This document discusses stereotactic radiotherapy and radiosurgery. It begins by explaining that stereotactic radiotherapy precisely delivers radiation doses to defined tumor volumes, sparing surrounding normal tissues, using an external coordinate system attached to the patient. Stereotactic radiotherapy involves fractionated doses while radiosurgery delivers a high single dose. Imaging is used to delineate the target and organs at risk. Treatment planning software is then used to plan radiation techniques delivering a steep dose gradient. Quality assurance protocols ensure precise dose delivery. Indications, advantages, and limitations of stereotactic radiotherapy and radiosurgery are provided. The document concludes by discussing advances and other modalities like proton radiosurgery.
Radiosurgery is a discipline that utilizes externally generated ionizing radiation in certain cases to inactivate or eradicate a defined target(s) in the head or spine without the need to make an incision. Its uses in Neurosurgery is immense.
Radiosurgery is a discipline that utilizes externally generated ionizing radiation in certain cases to inactivate or eradicate a defined target(s) in the head or spine without the need to make an incision. Its uses in Neurosurgery is immense.
Conventional radiotherapy treatments are delivered with radiation beams that are of uniform intensity across the field (within the flatness specification limits). Wedges or compensators are used to modify the intensity profile to offset contour in irregularities and produce more uniform composite dose distributions such as in techniques using wedges. This process of changing beam intensity profile to meet the goals of a composite plan is called intensity modulation
IMRT refers to a radiation therapy technique in which nonuniform fluence is delivered to the patient from any given position of the treatment beam to optimize the composite dose distribution. The optimal fluence profiles for a given set of beam directions are determined through inverse planning. The fluence files thus generated are electronically transmitted to the linear accelerator, which is computer controlled, to deliver intensity modulated beams (IMBs) as calculated.
The vmat vs other recent radiotherapy techniquesM'dee Phechudi
VMAT is a new type of intensity-modulated radiation therapy (IMRT) treatment technique that uses the same hardware (i.e. a digital linear accelerator) as used for IMRT or conformal treatment, but delivers the radiotherapy treatment using a rotational or arc geometry rather than several static beams.
This technique uses continuous modulation (i.e. moving the collimator leaves) of the multileaf collimator (MLC) fields, continuous change of the fluence rate (the intensity of the X rays) and gantry rotation speed across a single or multiple 360 degree rotations
A summary of recent innovations in radiation oncology focussing on the priniciples of different techniques and their application. An overview of clinical results has also been given
This is a presentation on total body irradiation. This presentation explains about various techniques. positions used for TBI. Advantages and disadvantages of TBI.
It also gives an idea on Dosage and side effects.
Conventional radiotherapy treatments are delivered with radiation beams that are of uniform intensity across the field (within the flatness specification limits). Wedges or compensators are used to modify the intensity profile to offset contour in irregularities and produce more uniform composite dose distributions such as in techniques using wedges. This process of changing beam intensity profile to meet the goals of a composite plan is called intensity modulation
IMRT refers to a radiation therapy technique in which nonuniform fluence is delivered to the patient from any given position of the treatment beam to optimize the composite dose distribution. The optimal fluence profiles for a given set of beam directions are determined through inverse planning. The fluence files thus generated are electronically transmitted to the linear accelerator, which is computer controlled, to deliver intensity modulated beams (IMBs) as calculated.
The vmat vs other recent radiotherapy techniquesM'dee Phechudi
VMAT is a new type of intensity-modulated radiation therapy (IMRT) treatment technique that uses the same hardware (i.e. a digital linear accelerator) as used for IMRT or conformal treatment, but delivers the radiotherapy treatment using a rotational or arc geometry rather than several static beams.
This technique uses continuous modulation (i.e. moving the collimator leaves) of the multileaf collimator (MLC) fields, continuous change of the fluence rate (the intensity of the X rays) and gantry rotation speed across a single or multiple 360 degree rotations
A summary of recent innovations in radiation oncology focussing on the priniciples of different techniques and their application. An overview of clinical results has also been given
This is a presentation on total body irradiation. This presentation explains about various techniques. positions used for TBI. Advantages and disadvantages of TBI.
It also gives an idea on Dosage and side effects.
A 4 part seminar on 3D cbct technology for seminar presentations. with added technical details and considerations with differences between a CT technology.
Also it features the technical parameters ,uses and how it is considered useful in each departments of medicine and dentistry.
Intensity Modulated Radiation Therapy (IMRT) is an advanced mode of high-precision radiotherapy that uses computer-controlled linear accelerators to deliver precise radiation doses to a malignant tumor or specific areas within the tumor by reducing radiation dose to the nearby normal tissues.
Image registration and data fusion techniques.pptx latest saveM'dee Phechudi
Medical imaging is the fundamental tool in conformal radiation therapy. Almost every aspect of patient management involves some form of two or three dimensional image data acquired using one or more modality.
Image data are now used for diagnosis and staging, for treatment planning and delivery and for monitoring patients after therapy.
Similar to Stereotactic Radiosurgery/ Radiotherapy (20)
Acute scrotum is a general term referring to an emergency condition affecting the contents or the wall of the scrotum.
There are a number of conditions that present acutely, predominantly with pain and/or swelling
A careful and detailed history and examination, and in some cases, investigations allow differentiation between these diagnoses. A prompt diagnosis is essential as the patient may require urgent surgical intervention
Testicular torsion refers to twisting of the spermatic cord, causing ischaemia of the testicle.
Testicular torsion results from inadequate fixation of the testis to the tunica vaginalis producing ischemia from reduced arterial inflow and venous outflow obstruction.
The prevalence of testicular torsion in adult patients hospitalized with acute scrotal pain is approximately 25 to 50 percent
New Directions in Targeted Therapeutic Approaches for Older Adults With Mantl...i3 Health
i3 Health is pleased to make the speaker slides from this activity available for use as a non-accredited self-study or teaching resource.
This slide deck presented by Dr. Kami Maddocks, Professor-Clinical in the Division of Hematology and
Associate Division Director for Ambulatory Operations
The Ohio State University Comprehensive Cancer Center, will provide insight into new directions in targeted therapeutic approaches for older adults with mantle cell lymphoma.
STATEMENT OF NEED
Mantle cell lymphoma (MCL) is a rare, aggressive B-cell non-Hodgkin lymphoma (NHL) accounting for 5% to 7% of all lymphomas. Its prognosis ranges from indolent disease that does not require treatment for years to very aggressive disease, which is associated with poor survival (Silkenstedt et al, 2021). Typically, MCL is diagnosed at advanced stage and in older patients who cannot tolerate intensive therapy (NCCN, 2022). Although recent advances have slightly increased remission rates, recurrence and relapse remain very common, leading to a median overall survival between 3 and 6 years (LLS, 2021). Though there are several effective options, progress is still needed towards establishing an accepted frontline approach for MCL (Castellino et al, 2022). Treatment selection and management of MCL are complicated by the heterogeneity of prognosis, advanced age and comorbidities of patients, and lack of an established standard approach for treatment, making it vital that clinicians be familiar with the latest research and advances in this area. In this activity chaired by Michael Wang, MD, Professor in the Department of Lymphoma & Myeloma at MD Anderson Cancer Center, expert faculty will discuss prognostic factors informing treatment, the promising results of recent trials in new therapeutic approaches, and the implications of treatment resistance in therapeutic selection for MCL.
Target Audience
Hematology/oncology fellows, attending faculty, and other health care professionals involved in the treatment of patients with mantle cell lymphoma (MCL).
Learning Objectives
1.) Identify clinical and biological prognostic factors that can guide treatment decision making for older adults with MCL
2.) Evaluate emerging data on targeted therapeutic approaches for treatment-naive and relapsed/refractory MCL and their applicability to older adults
3.) Assess mechanisms of resistance to targeted therapies for MCL and their implications for treatment selection
Flu Vaccine Alert in Bangalore Karnatakaaddon Scans
As flu season approaches, health officials in Bangalore, Karnataka, are urging residents to get their flu vaccinations. The seasonal flu, while common, can lead to severe health complications, particularly for vulnerable populations such as young children, the elderly, and those with underlying health conditions.
Dr. Vidisha Kumari, a leading epidemiologist in Bangalore, emphasizes the importance of getting vaccinated. "The flu vaccine is our best defense against the influenza virus. It not only protects individuals but also helps prevent the spread of the virus in our communities," he says.
This year, the flu season is expected to coincide with a potential increase in other respiratory illnesses. The Karnataka Health Department has launched an awareness campaign highlighting the significance of flu vaccinations. They have set up multiple vaccination centers across Bangalore, making it convenient for residents to receive their shots.
To encourage widespread vaccination, the government is also collaborating with local schools, workplaces, and community centers to facilitate vaccination drives. Special attention is being given to ensuring that the vaccine is accessible to all, including marginalized communities who may have limited access to healthcare.
Residents are reminded that the flu vaccine is safe and effective. Common side effects are mild and may include soreness at the injection site, mild fever, or muscle aches. These side effects are generally short-lived and far less severe than the flu itself.
Healthcare providers are also stressing the importance of continuing COVID-19 precautions. Wearing masks, practicing good hand hygiene, and maintaining social distancing are still crucial, especially in crowded places.
Protect yourself and your loved ones by getting vaccinated. Together, we can help keep Bangalore healthy and safe this flu season. For more information on vaccination centers and schedules, residents can visit the Karnataka Health Department’s official website or follow their social media pages.
Stay informed, stay safe, and get your flu shot today!
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
Ethanol (CH3CH2OH), or beverage alcohol, is a two-carbon alcohol
that is rapidly distributed in the body and brain. Ethanol alters many
neurochemical systems and has rewarding and addictive properties. It
is the oldest recreational drug and likely contributes to more morbidity,
mortality, and public health costs than all illicit drugs combined. The
5th edition of the Diagnostic and Statistical Manual of Mental Disorders
(DSM-5) integrates alcohol abuse and alcohol dependence into a single
disorder called alcohol use disorder (AUD), with mild, moderate,
and severe subclassifications (American Psychiatric Association, 2013).
In the DSM-5, all types of substance abuse and dependence have been
combined into a single substance use disorder (SUD) on a continuum
from mild to severe. A diagnosis of AUD requires that at least two of
the 11 DSM-5 behaviors be present within a 12-month period (mild
AUD: 2–3 criteria; moderate AUD: 4–5 criteria; severe AUD: 6–11 criteria).
The four main behavioral effects of AUD are impaired control over
drinking, negative social consequences, risky use, and altered physiological
effects (tolerance, withdrawal). This chapter presents an overview
of the prevalence and harmful consequences of AUD in the U.S.,
the systemic nature of the disease, neurocircuitry and stages of AUD,
comorbidities, fetal alcohol spectrum disorders, genetic risk factors, and
pharmacotherapies for AUD.
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
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.
The prostate is an exocrine gland of the male mammalian reproductive system
It is a walnut-sized gland that forms part of the male reproductive system and is located in front of the rectum and just below the urinary bladder
Function is to store and secrete a clear, slightly alkaline fluid that constitutes 10-30% of the volume of the seminal fluid that along with the spermatozoa, constitutes semen
A healthy human prostate measures (4cm-vertical, by 3cm-horizontal, 2cm ant-post ).
It surrounds the urethra just below the urinary bladder. It has anterior, median, posterior and two lateral lobes
It’s work is regulated by androgens which are responsible for male sex characteristics
Generalised disease of the prostate due to hormonal derangement which leads to non malignant enlargement of the gland (increase in the number of epithelial cells and stromal tissue)to cause compression of the urethra leading to symptoms (LUTS
NVBDCP.pptx Nation vector borne disease control programSapna Thakur
NVBDCP was launched in 2003-2004 . Vector-Borne Disease: Disease that results from an infection transmitted to humans and other animals by blood-feeding arthropods, such as mosquitoes, ticks, and fleas. Examples of vector-borne diseases include Dengue fever, West Nile Virus, Lyme disease, and malaria.
- Video recording of this lecture in English language: https://youtu.be/lK81BzxMqdo
- Video recording of this lecture in Arabic language: https://youtu.be/Ve4P0COk9OI
- Link to download the book free: https://nephrotube.blogspot.com/p/nephrotube-nephrology-books.html
- Link to NephroTube website: www.NephroTube.com
- Link to NephroTube social media accounts: https://nephrotube.blogspot.com/p/join-nephrotube-on-social-media.html
2. Stereotactic radiotherapy dates back more than 50 years;
however, this form of treatment has entered the domain of
radiation oncology only in the past 10–15 years
Stereotaxy (stereo + taxis – Greek, orientation in space)
is a method which defines a point in the patient’s body by
using an external three-dimensional coordinate system
which is rigidly attached to the patient.
This results in a highly precise delivery of the radiation dose
to an exactly defined target (tumor) volume.
3. Stereotactic Radiotherapy
The delivery of multiple fractionated doses of radiation to a
definitive target volume sparing normal structure (both intra
as well as extracranial)
Stereotactic Radiosurgery
The delivery of a single, high dose of irradiation to a small and
critically located intracranial volume, sparing normal
structure
The aim is to encompass the target volume in the high dose
area and, by means of a steep dose gradient, to spare the
surrounding normal tissue
4. The intention of SRS is to produce enough cell kill within the
target volume in a single fraction in order to eradicate the
tumor.
This single high irradiation dose can produce considerable
side effects in normal tissue located close to the tumor or
within the target volume.
The SRT combines the precision of target localization and
dose application of SRS with the radiobiological advantage of
fractionated radiotherapy, i.e., breaking the total dose into
smaller parts and thus allowing repair of DNA damage in
normal tissue during the time between fractions.
Time intervals of more than 6 h between fractions can
significantly reduce the risk of side effects in normal tissue
5.
6. Conventional
Stereotactic
coplanar setup
non-coplanar setup
large volumes
small volumes
less no. of fields
more no. of fields
target volume delineation
precise delineation
positional accuracy ± 5 mm
positional accuracy ± 1 mm
Optical field, SSD indicator
Target volumes precisely
delineated
Marking on patient.s skin
Margins not necessary
Normal cells within the target
negligible
7. The first one to combine stereotactic
methodology with radiation therapy
was the Swedish neurosurgeon Lars
Leksell. Leksel performed the first
treatment in 1951, at the Karolinska
Institute, and called the new therapy
approach radiosurgery (RS)
Leksel continued his work and built
the first isotope radiation machine, in
1968, the Gamma knife
The stereotactic radiation therapy
with LINAC started in the early 1980s:
the Swedish physicist Larsson
proposed to use the LINAC instead Co
60 or protons (Larsson et al. 1974)
The first published reports on clinical
use of LINAC came from Buenos Aires
and Vicenza
In India AIIMS started SRS/SRT on
27th May 1997
8.
9. The stereotactic coordinates are a cartesian three-
dimensional coordinates system attached to the stereotactic
frame in a rigid relationship.
The origin of the stereotactic coordinates system is generally
in the center of the volume defined by the stereotactic frame:
The x and y axes correspond to the lateral and frontal side of
the frame and the z axis to the cranio-caudal direction
10. The main steps in the planning and delivering of stereotactic
irradiation treatment are:
1. Rigid application of the stereotactic frame to the patient
2. Imaging (CT, MRI, angiography) of the patient with the frame
and localizer attached to the frame
3. Treatment planning
4. Positioning of the patient for the stereotactic radiation
therapy
5. Delivery of the irradiation
6. Quality assurance
11. Stereotactic radiotherapy is based on the rigid connection of
the stereotactic frame to the patient during CT, MRI, and
angiography imaging
The stereotactic frame is the base for the fixation of the other
stereotactic elements (localizer and positioner) and for the
definition of the origin (point 0) of the stereotactic
coordinates.
During the whole treatment procedure, from the
performance of the stereotactic imaging to the delivery of the
irradiation treatment, the stereotactic frame must not be
removed from the patient.
In case of relocatable frames it must be assured that the
position of the patient is exactly the same relative to the
frame after reapplication of the relocatable frame
12. For the treatment of cranial
lesions by RS the frame
system is neurosurgically
fixed onto the patient’s skull
For SFR the head is fixed
non-invasively in a
relocatable thermoplastic
mask attached on the
stereotactic frame
13. There are different stereotactic frame systems
described in detail in the literature:
the BRW system
the CRW system
the Leksell system
the BrainLAB system
Each system is different with regard to
material of the stereotactic frame, design, and
connection with the localizer and positioner
and accuracy of repositioning
14. Imaging is used in stereotactic radiotherapy for:
(a) Localization and positioning;
(b) Definition of target volume and organs at risk; and
(c) Calculation and 3D representation of the isodose
distribution
MRI describes the anatomical structures of soft tissue with a
high accuracy
CT is important for the delineation of bone and soft tissue
Positron emission tomography (PET) and single photon
computed emission tomography (SPECT) offer additional
information about tumor extension and biology
Angiography is essential for the visualization of the arteriovenous malformations
15.
16. Most stereotactic systems use CT for localization
During the CT investigation the localizer is attached to the frame
The localizer is a box with CT-compatible fiducial markers on each
plane, which are visualized on CT on each scan; thus, the localizer
defines the link between the stereotactic coordinates and the imaging
coordinates, so that for any point in the imaging the 3D stereotactic
coordinates can be determined.
The stereotactic frame, the patient fixation system, and the localizer
form a fix unit.
17. Definition of Target Volume and Organs
at Risk
Definition of the Stereotactic Target
Point
Planning of the Radiation Technique
3D Dose Calculation
Dose Specification
Visualization of the Dose Distribution
18. The tumor-specific morphology, the growth pattern of the
tumor, and the anatomical relationship to the normal tissue
are essential parameters in defining the target volume.
Of major importance for the stereotactic radiation therapy is
the delineation of the organs at risk.
All the organs at risk which may get significant dose have to
be delineated
19. The target point is the point in the target volume that must be
positioned with exact precision in the isocenter of the LINAC.
The position of the target point can be defined interactively.
One or more target points can be defined.
In stereotactic planning programs the coordinates of the target
points are related in such way that the resulting dose distribution
meets the clinical requirements.
The planning system outputs the position of these points in
stereotactic coordinate.
Prior to therapy, these coordinates will be used to correctly
position the patient.
This is performed with a positioner, a device attached to the
stereotactic frame, which allows the connection of the stereotactic
coordinate system to the room coordinate system, where the
isocenter of the treatment device is defined
20.
21. The following parameters can be defined interactively in the
process of radiation planning:
the number and position of the target points;
the number of the radiation arcs and static fields and
their shape;
the position of the gantry and radiation table; and
the radiation dose in the target point for each field or
arc.
By combining these parameters the radiation plan is
developed.
22. The stereotactic radiation is characterized by a very steep
dose fall-off on the margin of the target volume.
The steep dose gradient is achieved by the use of appropriate
collimators and a multitude of radiation directions.
Stereotactic Collimators. Tertiary stereotactic collimators
for circular or oval target volumes are attached to the tray
holder of the LINAC. The diameter of the irradiated area is
defined by the size of the circular collimators and varies
usually between 1 and 35 mm
23. Micro-multileaf collimators have recently become available . The
beam shape can be selected by computer or by hand. In this way the
contours of the irradiation field can be adjusted individually to the
tumor shape. Micro-multileaf collimators, in comparison with the
traditional multi-leaf collimators, have the advantage of a decreased leaf
width and therefore optimized the resolution (between 1 and 3 mm).
24. Convergent Radiation Techniques. The radiation techniques are
in general isocentric and implemented by using a rotational
technique (using circular collimators or dynamic fields) or a
static-field technique; both can be combined with an isocentric
table rotation.
In the rotational technique usually five to ten radiation arcs are
used.
The size and the angle between the arcs are variable and are
responsible for the conformal isodose distribution.
The stereotactic irradiation with the micro-multileaf collimator is
done with multiple static irradiation fields (usually 6–12 fields)
25.
26. Most of the planning systems use CT images for the calculation of the
correct dose.
The planning software converts the Hounsfield number of the CT data
into an electron density.
Some planning software programs use MRI information only, by
considering homogenous soft tissue density for the calculation of the
dose.
Stereotactic radiation therapy can use simple dose-calculation
algorithms because no large-density inhomogeneities are in the brain.
27. The prescribed dose, Do, is the isodose surface which is
intended to completely encompass the PTV.
The minimal dose, Dmin, and the maximal dose, Dmax, in
the PTV have to be specified as well.
In the radiation plan, based on ICRU 50, different volumes
have to be considered as well: PTV, treated volume, as well as
the percentage of the target volume which will be irradiated
with a dose higher than Do.
The maximal dose in the area of risk structures has to be
defined as well.
28. The decision for the best
radiation plan is made after
evaluation of the dose
distribution based on the
isodose curves dose volume
histograms, conformity index,
or mathematical models for
the normal tissue complication
probability and tumor control
probability, similar to the
conventional 3D radiation.
The definitive decision for the
best treatment plan must be
made by the physician, using
clinical judgment, after the
rigorous evaluation of the dose
distribution in the complete
3D data base.
29. The positioning of the patient
on the LINAC is done by using a
stereotactic positioner .
This instrument allows to
project the coordinates of the
target point onto orthogonal
planes attached to the
stereotactic frame.
By the use of this projected
target point, the patient can be
positioned in a way that the
target point and the isocenter of
the LINAC overlap exactly.
The position of the isocenter
is indicated by a room-based
laser positioning system
30. After positioning the patient, the target
instrument (positioner) is removed and
the radiation can start.
The most important requirement for the
use of the isocentric LINAC for RS and
stereotactic radiation therapy is the
accuracy of the isocenter: under ideal
conditions the axis of the gantry
rotation, the central axis of the beams
and the rotation axis of the rotation
table convert in one point, the isocenter
In general, it is acceptable that the three
axes – gantry rotation axis, central axis,
and table rotation axis – meet in a
sphere which coincides with the
isocenter and has a diameter of
approximately 1 mm.
They must be constantly controlled
during regular quality-control
procedures.
31. The essential requirement for the clinical use of the LINAC is
quality control based on well-defined protocols
The quality-assurance protocols address the precision of the target
volume and target point with CT, MRI, PET and angiography, the
dosimetry, the planning of the irradiation, and especially with the
calibration of the absolute dose and of the dose application.
For the quality-assurance assessment proper phantoms and
specialized dosimetric instruments must be available.
32. Tumor volume — As the size of the target lesion for SRS
increases, incidental irradiation to the surrounding normal tissue
also increases. This may be important since a much higher dose of
irradiation is administered with SRS compared to fractionated RT.
SRS was not recommended for lesions >4 cm because adequate
control could not be achieved without an unacceptable level of
radiation toxicity to surrounding normal tissue.
Proximity to cranial nerves — The proximity of a target to
cranial nerves can cause radiation neurotoxicity, despite the steep
decrease in dose outside the intended target Fractionated RT
should be considered when SRS may jeopardize cranial nerve
function.
Cranial nerves II and VIII are more sensitive to radiation injury
than the other cranial nerves. SRS is generally avoided if the
maximal dose delivered to the optic nerve exceeds 10 Gy.
Location of the lesion — The risk of developing permanent
damage following SRS varies dramatically with the location of the
lesion in the brain. Fractionated RT is often preferred to SRS for
the treatment of lesions in the deep gray matter or the brainstem
48. Gamma Knife- In 1999, the model C
version of the gamma knife was
introduced with the option to use
robotic positioning to set treatment
coordinates. This expedites execution
of multiple-isocenter treatment plans.
The model 4-C, introduced in 2005,
was equipped with enhancements
designed to improve workflow,
increase accuracy, and provide
integrated imaging capabilities. The
Perfexion model introduced in 2006
uses a larger patient aperture and
internally mounted secondary
collimators
RGS-A radiosurgery device called
the rotating gamma system (RGS)
was developed in China. The rotating
gamma system employs 30 cobalt-60
radiation sources in a revolving
hemispherical shell. The secondary
collimator is a coaxial hemispheric
shell with six groups of five different
collimators to produce spherical
treatment volumes of different
diameter
49. Proton Radiosurgery
The chief advantage of charged proton
radiosurgery is that the beams stop at
a depth related to the beam's energy.
The lack of an exit dose and the sharp
beam profile of protons allow target
irradiation with lower integral doses
than are delivered with photon (Linac
x-ray or cobalt-60 gamma) irradiation.
An unmodified proton beam
irradiation deposits increased energy
in the last couple of millimeters of the
path length.
This area of increased ionization,
where cell killing is even higher
because of an increased radiobiologic
effect, is termed the Bragg peak or
Bragg-Gray peak
The first treatment of a malignant
tumor by irradiation with a proton
beam Bragg peak was carried out in
1957 and followed by functional
neurosurgery for advanced
Parkinson's disease in 1958.
50. LINAC Radiosurgery
Many LINAC-based systems
such as Xknife, Novalis, the
Peacock System, and
Cyberknife are commercially
available
The Cyberknife combines a
miniaturized LINAC mounted
on an industrial robot with a
system for target tracking and
beam realignment
Cyberknife plans use multiple
fixed-beam positions and
multiple isocenters.
Before the radiation is
delivered from any beam
position, the target position is
tracked using an integrated xray image processing system,
consisting of two orthogonal
diagnostic x-ray cameras and an
optical tracking system.
51. Tomotherapy rapidly rotates the beam around the patient
(and inside the housing of the unit), thus allowing the beam
to enter the patient from many different angles in succession
52. The combination of the stereotactic radiation therapy of the
LINAC with IMRT opens new perspectives for those entities
where exact conformal and high doses must be delivered
The first analysis of RS with dynamic field shaping technique
in comparison with conformal static beams and multi-isocentric
non-coplanar circular arcs showed that the dynamic-arc
technique combines simple planning, short treatment times,
dose homogeneity within the target, and rapid dose falloff in
normal tissue
A new method under development is robot-assisted RS. The
LINAC in this device is mounted on a robotic arm with 6 degrees
of freedom
In past years progress has been made in the field of frameless
stereotactic radiation therapy.
For neuronavigation internal and external markers are used
for positioning the patient with stereoscopic video cameras
and X-ray machines
53. AIIMS, New Delhi
Apollo Hospitals India
Yashoda Hospital Hyderabad
HCG group of hospitals Bangalore
Adyar Cancer Institute
Dharamshila Hospital Delhi
And many more.