VMAT QA: Measurement-guided 4D dose reconstruction on a patient
Purpose: To develop and validate a volume-modulated arc therapy (VMAT) quality assurance (QA) tool that takes as input a time-resolved, low-density (∼10 mm) cylindrical surface dose map from a commercial helical diode array, and outputs a high density, volumetric, time-resolved dose matrix on an arb...
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| Veröffentlicht in: | Medical physics (Lancaster) 2012-07, Vol.39 (7), p.4228-4238 |
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| creator | Nelms, Benjamin E. Opp, Daniel Robinson, Joshua Wolf, Theresa K. Zhang, Geoffrey Moros, Eduardo Feygelman, Vladimir |
| description | Purpose:
To develop and validate a volume-modulated arc therapy (VMAT) quality assurance (QA) tool that takes as input a time-resolved, low-density (∼10 mm) cylindrical surface dose map from a commercial helical diode array, and outputs a high density, volumetric, time-resolved dose matrix on an arbitrary patient dataset. This first validation study is limited to a homogeneous “patient.”
Methods:
A VMAT treatment is delivered to a diode array phantom (ARCCHECK, Sun Nuclear Corp., Melbourne, FL). 3DVH software (Sun Nuclear) derives the high-density volumetric dose using measurement-guided dose reconstruction (MGDR). MGDR cylindrical phantom results are then used to perturb the three-dimensional (3D) treatment planning dose on the patient dataset, producing a semiempirical volumetric dose grid. Four-dimensional (4D) dose reconstruction on the patient is also possible by morphing individual sub-beam doses instead of the composite. For conventional (3D) dose comparison two methods were developed, using the four plans (Multi-Target, C-shape, Mock Prostate, and Head and Neck), including their structures and objectives, from the AAPM TG-119 report. First, 3DVH and treatment planning system (TPS) cumulative point doses were compared to ion chamber in a cube water-equivalent phantom (“patient”). The shape of the phantom is different from the ARCCHECK and furthermore the targets were placed asymmetrically. Second, coronal and sagittal absolute film dose distributions in the cube were compared with 3DVH and TPS. For time-resolved (4D) comparisons, three tests were performed. First, volumetric dose differences were calculated between the 3D MGDR and cumulative time-resolved patient (4D MGDR) dose at the end of delivery, where they ideally should be identical. Second, time-resolved (10 Hz sampling rate) ion chamber doses were compared to cumulative point dose vs time curves from 4D MGDR. Finally, accelerator output was varied to assess the linearity of the 4D MGDR with global fluence change.
Results:
Across four TG-119 plans, the average PTV point dose difference in the cube between 3DVH and ion chamber is 0.1 ± 1.0%. Average film vs TPSγ-analysis passing rates are 83.0%, 91.1%, and 98.4% for 1%/2 mm, 2%/2 mm, and 3%/3 mm threshold combinations, respectively, while average film vs 3DVH γ-analysis passing rates are 88.6%, 96.1%, and 99.5% for the same respective criteria. 4D MGDR was also sufficiently accurate. First, for 99.5% voxels in each case, the doses from 3D and |
| doi_str_mv | 10.1118/1.4729709 |
| format | Article |
| fullrecord | <record><control><sourceid>proquest_osti_</sourceid><recordid>TN_cdi_osti_scitechconnect_22100645</recordid><sourceformat>XML</sourceformat><sourcesystem>PC</sourcesystem><sourcerecordid>1030076675</sourcerecordid><originalsourceid>FETCH-LOGICAL-o2779-2712119949c46da37e4b409c4a52d57e47cc7d37cb9d2574f64dfcd7450a012f3</originalsourceid><addsrcrecordid>eNp90F1LwzAUBuAgipvTC_-AFLwRofMkTRvjjYz5CRsqTG9DlqRa6ZdNquzfm9I5BEEIHA55kpy8CB1iGGOMz8_wmDLCGfAtNCSURSElwLfREIDTkFCIB2jP2ncASKIYdtGAkPMIWJwM0eXLfLIIniYXwdxI2zamMKULX9tMGx3Qq0BX1gSNUVVpXdMql1Vl4JcMaukyT_fRTipzaw7WdYSeb64X07tw9nB7P53MwoowxkPCMMGYc8oVTbSMmKFLCr6RMdGx75hSTEdMLbkmMaNpQnWqNKMxSMAkjUbouL-3si4TVmXOqDc_VWmUE4Rg_zUae3XSq7qpPlpjnSgyq0yey9JUrRUYIgCWJKyjR2vaLgujRd1khWxW4icaD8IefGW5WW32MYguc4HFOnMxf-yK96e974aTXVCbM59V88vXOv0P_3kg-gaTDYrw</addsrcrecordid><sourcetype>Open Access Repository</sourcetype><iscdi>true</iscdi><recordtype>article</recordtype><pqid>1030076675</pqid></control><display><type>article</type><title>VMAT QA: Measurement-guided 4D dose reconstruction on a patient</title><source>MEDLINE</source><source>Wiley Journals</source><source>Alma/SFX Local Collection</source><creator>Nelms, Benjamin E. ; Opp, Daniel ; Robinson, Joshua ; Wolf, Theresa K. ; Zhang, Geoffrey ; Moros, Eduardo ; Feygelman, Vladimir</creator><creatorcontrib>Nelms, Benjamin E. ; Opp, Daniel ; Robinson, Joshua ; Wolf, Theresa K. ; Zhang, Geoffrey ; Moros, Eduardo ; Feygelman, Vladimir</creatorcontrib><description>Purpose:
To develop and validate a volume-modulated arc therapy (VMAT) quality assurance (QA) tool that takes as input a time-resolved, low-density (∼10 mm) cylindrical surface dose map from a commercial helical diode array, and outputs a high density, volumetric, time-resolved dose matrix on an arbitrary patient dataset. This first validation study is limited to a homogeneous “patient.”
Methods:
A VMAT treatment is delivered to a diode array phantom (ARCCHECK, Sun Nuclear Corp., Melbourne, FL). 3DVH software (Sun Nuclear) derives the high-density volumetric dose using measurement-guided dose reconstruction (MGDR). MGDR cylindrical phantom results are then used to perturb the three-dimensional (3D) treatment planning dose on the patient dataset, producing a semiempirical volumetric dose grid. Four-dimensional (4D) dose reconstruction on the patient is also possible by morphing individual sub-beam doses instead of the composite. For conventional (3D) dose comparison two methods were developed, using the four plans (Multi-Target, C-shape, Mock Prostate, and Head and Neck), including their structures and objectives, from the AAPM TG-119 report. First, 3DVH and treatment planning system (TPS) cumulative point doses were compared to ion chamber in a cube water-equivalent phantom (“patient”). The shape of the phantom is different from the ARCCHECK and furthermore the targets were placed asymmetrically. Second, coronal and sagittal absolute film dose distributions in the cube were compared with 3DVH and TPS. For time-resolved (4D) comparisons, three tests were performed. First, volumetric dose differences were calculated between the 3D MGDR and cumulative time-resolved patient (4D MGDR) dose at the end of delivery, where they ideally should be identical. Second, time-resolved (10 Hz sampling rate) ion chamber doses were compared to cumulative point dose vs time curves from 4D MGDR. Finally, accelerator output was varied to assess the linearity of the 4D MGDR with global fluence change.
Results:
Across four TG-119 plans, the average PTV point dose difference in the cube between 3DVH and ion chamber is 0.1 ± 1.0%. Average film vs TPSγ-analysis passing rates are 83.0%, 91.1%, and 98.4% for 1%/2 mm, 2%/2 mm, and 3%/3 mm threshold combinations, respectively, while average film vs 3DVH γ-analysis passing rates are 88.6%, 96.1%, and 99.5% for the same respective criteria. 4D MGDR was also sufficiently accurate. First, for 99.5% voxels in each case, the doses from 3D and 4D MGDR at the end of delivery agree within 0.5% local dose-error/1 mm distance. Moreover, all failing voxels are confined to the edge of the cylindrical reconstruction volume. Second, dose vs time curves track between the ion chamber and 4D MGDR within 1%. Finally, 4D MGDR dose changes linearly with the accelerator output: the difference between cumulative ion chamber and MGDR dose changed by no more than 1% (randomly) with the output variation range of 10%.
Conclusions:
Even for a well-commissioned TPS, comparison metrics show better agreement on average to MGDR than to TPS on the arbitrary-shaped measurable “patient.” The method requires no more accelerator time than standard QA, while producing more clinically relevant information. Validation in a heterogeneous thoracic phantom is under way, as is the ultimate application of 4D MGDR to virtual motion studies.</description><identifier>ISSN: 0094-2405</identifier><identifier>EISSN: 2473-4209</identifier><identifier>DOI: 10.1118/1.4729709</identifier><identifier>PMID: 22830756</identifier><identifier>CODEN: MPHYA6</identifier><language>eng</language><publisher>United States: American Association of Physicists in Medicine</publisher><subject>4D dose reconstruction ; 60 APPLIED LIFE SCIENCES ; Algorithms ; Anatomy ; COMPARATIVE EVALUATIONS ; COMPUTER CODES ; Computer software ; Digital computing or data processing equipment or methods, specially adapted for specific applications ; Dose‐volume analysis ; DOSIMETRY ; Dosimetry/exposure assessment ; grid computing ; HEAD ; Intensity modulated radiation therapy ; Interpolation ; ionisation chambers ; IONIZATION CHAMBERS ; Linear accelerators ; Measurement of nuclear or x‐radiation ; medical computing ; Medical treatment planning ; Multileaf collimators ; Multiprogramming arrangements ; NECK ; PATIENTS ; PHANTOMS ; PLANNING ; PROSTATE ; QUALITY ASSURANCE ; Quality Assurance, Health Care - methods ; RADIATION DOSE DISTRIBUTIONS ; RADIATION DOSES ; RADIATION MONITORING ; Radiation monitoring, control, and safety ; RADIATION PROTECTION AND DOSIMETRY ; Radiation therapy ; Radiometry - instrumentation ; Radiometry - methods ; RADIOTHERAPY ; Radiotherapy Dosage ; Radiotherapy Planning, Computer-Assisted - methods ; Radiotherapy, Conformal - instrumentation ; Radiotherapy, Conformal - methods ; Reproducibility of Results ; rotational therapy ; SEMICONDUCTOR DETECTORS ; Sensitivity and Specificity ; Surface reconstruction ; SURFACES ; TIME RESOLUTION ; Tubes for determining the presence, intensity, density or energy of radiation or particles ; VMAT QA</subject><ispartof>Medical physics (Lancaster), 2012-07, Vol.39 (7), p.4228-4238</ispartof><rights>American Association of Physicists in Medicine</rights><rights>2012 American Association of Physicists in Medicine</rights><lds50>peer_reviewed</lds50><woscitedreferencessubscribed>false</woscitedreferencessubscribed></display><links><openurl>$$Topenurl_article</openurl><openurlfulltext>$$Topenurlfull_article</openurlfulltext><thumbnail>$$Tsyndetics_thumb_exl</thumbnail><linktopdf>$$Uhttps://onlinelibrary.wiley.com/doi/pdf/10.1118%2F1.4729709$$EPDF$$P50$$Gwiley$$H</linktopdf><linktohtml>$$Uhttps://onlinelibrary.wiley.com/doi/full/10.1118%2F1.4729709$$EHTML$$P50$$Gwiley$$H</linktohtml><link.rule.ids>230,314,780,784,885,1417,27924,27925,45574,45575</link.rule.ids><backlink>$$Uhttps://www.ncbi.nlm.nih.gov/pubmed/22830756$$D View this record in MEDLINE/PubMed$$Hfree_for_read</backlink><backlink>$$Uhttps://www.osti.gov/biblio/22100645$$D View this record in Osti.gov$$Hfree_for_read</backlink></links><search><creatorcontrib>Nelms, Benjamin E.</creatorcontrib><creatorcontrib>Opp, Daniel</creatorcontrib><creatorcontrib>Robinson, Joshua</creatorcontrib><creatorcontrib>Wolf, Theresa K.</creatorcontrib><creatorcontrib>Zhang, Geoffrey</creatorcontrib><creatorcontrib>Moros, Eduardo</creatorcontrib><creatorcontrib>Feygelman, Vladimir</creatorcontrib><title>VMAT QA: Measurement-guided 4D dose reconstruction on a patient</title><title>Medical physics (Lancaster)</title><addtitle>Med Phys</addtitle><description>Purpose:
To develop and validate a volume-modulated arc therapy (VMAT) quality assurance (QA) tool that takes as input a time-resolved, low-density (∼10 mm) cylindrical surface dose map from a commercial helical diode array, and outputs a high density, volumetric, time-resolved dose matrix on an arbitrary patient dataset. This first validation study is limited to a homogeneous “patient.”
Methods:
A VMAT treatment is delivered to a diode array phantom (ARCCHECK, Sun Nuclear Corp., Melbourne, FL). 3DVH software (Sun Nuclear) derives the high-density volumetric dose using measurement-guided dose reconstruction (MGDR). MGDR cylindrical phantom results are then used to perturb the three-dimensional (3D) treatment planning dose on the patient dataset, producing a semiempirical volumetric dose grid. Four-dimensional (4D) dose reconstruction on the patient is also possible by morphing individual sub-beam doses instead of the composite. For conventional (3D) dose comparison two methods were developed, using the four plans (Multi-Target, C-shape, Mock Prostate, and Head and Neck), including their structures and objectives, from the AAPM TG-119 report. First, 3DVH and treatment planning system (TPS) cumulative point doses were compared to ion chamber in a cube water-equivalent phantom (“patient”). The shape of the phantom is different from the ARCCHECK and furthermore the targets were placed asymmetrically. Second, coronal and sagittal absolute film dose distributions in the cube were compared with 3DVH and TPS. For time-resolved (4D) comparisons, three tests were performed. First, volumetric dose differences were calculated between the 3D MGDR and cumulative time-resolved patient (4D MGDR) dose at the end of delivery, where they ideally should be identical. Second, time-resolved (10 Hz sampling rate) ion chamber doses were compared to cumulative point dose vs time curves from 4D MGDR. Finally, accelerator output was varied to assess the linearity of the 4D MGDR with global fluence change.
Results:
Across four TG-119 plans, the average PTV point dose difference in the cube between 3DVH and ion chamber is 0.1 ± 1.0%. Average film vs TPSγ-analysis passing rates are 83.0%, 91.1%, and 98.4% for 1%/2 mm, 2%/2 mm, and 3%/3 mm threshold combinations, respectively, while average film vs 3DVH γ-analysis passing rates are 88.6%, 96.1%, and 99.5% for the same respective criteria. 4D MGDR was also sufficiently accurate. First, for 99.5% voxels in each case, the doses from 3D and 4D MGDR at the end of delivery agree within 0.5% local dose-error/1 mm distance. Moreover, all failing voxels are confined to the edge of the cylindrical reconstruction volume. Second, dose vs time curves track between the ion chamber and 4D MGDR within 1%. Finally, 4D MGDR dose changes linearly with the accelerator output: the difference between cumulative ion chamber and MGDR dose changed by no more than 1% (randomly) with the output variation range of 10%.
Conclusions:
Even for a well-commissioned TPS, comparison metrics show better agreement on average to MGDR than to TPS on the arbitrary-shaped measurable “patient.” The method requires no more accelerator time than standard QA, while producing more clinically relevant information. Validation in a heterogeneous thoracic phantom is under way, as is the ultimate application of 4D MGDR to virtual motion studies.</description><subject>4D dose reconstruction</subject><subject>60 APPLIED LIFE SCIENCES</subject><subject>Algorithms</subject><subject>Anatomy</subject><subject>COMPARATIVE EVALUATIONS</subject><subject>COMPUTER CODES</subject><subject>Computer software</subject><subject>Digital computing or data processing equipment or methods, specially adapted for specific applications</subject><subject>Dose‐volume analysis</subject><subject>DOSIMETRY</subject><subject>Dosimetry/exposure assessment</subject><subject>grid computing</subject><subject>HEAD</subject><subject>Intensity modulated radiation therapy</subject><subject>Interpolation</subject><subject>ionisation chambers</subject><subject>IONIZATION CHAMBERS</subject><subject>Linear accelerators</subject><subject>Measurement of nuclear or x‐radiation</subject><subject>medical computing</subject><subject>Medical treatment planning</subject><subject>Multileaf collimators</subject><subject>Multiprogramming arrangements</subject><subject>NECK</subject><subject>PATIENTS</subject><subject>PHANTOMS</subject><subject>PLANNING</subject><subject>PROSTATE</subject><subject>QUALITY ASSURANCE</subject><subject>Quality Assurance, Health Care - methods</subject><subject>RADIATION DOSE DISTRIBUTIONS</subject><subject>RADIATION DOSES</subject><subject>RADIATION MONITORING</subject><subject>Radiation monitoring, control, and safety</subject><subject>RADIATION PROTECTION AND DOSIMETRY</subject><subject>Radiation therapy</subject><subject>Radiometry - instrumentation</subject><subject>Radiometry - methods</subject><subject>RADIOTHERAPY</subject><subject>Radiotherapy Dosage</subject><subject>Radiotherapy Planning, Computer-Assisted - methods</subject><subject>Radiotherapy, Conformal - instrumentation</subject><subject>Radiotherapy, Conformal - methods</subject><subject>Reproducibility of Results</subject><subject>rotational therapy</subject><subject>SEMICONDUCTOR DETECTORS</subject><subject>Sensitivity and Specificity</subject><subject>Surface reconstruction</subject><subject>SURFACES</subject><subject>TIME RESOLUTION</subject><subject>Tubes for determining the presence, intensity, density or energy of radiation or particles</subject><subject>VMAT QA</subject><issn>0094-2405</issn><issn>2473-4209</issn><fulltext>true</fulltext><rsrctype>article</rsrctype><creationdate>2012</creationdate><recordtype>article</recordtype><sourceid>EIF</sourceid><recordid>eNp90F1LwzAUBuAgipvTC_-AFLwRofMkTRvjjYz5CRsqTG9DlqRa6ZdNquzfm9I5BEEIHA55kpy8CB1iGGOMz8_wmDLCGfAtNCSURSElwLfREIDTkFCIB2jP2ncASKIYdtGAkPMIWJwM0eXLfLIIniYXwdxI2zamMKULX9tMGx3Qq0BX1gSNUVVpXdMql1Vl4JcMaukyT_fRTipzaw7WdYSeb64X07tw9nB7P53MwoowxkPCMMGYc8oVTbSMmKFLCr6RMdGx75hSTEdMLbkmMaNpQnWqNKMxSMAkjUbouL-3si4TVmXOqDc_VWmUE4Rg_zUae3XSq7qpPlpjnSgyq0yey9JUrRUYIgCWJKyjR2vaLgujRd1khWxW4icaD8IefGW5WW32MYguc4HFOnMxf-yK96e974aTXVCbM59V88vXOv0P_3kg-gaTDYrw</recordid><startdate>201207</startdate><enddate>201207</enddate><creator>Nelms, Benjamin E.</creator><creator>Opp, Daniel</creator><creator>Robinson, Joshua</creator><creator>Wolf, Theresa K.</creator><creator>Zhang, Geoffrey</creator><creator>Moros, Eduardo</creator><creator>Feygelman, Vladimir</creator><general>American Association of Physicists in Medicine</general><scope>CGR</scope><scope>CUY</scope><scope>CVF</scope><scope>ECM</scope><scope>EIF</scope><scope>NPM</scope><scope>7X8</scope><scope>OTOTI</scope></search><sort><creationdate>201207</creationdate><title>VMAT QA: Measurement-guided 4D dose reconstruction on a patient</title><author>Nelms, Benjamin E. ; Opp, Daniel ; Robinson, Joshua ; Wolf, Theresa K. ; Zhang, Geoffrey ; Moros, Eduardo ; Feygelman, Vladimir</author></sort><facets><frbrtype>5</frbrtype><frbrgroupid>cdi_FETCH-LOGICAL-o2779-2712119949c46da37e4b409c4a52d57e47cc7d37cb9d2574f64dfcd7450a012f3</frbrgroupid><rsrctype>articles</rsrctype><prefilter>articles</prefilter><language>eng</language><creationdate>2012</creationdate><topic>4D dose reconstruction</topic><topic>60 APPLIED LIFE SCIENCES</topic><topic>Algorithms</topic><topic>Anatomy</topic><topic>COMPARATIVE EVALUATIONS</topic><topic>COMPUTER CODES</topic><topic>Computer software</topic><topic>Digital computing or data processing equipment or methods, specially adapted for specific applications</topic><topic>Dose‐volume analysis</topic><topic>DOSIMETRY</topic><topic>Dosimetry/exposure assessment</topic><topic>grid computing</topic><topic>HEAD</topic><topic>Intensity modulated radiation therapy</topic><topic>Interpolation</topic><topic>ionisation chambers</topic><topic>IONIZATION CHAMBERS</topic><topic>Linear accelerators</topic><topic>Measurement of nuclear or x‐radiation</topic><topic>medical computing</topic><topic>Medical treatment planning</topic><topic>Multileaf collimators</topic><topic>Multiprogramming arrangements</topic><topic>NECK</topic><topic>PATIENTS</topic><topic>PHANTOMS</topic><topic>PLANNING</topic><topic>PROSTATE</topic><topic>QUALITY ASSURANCE</topic><topic>Quality Assurance, Health Care - methods</topic><topic>RADIATION DOSE DISTRIBUTIONS</topic><topic>RADIATION DOSES</topic><topic>RADIATION MONITORING</topic><topic>Radiation monitoring, control, and safety</topic><topic>RADIATION PROTECTION AND DOSIMETRY</topic><topic>Radiation therapy</topic><topic>Radiometry - instrumentation</topic><topic>Radiometry - methods</topic><topic>RADIOTHERAPY</topic><topic>Radiotherapy Dosage</topic><topic>Radiotherapy Planning, Computer-Assisted - methods</topic><topic>Radiotherapy, Conformal - instrumentation</topic><topic>Radiotherapy, Conformal - methods</topic><topic>Reproducibility of Results</topic><topic>rotational therapy</topic><topic>SEMICONDUCTOR DETECTORS</topic><topic>Sensitivity and Specificity</topic><topic>Surface reconstruction</topic><topic>SURFACES</topic><topic>TIME RESOLUTION</topic><topic>Tubes for determining the presence, intensity, density or energy of radiation or particles</topic><topic>VMAT QA</topic><toplevel>peer_reviewed</toplevel><toplevel>online_resources</toplevel><creatorcontrib>Nelms, Benjamin E.</creatorcontrib><creatorcontrib>Opp, Daniel</creatorcontrib><creatorcontrib>Robinson, Joshua</creatorcontrib><creatorcontrib>Wolf, Theresa K.</creatorcontrib><creatorcontrib>Zhang, Geoffrey</creatorcontrib><creatorcontrib>Moros, Eduardo</creatorcontrib><creatorcontrib>Feygelman, Vladimir</creatorcontrib><collection>Medline</collection><collection>MEDLINE</collection><collection>MEDLINE (Ovid)</collection><collection>MEDLINE</collection><collection>MEDLINE</collection><collection>PubMed</collection><collection>MEDLINE - Academic</collection><collection>OSTI.GOV</collection><jtitle>Medical physics (Lancaster)</jtitle></facets><delivery><delcategory>Remote Search Resource</delcategory><fulltext>fulltext</fulltext></delivery><addata><au>Nelms, Benjamin E.</au><au>Opp, Daniel</au><au>Robinson, Joshua</au><au>Wolf, Theresa K.</au><au>Zhang, Geoffrey</au><au>Moros, Eduardo</au><au>Feygelman, Vladimir</au><format>journal</format><genre>article</genre><ristype>JOUR</ristype><atitle>VMAT QA: Measurement-guided 4D dose reconstruction on a patient</atitle><jtitle>Medical physics (Lancaster)</jtitle><addtitle>Med Phys</addtitle><date>2012-07</date><risdate>2012</risdate><volume>39</volume><issue>7</issue><spage>4228</spage><epage>4238</epage><pages>4228-4238</pages><issn>0094-2405</issn><eissn>2473-4209</eissn><coden>MPHYA6</coden><abstract>Purpose:
To develop and validate a volume-modulated arc therapy (VMAT) quality assurance (QA) tool that takes as input a time-resolved, low-density (∼10 mm) cylindrical surface dose map from a commercial helical diode array, and outputs a high density, volumetric, time-resolved dose matrix on an arbitrary patient dataset. This first validation study is limited to a homogeneous “patient.”
Methods:
A VMAT treatment is delivered to a diode array phantom (ARCCHECK, Sun Nuclear Corp., Melbourne, FL). 3DVH software (Sun Nuclear) derives the high-density volumetric dose using measurement-guided dose reconstruction (MGDR). MGDR cylindrical phantom results are then used to perturb the three-dimensional (3D) treatment planning dose on the patient dataset, producing a semiempirical volumetric dose grid. Four-dimensional (4D) dose reconstruction on the patient is also possible by morphing individual sub-beam doses instead of the composite. For conventional (3D) dose comparison two methods were developed, using the four plans (Multi-Target, C-shape, Mock Prostate, and Head and Neck), including their structures and objectives, from the AAPM TG-119 report. First, 3DVH and treatment planning system (TPS) cumulative point doses were compared to ion chamber in a cube water-equivalent phantom (“patient”). The shape of the phantom is different from the ARCCHECK and furthermore the targets were placed asymmetrically. Second, coronal and sagittal absolute film dose distributions in the cube were compared with 3DVH and TPS. For time-resolved (4D) comparisons, three tests were performed. First, volumetric dose differences were calculated between the 3D MGDR and cumulative time-resolved patient (4D MGDR) dose at the end of delivery, where they ideally should be identical. Second, time-resolved (10 Hz sampling rate) ion chamber doses were compared to cumulative point dose vs time curves from 4D MGDR. Finally, accelerator output was varied to assess the linearity of the 4D MGDR with global fluence change.
Results:
Across four TG-119 plans, the average PTV point dose difference in the cube between 3DVH and ion chamber is 0.1 ± 1.0%. Average film vs TPSγ-analysis passing rates are 83.0%, 91.1%, and 98.4% for 1%/2 mm, 2%/2 mm, and 3%/3 mm threshold combinations, respectively, while average film vs 3DVH γ-analysis passing rates are 88.6%, 96.1%, and 99.5% for the same respective criteria. 4D MGDR was also sufficiently accurate. First, for 99.5% voxels in each case, the doses from 3D and 4D MGDR at the end of delivery agree within 0.5% local dose-error/1 mm distance. Moreover, all failing voxels are confined to the edge of the cylindrical reconstruction volume. Second, dose vs time curves track between the ion chamber and 4D MGDR within 1%. Finally, 4D MGDR dose changes linearly with the accelerator output: the difference between cumulative ion chamber and MGDR dose changed by no more than 1% (randomly) with the output variation range of 10%.
Conclusions:
Even for a well-commissioned TPS, comparison metrics show better agreement on average to MGDR than to TPS on the arbitrary-shaped measurable “patient.” The method requires no more accelerator time than standard QA, while producing more clinically relevant information. Validation in a heterogeneous thoracic phantom is under way, as is the ultimate application of 4D MGDR to virtual motion studies.</abstract><cop>United States</cop><pub>American Association of Physicists in Medicine</pub><pmid>22830756</pmid><doi>10.1118/1.4729709</doi><tpages>11</tpages></addata></record> |
| fulltext | fulltext |
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| ispartof | Medical physics (Lancaster), 2012-07, Vol.39 (7), p.4228-4238 |
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| language | eng |
| recordid | cdi_osti_scitechconnect_22100645 |
| source | MEDLINE; Wiley Journals; Alma/SFX Local Collection |
| subjects | 4D dose reconstruction 60 APPLIED LIFE SCIENCES Algorithms Anatomy COMPARATIVE EVALUATIONS COMPUTER CODES Computer software Digital computing or data processing equipment or methods, specially adapted for specific applications Dose‐volume analysis DOSIMETRY Dosimetry/exposure assessment grid computing HEAD Intensity modulated radiation therapy Interpolation ionisation chambers IONIZATION CHAMBERS Linear accelerators Measurement of nuclear or x‐radiation medical computing Medical treatment planning Multileaf collimators Multiprogramming arrangements NECK PATIENTS PHANTOMS PLANNING PROSTATE QUALITY ASSURANCE Quality Assurance, Health Care - methods RADIATION DOSE DISTRIBUTIONS RADIATION DOSES RADIATION MONITORING Radiation monitoring, control, and safety RADIATION PROTECTION AND DOSIMETRY Radiation therapy Radiometry - instrumentation Radiometry - methods RADIOTHERAPY Radiotherapy Dosage Radiotherapy Planning, Computer-Assisted - methods Radiotherapy, Conformal - instrumentation Radiotherapy, Conformal - methods Reproducibility of Results rotational therapy SEMICONDUCTOR DETECTORS Sensitivity and Specificity Surface reconstruction SURFACES TIME RESOLUTION Tubes for determining the presence, intensity, density or energy of radiation or particles VMAT QA |
| title | VMAT QA: Measurement-guided 4D dose reconstruction on a patient |
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