Abdomen-Pelvis is from 8 – 14mSv. The mean effective dose from the Chest CT is 21.8mSv and from the Abdomen-Pelvis is 31.9mSv.
Thesis / Doctoral Project / Dissertation Proposal
Student Information:
Student GUID Number:
833168318
Student Name: (As it appears on your transcript)
Abdullatif Abdullah
Address:
1850 Columbia Pike Apt 406, Arlington, Virginia, 22204
E-Mail Address:
[email protected]
Phone Number:
571-340-6065
Degree:
Masters in Health Physics
Expected Graduation Month/Year
05 / 2022
Dept./Major:
Health Physics
I. Title:
Estimation of Peak Skin Dose and Its Relation to the Size Specific Dose Estimate
II. Problem or Hypothesis:
The CT Dose Index (CTDIvol) was originally designed as an index of dose associated with various CT diagnostic procedures not as a direct dosimetry method for individual patient dose assessments. There is no current method for calculating peak skin dose (PSD) using the key metrics provided from the radiation dose structure report of a CT scanner. Every CT study is required to output the kVp and mAs that were used, the dose length product and CT dose index volume which will all be shown on the CT console, but there is no direct method to go straight to the PSD. This project will test the hypothesis that the SSDE has a sufficiently strong linear relationship with PSD to allow direct calculation of the PSD directly from the SSDE.
III. Review of Related Literature:
The highest radiation dose accruing at a single site on a patient’s skin is referred to as the peak skin dose (PSD) which is related to the Computed Tomography dose index (CTDIvol) that is displayed on the console of CT scanners. However, the CT Dose Index was originally designed as an index not as a direct dosimetry method for patient dose assessment. More recently, modifications to original CTDI concept have attempted to convert it into to patient dosimetry method, but have with mixed results in terms of accuracy. Nonetheless, CTDI-based dosimetry is the current worldwide standard for estimation of patient dose in CT. Therefore, CTDIvol is often used to enable medical physicists to compare the dose output between different CT scanners.
Fearon, Thomas (2011) explained that current estimation of radiation dose from CT scans on patients has relied on the measurement of Computed Tomography Dose Index (CTDI) in standard cylindrical phantoms, and calculations based on mathematical representations of “standard man.” The purpose of this study was to investigate the feasibility of adapting a radiation treatment planning system (RTPS) to provide patient-specific CT dosimetry. A radiation treatment planning system was modified to calculate patient-specific CT dose distributions, which can be represented by dose at specific points within an organ of interest, as well as organ dose-volume (after image segmentation) for a GE Light Speed Ultra Plus CT scanner. Digital representations of the phantoms (virtual phantom) were acquired with the GE CT scanner in axial mode. Thermoluminescent dosimeter (TLDs) measurements in pediatric anthropomorphic phantoms were utilized t ...
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Title: Sense of Taste
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 structure and function of taste buds.
Describe the relationship between the taste threshold and taste index of common substances.
Explain the chemical basis and signal transduction of taste perception for each type of primary taste sensation.
Recognize different abnormalities of taste perception and their causes.
Key Topics:
Significance of Taste Sensation:
Differentiation between pleasant and harmful food
Influence on behavior
Selection of food based on metabolic needs
Receptors of Taste:
Taste buds on the tongue
Influence of sense of smell, texture of food, and pain stimulation (e.g., by pepper)
Primary and Secondary Taste Sensations:
Primary taste sensations: Sweet, Sour, Salty, Bitter, Umami
Chemical basis and signal transduction mechanisms for each taste
Taste Threshold and Index:
Taste threshold values for Sweet (sucrose), Salty (NaCl), Sour (HCl), and Bitter (Quinine)
Taste index relationship: Inversely proportional to taste threshold
Taste Blindness:
Inability to taste certain substances, particularly thiourea compounds
Example: Phenylthiocarbamide
Structure and Function of Taste Buds:
Composition: Epithelial cells, Sustentacular/Supporting cells, Taste cells, Basal cells
Features: Taste pores, Taste hairs/microvilli, and Taste nerve fibers
Location of Taste Buds:
Found in papillae of the tongue (Fungiform, Circumvallate, Foliate)
Also present on the palate, tonsillar pillars, epiglottis, and proximal esophagus
Mechanism of Taste Stimulation:
Interaction of taste substances with receptors on microvilli
Signal transduction pathways for Umami, Sweet, Bitter, Sour, and Salty tastes
Taste Sensitivity and Adaptation:
Decrease in sensitivity with age
Rapid adaptation of taste sensation
Role of Saliva in Taste:
Dissolution of tastants to reach receptors
Washing away the stimulus
Taste Preferences and Aversions:
Mechanisms behind taste preference and aversion
Influence of receptors and neural pathways
Impact of Sensory Nerve Damage:
Degeneration of taste buds if the sensory nerve fiber is cut
Abnormalities of Taste Detection:
Conditions: Ageusia, Hypogeusia, Dysgeusia (parageusia)
Causes: Nerve damage, neurological disorders, infections, poor oral hygiene, adverse drug effects, deficiencies, aging, tobacco use, altered neurotransmitter levels
Neurotransmitters and Taste Threshold:
Effects of serotonin (5-HT) and norepinephrine (NE) on taste sensitivity
Supertasters:
25% of the population with heightened sensitivity to taste, especially bitterness
Increased number of fungiform papillae
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Computed Tomography Dose Index
1. Dose represents the amount of energy deposited
in tissue from radiation per mass of tissue, and is
measured in J/kg = Gray (Gy).
Unfortunately, this energy damages the tissues it hits.
Consequence:
Deterministic
effect:Erythema,
Ulceration, necrosis
Stochastic Effects:
cancer
2. • Deterministic effects relate directly to the amount of radiation a
single cell receives; these require a large dose to become apparent.
• Stochastic effects can occur (randomly) with very small doses, and
even one cell can turn cancerous.
Generally speaking, in CT we are mostly
interested in the stochastic effects.
4. How is radiation dose measured in CT?
• CT dose is not measured directly on patient.
• CT dose is measured using standard phantoms.
• Measurements are then used to estimate patient dose.
6. How is Radiation dose measured?
CTDI 100 CTDI W CTDI VOL DLP Effective
dose
Dose
Distribution
Pitch
Scan
Length
Computed Tomography Dose Index (CTDI)
Measurement done at the centre of phantom of a single slice
7. CTDI
• Obtained by making
measurement in acryllic
cylinder phantom.
• Holes in centre and periphery
• Placement of pensil shaped
ionization chamber.
8.
9.
10.
11.
12. CTDI100 – Dose Distribution
In CT: the highest dose delivered is at the
periphery
Dose is uniform on the surface but
decreases towards centre.
13.
14.
15.
16. • CTDI VOL :15mGy
• Independent of scan
length
17. Computed Tomography Dose Index (CTDI):
Measurement done at the centre of phantom
of a single slice:
cannot accommodate the anatomy covered
because we do just confine to single slice.
18.
19.
20. •Volume CTDI in mGy (CTDI VOL):
•X ray tube voltage (KV)
•X ray tube current (mA)
•X ray tube rotation time (s)
•CT Pitch (P)
•Phantom size (S or L)
21. • CTDI is the rate at which
you the energy is put on
the patient.
• DLP is total amount of the
energy that you are
putting the patient.
CTDI = Radiation Intensity
DLP = Total radiation used to perform a CT Scan.
22.
23.
24. CTDI Phantoms
• 16cm (S) (Head Phantom)
• 32cm (L) (Body Phantom)
Large CTDI is =
2 X Small CTDI
29. CTDI VOL “Universal Parameter”
• CTDI VOL for Head = 60mGy on Small Phantom
• KV
• X ray filter: Head, Body or pediatric
• Model: Type of CT Scanner
• Vendor: Philips/ Toshiba/ GE
• CTDI vol >>> mAs !
31. • CTDI Vol is the radiation incident on patient, not the patient dose.
• CTDI VOL = 20mGy:
CTDI Vol is not the
indicator of any kind of
patient dose.
33. • Organ dose can be calculated. It can help to predict the
corresponding organ dose.
• Monte Carlo Simulation: The most complete computational method
for estimating organ and tissue doses is based on Monte Carlo
simulations. The simulations account for many scanner and technique
specifics,including scanner geometry, bow-tie filtration, beam
collimation, tube potential, and current as well as the CT dose index
(CTDI).
34. • Jones and Shrimpton used a simulated hermaphroditic patient (MIRD-
5 phantom) having mathematically modeled organs and tissues .
• The mathematic phantom was divided from head to mid thigh into
208 axial slabs of 5 mm thickness. Then, accounting for tube voltage
and using CT scanner–specific data for geometry and beam shaping,
they simulated a
• CT scan and calculated absorbed doses to all organs of the body for
the irradiation of each axial slab. Summing contributions from all
slabs exposed during a particular CT examination yielded the total
organ doses.
35. Effective Dose
• Effective dose is a parameter meant to reflect the relative risk from
exposure to ionizing radiation.
• The effective dose (E) is a measure of the risk of cancer induction in
the patient from the effects of the radiation.
• It takes into account the total amount of absorbed dose received and
averages it to give a whole body effective dose.
36. Method 1: Using Organ dose estimates and
ICRP 26, 60, 103
• Tissue-weighting factors are meant to represent the relative radiation
sensitivity of each type of body tissue as determined from population
averages over age and sex and are derived primarily from the atomic
bomb survivors cohort.
• For partial-body irradiation, effective dose is the weighted summation
of the absorbed dose to each specified organ and tissue multiplied by
the ICRP-defined tissue-weighting factor for that same organ or
tissue.
37. Revisions were intended to reflect
advances in knowledge about the
radiation sensitivity of various
organs and tissues.
Tissue-weighting factors are meant
to represent the relative radiation
sensitivity of each type of body
tissue as determined from
population averages over age and
sex and are derived primarily from
the atomic bomb survivors cohort
38. • E = Effective Dose
• T = all ICRP specified tissue and organ
• W t = ICRP specified tissue weighting factor
• H t = Dose to particular organ or tissue
• E T = overall tisue
• Ez = Overall irradiated Slabs
39. Using DLP and K Coefficients from the
European Guideline
• E = k × DLP,
• where k
coefficient
is specific
only to the
anatomic
region
scanned.
40. Measuring Effective Dose
Effective Dose in NCCT Head: (1100X 0.0021 ) + 4.4 X 0.0021 = 2.31
msv
Effective Dose in CT IVU: ((771.7 X 3) + 4.7 ) X 0.015 = 34.79 msv
47. CT Dosimetry
CTDI 100 Effective dose
DLP
CTDIVOL
CTDIW
Measurement done on a
standard phantom using 100 cm
chamber.
Taking into account the distribution
variation based on large and small
patient.
When the scan involves pitch.
Taking account of the whole length
exposure
Risk estimation to the body
48. Automatic Tube Current Modulation
• mA is varied: Around the patient, Along the patient(scan length), &
between patient
49. Quality Reference mAs
• Quality Reference mAs = Effective mAs
• Effective mAs = mAs/pitch
• Once set in protocol and is different for different body region.
• Can convert Effective mAs in CTDI Vol i.e the Universal parameter.
• Modulation: Five Strength
52. Refrences
• Estimating Effective Dose forCT Using Dose–Length Product Compared With Using Organ Doses:
Consequences of Adopting International Commission on Radiological Protection Publication 103
or Dual-Energy Scanning, Jodi A Christner, Mayo Clinic, Available from www.ajronline.org,
DOI:10.2214/AJR.09.3462
• Videos from Walter Huda, available on Youtube.
Editor's Notes
In Radiography and Fluroscopy the entrance skin dose is higher and the radiation dose decreases as it pass through the patient. In CT the surface dose is maximum compared to centre.
More like a bell curved, peak dose is delivered only to certain central slice. There is more the tail portion
Larger the anatomy exposed , greater the biological risk.
For the same amount of incident raiation, the newborn infant and children dose will be quite large, whereas for an adult due to size of attenuation due to large mass, their dose will be much lower.