Transcript
Radiology accidents and crisis21/11/2012
Dr Belal El HawwariConsultant Radiation Clinical Oncologist
The Hashemite Kingdom of Jordan
• Population• 6,508,271 (July 2011 est.)
• Age structure• 0-14 years:• 35.3% (male 1,180,595/female 1,114,533)
15-64 years:
• 59.9% (male 1,977,075/female 1,921,504)
65 years and over• : 4.8% (male 153,918/female 160,646) (2011 est.)
Trend of cancer in Jordan, 1980-2010
Ten most common cancers among Jordanian Males, 2010
Rank Cancer No %
1Colorectal 332 14.2
2Lung 311 13.3
3Prostate 218 9.4
4U.Bladder 186 8
5 Leukemia 127 5.5
6 Non- Hodgkin's Lymphoma 120 5.2
7Brain & CNS 106 4.5
8Stomach
90 3.9
9Larynx 74 3.2
10Hodgkin's Disease 65 2,8
Ten most common cancers among Jordanian Females , 2010
Rank Cancer No %
1 Breast 941 37.4
2 Colorectal 226 9.0
3 Thyroid 136 5.4
4Non-Hodgkin lymphoma 130 5.2
5 Uterus 113 4.5
6 Leukemia 91 3.6
7 Ovary 84 3.3
8 Lung 68 2.7
9 Hodgkin disease 67 2.7
10 Stomach 62 2.5
Top ten cancers among Jordanian both sexes, 2010
Annual incidence and mortality of the most common cancers
Stewart, B. World Cancer Report. IARC Press 2003. 2003 International Agency for Research on Cancer.
2 5
The most prevalent cancers worldwide in 2000, expressed as
thousands of persons dx with ca within the previous 5 yrs
Stewart, B. World Cancer Report. IARC Press 2003. 2003 International Agency for Research on Cancer.
46
Age-Standardized Incidence Rate per (100,000 )population for Male cancers ( all sites) , Jordan compared with other countries .
USA ( White)
UK,Scotland
New zealand
Canada
Norway
Poland
Malysia
Jordan
Lebanon
Tunisia
Kuwait
Qatar
Bahrain
Egypt-Ghariah
0 50 100 150 200 250 300 350 400 450
371.7
323.7
345.7
330.5
328
201
134.4
132.1
179
113
125.1
165.5
162.2
161.7
Age-Standardized Incidence Rate per ( 100,000 )population for Female cancers ( all sites) , Jordan compared with other
countries.
USA ( White)
UK,Scotland
New zealand
Canada
Norway
Poland
Malysia
Jordan
Lebanon
Tunisia
Kuwait
Qatar
Bahrain
Egypt-Ghariah
0 50 100 150 200 250 300
284.5
268.5
274.8
257.3
271
107.3
154.1
143.1
180.3
89
136.6
164.5
150
120.8
Cell Kill by Radiation-How does radiation kill cells?
-Radiation-induced DNA damage
IDS 502
What is radiation?• Radiation is electromagnetic waves, just like light.
Radiation is made of photons (packets of energy) each type of radiation has its own energy (which is closely related to frequency).
• X-rays and -rays are part of the radiation spectrum that includes visible light. They posses high frequency.
Light photon
X-ray photon
Gamma photon
X-ray Production• Electrons emit ‘characteristic’ x-ray when they
go from a high atomic energy level to a lower energy level.
E1
E2
Nucleus
X-rayE = E1 – E2
electron
Continue...
• X-rays can also be generated by suddenly stopping fast electrons with a target, bremsstahlung x-rays.
• -rays are emitted from the nucleus of a radioactive element.
• When protons descend from a high energy level to a lower energy level (inside the nucleus) they emit -rays. Diagnostic X-ray
machines and therapeutic radiology machines.
Before discussing the damage done to cells from radiation let’s look at how radiation interacts with material
Photoelectric effect
+
-
Result: An energetic electron and a positive ion.
Compton Scattering
e-
EE
e-
Result: An energetic electron, a positive ion, and a lower energy photon.
Pair Production
e-
e+
Result: An energetic electron and a positron
?
Nucleus
• Any of the above interactions may happen directly with the DNA molecule or, most probably, with water leading to the creation of free radicals.
Free Radicals???
• 2/3 of x-ray damage to mammalian cells is due to the hydroxy radical (the free radical produced after radiation interacts with water).
OHOHOHOH
eOHOH
322
22
H2O+: An ion radicalOH: A free radical.
They are molecules or atoms carrying an unpaired e- in their outer orbit. They posses high
degree of chemical reactivity.
Radiation
Fast electrons Ion radicals
Free radicals
Chemical changes:Broken bonds
Biological effects
Radiation-Induced DNA Damage
Single-basedam age
"O f no b io lo g ica l co nse q ue n ce"
Single-stranddam age
N O b io lo g ica l co n s.
Carcinogenesis induction
-T ra n s lo c a tio n-D ele tio n
Non-lethal DNA dam age
Translocation...
Interchange of genetic material between two nearby chromosomes.
Associated with several human malignancies, e.g. lymphomas and leukemias.
A
A
A
A
B
B
B
B
Graphs from this slide onward are taken from the book Radiobiology for the Radiologist, by Eric Hall.
Deletion...Break occurs in the same arm in an interphase chromosome. Damage repair may lead to deletion of parts of the chromosome.
Carcinogenesis may result if the deleted part contains a suppressor gene.
More than 20 solid tumors: Breast and prostatic adeno-carcinoma, lung small cell carcinoma, ...
Dicentric
P re -re p lica tio n D N A
Ring
P re -re p lica tio n D N A
Anaphase bridge
P o s t-re p lica tio n D N A
Letha l D NA dam age
Dicentric...
Ring...
Anaphase bridge...
Normal anaphase
Radiation-induced apoptosis
• Radiation increases death by apoptosis.• If a tumor responds rapidly to a relatively
low dose of radiation, it means that apoptosis is involved.
• 50% to 60% of a lymphoma die by apoptosis in the first 3 hours of irradiation.
• Radiation induced apoptosis is p53-dependent.
Other Radiation-induced damages
• Changes in morphology “Giant cells”. Giant cells are ‘dead-cells’ in the waiting.
• Division inhibition A cancer cell is “as good as dead” if it doesn’t reproduce.
We started with how does radiation kill cells?BUT more questions arise.
? Specialized cells are less sensitive to radiation, it takes more radiation dose to kill them. Why?
? Radiation is delivered in small fractions. Everyday a small dose is given until the entire dose has been delivered. What are the biological considerations for fractionations?
? The normal cells surrounding the tumor gets irradiated as well. How does these cells repair the damage incurred?
Makes good future talks…
Linear accelerator - electron and X-ray beams
Rush University Medical Center, Chicago, IL
Courtesy Of Dr. Shada Ramahi, KHCC
Simulator
Rush University Medical Center, Chicago, IL
Courtesy Of Dr. Shada Ramahi, KHCC
Co60 machine - ray beam
Three dimensional conformal radiotherapy - ADAC’s Pinnacle planning system
Three dimensional conformal radiotherapy - ADAC’s Pinnacle planning system
Room’s eye view (REV)
3D rendering, with a transverse cut-plane.
Prostate Implant
Clinical ...5. Interstitial and intracavitary Implants -> Brachytherapy procedures
Brachytherapy: Treatment of cancer through implanting radioactive elements (I125,Ir192, Cs226) inside the body or in a cavity inside the body in close proximity to the tumor.
Recurrent Glioma
Base of tongue Head and neck
Brachytherapy implants
Radiation Accidents:
The causes and the prevention
Panama, June 2001Panama National Institute of Oncology
IAEA report:
1. Misuse of the treatment planning system in entering blocks
2. Computer printout appeared normal
3. No manual verification was performed
Result?28 patients overexposed to radiation, 20%-100% overdose.
8 patients died. 5 deaths related directly to overexposure, 1 related to cancer, 2 not enough information.
20 survivals: developed persistent bloody diarrhoea, necrosis (tissue death), ulceration and anaemia. 3/4 expected to develop serious, ultimately fatal, complications.
IAEA recommendations:
Follow written quality assurance procedures, which include:
Ensuring that the procedures require manual checks of the
doses to the prescription points as calculated by computer, for each individual patient, before the first treatment;
Performing verification measurements using a phantom in exceptional cases of complicated treatments, for which manual calculations may not be practicable.
http://www.iaea.org/worldatom/Press/P_release/2001/panam_adv_info2.shtml
Costa Rica, August 1996San Juan de Dios Hospital, San José
NCRP report:
1. Miscalibration of Co60 unit, by a recent biology grad, with no training in Medical Physics.
2. Poor quality control protocols.
Result?
Minimum of 60% radiation overexposure to patients, who developed severe radiation complications.
http://www.acmp.org/newsletters/newsletter_apr99/NCRP.html
United States, November 92Indiana regional Cancer Center, Pennsylvania
1. High dose rate (HDR) treatment for an elderly patient.
2. Cable-head with Ir192 source broke inside the patient.
3. Therapist did not perform patient survey at the end of the treatment.
4. Therapist completely ignored radiation signals indicating the source is still ‘outside’. And sent the elderly patient to the nursing home.
Result?Patient received lethal dose and died.
Ambulance workers, nurses and other residents at the center received various amounts of radiation dose.
Brazil, September 1987Cancer Clinic, Goiania
Worst Radiation Accident after Chernobyl
3 doctors owned a private downtown radiation therapy clinic...when they left [in 1985], they simply abandoned the radiotherapy machine.
2 yrs later, ‘87, abandoned equipment found. A lead canister containing 1400 curies of cesium-137, 20 g of cesium chloride was opened.
The cesium was a "luminous blue powder”. Children and adults rubbed it on their bodies. 6 yr. old Leide das Neves Ferreira "rubbed the powder on her body so that she glowed and sparkled." She reportedly received 5 to 6 times the lethal dose [of radiation] for adults.
Brazil, September 1987Cancer Clinic, Goiania
Worst Radiation Accident after Chernobyl
The cesium was parceled out to friends and family.
On September 28, a week later, "Devair Ferreira went to the Goiania public clinic where a health care worker correctly diagnosed radiation illness and alerted authorities.”
Brazil, September 1987Cancer Clinic, Goiania
Worst Radiation Accident after Chernobyl
Brazilian Nuclear Energy Commission dispatched a team equipped to handle a radiation accident. They found:
244 person contaminated, 54 seriously enough to be hospitalized. 34 were treated and released. The 10 sickest patients were airlifted to the Navy hospital, Dias, in Rio
Brazilian government requested help from the International Atomic Energy Commission (IAEC). IAEC found:
1. The patients themselves were radioactive
2. The 20 most seriously irradiated had received doses ranging from 100 to 800 rads.
Brazil, September 1987Cancer Clinic, Goiania
Worst Radiation Accident after Chernobyl
IAEC report, conti.:
19 of the 20 had radiation-induced skin burns.
!!Money, furniture, homes, businesses and soil were contaminated.
What could not be decontaminated was collected or dismantled andplaced in concrete lined drums for disposal as nuclear waste.
Within a week, 4 patients had died, overwhelmed by pneumonia, blood poisoning and hemorrhaging
Several suffered radiation poisoning, nausea, vomiting, headaches, diarrhea
Brazil, September 1987Cancer Clinic, Goiania
CAUSES:
1. The lack of regulation surrounding the use and abandonment of nuclear materials in Brazil, by both national and international regulation committees.
2. Lack of adequate preparation for such a disaster -> as a result of lack of regulations.
Sun, Marjorie. Radiation Accident Grips Goiania. Science. 238; p1028-1031
International Newsletter on Physics Education, Number 35, November 1997
What have we learned?
1. The need for regulations governing all aspects of handling radioisotopes and radiation-producing equipment.
2. The need for a trained medical physicist to calibrate and assure the performance of the machines, and to correctly deliver treatment.
3. Physicist, doctors and therapists should follow regulations.
Brazil, December 1983Centro Médico in Juarez
Vicente Sotelo Alardin was sent to haul away some unused material from a warehouse operated by the Centro Médico. Among the junk was a 20-year-old Picker 3000 (Co60) radiotherapy machine purchased from an American clinic.
Sotelo stole an unmarked capsule, which he later opened to spill 6,010 small, silvery pellets of highly radioactive Co60.
Each pellet in the capsule was capable of producing a dose of 25 rads per hour.
Brazil, December 1983Centro Médico in Juarez
Some of the pellets rolled into the truck bed and into the road, others remaind inside the capsule which Sotelo sold as scrap to a junkyard.
One shipment of contaminated metals, became metal table legs. It was shipped to a restaurant-table distributor in the U.S.
From the junkyard, an estimated 300 curies of radioactive cobalt found their way to the steel and metal industry.
The other shipment of produced steel rods used in the reinforcement of concrete building projects.
Brazil, December 1983Centro Médico in Juarez
About 600 tons of the contaminated steel were shipped to the U.S. from December 1983 to January 1984
Later in the month, a different truck--this one transporting table legs--set off a radiation monitor in an Illinois State Police officer's patrol car.
On January 17, 1984, a radiation alarm went off when a delivery truck took a wrong turn near the gates of Los Alamos National Laboratory in New Mexico
Brazil, December 1983Centro Médico in Juarez
Authorities eventually traced the radioactivity to the Juarez junkyard, which was closed.
Brazil health officials also ordered the demolition of 109 houses built with reinforcing rods containing the radioactive material.
It took two months track down the contaminated table legs and steel rods at sites in Canada, Mexico, and 23 different U.S. states, including Texas.
Because pellets have fallen anywhere on the roads between Chihuahua and Juarez, officials flew over the area in a special reconnaissance helicopter. They found 22 radioactive sites and actually dug eight pellets out of the highway asphalt
Brazil, December 1983Centro Médico in Juarez
In the years since, one worker at the junkyard has died from a rare bone cancer. Others have suffered sterility, skin discoloration, and other disorders.
Hundreds of Juarez residents have been tested for radiation poisoning, and at least a dozen have shown chromosome damage.
Brazil, September 1987 Centro Médico, Juarez
CAUSES:
1. Lack of regulation surrounding purchasing and shipping radioactive sources from outside the country.
2. Lack of regulations on storing nuclear materials in Brazil, by both national and international regulation committees.
http://www.window.state.tx.us/border/ch09/cobalto.html
Lack of regulation:
My father was a radiologist and assured me that radiation was NOT hazardous
KEEP IN MIND!Radiation DOES NOT create monsters, it merely increases the incidents of the same mutations that occur spontaneously in a given population.
Radiation Induced Second Malignancy Following Treatment for Breast Cancer
Case PresentationBelal El Hawwari 2006
Case
• 66 yr female• June’04- severe cough which resolved after 2-
3/52 without medication• Sept/Oct’04- right upper chest abn feeling
with resolution• Dec ‘04- cough and CXR January’05 RUZ Abn
with widened mediastinum• CT chest/abdo- RUZ lesion with mediastinal
Lymphadenopathy
Case contd
• CT guided biopsy- small cell carcinoma• PMHx- • 1985- R infiltrating ductal adenocarcinoma
LIQ breast, 35x25x25mm, extending macro to within 0.4cm from skin surface, micro extending into adipose tissue w/ early invasion of muscle and perineural invasion.
• Treated with WLE, CMF chemotx and 50Gy in 25# to breast, axilla, internal mammary.
Case contd
• PMHx contd-• osteopaenia/OA, appendicectomy,
tonsillectomy,hysterectomy and R salpingectomy for cysts in 1982, menopause during chemo at age 45.
• Non smoker• IMPRESSION- Radiation induced small cell ca
• Staging- PET- inrc uptake RUL with evidence of nodal disease. Consistent with stage IIIA.
Case contd
Mx-• Carboplatin and Etoposide with post chemo
radiotx of 45 Gy in 25# to mediastinum.• Decision for Radiotx and field made after
thorough review of imaging and previous radiotx fields. Acceptance of some overlap in treatment of lung lesion and small overlap in skin overlying central chest.
Radiation Induced Malignancies following breast radiotx
• British Journal of Cancer 2004-• retospective study using Thames Cancer
Registry database from 1960-2000. Compared incidence of 2nd primary cancers in women who received radiotx with those who did not receive radiotx (pts who received chemotx were excluded)
• 62,782 women in total (33,763 received post op radiotx)
Rad induced 2nd malignancy contd
• 5217 2nd primary tumours detected.• 2857 at one of primary sites of interest of study
(lung, colon, oesophagus,thyroid, mal melanoma, myeloid leukaemia, breast)
• elevated RR in lung ca at >10 yrs of 1.49-1.62 (95% CI 1.05-2.54)
• elevated RR myeloid leukaemia at 1-5 yrs 2.99 (95% CI 1.13-9.33)
• elevated RR in oesophageal ca at >15 yrs of 2.19 (95%CI 1.10-4.62)
Rad induced 2nd Malignancy contd
• Elevated RR in Breast ca in both grps yet at >5 yrs excess in RT group with RR 1.34 (95% CI 1.10-1.63)
• no sig differences b/w groups for colon, thyroid, malignant melanoma
• They concluded that benefits of radiotx still outweigh risks in appropriate pts, yet aim should be to minimise radiation dose to surrounding tissues or volume of exposed tissues
• Also, other factors may contribute such as genetic predisposition, e’ment exposures, reproductive factors, incr medical surveillance.
Proposed Pathogenesis• International Journal of Cancer 2003• study performed at Center for Radiological
Research in NYC• used immortalised human breast epithelial cell line
(MCF 10F) in combination with oestrogen and radiation as model- step wise neoplastic transformation of cell line
• identified 3 regions on chromosone 11- high incidence of loss of heterozygosity/microsatellite instability- potential role for carcinogenesis.
Proposed Pathogenesis contd
• Same centre published another study using same cell line in Carcinogenesis 2001
• high rate of allele imbalance at regions on chromosome 6 and 17- suggests presence and inactivation of one or more tumour suppressor genes in these regions.
Proposed Pathogenesis contd• Oncogene 2003- Study at Dept of Molecular
and Cellular Pathology UK• radiation induced bystander effects from
cells in contact with irradiated cells (intercellular signalling, cytokine production, free radical generation)
• radiation induced genomic instability in descendents of irradiated cells
Radiation and Carcinogenesis• Paper Published in Medical and Paediatric
Oncology 2001• reviewed 14 cohort studies around world• important points- linearity in dose response;
risk inversely related to age at exposure; minimal effect of fractionating dose on risk; decrease in risk at highest dose levels related to killing rather than transformation.
Sarcoma
• Criteria for diagnosis of Radiation Induced Sarcoma- prior Hx of radiotx; latency of several years; sarcoma in previously irradiated field or adjacent tissues; histologic confirmation of sarcoma;
• Paper in Cancer Control 1998 (literature r/v)• Radiation Induced Sarcoma in 0.03%- 0.2% of
patients following treatment for breast ca• average latency >10 yrs and likely correlates
with dose and technique of radiation Tx
Sarcoma Contd• Of note- improvements in radiotx techniques
last 20 yrs with improved dose distribution and limitation of lymphatic field irradiation- likely to translate into reduction of future risk
• important to emphasise that risk of RIS is no greater than risk of operative death thus risk of 2nd malignancies should not influence decision to tx pt with radiotx.
Sarcoma contd• UK Dept of Clinical Radiology in Dundee- Reviewed
post radiation sarcomas in 63 cases- Published in Clinical Radiology 2001
• did include patients who were treated for primary breast cancer in addition to lymphoma and head and neck.
• Mean age 52.8 yrs and mainly osteosarcomas/MFH• mean radiation dose 50.1 Gy with mean latency of
15.5 yrs.• They concluded imaging findings not
pathognomonic, yet realising latency may help to suggest diagnosis.
Sarcoma contd• Large single institution retrospective cohort study
from Institut Curie in Paris and published in Cancer in Sept, 2005
• reviewed records of 16,705 patients with breast cancer where 13,472 had MV radiotx and 3233 without between 1981-1997. Median doses 50-55 Gy in 25-27 # +/- boost 16-26 Gy.
• RT pts treated via high energy photons of a cobolt unit and/or linear accelerator
• after mastectomy- electrons to chest wall ? No• some pts ? No - axillary and/or internal mamm RT
Sarcoma contd• Results- 35 pts sarcoma with 27/35 fulfilling
criteria for RIS• mean f/u 9.3 yrs (1-22.4 yrs)• latency- 3-20.3 yrs• 13 breast, 5 chest wall, 3 sternum, 2 SC, 1
scapula, 3 axilla• 13 angiosarcomas, 3 osteosarcomas, 5 undiff
sarcomas, 1 MFH, 2 leiomyomyosarcomas, 1 fibrosarcoma, 1 rhabdomyosarcoma, 1 myosarcoma
Sarcoma contd• Cumulative RIS incidence- 0.07% +/- 0.02 at 5yrs;
0.27% +/- 0.05 at 10 yrs; 0.48 % +/- 0.11 at 15 yrs.• Incidence ratio for irradiated pts- 10.2 (95%CI 9.03-
11.59) and for non irradiated pts- 1.3 (95% CI 0.3-3.6)
• limited no of patients has not allowed study of different risk factors.
• They concluded shorter latency periods related to MV rather than orthovoltage and that careful long term f/u is needed for early detection and efficacious tx of these malignancies.
Oesophageal Carcinoma• Retrospective analysis published in American
Journal of Epidemiology 2005• reviewed 1973-2000 data from Population based
surveillance, epidemiology,end results program for patients who received post mastectomy radiotx
• estimated relative risks- RR 2.83 (95% CI 1.35-5.92) for SCC oesophageal ca at 5-9yrs and RR 2.17 (95% CI 1.67-4.02) at >10 yrs
• no increase risk in adenocarcinoma (? Related to lower 1/3rd oesophagus not being treated)
• stated that risk following radiotx post WLE yet to be determined
Oesophageal carcinoma contd• An Australian group at Princess Alexandra
Hospital QLD- retrospective cohort using database of >220,000 women with primary breast cancer 1973-1993
• published in Radiotherapy and Oncology 2002
• 12 patients identified with second primary oesphageal ca and 9/12 fitted criteria for radiation induced malignancy
• all patients had post mastectomy radiotx
Oesophageal carcinoma contd• Mean age at radiotx- 54 yrs• mean age at diagnosis of oesophageal ca- 72
yrs• all SCC; RR 5.42 (95% CI 2.33-10.68) • radiotx techniques were combinations of ant
and post fields with varying boosts• estimated oesophageal dose- 35-40 Gy MV in
20#
Oesophageal Carcinoma contd• They concluded main associated factor
identified was previous supraclavicular nodal irradiation as oesophagus is likely to be irradiated if direct anterior fields are used.
• Risks assoc with current practices will become clear with time and further analysis.
Oesophageal carcinoma contd
• Population Based retrospective cohort study using population based US cancer registries
• Published in Annals of Internal Medicine 1998
• 220,806 women with primary breast ca diagnosed b/w 1973-1993
• RR oesophageal SCC 5.42 (95% CI 2.33-10.68) >10 yrs post radiotx
Oesophageal Carcinoma contd• They also found RR for oesophageal
adenocarcinoma 4.22 (95% CI 0.47-15.25) >10 yrs post radiotx
• no increased RR in those who did not receive radiotx
• they concluded that future studies required to determine the role of other risk factors in oesophageal carcinogenesis such as cigarette smoking, ETOH, BMI etc. and their interaction with radiotx.
Impact of 3D- CRT and IMRT
• May, 2003 International Journal of Radiation Oncology, Biology, Physics (Center for Radiological Reasearch, NY)
• some animal and human data suggest decrease in 2nd malignancies at higher doses due to cell killing
• excess sarcomas in heavily irradiated in- field tissues and incidence of carcinomas, s’times in sites remote from tx fields
• 3D-CRT- incr. in dose to target tissue with reduction of normal tissue receiving dose compared to prior conventional radiotx
IMRT contd
• Paper suggests, move to IMRT involves more fields and as a consequence a greater volume of normal tissue is exposed to lower doses.
• Potential for increase in no of 2nd malignancies.
• They predict increase of 0.75% for patients surviving >10 yrs.
Conclusions• Radiation Induced Second Malignancies are a
real risk, yet low risk• Risk should not interfere with decision to
treat with radiotx in appropriate patients, yet care should be taken to reduce radiation exposure to normal tissues.
• Risk likened to risk of operative death• Inclusion in differential in those patients who
have been treated with radiotx many years prior with new second malignancy
Conclusion contd
• Future studies are required to determine risk and occurrence in patients treated with more recent practices
• IMRT may potentially increase risk
Calculation of the Shielding Materials for Mega-Voltage X-Ray Linear Accelerators
Introduction
• Before the installation of a new mega-voltage x-ray linear accelerator the room should be shielded with different types of materials. The responsibility of the calculation for this shielding is one of the physicist duties. Many theories talked about methods to consider the scattered radiation and neutrons contamination.
Objective
• The purpose of this paper is to introduce a method to calculate the shielding for a new mega voltage linear accelerators taking into consideration scattered radiation and neutron contamination. In addition we present a protocol to check the amount radiation in the areas around and above the accelerator room and the leakage around the accelerator inside the room.
Method • ADD: Average Daily Dose (Gy)• Pno.: Patient number per day for conformal and
conventional radiation therapy.• PWL: patient work load.• TPW: total primary work load. • Total Pno: number of patients of conformal
conventional.• U.F.: using factor of the accelerator.• Occ.F.: Occupancy factor.• L.F.: Leakage factor
100cm concert
450 cm
100 cm
Beam 1Beam 2Beam 3Beam 4
175 cm 150 cm
130 cm
Use factor for barrier (U) primary (U)leakage
G. down Floor 1 1
G.Up Ceiling 0.5 1
G. Lat Wall 0.25 1
Occupancy factor Occupancy .Factor (T)
Full Occupancy (offices, nurses station, ----) 1
Partial Occupancy (corridors, rest rooms, parking) 0.25
Waiting room, toilets. 0.07
TVL
cobalt60 6MeV 10MeV 15MeV
Concrete (cm) 28 32 38 41
Lead (cm) 4.2 4.7 5 5
Ilmenite (cm) 14 20 23 23
Steel (cm) 9 9.9 9.7-10.5 10.7
Equations
• Physics QA =20% ×ADD × (Total Pno./daiy) × (days /week) × (weeks /year) • (A)Primary=1000 ×TPW × (d0/d) 2 ×U.F. ×Occ.F × (1/Dose equivalent limit (HL) • (B) Secondary=1000 ×TPW (d0/d) 2 ×U.F.(=1) ×Occ.F ×L.F. × (1/Dose equivalent limit (HL) • No.of (TVL) for primary shielding=log10 (A)• Thickness of primary shielding =No.of (TVL) for primary shielding × material (TVL) thickness • No.of (TVL) for secondary shielding=log10 (B) • Thickness of secondary shielding =No.of (TVL) for secondary shielding ×
material (TVL) thickness
r)(weeks/yea)(Days/week.PnoADDPWL
%20PWLTPW
Conclusion
• This study yield to measure accurate values for different materials thickness that can be used to avoid the radiation hazarded for both radiation workers and non radiation workers. However the amount of radiation checking protocol guarantee the safety of the stuff working around the medical radiation facilities
Thank you
top related