| Background and AimsCancer has a serious impact on the health and longevity of people around the world.According to the World Health Organization's statistics of 172 countries in 2015,cancer was the first or second leading cause of death among people under the age of 70 in 91 countries,while it ranked third or fourth among other 22 countries.By 2018,there would be an estimated 18.1 million new cancer cases and 9.6 million cancer deaths worldwide,according to the global cancer statistics 2018:a big data analysis of 36 cancers in 185 countries published on the CA:A Cancer Journal for Clinicians.The morbidity and mortality of malignant tumors in China were also rising year by year.There are many ways to treat tumors,but the effect is limited,and the short-term and long-term side effects are obvious.For example,about 36%of patients with pelvic malignancy after radiotherapy developed gastrointestinal symptoms of radiation proctitis such as incontinence,pain,mucus secretion,and bleeding.In cervical cancer,radiation treatment was prone to vaginal mucosal inflammation,bleeding and pain.Compared with external beam radiotherapy(EBRT),the stereotactic brachytherapy with 1-125 particles can provide a high dose of radiation to the tumor target,while the normal tissues adjacent to the tumor lesions can only receive a low dose due to the rapid dose drop.This feature makes it possible to obtain a better tumor control rate,while the incidence of radiation-related complications in adjacent tissues is low.Therefore,as an important supplement to tumor treatment,I-125 particles stereotactic brachytherapy has rapidly developed:the FDA approved I-125 particles for the treatment of prostate cancer by the year 1984;In 2003,the Japanese Cancer Association published the clinical,guidelines of 1-125 particles implantation for the treatment of tumors;In the same year,Germany issued clinical guidelines for the treatment of tumors with I-125 particles;I-125 particles brachytherapy was introduced into China in the 1990s and developed rapidly in cities such as Beijing,Shanghai,Guangzhou and Nanjing.In 2009,China promulgated the"technical management standards for radioactive particle implantation therapy",and in the same year,the ministry of health approved the radioactive particle implantation therapy technology as the third type of medical technology.At present,the technology has been widely used in the treatment of prostate cancer,nasopharyngeal cancer,brain tumor,liver cancer,lung cancer,pancreatic cancer and other tumors,and achieved good short-term efficacy and palliative treatment effect.Increasing the radiation dose to the tumor target area can improve the efficacy,but the dose escalation is limited by dose-dependent radiation damage in normal tissues.In order to reduce radiotoxicity of the adjacent normal organs and tissues induced by stereotactic brachytherapy with I-125 particles and escalate the target dosage as much as possible,a variety of ways are used,such as clearer images(MRI),optimization designs and implant procedures(preplanning,intraoperative planning,etc.),and improvement of puncture accuracy with the aid of auxiliary equipment(coplanar template,3D printing non templates and auto-positioning system),etc.These methods ensure the optimal dose distribution by continuously and accurately correcting the intraoperative morphology of the tumor,needle placement and the position of I-125 particles.However,no matter which method is proposed above,the low-dose area can only reach the dose requirement by increasing the I-125 particles.The high-dose area that has been formed beyond the dose limit cannot be remedied.If normal organs or tissues are located in the high-dose area,dose-related toxicity may occur.Therefore,other scholars proposed the concept of spacer,which means to implant a material of spacer to keep the organ at risk away from the high-dose area.What these spacers have in common is that they are well tolerated during implantation.remaining in a stable position during radiotherapy,and are not allergenic or toxic.Previous studies have used materials such as hyaluronic acid,human collagen,inflatable balloon and hydrogels.By injecting the spacer into the anterior space of the rectum,the dosage of the rectum is decreased,thereby reducing the complications of radiation enteritis.At present,this technique has been applied in the treatment of prostate cancer and other tumors abroad.Hyaluronic acid(HA)has been widely used in medical field due to its biocompatibility and biodegradability.Foreign scholars used it in the stereotactic brachytherapy of prostate cancer patients with 1-125 particles,and injected it into the anterior rectal space to protect the rectum.These studies evaluated the efficacy of HA in protecting organs at risk in vivo through dose calculation,which was a theoretical simulation,and patients' main complaint symptoms,which were largely affected by patients' subjective factors.Meanwhile,there are few reports on clinical application,dosimetry and safety in China.Our research group first reviewed the clinical efficacy and complications of stereotactic brachytherapy with 1-125 particles for locally advanced and recurrent metastatic malignant tumors.This technique was effective in the treatment of tumors,but the complications caused by its radiation damage should not be ignored.To validate the hypothesis that HA can reduce the radioactive damage to organs at risk as a spacer,by increasing the distance away from the high-dose area,we designed the theory model of protecting organs at risk used in stereotactic radiotherapy with 1-125 particles,and further more visually observed the protection of organs at risk through the animal experiment research by HA injecting.Finally,a clinical observation was made on the application of HA in stereotactic brachytherapy of 1-125 particles to reduce the dose to organs at risk.Part 1 Observation of the clinical efficacy and complications ofstereotactic brachytherapy with 1-125 particles for locally advanced,recurrent and metastatic malignant tumorsObjectiveTo observe the clinical efficacy and complications of stereotactic brachytherapy with I-125 particles for locally advanced,recurrent and metastatic malignant tumors.MethodsA total of 33 patients with 35 lesions underwent CT-guided percutaneous stereotactic brachtherapy with I-125 particles in the department of comprehensive health care(oncology)of the east Hospital of Shandong Provincial Hospital affiliated to Shandong University from September 2014 to February 2016.Complete blood count,liver and kidney function,coagulation function were required within 1 week before surgery.The DICOM format enhanced CT images were transferred into BTPS for target delineation,including gross tumor volume(GTV),clinical target volume(CTV),and planning target volume(PTV).CTV was 0.5cm outside the GTV boundary.PTV=CTV.Designed puncture paths and distribution of I-125 particles,set prescription dose(PRD)as 120 Gy,obtained D90(the dose delivered to 90%of the target volume),D100(the dose delivered to 100%of the target volume),V90(the percentage of the target volume receiving 90%of the prescription dose),V100(the percentage of the target volume receiving 100%of the prescription dose),V150(the percentage of the target volume receiving 150%of the prescription dose).The dosimetric parameters should conform to criteria,D90?100%-125%of PRD and V100?90%,according to the British Columbia Cancer Agency(BBCA)brachytherapy quality assurance program.Ordered I-125 particles following the preoperative plan.The patient was fixed on the CT machine with a negative pressure vacuum pad according to the postures preoperatively formulated.A 5mm-thick CT scan was performed.I-125 particles were implanted into the tumor target guided by the preoperative plan and intraoperative real-time CT scan.After the implantation,CT scan was performed again to acquire the spatial distribution of particles and observe whether there were any complications.BTPS was used for dose verification,and dosimetric parameters such as D90,V90,D100,V100,V150 and dose volume histogram(DVH)were recorded.CT scan was performed 1,3 and 6 months after the operation to evaluate the efficacy.Response evaluation criteria in solid tumors(RECIST 1.1)were used to evaluate the therapeutic effect:complete response(CR),partial response(PR),stable disease(SD),and progressive disease(PD).Local control rate(LCR)and response rate(RR)were recorded.LCR=(CR+PR+SD)/total number of patients×100%;Response rate(RR)=(CR+PR)/total number of patients×100%.Complications were observed after the operation and during the period of follow up,including intrapulmonary hemorrhage,hemoptysis,thoracic hemorrhage,pneumothorax,subcutaneous emphysema,particle migration,radioactive pneumonia,radioactive liver injury,bile fistula,intestinal fistula,and digestive tract bleeding.SPSS 22.0 software was used,and all data in the experiment were expressed as mean±standard deviation(mean±SD).The cross-list analysis ?~2 test was used to compare the efficacy of different groups,and the test standard was?=0.05.Results1.Dosimetric outcomesThe prescription dose was 120Gy.The particle activity range was 18.5?29.6MBq(0.5-0.8mCi).The total number of particles ranged from 5 to 99,with an average of 34.D90 ranged from 11.7Gy to 342.8Gy,with an average of 121.5Gy.V90 ranged from 12.1%to 100%;with an average of 79.9%.V100 ranged from 10.7%to 100%,with an average of 76.9%.D100 ranged from 36.6Gy to 139.5Gy,with an average of 57.7Gy.V150 ranged from 6.4%to 99.7%,with an average of 60.8%.2.Short-term efficacy evaluationAll the 33 patients in this group were followed up after I-125 particles implantation.There were 7 cases of CR,22 cases of PR,3 cases of SD and 3 cases of PD one month after the operation.The LCR was 91.5%and the RR was 83%.There were 4 cases of CR,19 cases of PR,3 cases of SD and 4 cases of PD three months after the operation.The LCR was 86.6%and the RR was 76.6%.There were 3 cases of CR,16 cases of PR,2 cases of SD and 4 cases of PD six months after the operation.The LCR was 84.0%and the RR was 76.0%.There were 3 cases of CR,8 cases of PR,2 cases of SD and 4 cases of PD nine months after the operation.The LCR was 76.5%and the RR was 64.7%.3.Effect of synchronous chemotherapy on LCR and RRThere was no significant diffrence in LCR between the synchronous chemotherapy group and the non-synchronous chemotherapy group 1 month,3 months,6 months or 9 months after the operation(?~2=0.365,P=0.546;?~2=0.072,P=0.788;?~2=0.287,P=0.592;?~2=0.006,P=0.937).There was no statistically significant difference in RR between the synchronous chemotherapy group and the non-synchronous chemotherapy group 1 month,3 months,6 months or 9 months after the operation(?~2=0.05,P=0.823;?~2=0.186,P=0.666;?~2=0.003,P=0.959;?~2=0.243,P=0.622).4.ComplicationsAll patients were successfully completed the implantation,without serious current complications.Certain mild complications occurred including pulmonary hemorrhage in 7 cases(20%),needle hemorrhage in 4 cases(11.4%),subcutaneous hematoma in 2 cases(5.7%),pain in 5 cases(14.3%),mild pneumothorax in 1 case(2.9%),moderate and massive pneumothorax needed closed chest drainage in 5 patients(14.3%),late-onset pneumothorax in 1 case(2.9%),haemoptysis in 3 patients(8.6%),subcutaneous emphysema in 1 case(2.9%),and I-125 particles migration in 1 case(2.9%).None of the 33 patients in this group had serious complications such as large hemoptysis,massive hemorrhage,radioactive liver injury,biliary fistula,intestinal fistula,and gastrointestinal bleeding.ConclusionStereotactic brachytherapy with radioactive I-125 particles in the treatment of malignant tumors is a technique worthy of clinical promotion,which has the advantages of positive clinical efficacy,less trauma and fewer complications.The correlations between the curative effect and the pathological type,dose and combination of chemotherapy are not clear yet.Although complications are rare,the risk of complications increases after the dosage increased,and some complications are serious and require medical intervention.Part 2 A theoretical model established for the protection of organs at risk by stereotactic brachytherapy with 1-125 particlesObjectiveTo simulate the law of radiation dose decreasing with distance increasing theoretically,by establishing a target model for distributing 1-125 radioactive particles according to a certain prescription dose and simulating organs at risk of different distances from the target.Methods1.The establishment of tumor modelA circle with a diameter of 2cm was drawn by Photoshop.Numbered 1 in the bottom left corner of the picture,and save the picture in BMP format.Created a new file and drew a circle of the same diameter at the same place on the canvas using the method above.Numbered 2,3,4,5,6 and 7 in the bottom left corner of the picture respectively,and the pictures were saved as BMP images.The BMP images above named as 1,2,3,4,5,6 and 7 according to the number in the lower left corner were imported to BTPS in sequence,and rebuilt the sequence with spacing of 5mm.That was to build a cylindrical transversal image with a diameter of 2cm and a height of 3cm.2.The establishment of tumor target modelA new plan was created and the target was delineated along the circles with a diameter of 2cm using the green line as clinical target volume(CTV),which was a cylinder with a diameter of 2cm and a height of 3cm.3.Establishment of organs at risk modelSix rectangles with a width of 2mm and a length of 2cm were outlined on each layer.The closest long side of the rectangle to CTV was the reference line,and the distance between the organ at risk and the outer boundary of CTV was defined as the shortest length from the reference line to the outer boundary of CTV.Each layer was connected to form a cuboid with a height of 3cm.In other words,the distance between the cuboid tangent to the edge of CTV and the outer boundary of CTV is Omm.We named this cuboid OARO and delineated it in carmine.The cuboid with a distance of 2mm from the outer boundary of CTV was named OAR2,which was shown in deep red.The cuboid with a distance of 4mm from the outer boundary of CTV was named OAR4,which was shown in dark blue.The cuboid with a distance of 6mm from the outer boundary of CTV was named OAR6,which was indicated by light blue.The cuboid with a distance of 8mm from the outer boundary of CTV was named OAR8,which was represented by purple.The cuboid with a distance of 10mm from the outer boundary of CTV was named OAR 10,which was shown in orange.In order to avoid the distribution difference of isodose curve in all directions of the target due to the uneven distribution of particles in the CTV,the six simulated organs at risk were arranged in the same side of the CTV and in the same direction parallelly.4.Grouping and simulating distribution of 1-125 particlesThe activities of chosen particles were 0.3mCi(11.1MBq),0.6mCi(22.2MBq)and 0.8mCi(29.6MBq).And I-125 particles were distributed when the prescription doses were 80Gy,120Gy and 160Gy respectively.The dosimetric parameters were ensured reach the standard of D90?100?125%of the prescription dose and V100?90%.5.Calculation of dosimetric parameters and output of dose volume histogram(DVH)Dosimetric parameters related to CTV and OARs were calculated by BTPS and the DVH was generated.The CTV-related dosimetric parameters:D90,D100,V90,V100 and V150.The OAR-related dose parameters;D0.1cc(the maximum dose to 0.1 cc at the organ).6.Falling trend analysis of D0.1 cc(? D0.1 cc and ?D0.1 cc%)?D0.1 cc(the difference of adjacent OAR's DO.1cc):?2-0=D0.1cc(OAR2)-D0.1cc(OARO),?4-2=D0.1cc(OAR4)-D0.1cc(OAR2),?6-4=D0.1cc(OAR6)-D0.1cc(OAR4),?8-6=D0.1cc(OAR8)-D0.1cc(OAR6),?10-8=D0.1cc(OAR10)-D0.1 cc(OAR8).?D0.1cc%(the percentage of the decline of adjacent OAR's D0.1cc):?2-0%=?2-0/D0.1cc(OARO)×100%,?4-2%=?4-2/D0.1 cc(OAR2)×100%,A6-4%=?6-4/D0.1 cc(OAR4)×100%,?8-6%=?8-6/D0.1 cc(OAR6)×100%,?-8%=?10-8/D0.1 cc(OAR8)×100%.7.Statistical analysisMicrosoft Excel 2007 was used.The averages and standard deviations of D90,D100,V100 and V150 were calculated.The graphs of D0.1 cc,AD0.1 cc and AD0.1 cc%were drawn.The logarithm was taken,and the corresponding function formulas of D0.1cc were resulted in by curve fitting.Results1.Dosimetric parameters related to CTVGroup 1:the I-125 particle activity was 0.8mCi and the prescription dose was 80Gy.Group 2:the I-125 particle activity was 0.8mCi and the prescription dose was 120Gy.Group 3:the I-125 particle activity was 0.8mCi and the prescription dose was 160Gy.Group 4:the I-125 particle activity was 0.6mCi and the prescription dose was 80Gy.Group 5:the I-125 particle activity was 0.6mCi and the prescription dose was 120Gy;Group 6:the I-125 particle activity was 0.6mCi and the prescription dose was 160Gy;Group 7:the I-125 particle activity was 0.3mCi and the prescription dose was 80Gy;Group 8:the I-125 particle activity was 0.3mCi and prescription dose was 120Gy;Group 9:the I-125 particle activity was 0.3mCi and the prescription dose was 160Gy.The CTV volume of each group was constant.D90 was 90.7?193.22Gy(average 141.3±41.93Gy),D100 was 71.33?151.79Gy(average 107.29±29.47Gy),V100 was 97.1%?100%(average 98.66±1.01%),and V150 was 62.8%?73.6%(average 69.4±3.53%).The dosimetric parameters related to CTV in each group reached D90?100?125%of the prescription dose and V100?90%.2.D0.1cc of organs at riskGroup 1 for example:D0.1cc of OARO was 76.94Gy.D0.1cc of OAR2 was 56.09Gy.D0.1cc of OAR4 was 42.16Gy.D0.1cc of OAR6 was 32.48Gy.D0.1cc of OAR8 was 26.41Gy.DO.lcc of OAR10 was 21.36Gy.The dose to the organs at risk decreased gradually,and the D0.1cc of other groups of organs at risk also showed a decreasing trend from OARO to OAR10.The falling trends of group 1,4 and 7 were similar,while the curves were similar in group 2,5 and 8,so as the group 3,6 and 9.In other words,the falling trend of D0.1cc was more correlated with the prescription dose,but less correlated with the I-125 particle's activity.The corresponding function formulas of DO.lcc resulted in by curve fitting were similar in group 1,4 and 7,while the corresponding function formulas of D0.1 cc were approximate in group 2,5 and 8,so as the group 3,6 and 9.It could be further confirmed by the formula that the falling trend of dose was less correlated with the I-125 particle's activity,but was more correlated with the prescription dose.3.Dose volume histogram(DVH)The DVH of each group showed that the area under the curve of the organ at risk decreased gradually from OARO to OAR10,and the relationship between the DVH curve and the abscissa indicated that the volume of the high dose of organs at risk from OARO to OAR10 decreased gradually too.With the increase of the distance between the organs at risk and CTV,the dose to the organs at risk decreased gradually,and the volumes received high dose also decreased gradually4.Falling trend analysis of D0.1cc(?D0.1cc and AD0.1cc%)A broken line graph of ?D0.1cc was drawn.There were no obvious grouping trend among the curves of all groups,all of which had a significant decline at the beginning and gradually become smooth later.The higher the prescription doses were,the steeper the curves were.The lower the prescription doses were,the smoother the curves were.The curves almost coincided with each other according to the broken line graph of ADO.lcc%.And the data of each group decreased by a certain percentage,which decreased gradually with the increase of distance.Regardless of the prescription dose and the I-125 particle activity,the dose to the organ at risk decreased by a certain percentage when the distance of which increased with a certain lengthConclusionWhen the dosimetric parameters of the CTV reached the standard of D90?100?125%of the prescription dose and V100?90%,the dose to the organ at risk gradually decreased with the increase of the distance between the organ at risk and the CTV,and the volume received high dose gradually decreased too.Regardless of the prescription dose and the 1-125 particle activity,the dose to the organ at risk decreased significantly with the increase of distance at the beginning,then the decline trend gradually became smooth subsequently.The higher the prescription doses,the more obvious the changes were.And the percentage of dose decline had no significant correlation with the prescription dose or particle activity.Theoretically,by increasing the distance between the organ at risk and the CTV,the dose to the organ at risk can be reduced,and the formula can be derived from the established theoretical model to estimate the relationship between the distance and the dose to the organ at risk.Whether it can be used for clinical reference needs to be further verified.Part 3 The application of hyaluronic acid used for protection of the organ at risk during stereotactic brachytherapy with I-125 particles in the animal experimentObjectiveThe method of injecting HA subcutaneously to increase the distance between 1-125 radioactive particles and skin was observed through the animal experiment,and the changes of animal skin were observed to explore the feasibility,effectiveness and safety of this technique in reducing the dose to organs at risk.Methods1.Grouping and weighingSix 8-week-old Sprague-Dawley rats were divided into four groups and marked with amygdalic acid.There were one rat in the blank group marked with right hind leg,one rat in the HA group labeled right foreleg,two rats labeled left ear and right ear respectively in the 1-125 particle group and two rats labeled left hind leg and left foreleg respectively in the 1-125 particles+HA group.2.Anesthesia 1.5%pentobarbital(0.2ml/100g)was injected intraperitoneally.3.Shaving to expose the skinAfter anesthesia,the hair was removed from the back of the rats to expose the skin with an area about 3×5cm,so as to facilitate skin observation.4.I-125 partical implantationA 18Gx 1 Ocm intervention needle was inserted under the exposed skin of the rats,then the needle core was removed,and the donor was connected.Four 29.6MBq I-125 particles were implanted.Removed the applicator,placed the needle core,and pulled out the intervention needle.The operations above were performed on the I-125 group and the I-125+HA group.5.HA injection2ml-HA was injected subcutaneously into the exposed part of the skin of the rats through the intervention needle.The operations were performed on the HA group and the I-125+HA group.And in the I-125+HA group,HA was injected between the skin and I-125 particles.6.CT scanCT scans were performed immediately after the operation and at the 1st,3rd and 6th months,respectively,to observe the changes of thickness of HA and the relationship between I-125 particles and the position of HA.7.Skin observationThe living condition,skin color,integrity and hair growth of rats were observed and recorded every week.8.End pointThe rats were put to death after 6 months,and the I-125 particles were removed for recycling.Results1.Two months after the operation,1 rat in the I-125 group died,and the other rats were generally in good condition.2.The hair on the back of the rats in the blank group,HA group and I-125 particle+HA group gradually grew to complete coverage within 1 month,and the skin was intact.But the growth rates of the hair were different.The sequence from fast to slow was 1-125 particle+HA group,blank group and then HA group.On the other hand,1×1cm hair defects still existed on the backs of the I-125 group 1 month after the operation,which lasted until the end of the experiment,that is,6 months,with no obvious local ulceration.3.According to the comparison of CT images,the shape and thickness of HA in the HA group remained basically stable within 6 months.In the CT images of I-125 group and I-125+HA group,some particles showed displacement,while the shape of HA was slightly changed.ConclusionThe HA was injected subcutaneously to increase the distance between the I-125 radioactive particles and the skin,which had a protective effect on the skin of rats.Part 4 Clinical observation of hyaluronic acid in reducing the dose to the organ at risk in tumors treated by stereotactic brachytherapy with I-125 particlesObjectiveTo investigate the feasibility of HA injection to increase the distance between the skin and the radiation source and dose reduction of skin during stereotactic brachytherapy of subcutaneous metastatic tumors with 1-125 particles.MethodsEleven patients with subcutaneous malignancy were recruited between August and December 2017.The patient characteristics such as age,gender,pathological type of primary tumor,previous treatment,location of subcutaneous metastasis and other information were recorded.The preoperative enhanced CT scan was performed,and the image information should include subcutaneous metastasis.Images in DICOM format were stored,which were imported into BTPS.The external boundary of the tumor was delineated as the tumor target(GTV).On the basis of GTV,the clinical target,namely CTV,was generated by the outward expansion of 5mm.CTV was equivalent to PTV.A 2mm thick outline was delineated below the skin surface,representing the skin,the organ at risk,to be observed.The prescription doses were set as 100?140Gy,and the I-125 particle activities were 0.6?0.8mCi(22.2?29.6MBq).Preoperative planning was carried out to meet the dosimetric parameters:D90?100?125%of the prescription dose,and VI00?90%.According to the plan delivered by BTPS,the number of I-125 particles was expected to rise by 20%,when we ordered the radioactive particles.Under the guidance of CT,I-125 particles were implanted into the tumor target one by one following the preoperative plan.Immediately after the I-125 implantation,CT scan was performed to outline the tumor target,pick up the particles,reconstruct the source location and calculate the dose distribution on the newly acquired images.If the dosimetric parameters did not reach the target dose,the positions of needles and numbers of I-125 particles would be adjusted in real time.According to postoperative dosimetry verification,the skin area received high dose was found,then the needle passage and puncture point on skin required for HA injection were determined.The needle tip was placed in the high-dose area of the organ at risk,and HA was injected into the space between the tumor and the skin.The total volume of HA injection depended on the actual thickness of the spacer after injection and the dose to the organ at risk calculated by repeated real-time dose verification.The target volume,D90,V100,OAR-Max(the maximum dose to 0.1 cc at the skin),OAR-Mean(the mean dose to the skin)and DVH before and after HA injection were recorded,so as the HA dose,the thickness of spacer,the pathway of injection and the time needed for injection.All patients were followed up at the 1st,3rd and 6th months after HA injection.The follow-up contents included the skin status,evaluation of the radiation toxicity of the skin according to the Radiation Therapy Oncology Group(RTOG)scoring criteria for acute radiation injury,CT or MRI images of the HA injection site,and the thickness of HA for subcutaneous injection.Statistical analysis was performed using SPSS 22.0 statistical software(SPSS Inc.,Chicago,IL,USA).We selected the single tail paired t test to compare the dosimetric parameters before and after HA injection.P<0.05 was defined as a significant difference.Results1.Patient characteristicsThe 11 patients consisted of 10 males and 1 female with a median age of 61 years old(range 51 to 78 years old).The cases included primary cancers of the following:5 cases of lung cancer,1 case of gastric cancer,1 case of pleural mesothelioma,2 cases of lymphoma,1 case of malignant melanoma,and 1 case of adenocarcinoma of unknown primary foci.The implantation sites of I-125 particles were chest wall in 4 cases,neck in 3 cases,back in 1 case,abdominal wall in 1 case,arm in 1 case and groin in 1 case.All patients were treated with chemotherapy and had no previous history of radiotherapy.2.New space between tumor and skin created by HA injectionThe average volume of HA injection in the enrolled patients in this study was 4.2ml(range from 1.6 to 8.0ml),and the average thickness of new space created by HA injection was 1.0cm(range from 0.6 to 1.5cm).The average increased time due to HA injection was 17.2min(range from 5 to 36min),and the average increased number of needles was 1.1(ranging from 0 to 3).3.Dosimetric results before and after HA injectionThe average V100 of CTV before HA injection was 91.18%(range:69.6-100%),and the average V100 after HA injection was 91.17%(range:70.7?100%).The average D90 before HA injection was 142.47Gy(range:65.96?208.52Gy),and the average D90 after HA injection was 141.44Gy(range:70.66?213.02Gy).There was no significant difference in V100 and D90 of tumor targets before and after HA injection(p=0.50 and p=0.39,respectively).The average OAR-max and OAR-mean before HA injection were 100.66Gy and 49.20Gy,respectively,while the average OAR-max and OAR-mean after HA injection were 61.20Gy and 17.27Gy,respectively.The values after HA injection were significantly lower than those before HA injection(p=0.01 and p=0.04,respectively).4.Follow-upThe follow-up period ranged from 1 to 6 months,with an average of 3.36 months.No side effects associated with the injection or the compound itself were observed.All the radioactive skin lesions were ranged from 0 to 1 degree.During subsequent image review,HA itself remained stable in shape and position for 6 months.ConclusionIn patients with subcutaneous metastatic tumors,HA could be injected to obtain a space between the tumor and the skin,which could significantly reduce the skin dose in stereotactic brachytherapy with I-125 particles.This approach offers the possibility of preventing the delivery of high doses of radiation to adjacent normal tissues during tumor treatment. |
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