current situation is the result of the increasing number of cases of patients being diagnosed in an extended state of the disease ( ca 70% of cases  local extent ) and its frequent occurrence in elderly people ( 50% above 65 years old , 30% 70 years old ) , who are usually stressed with coexisting diseases . in these cases
an important element of cancer treatment is palliative treatment , which mainly aims at improving the quality of life by mitigating the symptoms associated with the disease .
the endobronchial location of the cancer can cause hemoptysis , atelectasis , and many other related symptoms , such as dyspnoea , cough , and chronic inflammation .
the removal of the endobronchial obstruction often significantly improves the health status of the patient , which in turn affects the quality of the patient 's life .
high - dose - rate ( hdr ) brachytherapy is one of the most effective methods used in palliative treatment [ 27 ] . in the application of treatment for endobronchial brachytherapy , the most commonly used orthogonal images are recorded using x - rays , which provide good visualization of the catheter and the bone tissue . in cases where one catheter is used , in order to illustrate the distribution of the isodoses around the guide , the dose can be defined by the reference points .
these points are located at a constant distance from the guide or can be designated at different distances from the catheter .
if many guides are used , the dose in the area of the envelope is calculated .
the envelope is the area containing the catheters , in which the dose is specified at the same depth .
the aim of this method is to choose a calculation point located between all of the guides , as well as those farthest from the nearest guide .
the selection of such a point allows for the inclusion of the minimal dose within the area of interest . during the treatment plans
, the use of a larger number of guides and handling these guides with different reference points allows for the reduction or increase of the dose in the area of the tumor , simultaneously with the least possible coverage of critical organs [ 8 , 9 ] .
the paper present comparison of treatment plans made by using 2d and 3d methods in the oncentra planning system 4.1 sp2 version , brachy planning module ( nucletron , an elekta company , elekta ab , stockholm , sweden ) , as well as to assess the quality of treatment plans using the 2d and 3d methods . as such
, the study is based on a group of patients treated in the brachytherapy department of the subcarpathian cancer center in brzozw .
the studies involved a group of 31 patients with advanced lung cancer treated in the brachytherapy department of the subcarpathian cancer center in brzozw from 2011 to 2013 . in total , 31 patients and 76 treatment plans were analyzed .
patients were treated with a microselectron unit ( nucletron , an elekta company , elekta ab , stockholm , sweden ) with an ir source , with a nominal activity of 10 ci .
the treatment was applied using the oncentra masterplan brachy 4.0 system ( nucletron , an elekta company , elekta ab , stockholm , sweden ) . in brachytherapy ,
the lumencath applicator set was used ( nucletron , an elekta company , elekta ab , stockholm , sweden ) .
all patient treatment was based on computed tomography of the thorax ( ct ge brightspeed , milwaukee , wi , usa ) .
the endobronchial brachytherapy procedures were performed using local anesthesia under the control of a bronchovideoscope . during the bronchoscopy
, guides were inserted in the bronchial tree and in the area of or near the tumor 's location . in the 3d method of treatment ,
three - dimensional images from computer tomography were used , so the physician could contour the volume of the tumor and critical structures .
the physicist reconstructed the catheter or catheters in the treatment plan system , activated the source position near the ptv area and then carried out the optimization of the treatment plan . in this method ,
performed using the 2d method , images from the simulix oldelft simulator were used ( nucletron , an elekta company , elekta ab , stockholm , sweden ) .
the dwell time was calculated in a different way : the catheter was created via virtual tomography , the length of the catheter , and the location of the source in it were the same as those in the 3d method , but the dose was specified to 1 cm from the catheter . the dwell time calculated in the 2d method
was transferred to the treatment plan performed based on the 3d imaging method . after changing the dwell time ,
a comparison was made of the reference dose coverage of the target ( ptv ) by the isodose of 100% and 85% , and the calculation of the dose at 2 cm to the critical organ ( spinal cord ) was performer .
comparison of ptv coverage in the 3d method to the 2d method highlighted the significant differences between these two methods .
reference dose coverage of the target ( ptv ) by isodose of 100% and 85% , as well as the dose to the critical organ received at 2 cm ( in this case , the spinal cord ) , were compared . for the comparison of the variables in the 3d and the 2d methods , tests from two independent trials
the tests assumed unequal variances , which were most suitable for comparing quantitative variables in the two groups . in the case of 100% ptv ,
the p value was 0.0001 , indicating that the statistical differences between the 3d and the 2d methods are significant . 

figure 1 depicts that the average method for the 3d and 2d was 75.82% and 45.05% , respectively .
the standard deviation for the 3d method was 22.72% , and for the 2d method  25.63% , meaning there was a greater variation among the 2d results within the trial .
however , the maximal values did not differ significantly between the 3d method and the 2d method ( the maximal value in the 2d method was 0.33% higher than the maximal value in the 3d method ) .
the reverse was observed for the minimal values ; for the 3d method , the minimal value was 20.26% , and for the 2d method it was 8.16% .
basic measures of outcomes : ptv100 in the 3d and the 2d methods in cases where ptv was 85% ( just as when ptv was 100% ) , the p value was 0.0001 , which means that the statistical differences between the 3d method and the 2d method are significant .
figure 2 presents that the average in the 3d method is 36.31% higher than in the 2d method , and the median in the 3d method is 30.58% higher than in the 2d method .
the minimal value in the 3d method was 36.1% and in the 2d method it was 14.82% .
however , the maximal values did not differ significantly between the 3d and 2d methods .
basic measures of outcomes : ptv85 in the 3d and 2d methods when the dose was used on the spinal cord every 2 cm , the p value was 0.009 , implying significant statistical differences between the 3d method and the 2d method .
figure 3 shows that the average value of the results for the 3d method are 0.17 gy higher than in the 2d method . in the case of maximal values ,
the results for the 2d method are 0.44 gy higher than for the 3d method .
the standard deviation is not significantly higher ( about 0.02 gy ) for the 2d method than for the 3d method , when the dose was used on the spinal cord every 2 cm . 
 
basic measures of outcomes : dose used on the spinal cord every 2 cm in the 3d and 2d methods
for the comparison of the variables in the 3d and the 2d methods , tests from two independent trials were used .
the tests assumed unequal variances , which were most suitable for comparing quantitative variables in the two groups . in the case of 100% ptv ,
the p value was 0.0001 , indicating that the statistical differences between the 3d and the 2d methods are significant . 

figure 1 depicts that the average method for the 3d and 2d was 75.82% and 45.05% , respectively .
the standard deviation for the 3d method was 22.72% , and for the 2d method 
25.63% , meaning there was a greater variation among the 2d results within the trial .
however , the maximal values did not differ significantly between the 3d method and the 2d method ( the maximal value in the 2d method was 0.33% higher than the maximal value in the 3d method ) .
the reverse was observed for the minimal values ; for the 3d method , the minimal value was 20.26% , and for the 2d method it was 8.16% .
in cases where ptv was 85% ( just as when ptv was 100% ) , the p value was 0.0001 , which means that the statistical differences between the 3d method and the 2d method are significant .
figure 2 presents that the average in the 3d method is 36.31% higher than in the 2d method , and the median in the 3d method is 30.58% higher than in the 2d method .
the minimal value in the 3d method was 36.1% and in the 2d method it was 14.82% .
however , the maximal values did not differ significantly between the 3d and 2d methods .
when the dose was used on the spinal cord every 2 cm , the p value was 0.009 , implying significant statistical differences between the 3d method and the 2d method .
figure 3 shows that the average value of the results for the 3d method are 0.17 gy higher than in the 2d method . in the case of maximal values ,
the results for the 2d method are 0.44 gy higher than for the 3d method .
the standard deviation is not significantly higher ( about 0.02 gy ) for the 2d method than for the 3d method , when the dose was used on the spinal cord every 2 cm . 
 
basic measures of outcomes : dose used on the spinal cord every 2 cm in the 3d and 2d methods
complications that can occur after endobronchial brachytherapy such as hemorrhages , shunts , radiation - induced pneumonia or bronchitis and radiation - induced stenosis have justified the search for new and better solutions that can reduce these side effects [ 10 , 11 ] .
the planning of treatment with the use of two - dimensional images can not precisely determine where to find the area of the tumor .
specifying the dose of the points that are located at a distance of 1 cm from the applicator , we have no possibility to optimize the treatment plan while considering critical organs . with the 2d method
, the dose to critical organs often exceeds the limit values and simultaneously disqualifies the treatment plan . in the 3d method
, we can precisely determine the position of the tumor and critical organs , which allows us to optimize the treatment and limit the dose to critical organs . 

figure 4 provides a comparison between the dvh for both methods , where it can be seen that a much better coverage of ptv dose is required in the 3d method than the 2d . at the same time
, we can notice that the dose the critical organs receive is slightly different in the two methods .
we can clearly state that a plan using 3d images gives better results in terms of treatment planning .
technological progress and the utilization of computed tomography increases the possibility for treatment and reduces its toxicity . applying treatment with the 3d method
, there is a possibility for dose optimization , decreasing the dose for the critical organs , and as a result , reducing the toxic effects of treatment on healthy tissue [ 6 , 12 , 13 ] .
comparison of dvh for treatment plans in 3d ( purple line ) and 2d ( brown line ) methods and the spinal cord ( 3d  green line , 2d  blue line ) the main advantages of hdr brachytherapy include the simplicity of the procedure , short duration of treatment , and the possibility for patient to undergo the therapy in an outpatient setting .
computed tomography allows for precise determination of the size of the tumor before the procedure , as well as determination of the changes in the bronchial tree that have occurred during therapy . in facilities that are ct - equipped
, the 3d method should be routinely used in applying treatment in different localizations of tumors . the 3d method based on dynamic imaging
the conclusions from the analysis and interpretation of the results of the research are as follows : reference doses with 100% coverage of the ptv in treatment applied with the 3d method are 31% higher than when applied with the 2d method.determination of the target area and the area of critical tissues is possible to a far greater extent by the application of the 3d method than is the case with the 2d method .
the former method allows for the administration of high therapeutic doses , while minimizing any impact on critical organs.in the 2d method , application of dose is specified 1 cm from the catheter .
 hot points  are those areas where the dose is much higher than specified .
such problems do not occur in the 3d method , which allows for uniformity of high doses . 
 
reference doses with 100% coverage of the ptv in treatment applied with the 3d method are 31% higher than when applied with the 2d method .
determination of the target area and the area of critical tissues is possible to a far greater extent by the application of the 3d method than is the case with the 2d method .
the former method allows for the administration of high therapeutic doses , while minimizing any impact on critical organs . in the 2d method ,
such problems do not occur in the 3d method , which allows for uniformity of high doses .
 purposeto present comparison of treatment plans made by using 2d and 3d methods in the planning system , as well as to assess the quality of treatment plans using the 2d and 3d methods.material and methodsthe studies involved a group of 31 patients with advanced lung cancer treated in the brachytherapy department of the subcarpathian cancer center in brzozw from 2011 to 2013 . in total 
 , 31 patients and 76 treatment plans were analyzed . 
 we compared coverage of ptv planned in 3d and 2d . in the 3d method of treatment , 
 three - dimensional images from computer tomography were used . in treatment plans 
 performed using the 2d method , images from the simulator were used.resultsthe comparison of treatment plans made by using 2d and 3d methods is described . 
 this comparison highlighted the significant differences between these two methods assessing reference dose coverage of the ptv by 100% and 85% isodose.conclusionsreference doses with 100% coverage of the ptv in treatment applied with the 3d method are 31% higher than when applied with the 2d method . 
Purpose
Material and methods
Results
Dose coverage 100% PTV
Dose coverage 85% PTV
Dose for the spinal cord per every 2 cm
Discussion
Conclusions
Disclosure