A radiation treatment planning system, comprising: a processor; a display device coupled to the processor; and memory coupled to the processor and comprising instructions that, when executed, cause the processor to perform a method, the method comprising: generating a dose-rate volume histogram for a target volume, the dose-rate volume histogram indicating dose rates and percentages of the target volume that receive the dose rates, the dose-rate volume histogram generated based on values of parameters in a proposed treatment plan; displaying a graphical user interface comprising a rendering of a target volume, the target volume comprising a plurality of sub-volumes; and accessing information in the memory, the information comprising a dose rate received by each sub-volume of the sub-volumes, the dose rate received by a sub-volume determined using said parameters; wherein said displaying comprises: associating a value of an attribute to said each sub-volume, wherein the value corresponds to an amount of the dose rate received by said each sub-volume; rendering said each sub-volume according to the value that corresponds to said each sub-volume; and displaying the dose-rate volume histogram as part of the GUI; wherein the method performed by the processor further comprises adjusting values of parameters that can have an effect on dose rate until the dose rate-volume histogram satisfies objectives associated with treatment of a patient and generating a final radiation treatment plan using the dose rate-volume histogram. a processor; a display device coupled to the processor; and memory coupled to the processor and comprising instructions that, when executed, cause the processor to perform a method, the method comprising: generating a dose-rate volume histogram for a target volume, the dose-rate volume histogram indicating dose rates and percentages of the target volume that receive the dose rates, the dose-rate volume histogram generated based on values of parameters in a proposed treatment plan; displaying a graphical user interface comprising a rendering of a target volume, the target volume comprising a plurality of sub-volumes; and accessing information in the memory, the information comprising a dose rate received by each sub-volume of the sub-volumes, the dose rate received by a sub-volume determined using said parameters; wherein said displaying comprises: associating a value of an attribute to said each sub-volume, wherein the value corresponds to an amount of the dose rate received by said each sub-volume; rendering said each sub-volume according to the value that corresponds to said each sub-volume; and displaying the dose-rate volume histogram as part of the GUI; generating a dose-rate volume histogram for a target volume, the dose-rate volume histogram indicating dose rates and percentages of the target volume that receive the dose rates, the dose-rate volume histogram generated based on values of parameters in a proposed treatment plan; displaying a graphical user interface comprising a rendering of a target volume, the target volume comprising a plurality of sub-volumes; and accessing information in the memory, the information comprising a dose rate received by each sub-volume of the sub-volumes, the dose rate received by a sub-volume determined using said parameters; wherein said displaying comprises: associating a value of an attribute to said each sub-volume, wherein the value corresponds to an amount of the dose rate received by said each sub-volume; rendering said each sub-volume according to the value that corresponds to said each sub-volume; and displaying the dose-rate volume histogram as part of the GUI; associating a value of an attribute to said each sub-volume, wherein the value corresponds to an amount of the dose rate received by said each sub-volume; rendering said each sub-volume according to the value that corresponds to said each sub-volume; and displaying the dose-rate volume histogram as part of the GUI; wherein the method performed by the processor further comprises adjusting values of parameters that can have an effect on dose rate until the dose rate-volume histogram satisfies objectives associated with treatment of a patient and generating a final radiation treatment plan using the dose rate-volume histogram.