Intracystic irradiation for craniopharyngiomas.

Data collected over a 36-year period were used to assess the value of stereotactically applied intracystic colloidal yttrium-90 (YTx) for the treatment of recurrent cystic craniopharyngiomas (CRF's). The article compares data from 95 YTx procedures carried out on 78 patients during the years 1975 and 2011, using a cumulative beta dose of 270 Gy aimed at the inner surface of the cyst wall. After YTx, the initial cyst volumes decreased an average of 74.7 %. In 54 patients, the volume reduction exceeded 80 %. In 32 patients, the cyst disappeared completely within one year. The mean survival rate following YTx was 7.5 years (range 0.7-31 years). The survival rates at 5, 10, 15, 20, 25, and 30 years were 56, 29, 15, 8, 3, and 1 %, respectively. Late complications of YTx were related to the anatomical location of the cyst, either presellar or retrosellar. A presellar, that is, prechiasmatic/suprasellar localization resulted in neuro-ophthalmological complications in 5.1 % of the cases, while internal carotid artery injury accounted for 1.4 % of the complications. The treatment of retrosellar (retrochiasmatic, suprasellar) tumors may cause hypothalamic, fornix, or pontomesencephalothalamic damage, from untoward radiation to the so-called perforating arteries. This complication occurred in 5.2 % of the cases. In the multimodality management of craniopharyngioma cysts, intracavity YTx irradiation is a valuable treatment alternative despite sporadic complications arising in some surgical cases. The formula for the calculation of the dynamics of reduction of CRF's following yttrium-90 colloid brachytherapy was supported by correlating the collected data. The focus was on our minimally invasive YTx following multiple surgeries of cystic CRFs.

[Extension of polynomial analysis of interstitial I-125 brachytherapy for 48 months]. / Gliomák 125I-brachytherapiáját leíró polinomiális analízis kiterjesztese 48 hónapos idotartamra--kiegészíto közlemény.

OBJECTIVE: Previously we described from 20 patients' data with our new "polynomial prediction approach" the volumetrical changes following gliomas 1-125 brachytherapy. The aim of this study is to extend the polynomials for 48 months, and to carry out multivarial analysis of several different aspects. METHODS: 20 inoperable low-grade gliomas were followed for a 48-month period after 1-125 interstitial irradiation. The delivered dose on the tumor surface was 50-60 Gy. Dose planning and image fusion were done with the BrainLab Target 1.19 software, mathematical and statistical computations were carried out with the Matlab numeric computation and visualization software. Volumes of tumor necrosis, reactive zone and edema referred to as "triple ring" were measured on image fused control MRI and planning CT images. The measured volumes were normalized with respect to the reference volumes. Mean values of volumes were determined, then polynomials were fitted to the mean using the polynomial curve fitting method. The accuracy of our results was verified by correlating the predicted data with the measured ones. RESULTS: We have found that the edema reaches its maximum two times after irradiation during the 48 months follow up period. We have shown that small tumors react more rapidly and creating greater volumes of the "triple ring" than bigger ones. CONCLUSIONS: The polynomial prediction approach proposed here reveals the dynamics of triple ring for 48 months. The derived polynomials and the multivarial analysis carried out afterwards help to (i) design the best treatment, (ii) follow up the patient's condition and (iii) plan reirradiation if necessary.

[Shrinkage dynamics of cystic craniopharyngeomas after Yttrium-90 colloid brachytherapy]. / Cystás craniopharyngeomák zsugorodásának dinamikája 90ittrium-brachytherapia után.

OBJECTIVE: The aim of this study is to reveal the long-term effect of Yttrium-90 colloid radioisotope brachytherapy applied for the treatment of cystic craniopharyngiomas. To provide a mathematical expression that can describe the cyst reduction as a function of time in an accurate matter. METHODS: Fourteen cystic craniopharyngiomas were selected for intracavital irradiation with stereotactically implanted beta-emitting radioisotope Yttrium-90 silicate colloid. The cumulative dose aimed at the inner surface of the cyst wall was ranging between 180-300 Gy. Volumes of the cysts were measured on image-fused control CT/MRI images for a 28-month period. Dose planning was done with our own software, while stereotactic calculations, volume calculations and image fusion were done with the BrainLab Target 1.19 software. Mathematical and statistical computations were carried out with the Matlab numeric computation and visualization software. To determine the volumes, the control images were fused with the planning images. RESULTS: Relative volumes normalized with respect to the volume of cysts before irradation were determined from the patients' measured data, the mean values of volumes were calculated, then a polynomial was fitted to the mean values using the polynomial curve fitting method. We have found that the dynamics describing the reduction of cysts can be expressed mathematically by the polynomial V=93.627-18.091t + 1.473t2 - 0.054t3 + 0.0007t4, where "t" denotes the time in months passed after irradiation. The accuracy of our results was verified by correlating the predicted data with the measured ones. CONCLUSIONS: Our long-term results support the view, that intracavitary Yttrium-90 irradiation is a non invasive and very effective method for treatment of craniopharyngioma cysts. The derived polynomial helps to 1. design the best treatment, 2. follow up patients' condition and 3. plan a reirradiation if necessary.

Image fusion guided brachytherapy of brain tumors.

The paper is the summary of mostly published works of the clinical results of intracavitary Yttrium-90 colloid irradiation of recurrent cystic craniopharyngiomas, and Iodine-125 interstitial irradiation of gliomas, pinealomas, brainstem tumors, recurrent meningeomas, solid craniopharyngiomas and metastases. It concisely demonstrates the usefulness of image fusion in the verification of isotope seeds and catheters, the comparison of 125 Iodine stereotactic brachytherapy and LINAC radiosurgery modalities on physical dose distribution and radiobiological efficacy, and the analysis of volumetric changes after interstitial irradiation of gliomas. Results of the immunohistochemical study deal with the role of microglia/macrophage system in the tissue response to 1-125 interstitial brachytherapy of cerebral gliomas. Due to financial reasons, gamma knife and Linac are not available to many countries and neurosurgical institutes. In the absence of the above mentioned radiosurgical methods, we have shown brachytherapy as an alternative solution in the treatment of different types of inoperable or recurrent brain tumors. The observed results may be noticable at LINAC and gamma knife irradiation too.

Prediction of volumetric change in the "triple ring" caused by glioma I-125 brachytherapy.

The aim of this study was to reveal the volumetric changes in tumor necrosis, reactive zone, and edema referred to as the "triple ring" appearing after low-dose-rate iodine-125 (I-125) interstitial irradiation of 20 inoperable low-grade gliomas. To enable prediction of these volumetric changes, we provide mathematical expressions that describe the dynamics of the triple ring. Volumes of the three regions on image-fused control CT/MR images were measured for a 24-month period. The delivered dose on the tumor surface was 50-60 Gy. Dose planning and image fusion were performed with Brain-Lab Target 1.19 software; mathematical and statistical computations were carried out with Matlab numeric computation and visualization software. To determine the volumes, control images with the triple rings were fused with the planning images. Relative volumes normalized with respect to the volume of reference dose were calculated and plotted in the time domain. First, the mean values of volumes were determined from the patients' measured data; then, polynomials were fitted to the mean values using the polynomial curve-fitting method. The accuracy of our results was verified by correlating the predicted data with the measured ones. The polynomial prediction approach proposed here reveals the dynamics of the triple ring. These polynomials will assist with (1) designing the best treatment, (2) following the patient's condition, and (3) planning reirradiation if necessary.

[Chronologic dynamics of the "triple ring," caused by interstitial Iodine-125 brachytherapy with a novel method of image fusion]. / A szövetközi 125-jód-brachytherapia következményeként kialakuló "hármas gyûrû" idôbeli változása, dinamikája új, polinomillesztésen alapuló módszerrel.

OBJECTIVE: The aim of this study is to reveal the volumetric changes in tumor necrosis, reactive zone and edema following low-dose rate 1-125 interstitial irradiation of 20 inoperable (partially non-resectable, partially inoperable) low-grade gliomas. METHODS: The volumes of the three regions on image-fused control CT/MRI images were measured for a 24-month period with 36 occasions. The delivered dose on the tumor surface (GTV) was 50-60 Gy. Dose planning and image fusion were performed with the BrainLab Target 1.19 software, mathematical and statistical computations were carried out with the Matlab Numeric Computation and Visualization software. The control images with the "triple ring" were fused with the planning images, and the isodose curves were adjusted to them. RESULTS: Relative volumes normalized to volume of the reference dose were calculated and plotted in the time domain. The mean values of volumes were determined from the patients' measured data then a polynom was fitted to the mean values using the polynomial curve fitting method. The accuracy of our results were verified by statistical tools. CONCLUSIONS: The new polynomial prediction approach using image fusion analysis of the volume of tumor necrosis, reactive ring and edema caused by interstitial irradiation as a function of time provides valuable information for 1. selecting the best patient's treatment option, 2. following up patient's condition and 3. planning reirradiation or reoperation if necessary.

Long-term results and late complications after intracavitary yttrium-90 colloid irradiation of recurrent cystic craniopharyngiomas.

OBJECTIVE: Data were analyzed to assess the value of stereotactically applied intracystic colloidal yttrium-90 (YTx) for the treatment of recurrent cystic craniopharyngiomas during a 30-year period. METHODS: This article compares data from 73 YTx procedures in 60 patients between 1975 and 2006. The cumulative beta dose aimed at the inner surface of the cyst wall was 300 Gy. RESULTS: After YTx, the initial cyst volumes decreased an average of 79%. In 47, the reduction was more than 80%; in 27 of them, the cyst disappeared completely within 1 year. The mean survival after YTx was 9.4 years (range, 0.7-30 yr). Actuarial survival rates at 5, 10, 15, 20, 25, and 30 years were 81, 61, 45, 18, 2, and 0%, respectively. Late complications of YTx were related to the anatomic localization of the cyst, either presellar and retrosellar, e.g., a presellar (prechiasmatic/suprasellar) localization caused neuro-ophthalmological complications in 5.8% and internal carotid artery injury in 1.6%. The treatment of retrosellar (retrochiasmatic, suprasellar) tumors occasionally induced hypothalamic and/or pontomesencephalothalamic damage obviously by untoward radiation to the so-called perforating arteries. This occurred in 3.2% of these latter patients. CONCLUSION: Despite sporadic complications, intracavitary YTx irradiation is a valuable treatment alternative for craniopharyngioma cysts, sometimes as part of a multimodality management in these tumors, especially in precarious surgical cases.

[The possibilities of fractionated external beam repeat irradiation of relapsed primary brain tumours: the first Hungarian experience]. / Az ismételt frakcionált külso sugárkezelés (reirradiáció) elsodleges központi idegrendszeri daganatok kiújulásának kezelésére: az elsô hazai tapasztalatok.

INTRODUCTION: The practice of image-based three dimensional treatment planning and conformal radiotherapy techniques offer the opportunity to elaborate novel treatment forms, e.g. repeat irradiation techniques for primary brain tumours. AIM: The authors analysed the effect on survival and toxicity of fractionated external beam repeat irradiation in brain tumour patients. METHODS: At the National Institute of Oncology, between 2002 and 2006, fractionated external beam repeat irradiation was performed in eleven patients with recurrent primary brain tumour, with total of 50-54 Gy or near total of 34-40 Gy doses. All patients were previously treated with total radiotherapy doses of 50-64 Gy. The intervals between radiotherapy courses were in the range of 7-30 years. All the treatments were carried out with 3D image-based conformal methods, the fractionation was conventional, with 1,8-2,0 Gy daily fractions in all cases. RESULTS: The repeat irradiation was tolerated well in the material. No grade 3-4 acute toxicity was detected, and serious, grade 3 mental deterioration, not related tumour progression was observed in only one case. In one case reoperation was necessary due to histologically verified radio-necrosis with mass-effect, and we believe that late neurotoxicity caused serious functional inabilities in one case. The median progression free survival was 8 (2-33) months, the median survival was 13 (4,5-33) months. Three of our patients were alive at the end of the study. CONCLUSIONS: Based on this experience and current knowledge, in absence of other treatment possibilities, the fractionated external beam repeat irradiation with near total doses could be a therapeutic choice in case of recurrent primary brain tumours, if having appropriate background. To define the optimal treatment strategy and regimens, further clinical trials should be carried out.

The role of microglia/macrophage system in the tissue response to I-125 interstitial brachytherapy of cerebral gliomas.

OBJECTIVE: To study histopathologic changes and the role of the microglia/macrophage cell in the therapeutic effect of I-125 interstitial brachytherapy on the cerebral gliomas. METHODS: Out of a series of 60 cases with cerebral astrocytomas and other brain tumors treated with I-125 interstitial brachytherapy, autopsy materials were available in ten cases 0.75 and 60 months after irradiation. The patients were treated with the maximum dosage (60 Gy) on the tumor periphery. Besides the routine hematoxylin-eosine and Mallory's PTAH trichrome staining, immunohistochemical reactions were carried out for CD15, CD31, CD34, CD45, CD68, CPM, HAM56 and HLR-DR antigens on paraffin sections to study immunologic phenotypic characteristics of the reaction cell population around gliomas after I-125 treatment. RESULT: One month after irradiation, a necrotic zone developed around the I-125 seeds within the 72 Gy isodose curve. Histologically, there was a fresh coagulation necrosis in the center of the lesion. Reactive zone has not yet developed but scattered interstitial and perivascular CD68 positive macrophages were present in the surrounding brain tissues. Six months after the I-125 isotope treatment, a reactive zone developed: a microglial rim around the necrosis tissue, and a broad area of proliferating vessels and glial fibrillary acidic protein (GFAP) positive astroglial cells which contained CD68 positive activated microglial and macrophage cells. Fifty-four months after I-125 interstitial irradiation, the necrotic center became colliquative and cystic. The microglial rim was replaced by round end stage (HLR-DR and CD31 positive) macrophages. The reactive zone was characterized by astrocytic gliosis but vascular proliferation and macrophages were lacking. CONCLUSION: Results of the present immunohistochemical study suggest that the early lesions are characterized by migrating macrophages apparently concerned with the removal of necrotic debris. The established phase of reactive zone around the necrotic center is characterized by a narrow inner rim of microglial accumulation and a broad outer area characterized by astrocytic gliosis, vascular proliferation, activated microglia and infiltration by macrophages. In the burned-out phases of I-125 interstitial brachytherapy of gliomas, the necrosis undergoes liquefaction and the microglial rim is replaced by astrocytic gliosis which can be considered as equivalent to the scar tissue formed around necrosis outside the central nervous system.

Image fusion analysis of volumetric changes after interstitial low-dose-rate iodine-125 irradiation of supratentorial low-grade gliomas.

The aim of this study was to compare the volumes of tumor necrosis, reactive zone and edema with the three-dimensional dose distributions after brachytherapy treatments of gliomas. The investigation was performed an average of 14.2 months after low-dose-rate (125)I interstitial irradiation of 25 inoperable low-grade gliomas. The prescribed dose was 50-60 Gy to the tumor surface. Dose planning and image fusion were performed with the BrainLab-Target 1.19 software. In the CT/ MRI images, the "triple ring" (tumor necrosis, reactive ring and edema) developing after the interstitial irradiation of the brain tumors was examined. The images with the triple ring were fused with the planning images, and the isodose curves were superimposed on them. The volumes of the three regions were measured. The average dose at the necrosis border was determined from the isodose distribution. For quantitative assessment of the dose distributions, the dose nonuniformity ratio (DNR), homogeneity index (HI), coverage index (CI) and conformal index (COIN) were calculated. The relative volumes of the different parts of the triple ring after the interstitial irradiation compared to the reference dose volume were the following: necrosis, 40.9%, reactive zone, 47.1%, and edema, 367%. The tumor necrosis developed at 79.1 Gy on average. The average DNR, HI, CI and COIN were 0.45, 0.24, 0.94 and 0.57, respectively. The image fusion analysis of the volume of tumor necrosis, reactive ring and edema caused by interstitial irradiation and their correlation with the dose distribution provide valuable information for patient follow-up, treatment options, and effects and side effects of radio therapy.

Stereotactic intracavitary irradiation of cystic craniopharyngiomas with yttrium-90 isotope.

The authors analyzed data from nearly 30-year follow-up period to assess the value of intracavitary irradiation with stereotactically implanted beta-emitting radioisotope yttrium- 90 (90Y) silicate colloid for the treatment of cystic craniopharyngiomas. Seventy-three cysts in 60 patients were selected for retrospective analysis. The cumulative dose aimed at the inner surface of the cyst wall was 300 Gy. An average of 79% (mean 88.3%) shrinkage of the initial cyst volume was observed. In 47 cysts, the reduction was more than 80%, and the cyst disappeared totally in 29 out of those 47 cases, usually within a year. Mean survival duration after intracavitary irradiation was 9.4 years. Neuroophthalmological prognosis was only favorable when the optic disc was normal or nearly normal at the time of the treatment. In the presence of preexisting optic atrophy, visual damage proved to be irreversible. The long-term results support the view that intracavitary 90Y irradiation is a noninvasive and effective method for the treatment of craniopharyngioma cysts. Because of the mean penetration pathway of beta irradiation is 3.6mm in the soft tissues (maximum 11 mm) it cannot influence the solid part of the tumor; therefore, the best result can be expected in solitary cysts.

Pathological findings in cystic craniopharyngiomas after stereotactic intracavitary irradiation with yttrium-90 isotope.

Histopathological, ultrastructural and polyacrylamide gel electrophoretic examinations were carried out on biopsy, cyst fluid, surgical pathology and autopsy specimens obtained from 7 cystic craniopharyngioma cases before and after yttrium-90 silicate colloid (90Y) irradiation. Light microscopy revealed that the lining epithelial tumor cell layer of the cyst wall was destroyed, and scar tissue containing large amount of hyaline degenerated collagen bundles replaced it. Proliferative postirradiation vasculopathy was also demonstrated in the cyst wall following 90Y installation. Electrophoretic property of cyst fluid was similar to the normal human serum. Considering that scar tissue has a certain propensity to shrink, the fibrosis in the cyst wall together with destruction of neoplastic epithelium and vascular changes might explain diminished fluid production and cyst volume reduction after 90Y treatment.

Image fusion-guided stereotactic iodine-125 interstitial irradiation of inoperable and recurrent gliomas.

Between 1996 and 2004, 27 patients with low grade gliomas (WHO grade I-II), 10 patients with WHO grade III gliomas and 6 patients with glioblastoma multiforme (WHO grade IV) were treated with stereotactic brachytherapy using low-dose rate iodine-125 (125I) isotope seeds at the Department of Neurosurgery, St. John's Hospital, Budapest, Hungary. In all 43 cases, brachytherapy was used for surgically inoperable gliomas: in 32 cases for recurrent gliomas and in 11 cases as a primary treatment. Results of this study suggest that 125I brachytherapy for inoperable and recurrent gliomas is an effective method and offers a chance for longer-term survival.

Tissue response to iodine-125 interstitial brachytherapy of cerebral gliomas.

The purpose of this study was to investigate histopathological changes and the role of the microglia/macrophage cell system in the therapeutic effect of iodine-125 (125I) interstitial brachytherapy on cerebral gliomas. Out of a series of 60 cases harboring cerebral astrocytomas and other brain tumors treated with 125I interstitial brachytherapy, autopsy material was available in 10 cases between 0.75 and 60 months after irradiation. The patients were treated with 60-Gy maximum doses at the tumor periphery. Besides the routine HE and Mallory's PTAH trichrome staining, immunohistochemical reactions were carried out for CD15, CD31, CD34, CD45, CD68 (PG-M1), CPM, HAM 56 and HLA-DR antigens to study immunological characteristics of the reactive cell population around gliomas after 125I treatment. The present immunohistochemical study demonstrated that the early lesions following 125I interstitial brachytherapy of gliomas are characterized by migrating macrophages apparently concerned with the removal of necrotic debris. The established phase of reactive zone around the necrotic center disclosed a narrow inner rim of microglial accumulation, and a broad outer area consisting of astrocytic gliosis, vascular proliferation, activated microglia and infiltration by macrophages. In the burned-out phase, the necrosis undergoes liquefaction, the microglial rim is replaced by end-stage macrophages, and the reactive zone is transformed into astrocytic gliosis, which can be considered as equivalent to scar tissue formed around necrosis outside of the central nervous system.

Comparison of (125)I stereotactic brachytherapy and LINAC radiosurgery modalities based on physical dose distribution and radiobiological efficacy.

The goal of this study was to make a comparison between stereotactic brachytherapy implants and linear accelerator-based radiosurgery of brain tumors with respect to physical dose distributions and radiobiological efficacy. Twenty-four treatment plans made for irradiation of brain tumors with low-dose-rate (125)I brachytherapy and multiple-arc LINAC-based radiosurgery were analyzed. Using the dose-volume histograms and the linear-quadratic model, the brachytherapy doses were compared to the brachytherapy-equivalent LINAC radiosurgery doses with respect to the predicted late effects of radiation on normal brain tissue. To characterize the conformity and homogeneity of dose distributions, the conformal index, external volume index, and relative homogeneity index were calculated for each dose plan and the mean values were compared. The average tumor volume was 5.6 cm(3) (range: 0.1-19.3 cm(3)). At low doses, the calculated radiobiological late effect on normal tissue was equivalent for external-beam and brachytherapy dose delivery. For brachytherapy at doses greater than 30 Gy, the calculated equivalent dose to normal tissues was less than for external-beam radiosurgery. However, the dose-calculated homogeneity was better for the LINAC radiosurgery, with a mean relative homogeneity index of 0.62 compared to the calculated value of 0.19 for the brachytherapy (P=0.0002). These results are only predictions based on calculations concerning normal tissue tolerance. More data and research are needed to understand the clinical relevance of these findings.

[125-I brachytherapy of pineal parenchymal tumours in two patients and review of the literature]. / Két pinealoblastomás beteg 125-jód-brachytherapiája során nyert tapasztalatok es irodalmi áttekintés.

INTRODUCTION: Pineal parenchymal tumours make up 0.3% of all brain tumours. Stereotactic biopsy has by now become an indispensable method to detect these tumours and it can be safely performed. PATIENTS AND METHOD: Two patients with pineoblastoma were treated with 125I brachytherapy. The MRI and CT images taken 15 and 18 months after irradiation showed significant tumour shrinkage. RESULTS: Tumour volume was 0.76 cm3 in the control CT image in Case 1, a shrinkage by 73% compared to 2.87 cm3 measured at the time of planning the interstitial irradiation. In Case 2, tumour volume measured on the control MRI examination was 0.29 cm3 as opposed to 1.27 cm3 of original tumour volume, which represents a 77% shrinkage. CONCLUSION: The insertion of isotope seeds was performed at the same time as the biopsy, because thus the knowledge of the histological diagnosis could spare the patients from a second stereotactic intervention. The CT- and image fusion guided 125I stereotactic brachytherapy is a procedure that can be dosimetrically precisely planned and surgically accurately and safely performed.

[Volumetric changes following 125I interstitial brachytherapy of gliomas]. / Térfogatváltozások agydaganatok 125-jód-izotópos brachytherapiája után.

BACKGROUND: Image fusion permits quantitative analysis of the consequences of 125 Iodine interstitial irradiation of brain tumors. The volume of tumor necrosis, reactive zone and edema can be compared to the dosimetric data. PATIENTS AND METHOD: Nineteen patients with low grade glioma were analyzed on the average 14.5 months following 125 Iodine interstitial irradiation. Dose planning and image fusion were performed with the Target 1.19 (BrainLab) software. The CT/MR images showing the so called "triple ring" (necrosis, reactive ring and edema) developing after the interstitial irradiation of brain tumors were fused with the planning images and the isodose curves. The volume of the three regions was measured. Values at the intersections of isodose curves and necrosis borders were averaged and used for calculation of tumor necrosis. The volume of normal brain tissue irradiated by given dose values, as well as homogeneity and conformality indices were also determined. RESULTS: The relative volumes of the different parts of the "triple-ring" compared to the reference dose volume were the following: necrosis 54.9%, reactive zone 59.7%, and edema 445.3%. Tumor necrosis developed at 71.9 Gy dose. At the irradiation of an average size glioma with a volume of 12.7 cm3, 5 to 7 cm3 normal brain tissue around the tumor received 60-70 Gy dose. The average homogeneity and conformality indices were 0.24 and 0.57, respectively. CONCLUSION: The analysis of changes in the volume of edema, reactive ring and necrosis caused by interstitial irradiation, and their correlation with the dosimetric data using the image fusion method provide useful information for patient follow-up, clinical management and further therapeutic decisions.

The importance of postoperative CT image fusion verification of stereotactic interstitial irradiation for brain tumors.

PURPOSE: The aim of our study was verification of the position of implanted catheters with (125)I seeds after the catheter implantation for the brachytherapy of brain tumors. METHODS AND MATERIALS: The fusion of the CT image used at planning and after the implantation of the catheters enabled us to verify the position of the catheters containing the isotopes. After this, the tumor volume covered by the prescribed dose (TV(PD)) and the normal tissue volume covered by the prescribed dose (NTV(PD)) were compared between the plan and the actual result. The image fusion was performed by the BrainLab-Target 1.19 software on an Alfa 430 (Digital) workstation. RESULTS: The position of the catheters was adjusted in 14 (20%) of the 70 image fusion cases being studied. The position of 16 of the 116 catheters (13.8%) required adjustment after the fusion of control images in the 70 cases studied. The Student t probe revealed a significant difference between the TV(PD) values of the reality and the plans (75.8% vs. 92.4%, p < 0.0001). There was a significant difference between values of the real performances and planning for NTV(PD) (86.8% vs. 76%, p = 0.001) and for the conformity index (0.37 vs. 0.54, p = 0.0001), too. CONCLUSION: The application of the interstitial irradiation with CT control allows us to identify and correct possible inaccuracies in catheter positioning during the operation. The procedure then becomes far more accurate and reliable, and as such, the irradiation becomes more conformal than without catheter adjustment.

Iodine-125 brachytherapy of brain stem tumors.

PURPOSE: To report on iodine-125 ((125)I) interstitial irradiation in the treatment of brain stem tumors. PATIENTS AND METHODS: Two patients with brain stem tumors were treated with CT- and image fusion-guided (125)I stereotactic brachytherapy. RESULTS: By March 2003, the patients had been followed up for 47 and 13 months, respectively. In case 1, the tumor volume was 1.98 cm(3) on the control CT, indicating a 65.5% shrinkage as compared to a target volume of 5.73 cm3 at the time of brachytherapy. In case 2, shrinkage was more distinct. After irradiation, the cyst volume was 0.16 cm(3) on the control MRI, indicating a 97.4% shrinkage as compared to a target volume of 6.05 cm(3) at the time of brachytherapy, i. e., the metastasis had virtually disappeared. CONCLUSION: CT- and image fusion-guided (125)I stereotactic brachytherapy can be performed during the biopsy session. The procedure can be well planned dosimetrically and is surgically precise.

[Brachytherapy of brainstem tumors]. / Agytörzsi daganatok szövetközi besugárzása.

INTRODUCTIONS: The optimal therapy of brain stem tumours of different histopathology determines the expected length of survival. Authors report 125Iodine interstitial irradiation of brain stem tumours with stereotactic brachytherapy. CASE REPORTS: Two patients having brain stem tumours were suffering from glioma or from metastases of a carcinoma. In Case 1 the tumour volume was 1.98 cm3 at the time of planning interstitial irradiation. The control MRI examination performed at 42 months post-op showed a postirradiation cyst size of 5.73 cm3 indicating 65.5% shrinkage. In Case 2 the shrinkage was more apparent as the tumour volume measured on the control MRI at 8 months post-op was only 0.16 cm3 indicating 97.4% shrinkage of the 6.05 cm3 target volume at the time of brachytherapy with the metastasis practically disappearing. Quick access to histopathological results of the stereotactic intraoperative biopsy made it possible to carry out the 125Iodine stereotactic brachytherapy immediately after the biopsy, resulting in less inconvenience for patients of a second possible intervention. The control MRI scans show significant shrinkage of tumours in both patients. CONCLUSION: The procedure can be performed as a biopsy. The CT and image fusion guided 125Iodine stereotactic brachytherapy can be well planned dosimetrically and is surgically precise.