# US 7,609,811 B1 · Method for minimizing the tongue and groove effect in intensity modulated radiation delivery > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 7,609,811 B1 - Document ID: US7609811B1 - Status: Granted - Kind: B1 - Application number: 12/267,044 - Filed: 2008-11-07 - Granted: 2009-10-27 - Earliest claimed: 2008-11-07 - Assignees: Varian Medical Systems International AG - Inventors: Sami Pekka Siljamaki; Katja Marika Pesola - Web page: https://patentgrep.com/patent/US7609811B1 ## CPC - G21K 1/046: {varying the contour of the field, e.g. multileaf collimators} - A61N 5/1045: {using a multi-leaf collimator, e.g. for intensity modulated radiation therapy or IMRT} - A61N 5/1036: {Leaf sequencing algorithms} - G21K: HANDLING OF PARTICLES OR IONISING RADIATION NOT OTHERWISE PROVIDED FOR; IRRADIATION DEVICES; GAMMA RAY OR X-RAY MICROSCOPES - A61N: ELECTROTHERAPY; MAGNETOTHERAPY; RADIATION THERAPY; ULTRASOUND THERAPY (measurement of bioelectric currents A61B; surgical instruments, devices or methods for transferring non-mechanical forms of energy to or from the body A61B18/00; anaesthetic apparatus in general A61M; incandescent lamps H01K; infrared radiators for heating H05B) ## Abstract The present invention provides an intensity modulated radiation therapy (IMRT) method for treating a target region that minimizes the tongue and groove effect. By minimizing that effect, striping in the final delivered fluence is reduced, which improves the overall quality of the radiation delivery. In the method, compensating functions Ci(x) are added to leaf coordinates ai(x) and bi(x) for all of the leaf pairs i in a leaf sequence algorithm, where Ci(x) is chosen to match the mechanical limitations of the MLC and to minimize non-weighted or weighted sums of the tongue and groove effects, where the weighting is time-dependent, position-dependent, or time- and position-dependent, or to minimize the total treatment time, changes to the original MLC sequence, or the tongue and groove effect distribution variance in spatial or temporal coordinates. ## Claims ### Claim 1 A method of providing intensity modulated radiation therapy to a target region wherein the tongue and groove effect is minimized, comprising: obtaining a multi-leaf collimator (MLC) sequence from an external leaf-sequencing algorithm; and modifying the MLC sequence to compensate for the tongue and groove effect, wherein modifications are selected such that mechanical limitations of the MLC are not exceeded and at least one of the following is minimized: a non-weighted sum of the tongue and groove effects, a weighted sum of the tongue and groove effects using time-dependent weighting, a weighted sum of the tongue and groove effects using position-dependent weighting, a weighted sum of the tongue and groove effects using time- and position-dependent weighting, the tongue and groove effect distribution variance in spatial coordinates, or the tongue and groove effect distribution variance in temporal coordinates. ### Claim 2 (depends on 1) The method of claim 1, wherein the step of modifying the MLC sequence includes adding compensating functions Ci(x) to leaf coordinates ai(x) and bi(x) for all leaf pairs i. ### Claim 3 (depends on 1) The method of claim 1, wherein the step of modifying the MLC sequence includes minimizing the weighted sum of the tongue and groove effects using time-dependent weighting, further comprising a target fluence that changes with time. ### Claim 4 (depends on 1) The method of claim 1, wherein the step of modifying the MLC sequence includes minimizing the weighted sum of the tongue and groove effects using time-dependent weighting and wherein the target region is in motion. ### Claim 5 (depends on 1) The method of claim 1, wherein the step of modifying the MLC sequence includes minimizing the weighted sum of the tongue and groove effects using position-dependent weighting and wherein the position-dependent weights are generated by minimum-leaf-gap-effect optimization. ### Claim 6 (depends on 1) The method of claim 1, wherein the step of modifying the MLC sequence includes minimizing the weighted sum of the tongue and groove effects using position-dependent weighting and wherein the position-dependent weights are generated by three dimensional organ arrangements in the target region. ### Claim 7 (depends on 1) The method of claim 1, wherein the step of modifying the MLC sequence includes minimizing the weighted sum of the tongue and groove effects using position-dependent weighting and wherein the position-dependent weights are generated by a rotational fluence. ### Claim 8 (depends on 1) The method of claim 1, wherein the step of modifying the MLC sequence further comprises selecting compensating functions such that the total treatment time is minimized. ### Claim 9 (depends on 1) The method of claim 1, wherein the step of modifying the MLC sequence further comprises selecting compensating functions such that changes to the original MLC sequence are minimized. ### Claim 10 A computer readable medium including a computer program for controlling a multi-leaf collimator (MLC) to provide intensity modulated radiation therapy to a target region wherein the tongue and groove effect is minimized, comprising: software code executable on a computer to: obtain a multi-leaf collimator (MLC) sequence from an external leaf-sequencing algorithm; and modify the MLC sequence to compensate for the tongue and groove effect, wherein modifications are selected such that mechanical limitations of the MLC are not exceeded and at least one of the following is minimized: a non-weighted sum of the tongue and groove effects, a weighted sum of the tongue and groove effects using time-dependent weighting, a weighted sum of the tongue and groove effects using position-dependent weighting, a weighted sum of the tongue and groove effects using time- and position-dependent weighting, the tongue and groove effect distribution variance in spatial coordinates, or the tongue and groove effect distribution variance in temporal coordinates. ### Claim 11 (depends on 10) The computer readable medium of claim 10, wherein the software code executable on a computer to modify the MLC sequence adds compensating functions Ci(x) to leaf coordinates ai(x) and bi(x) for all leaf pairs i. ### Claim 12 (depends on 10) The computer readable medium of claim 10, wherein the software code executable on a computer to modify the MLC sequence selects compensating functions to minimize at least one of the total treatment time or changes to the original MLC sequence.