HDR 1000 Well Chamber
Contents
1. 0 999 1 271 x 108 7 05 Ci 4o2 Procedures for Calibration and Measurement of LDR Brachytherapy Sources 1 Place the HDR 1000 Plus Brachytherapy Well Chamber in the same room the measurements are to be done in for at least 30 minutes to equilibrate to ambient temperature and pressure Connect the HDR 1000 Plus chamber to a suitable electrometer and supply 300 V bias voltage Allow system to stabilize for at least 10 minutes Insert the appropriate source holder for the brachytherapy source to be measured into the cham ber Align the black dot on the well insert with the punch mark on the body of the chamber see Figure 2 in HDR iridium procedure Using appropriate safety procedures for brachytherapy sources insert the source into the source tube Measure the LDR brachytherapy source for a mini mum of 20 seconds for current measurements or for a reproducible set time for charge measurements Read and record the measured current or charge Use correction factor for temperature pressure elec trometer correction factor electrometer must be calibrated and isotope calibration factor to calculate the activity of the source The following equation can be used B R F E C Refer to step 9 on the previous page 3 Procedures for Specific Source Holders 70020 Source Holder for Cesium Manual Afterloading 5mm opening For Cs calibrations verify the plastic spacer inside the source holder insert is at the bo2. 0 998 5 1 0 mGym Y 24 Calibration of HDR 1000 Plus As is standard practice for other ion chambers it is recommended that the HDR 1000 Plus be calibrated every 2 years This calibration should be performed by an Ac credited Dosimetry Calibration Laboratory Standard Imaging offers calibrations from the University of Wiscon sin Accredited Dosimetry Calibration Laboratory You need only one purchase order to cover calibrations ship ping and handling and service Standard Imaging hand carries all instruments to and from the ADCL Constancy Check of HDR 1000 Plus Regular constancy checks should be performed by using a procedure such as the following The source holding insert may be removed to allow the stability of the HDR 1000 Plus to be checked by means of a constancy check source e g using a low dose rate Cs brachytherapy source with the insert in place or a Sr beta source Alternatively the stability can be monitored with the use of an external Co beam This value should be obtained upon receipt of the chamber and monitored for consistency thereafter Either place the chamber in the Co beam at a known distance with a standard field such as 10 cm x 10 cm or place the Sr or Cs source in a reproduc ible position and take a current reading A graph of the response corrected for decay should remain within 0 5 295 Maintenance Exterior cleaning of the device can be done with a soft brush
3. 4000 from Standard Imaging and apply 300 V bias voltage Allow the system to stabilize for at least 10 min 3 Connect a catheter such as the endobronchial French 6 blue catheter to HDR irradiator 4 Align the black dot on the well insert with the punch mark on the body of the chamber See Figure 2 5 Insert catheter end to bottom of chamber source holding insert The dead space at the catheter end must be known so that the center of the Ir source can be positioned at the most sensitive position of the chamber See Figure 1 for a typical axial response curve for the HDR 1000 Plus Normally the most sensitive spot for the HDR 1000 Plus chamber is between 50 and 53 mm from the bottom of the source tube This point is provided in the calibration report for each chamber The chamber sensitivity decreases by approximately 0 1 when the source is moved up or down by 5 mm from that position 6 Secure the catheter with the knurled catheter holding device 10 Figure 2 7 After performing all manufacturer recommended safety procedures for the HDR after loading device run the Ir source to the radiation sensitive axial point of the chamber for a minimum of 20 sec for current measurement or for a reproducible set time 1 min for charge measurement If the charge mode 1s used and the charge is accumulated while the source is in transit account for the transit time error of the source by making the standard timer end effect m
4. Imaging s examination Transportation charges are the buyer s responsibility STANDARD IM AGING INC SHALL NOT BE OTHERWISE LIABLE FOR ANY DAM AGES INCLUDING BUT NOT LIMITED TO INCIDENTAL DAM AGES CONSEQUENTIAL DAMAGES OR SPECIAL DAMAGES THIS WARRANTY IS IN LIEU OF ALL OTHER WARRANTIES EXPRESSED OR IMPLIED WHETHER STATUTORY OR OTHER WISE INCLUDING ANY IMPLIED WARRANTY OF FITNESS FOR A PARTICULAR PURPOSE IN NO EVENT SHALL STANDARD IM AGING INC BE LIABLE FOR ANY INCIDENTAL OR CONSEQUEN TIAL DAMAGES RESULTING FROM THE USE MISUSE OR ABUSE OF THE PRODUCT OR CAUSED BY ANY DEFECT FAILURE OR MALFUNCTION OF THE PRODUCT WHETHER A CLAIM OF SUCH DAMAGE IS BASED UPON THE WARRANTY CONTRACT NEGLI GENCE OR OTHERWISE Distributed by SeeDOS Ltd For further information or a quotation please Doc No 80026 06 05 09 02 30 pgs
5. for a user defined amount of time An explanation of how to perform sample measure ments is explained very well in the reference Verifi cation of manufacturer supplied I and Pd air kerma strengths Mellenberg and Kline Medical Physics 22 9 1495 1497 1995 A thorough review of this article is recommended Correction factors for varying numbers of seeds need to be determined for either iodine or palladium depending on which isotope is used This is due to the self absorption of the seeds in the source holder Once determined these factors should remain con stant Thereafter a set number of seeds i e 25 50 100 can be measured References 1 Verification of manufacturer supplied Land Pd air kerma strengths Mellenberg amp Kline Medical Physics 22 9 1495 1497 1995 2 Comprehensive QA for radiation oncology Report of AAPM Radiation Therapy Committee Task Group 40 Medical Physics 21 4 581 618 1994 ee 70023 Source Holder for RAPID Strand Iodine Seeds The source holder for RAPID Strand Iodine Seeds is designed for QA measurements of the RAPID Strand 6711 Iodine Seeds prior to use This insert works with the Standard Imaging HDR 1000 Plus Brachytherapy Well Chamber The RAPID Strand Source Holder is constructed to simultaneously measure five seeds at one end of the RAPID Strand while the RAPID Strand remains in the spacing jig The spacing jig is then inverted in the source holder an
6. Plus chamber for a measurement Source Holder 70026 for 5cc and 10cc Syringes includes one set of two syringe holders one for a 5cc syringe and one for a 10cc syringe Example For a Medastron source a 4mCi dose in a 5cc syringe gives an approximate 3 3 0 1nC signal in 60 seconds A 4mCi dose in a 10cc syringe gives an approximate 3 03 0 05nC signal in 60 seconds SOURCE HOLDER 70026 WELL CHAMBER 7 WELL CHAMBER REF 70026 22 9 Using the Bard EXPRESS SEEDING CARTRIDGE Source Holder REF 70032 Step 1 Adjust the Indexer Step 2 Thread the Seeding to display the number of Cartridge onto the Handler seeds to be tested in the as shown above Note the Seeding Cartridge The radiation shield is still over Indexer shown above is set the Seeding Cartridge for 4 seeds Step 3 Remove the radiation shield and insert the Seeding Cartridge through the Indexer and into the HDR 1000 Plus Well Chamber Step 4 Assembly ready for measurement with the HDR 1000 Plus Well Chamber The Bard EXPRESS SEEDING CARTRIDGE Source Holder is designed for QA measurements of palladium or iodine seeds prior to use When used with the Standard Imaging HDR 1000 Plus Well Chamber this Holder pro vides a check of the relative activity of the seeds held within an Bard EXPRESS SEEDING CARTRIDGE In addition the Holder can be gas sterilized or steam sterilized autoclaved Eva
7. SeeDOS Product User Manual HDR 1000 Plus Ionization Chamber Table of Contents General Precautions oocoonooononnnncnnoninnnnanonononnononanannnnnnos 2 Features and Specifications sseseseeseseseeeessererssreeses 3 General Procedures for Medical Measurements 4 OVEVI We tna aaa 6 A a i faces ye 8 Procedures for Calibration of HDR Ir sources 10 Procedures for Calibration and Measurement of LDR Brachytherapy Sources ooooccccoccccconcnonnnannnns 13 Procedures for Specific Source Holders 14 Calibration of HDR 1000 Plus oooooononncccncnnnonnnnnnnnos 25 Constancy Check of HDR 1000 Plus oe 25 Maintenance as 26 A O tes eboucsseabeds 26 Brachytherapy Parts List 04 2scvestsieeeteae ee hteeectntes 27 Bibliography HDR Iridium Measurements 28 Customer Responsibility ooocoonnncccnnnccconnnnnonnncnnnncnnnns 29 ATEST i iran DAA tds E E E IET 30 gt ls ee ee WARNING CAUTION CAUTION CAUTION CAUTION CAUTION General Precautions Electrical shock hazard when connected to 300 V bias supply Do not remove cover Proper use of this device depends on careful reading of all instructions and labels This device should never be submerged to clean or scrubbed with an abrasive cleaner Do not drop mishandle or disassemble unit since 1t may result in change of calibration factor Refer all servicing to qualified individuals Do not sharp
8. acceptable limits 3 Connect the ionization chamber to the electrometer and apply 100 voltage bias 4 Allow the electrometer and the ionization chamber system at least 10 minutes to stabilize making certain that all cabling is lying flat and unkinked 5 Verify the leakage of the ionization chamber is within the manufacturer s stated acceptable limits 6 Some electrometers such as the Standard Imaging MAX 4000 Electrometer allow the user to zero the device at any time If desired perform this system zeroing now 7 Check the system leakage Take a reading without exposing the chamber to radiation This reading should be less than 0 1 of the final signal expected 8 Measure the atmospheric temperature and pressure 10 11 Turn on or insert the radiation source s and take at least 3 measurements Generally the measurments should not be moving in only one direction i e three readings that continue to drop and hence may not yet be stabilized Analyze the data taking into account the average of the readings system leakage temperature pressure corrections calibration factors and any other appropriate corrections to be made Keep in mind that the calibration factor consists of the electrometer calibration factor and the ionization chamber calibra tion factor When all measurements are completed set bias voltage to OVDC turn off the electrometer and disconnect the ionization chamber Overview The Stan
9. and a cloth Gently brush all surfaces to remove dirt and dust Remove any remaining dirt with a cloth slightly dampened with a solution of mild detergent and water or a liquid disinfecting agent Be especially careful that this is an external cleaning only and do not permit any liquid to seep into the HDR 1000 Plus in any manner during clean ing Service There are no serviceable parts on the HDR 1000 Plus If the HDR 1000 Plus is disassembled the calibration factor will become invalid and necessitate recalibration Also the warranty will become void if the HDR 1000 Plus is disassembled If the triax connector and external cable are modified the value of the leakage may be affected Notice We welcome your evaluation of this manual Your comments and suggestions help us improve our publications 26 REF 90008 70010 70020 70003 70009 70016 70022 70023 70026 70024 70032 70008 70004 70007 76004 50004 70025 80010 80020 80025 A 80025 B 80040 A 80040 B 80035 Brachytherapy Parts List HDR 1000 PLUS Well Chamber Source holder for HDR Iridium 2 2mm opening Source holder for Cesium 5mm opening for 90008 HDR 1000 Plus Source holder for Cesium Remote Afterloading 7 1 mm opening Source holder for low dose rate Iridium Ribbons Source holder for Single LDR Seeds 1 2mm opening Source holder for LDR Seed Batch Assay up to 500 Pd or I seeds and for Iridium Wire Coil Source holder for RAPID Strand Iodi
10. ant When a brachytherapy source with a high dose rate is used it is imperative that there be an accurate and reliable calibration of the source strength by means of a suitable chamber such as the HDR 1000 Plus The initial activity of the Ir sources for high dose rate 6 brachytherapy applications is typically around 10 curies Ci or 370 gigabecquerels GBq The half life of Tr is 73 83 days Therefore frequent usually quarterly source replacements are required These sources must be calibrated when placed in use and should be checked periodically during use Suppliers of sources usually provide calibration certificates that can have an uncertainty of 10 necessitating an independent calibration for better accuracy This point is addressed in the article published in Int J Radiat Oncol Biol Phys 24 167 170 1992 and Chapter 5 of High Dose Rate Brachytherapy A Textbook ed S Nag Calibration methods for HDR sources using methods other than the HDR 1000 Plus well type chamber can be complicated time consuming and prone to error The HDR 1000 Plus is convenient for frequent use since the time required for calibration is only a fraction of that required for thimble ionization chamber techniques A recommended calibration technique is given in Med Phys 18 462 467 1991 Please note that the factors that are used in the calibration of these chambers are the most current and in some cases may be different than those us
11. d the five seeds at the other end are measured This provides a QA check of the relative activity of the five seeds on each end of the RAPID Strand RAPID Strand ai REF 70023 A RAPID Strand containing 10 iodine seeds was obtained and an extensive evaluation was performed with the HDR 1000 Plus and the RAPID Strand Source Holder 70023 Following the evaluation individual seeds of the RAPID Strand were cut from the strand and individually calibrated These mea surements were compared to the initial collective 18 seed measurements of the intact RAPID Strand in Source Holder 70023 to obtain a correction factor The correction factor was found to be approximately 1 15 times the 6711 iodine calibration factor from the University of Wisconsin Accredited Dosimetry Calibration Laboratory The RAPID Strand Source Holder REF 70023 can be gas sterilized or steam sterilized autoclaved To measure a RAPID Strand of iodine seeds place the spacing jig with the RAPID Strand in place into the source holder There is a plastic key on the bottom of the lead shielding to guide the spacing jig so the seeds are in the center of the well chamber There is no measurable rotational dependence Record the measured activity Invert the RAPID Strand and take another measurement A formula can be used to determine the average seed activity as a QA measurement of the sum of the activity of 5 seeds Seed Activit
12. dard Imaging HDR 1000 Plus Ionization chamber is a well type chamber It is specifically designed for use with both the brachytherapy high dose rate HDR remote afterloading irradiators and low dose rate LDR brachytherapy sources with the appropriate calibration It is recommended that the chamber be calibrated every two years as is standard practice for other ionization chambers Initially the calibration factor is given in the calibration report from the Accredited Dosimetry Calibration Labora tory ADCL The appendix provided with the calibration report discusses the calibration factors in greater detail Calibration factors should be obtained from an ADCL for each brachytherapy source that is being measured The ionization current expected from the HDR 1000 Plus is approximately 8 7 nA Ci for HDR brachytherapy sources Thus the measurement of all brachytherapy sources re quires an electrometer with a calibrated scale for measuring currents in the range from 10 A to 107A Alternatively a calibrated charge scale may be used with timed runs If integral charge techniques are used with the time deter mined by the HDR irradiator timer the contribution from the source transit time should be taken into account The HDR afterloading technique minimizes poten tial radiation exposure to medical personnel and permits brachytherapy treatments in a shorter time period Calibra tion of all brachytherapy sources with ionization chambers is import
13. duced in any form or by any means without prior written consent of Standard Imaging Inc 29 Warranty This product is sold by Standard Imaging Inc under the warranty herein set forth The warranty is extended only to the buyer purchasing the product directly from Standard Imaging Inc or as a new product from an authorized dealer or distributor of Standard Imaging Inc For a period of twenty four 24 months from the date of original delivery to the purchaser or a distributor this product is warranted against functional defects in materials and workmanship provided it is properly operated under conditions of normal use and that repairs and replacements are made in accordance herewith The foregoing warranty shall not apply if the product has been disassembled altered or repaired other than by Standard Imaging Inc or if the product has been subject to abuse misuse negligence or accident Standard Imaging s sole and exclusive obligation and the purchaser s sole and exclusive remedy under the above warranties are limited to re pairing or replacing free of charge at Standard Imaging s option a prod uct 1 which contains a defect covered by the above warranties 2 which are reported to Standard Imaging not later than seven 7 days after the expiration date of the 24 month warranty period 3 which are re turned to Standard Imaging promptly after discovery of the defect and 4 which are found to be defective upon Standard
14. easurements as described in High Dose Rate Brachytherapy A Textbook Nag ed Futura 1994 Note This value will differ depending on the length of the catheter The timer feature of the Standard Imaging MAX 4000 REF 90015 can be used to collect charge for set times and eliminate this effect 11 8 Read and record the measured current or charge 9 Use correction factors for temperature pressure electrometer correction factor electrometer must be calibrated and calibration factor for the HDR 1000 Plus given by the Accredited Dosimetry Calibration Laboratory to calculate the activity of the source The following equation can be used for example if the activity is desired the calibration factor for the activity from the calibration report would be used for C B R F E C where B the Activity of the source in Bq or Ci depending which calibration factor is used R the reading in A if current scale or in C s if charge scale measured for a set time in s F the temperature and pressure correction factor E the correction factor for the electrometer scale C the HDR 1000 Plus calibration factor in this case the activity calibration factor Note B can be divided by Ajon if desired to correct for recombination effects Since the HDR 1000 Plus has an Ajon of 1 000 this is not necessary For example if R 5 435 x 10 8 A F 1 021 E 0 999 and C 1 271 x 108 Ci A then B 5 435 x 10 8 1 021
15. ed in HDR treatment planning computers This difference if present should be accounted for during your treatment planning activities To avoid confusion the American Association of Physicists in Medicine has recommended that air kerma calibrations be used for brachytherapy sources AAPM Reports No 41 and 21 instead of source activity Operation The HDR 1000 Plus ionization chamber has a vent hole to maintain the internal air at ambient atmospheric pressure Thus the readings obtained must be corrected for ambient temperature and pressure to the temperature and pressure of calibration 22 C and 760 mm Hg at normal relative humidity 50 25 non condensing in the usual accepted manner The HDR 1000 Plus has available different inserts for HDR measurements including a quality assurance QA insert Note that the QA insert can provide information for source positioning verification timer accuracy and consistency of source activity for HDR applications This tool is described in Med Phys 22 April 1995 and in a separate instruction manual Contact Standard Imaging for further information The inserts are designed so that the center of all sources are located at the most sensitive spot of the chamber Figure 1 shows a typical axial response curve for the HDR 1000 Plus There is only a 0 1 decrease in sensitivity within 5 mm of center The HDR 1000 Plus utilizes a conventional triax connector and cable to be connected to a sui
16. luations were performed at the University 23 of Wisconsin ADCL and K amp S Associates ADCL which compared the collective seed measurements from this Source Holder to the sum of the individual seeds as mea sured with a Standard Imaging Single Seed Source Holder REF 70016 These measurements revealed the ratios or correction factors for palladium and iodine to be approxi mately 1 5 times and 1 2 times respectively the single seed calibration factors from the ADCLs Sources tested were Theragenics Theraseed Pd and SourceTech Medical STM 1251 12 The following formula can be used to determine the average seed activity as a QA measurement of the sum of the activity of seeds Note that this measurement assumes all seeds are the same activity Seed Activity R CF Cie EF N where reading CF correction ees 1 5 times the ADCL Pd pe or 1 2 times the ADCL I cal factor C correction t temperature and pressure EF electrometer correction factor 103 o and N number of seeds two 2 through six 6 For Example You receive a Seeding Cartridge with 5 Pd seeds of nominal activity of 1 0 mGym h per seed the cartridge is measured with the Source Holder REF 70032 and the palladium calibration factor 2 6 x 10 mGym h A is used Assume R 1 272 x 10 A CF 1 5 2 6 x 10 C 1 014 EF 0 998 and N 5 Then Seed Activity 1 272 x 10 11 1 5 2 6 x 10 yA 1 014
17. ly bend triax cable Damage to the cable may result in high leakage currents Insure source freely moves within secured catheter Proper location of source is necessary to assure proper calibration ADCL Calibrations Features and Specifications as requested Active Volume 245 cm Isotope Source Holder Comnector Two lug triax standard TNC or BNC Banana optional Range 0 01 mCi to 20 Ci Cable 1 meter 3 feet Bias Voltage Applied 300 volts typical Leakage Less than 50 fA Stability 0 2 Reproducibility over 2 years Response 0 5 over 25mm at center of axis Sensitivity Approximately 8 7 nA Ci typical for HDR Ir EN 0 9996 Case Wooden carrying case Dimensions Height 15 6 cm 6 1 in Diameter 10 2 cm 4 in Insert Diameter 3 5 cm 1 4 in Insert Height 12 1 cm 4 8 in Weight 2 7 kg 6 1 lbs Specifications are subject to change without notice HDR Ir and or LDR radionuclides 11 source holders available General Procedures for Medical Measurements The following procedures should be used any time that measurements are to be made with an ionization chamber and electrometer system This applies only to the setup of the ionization chamber and electrometer not to the setup of the ionization source 1 With nothing connected to the input jack of the electrometer turn the power on and wait at least 10 minutes for warm up 2 Verify the leakage of the electrometer is within the manufacturer s stated
18. ne Seeds Source holder for 5cc and 10cc Syringes Source holder for MICK Cartridge Source holder for Bard Express Seeding Cartridge Quality Assurance Tool Insert 10 meter cable with tri axial BNC connectors and protective caps connected by chains Other lengths available upon request Wall mount for HDR 1000 Plus Tube Standoff Replacement Kit Carrying Case for any HDR 1000 Ion Chamber One Inch thick lead ring to surround HDR 1000 Plus ADCL Calibration for High Dose Rate Ir 192 ADCL Calibration for Cesium ADCL Calibration for low dose rate Ir 192 Alpha Omega Services ADCL Calibration for low dose rate Ir 192 Best Medical International Other Calibrations available ADCL Calibration for Iodine Amersham 6702 ADCL Calibration for Iodine Amersham 6711 ADCL Calibration for Palladium 27 Bibliography HDR Iridium Measurements Calibration of 1921r High Dose Rate Afterloading Systems Goetsch Attix Pearson Thomadsen Med Phys 18 462 467 1991 Thermal and Scatter Effects on Radiation Sensitivity of Well Chambers used for HDR 1921r Calibrations Podgorsak DeWerd Thomadsen Paliwal Med Phys 19 1311 1314 1992 A New Re entrant Ionization Chamber for the Calibration of 192 High Dose Rate Sources Goetsch Attix DeWerd Thomadsen Int J Radiation Oncology Biol Phys 24 167 170 1992 Calibration Principles and Techniques L A DeWerd G A Ezzell and J F Williamson Chapter 5 of High Dose Rate Brachytherapy A Textb
19. nts will perform properly and reliably only when operated and maintained in accordance with the instructions contained in this manual and accompanying labels A defective device should not be used Parts which may be broken or missing or are clearly worn distorted or contaminated should be replaced immediately with genuine replacement parts manufactured by or made available from Stan dard Imaging Inc Caution Federal law in the U S A and Canada restricts the sale distribution or use of this device to by or on the order of a licensed medical practitioner The use of this device should be restricted to the supervision of a qualified medical physicist Measurement of high activ ity radioactive sources is potentially hazardous and should be performed by qualified personnel Should repair or replacement of this device become necessary after the warranty period the customer should seek advice from Standard Imaging Inc prior to such repair or replacement If this device is in need of repair 1t should not be used until all repairs have been made and the product is functioning properly and ready for use After repair the cham ber may need to be calibrated The owner of this device has sole respon sibility for any malfunction resulting from abuse improper use or main tenance or repair by anyone other than Standard Imaging Inc The information in this manual is subject to change without notice No part of this manual may be copied or repro
20. ook Subir Nag ed Futura Publishing Company Inc Armonk NY 1994 Calibration amp Quality Assurance I G A Ezzell J Hicks and L A DeWerd Chapter 54 pp 233 236 in International Brachytherapy Nucletron International B V publisher 1992 Radiation Sensitivity of Well Chambers for HDR Iridium 192 Calibrations M B Podgorsak L A DeWerd B R Thomadsen amp B R Paliwal Chapter 72 pp 311 314 in International Brachytherapy Nucletron International B V publisher 1992 The Half life of high dose rate Ir 192 sources Matthew B Podgorsak Larry A DeWerd and Bhudatt Paliwal Med Phys 20 4 1257 1259 1993 Evaluation of new re entrant ionization chambers for high dose rate brachytherapy calibrations Ezzell Endocurietherapy Hyperther mia Oncology 9 233 238 1993 Specification of Brachytherapy Source Strength Report of Task Group 32 American Association of Physicists in Medicine AAPM Re port No 21 1987 New York American Institute of Physics Remote Afterloading Technology Report of Task Group 41 American Association of Physicists in Medicine AAPM Report No 41 1993 New York American Institute of Physics Clinical implementation of AAPM Task Group 32 recommen dations on brachytherapy source strength specifications Williamson J F and Nath R 1991 Med Phys 18 439 448 28 Customer Responsibility This product and its compone
21. ource holder The source holder will place the seed at the most active area of the chamber Take a mea surement A seed can be removed by taking the source holder out of the HDR 1000 Plus chamber and inverting The Teflon tube will allow the seed to easily slide out ADCL calibrations are available for LDR iridium iodine and palladium seeds ADCL calibrations are not available for gold 15 70022 Source Holder for LDR Seed Batch Assay The Source Holder for LDR Seed Batch Assay REF 70022 is designed to hold up to 500 of the low dose rate iodine or palladium seeds The seeds to be measured are positioned at the most sensitive position on axis of the HDR 1000 Plus Brachytherapy Ion Chamber The purpose of this source holder is to enable physi cists to sample a subset typically 10 of the large numbers of seeds often received for treatment of cancer For example if several treatments for pros tate cancer are imminent 50 to 200 seeds may be used per case REF 70022 To measure a number of seeds place the desired number in the Source Holder for LDR Seed Batch Assay Place the source holder in the HDR 1000 Plus Ion Chamber The seeds are centered at the most sensitive part of the chamber A reading can be made with any standard electrometer For consistency of measurements and to save time the Standard Imag ing MAX 4000 Electrometer can be set to collect 16 charge
22. table electrometer A bias of 300 volts must be applied to the electrometer low impedance connection relative to chassis ground The voltage polarity effect is less than 0 1 If desired a second bias level of 150 volts can also be used to determine the ionic recombination loss at 300 V The ionic recombination loss is less than 0 05 and thus can be considered negligible The chamber calibration refers to the positive and negative voltage average 1 The equation used is Ajon 4 3 Q1 3Q where Qy is the charge or current measured at 300 V and Q is the charge or current measured at 150 V See Med Phys 11 714 1984 101 100 99 Percent Response 98 97 96 20 30 40 50 60 70 80 Distance from Bottom of Chamber mm Figure 1 Typical axial response shown as a percent with distance from the bottom of the chamber The step by step procedure for measurement of HDR sources is given The chamber should not be placed near a high scatter environment during measurements for the best accuracy 1t should be located at least 25 cm from a wall or other high scattering environment as described in Med Phys 19 1311 1992 Procedures for calibration of HDR Tr sources 1 Place the HDR 1000 Plus chamber in the same room as the HDR unit for at least 30 minutes before the measurement to allow it to equilibrate to ambient temperature and pressure 2 Connect the HDR 1000 Plus chamber to a suitable electrometer such as the MAX
23. ttom of the source holder Place the cesium source in the source holder for the measurement SORIA LX EA 2 REF 70020 REF 70003 70003 Source Holder for Cesium Remote Afterloading Systems 7 1mm opening Insert the remote afterloading catheter into the source holder Advance the cesium source to the bottom of the source holder Retract the source to the most sensitive area of the well chamber Take a measure ment 70009 Source Holder for Low Dose Rate Iridium Ribbons Insert the ribbon into the source holder so all seeds are in the helical portion of the source holder and not in the tube feeding the helix Take a measurement 14 A correction factor for Ir seeds in ribbons can be determined Select a ribbon that can be sacrificed Measure the signal for all seeds together On the same day cut the ribbon into individual seed sections and measure each seed individually Compare the sum of the activity of the individual seeds to the activity of the entire ribbon Calculate a correction factor for the ribbons This correction factor is the result of shadowing of the seeds by other seeds REF 70009 REF 70016 70016 Source Holder for Single LDR Seeds 1 2mm opening Insert an individual seed into the Teflon tube of the s
24. y R CF Cip EF N Seed Activity average seed activity as a QA mea surement R reading CF correction factor defined as approximately 1 15 times the ADCL 6711 iodine calibration factor N number of seeds C ip correction for temperature and pressure EF electrometer correction factor 19 For Example If you receive a strand with a nominal or average activity of 0 3uGym Y per seed the typical 5 seeds were measured and the iodine calibration factor of 2 6x 10 uGym 5 A is used Assume R 0 4957x 10 A CF 1 15 2 6 x 10 N 5 C 1014 T P EF 0 998 Seed Activity 0 4957 x 10 A 2 6 x 10 1 15 1 014 0 998 5 Seed Activity 0 3uGym h This average seed activity as a QA measurement can be compared to your expected RAPID Strand activity Note this is a QA measurement assuming the five seeds are the same activity 20 70024 Source Holder for MICK Cartridge This source holder allows for a constancy QA check of the seeds After the MICK cartridge is loaded insert the cartridge into the holder so that the black part is on top Screw the cartidge into the holder and make sure the seeds are not blocked by the metal posts See figure below Zoja 70026 Source Holder for 5cc and 10cc Syringes This source holder has been designed to provide a quick and convenient QA measurement of liquid sources in syringes Simply place the appropriate source holder in the HDR 1000
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