Survival and pattern of failure in brain metastasis treated with stereotactic gamma knife radiosurgery

2002 ◽  
Vol 97 ◽  
pp. 499-506 ◽  
Author(s):  
Zbigniew Petrovich ◽  
Cheng Yu ◽  
Steven L. Giannotta ◽  
Steven O'day ◽  
Michael L. J. Apuzzo
Keyword(s):  
Breast Cancer ◽  
Brain Metastasis ◽  
Gamma Knife ◽  
Tumor Volume ◽  
Systemic Disease ◽  
Gamma Knife Radiosurgery ◽  
Unknown Primary ◽  
Pattern Of Failure ◽  
Content Type ◽  
Fine Print

Object. Gamma knife radiosurgery (GKS) has become a well-established treatment modality in the management of selected patients with brain metastasis. The authors review the management patients with these tumors treated at a single center. Methods. Between 1994 and 2002, 458 consecutive patients with metastatic brain disease underwent GKS. There were 1305 lesions treated in 680 separate sessions. The histological diagnosis was melanoma in 231 (50%), lung cancer in 94 (20.5%), breast cancer in 38 (8.3%), renal cell carcinoma (RCC) in 29 (6.3%), colon carcinoma in 13 (2.8%), unknown primary site in 14 (3.1%), and other in 39 patients (8.5%). The median tumor volume was 0.9 cm3 and the median volume treated was 2.3 cm3. The median radiation dose was 18 Gy prescribed to a median isodose of 60%; the median dose was 20 Gy in melanoma, sarcoma, and RCC. Whole-brain radiotherapy (WBRT) either prior to or following GKS was performed in 114 patients (25%). Follow up ranged from 3 to 84 months with a median of 9 months. The median survival for all patients was 9 months and depended on tumor histology. Survival ranged from 6 months for patients with colon carcinoma, unknown primary tumors, and other tumors to 17 months for those with breast cancer. Median survival in patients with melanoma was 8 months. In multivariate analysis Karnofsky Performance Scale score (< 70 vs > 70), status of systemic disease (yes vs no), histological diagnosis, and total intracranial tumor volume were the only significant factors influencing survival. The number of brain metastases (one–five), WBRT (yes vs no), and age were not significant. Pattern of failure was different in patients with melanoma compared with those with other diagnoses. Cause of death in patients with melanoma was in 50% of the cases due to systemic disease and in 42% due to central nervous system causes, whereas it was 70% for the former and 23% for the latter in patients with other diagnoses. The treatment was well tolerated with significant late toxicity requiring craniotomy for removal of a necrotic focus in only 20 patients (4.7%). Conclusions. Gamma knife radiosurgery provided an excellent palliation with low incidence of toxicity. A Phase III prospective randomized trial is required to define the role of WBRT in combination with GKS.

Gamma knife radiosurgery for craniopharyngiomas

2000 ◽  
Vol 93 (supplement_3) ◽  
pp. 47-56 ◽  
Author(s):  
Wen-Yuh Chung ◽  
David Hung-Chi Pan ◽  
Cheng-Ying Shiau ◽  
Wan-Yuo Guo ◽  
Ling-Wei Wang
Keyword(s):  
Clinical Outcome ◽  
Gamma Knife ◽  
Tumor Volume ◽  
Gamma Knife Radiosurgery ◽  
Tumor Control ◽  
Content Type ◽  
Stereotactic Aspiration ◽  
Cystic Component ◽  
The Mean ◽  
Fine Print

Object. The goal of this study was to elucidate the role of gamma knife radiosurgery (GKS) and adjuvant stereotactic procedures by assessing the outcome of 31 consecutive patients harboring craniopharyngiomas treated between March 1993 and December 1999. Methods. There were 31 consecutive patients with craniopharyngiomas: 18 were men and 13 were women. The mean age was 32 years (range 3–69 years). The mean tumor volume was 9 cm3 (range 0.3–28 cm3). The prescription dose to the tumor margin varied from 9.5 to 16 Gy. The visual pathways received 8 Gy or less. Three patients underwent stereotactic aspiration to decompress the cystic component before GKS. The tumor response was classified by percentage reduction of tumor volume as calculated based on magnetic resonance imaging studies. Clinical outcome was evaluated according to improvement and dependence on replacement therapy. An initial postoperative volume increase with enlargement of a cystic component was found in three patients. They were treated by adjuvant stereotactic aspiration and/or Ommaya reservoir implantation. Tumor control was achieved in 87% of patients and 84% had fair to excellent clinical outcome in an average follow-up period of 36 months. Treatment failure due to uncontrolled tumor progression was seen in four patients at 26, 33, 49, and 55 months, respectively, after GKS. Only one patient was found to have a mildly restricted visual field; no additional endocrinological impairment or neurological deterioration could be attributed to the treatment. There was no treatment-related mortality. Conclusions. Multimodality management of patients with craniopharyngiomas seemed to provide a better quality of patient survival and greater long-term tumor control. It is suggested that GKS accompanied by adjuvant stereotactic procedures should be used as an alternative in treating recurrent or residual craniopharyngiomas if further microsurgical excision cannot promise a cure.

Gamma knife radiosurgery in patients with advanced breast cancer undergoing bone marrow transplant

2002 ◽  
Vol 97 ◽  
pp. 663-665 ◽  
Author(s):  
Kenneth J. Levin ◽  
Emad F. Youssef ◽  
Andrew E. Sloan ◽  
Rajiv Patel ◽  
Rana K. Zabad ◽  
...  
Keyword(s):  
Breast Cancer ◽  
Advanced Breast Cancer ◽  
Gamma Knife ◽  
Gamma Knife Radiosurgery ◽  
High Dose Chemotherapy ◽  
Advanced Breast ◽  
High Dose ◽  
Initial Management ◽  
Content Type ◽  
Fine Print

Object. Recent studies have suggested a high incidence of cognitive deficits in patients undergoing high-dose chemotherapy, which appears to be dose related. Whole-brain radiotherapy (WBRT) has previously been associated with cognitive impairment. The authors attempted to use gamma knife radiosurgery (GKS) to delay or avoid WBRT in patients with advanced breast cancer treated with high-dose chemotherapy and autologous bone marrow transplantation (HDC/ABMT) in whom brain metastases were diagnosed. Methods. A retrospective review of our experience from 1996 to 2001 was performed to identify patients who underwent HDC/ABMT for advanced breast cancer and brain metastasis. They were able to conduct GKS as initial management to avoid or delay WBRT in 12 patients following HDC/ABMT. All patients were women. The median age was 48 years (range 30–58 years). The Karnofsky Performance Scale score was 70 (range 60–90). All lesions were treated with a median prescription dose of 17 Gy (range 15–18 Gy) prescribed to the 50% isodose. Median survival was 11.5 months. Five patients (42%) had no evidence of central nervous system disease progression and no further treatment was given. Four patients were retreated with GKS and three of them eventually received WBRT as well. Two patients were treated with WBRT as the primary salvage therapy. The median time to retreatment with WBRT was 8 months after the initial GKS. Conclusions. Gamma knife radiosurgery can be effectively used for the initial management of brain metastases to avoid or delay WBRT in patients treated previously with HDC, with acceptable survival and preserved cognitive function.

Early complications following gamma knife radiosurgery for intracranial meningiomas

2000 ◽  
Vol 93 (supplement_3) ◽  
pp. 57-61 ◽  
Author(s):  
V. P. Singh ◽  
S. Kansal ◽  
S. Vaishya ◽  
P. K. Julka ◽  
V. S. Mehta
Keyword(s):  
Gamma Knife ◽  
Tumor Volume ◽  
Gamma Knife Radiosurgery ◽  
Primary Therapy ◽  
Early Complications ◽  
Content Type ◽  
Cavernous Sinus Meningioma ◽  
Perilesional Edema ◽  
Intracranial Meningiomas ◽  
Fine Print

Object. The purpose of this paper was to assess the early complications, defined as occurring within 1 year, following gamma knife radiosurgery (GKS) for the treatment of intracranial meningiomas. Methods. Seventy-seven of 306 patients undergoing GKS in the last 2.5 years harbored meningiomas. There were 35 men and 42 women with a mean age of 32.4 years (range 10–80 years). Tumor volume ranged from 0.35 to 28.6 cm3 (mean 7.9 cm3). Gamma knife radiosurgery was the primary therapy in 28 patients and followed surgery in 49 patients. There were 50 basal and 27 nonbasal meningiomas. The most common sites were parasagittal (23 patients) and cerebellopontine angle (14 patients). Ten to 15 Gy was administered to the tumor margins. Clinical and radiological follow up with a mean duration of 122 months was available in 40 patients. Seizures and increased headache were found in five and four patients, respectively. A temporary worsening of hemiparesis was seen in two patients (both with parasagittal tumors). One patient with a cavernous sinus meningioma developed a herpes labialis eruption. Perilesional edema was demonstrated in nine patients and was symptomatic in six. Six (22%) of the 27 patients with nonbasal tumors had edema (all parasagittal) and four patients were symptomatic. Only three (6%) of the 50 basal meningiomas had edema, and only one patient was symptomatic. The occurence of edema did not correlate with tumor volume, margin or maximum dose, or with radiation received by adjacent brain. A reduction in tumor size was seen in seven patients. In one patient a new recurrent lesion developed adjacent to the previously treated tumor. Conclusions. Although GKS provides good results for selected patients with meningiomas, caution is required in treating patients with parasagittal tumors as the incidence of perilesional edema is considerable.

Gamma knife radiosurgery for craniopharyngiomas: longterm results in the first Swedish patients

2002 ◽  
Vol 97 ◽  
pp. 613-622 ◽  
Author(s):  
Elfar Úlfarsson ◽  
Christer Lindquist ◽  
Maud Roberts ◽  
Tiit Rähn ◽  
Melker Lindquist ◽  
...  
Keyword(s):  
Gamma Knife ◽  
Tumor Volume ◽  
Gamma Knife Radiosurgery ◽  
Imaging Study ◽  
Term Treatment ◽  
Stereotactic Techniques ◽  
Content Type ◽  
Long Term Treatment ◽  
Fine Print

Object. The purpose of this study was to assess the long-term treatment efficacy and morbidity of patients who undergo gamma knife radiosurgery (GKS) for craniopharyngioma. Methods. Twenty-one consecutive Swedish patients were evaluated retrospectively: 11 children (≤ 15 years) and 10 adults. The time from diagnosis to the most recent follow-up imaging study was 6.3 to 34.3 years (mean 18.2 years, median 16.8 years). Tumor volumes and morbidity from GKS or other treatments were assessed at the time of the most recent imaging study or at the time of a subsequent new treatment. The observation period ranged from 0.5 to 29 years (mean 7.5 years, median 3.5 years). The prescription dose ranged from less than 3 Gy to 25 Gy. The mean tumor volume was 7.8 cm3 (range 0.4–33 cm3). There were 22 tumors in 21 patients treated with GKS. Five of these tumors were reduced in size, three were unchanged, and 14 increased. Tumor progression correlated with a low dose to the tumor margin. Eleven (85%) of 13 tumors that received a dose of less than 6 Gy to the margin increased in size, whereas only three (33%) of nine tumors that received 6 Gy increased. This difference was statistically significant (p = 0.01). In five of six patients tumors that became smaller after GKS there were no recurrences within a mean follow-up period of 12 years. Nine (82%) of 11 tumors in children ultimately increased after GKS, compared with five (50%) of 10 in adults. In eight patients there was a deterioration of visual function. In all except one this could be related to a volume increase but radiation-induced damage could not be excluded as a factor in any of them. Four patients developed pituitary deficiencies. Conclusions. Gamma knife radiosurgery is effective in controlling growth of craniopharyngiomas with a minimum dose of 6 Gy. The findings also suggest that other stereotactic techniques, such as cyst aspiration and intracystic treatment, are only of value in reducing tumor volume in preparation for safe GKS.

Gamma knife radiosurgery for simultaneous multiple metastatic brain tumors

2000 ◽  
Vol 93 (supplement_3) ◽  
pp. 30-31 ◽  
Author(s):  
Satoshi Suzuki ◽  
Junichi Omagari ◽  
Shunji Nishio ◽  
Eiichiro Nishiye ◽  
Masashi Fukui
Keyword(s):  
Survival Rate ◽  
Brain Metastasis ◽  
Brain Tumors ◽  
Gamma Knife ◽  
Gamma Knife Radiosurgery ◽  
Metastatic Brain Tumors ◽  
Content Type ◽  
Cumulative Survival ◽  
Kaplan Meier ◽  
Fine Print

Object. The authors assessed the efficacy of gamma knife radiosurgery (GKS) in the treatment of patients with 10 or more simultaneous metastatic brain tumors. Methods. Gamma knife radiosurgery was performed for the treatment of 10 or more simultaneous metastatic brain tumors in 24 patients. The performance status before and after GKS was expressed using the Karnofsky Performance Scale (KPS). The cumulative survival rate was analyzed using the Kaplan—Meier method. The level of satisfaction with the procedure was assessed by telephone interview. No patient has died due to brain metastasis—related symptoms, and all patients and/or their families were satisfied with the GKS. In 12 patients who had brain metastasis—related symptoms, five improved, six were unchanged, and one deteriorated, as reflected by the KPS scores. The cumulative survival rate calculated by the Kaplan—Meier method was 70.4%, 49.3%, and 12.3% at 12 weeks, 24 weeks, and 36 weeks, respectively. The median survival time was 11 weeks. Conclusions. Single-fraction GKS can achieve acceptable tumor control, low morbidity, and good quality of life in the treatment of multiple metastatic brain tumors even in cases with 10 or more simultaneous metastases.

Gamma knife radiosurgery as a single treatment modality for large cerebral arteriovenous malformations

2000 ◽  
Vol 93 (supplement_3) ◽  
pp. 113-119 ◽  
Author(s):  
D. Hung-Chi Pan ◽  
Wan-Yuo Guo ◽  
Wen-Yuh Chung ◽  
Cheng-Ying Shiau ◽  
Yue-Cune Chang ◽  
...  
Keyword(s):  
Gamma Knife ◽  
Arteriovenous Malformations ◽  
Radiation Treatment ◽  
Gamma Knife Radiosurgery ◽  
Consecutive Series ◽  
Content Type ◽  
Obliteration Rate ◽  
Complete Obliteration ◽  
Fine Print

Object. A consecutive series of 240 patients with arteriovenous malformations (AVMs) treated by gamma knife radiosurgery (GKS) between March 1993 and March 1999 was evaluated to assess the efficacy and safety of radiosurgery for cerebral AVMs larger than 10 cm3 in volume. Methods. Seventy-six patients (32%) had AVM nidus volumes of more than 10 cm3. During radiosurgery, targeting and delineation of AVM nidi were based on integrated stereotactic magnetic resonance (MR) imaging and x-ray angiography. The radiation treatment was performed using multiple small isocenters to improve conformity of the treatment volume. The mean dose inside the nidus was kept between 20 Gy and 24 Gy. The margin dose ranged between 15 to 18 Gy placed at the 55 to 60% isodose centers. Follow up ranged from 12 to 73 months. There was complete obliteration in 24 patients with an AVM volume of more than 10 cm3 and in 91 patients with an AVM volume of less than 10 cm3. The latency for complete obliteration in larger-volume AVMs was significantly longer. In Kaplan—Meier analysis, the complete obliteration rate in 40 months was 77% in AVMs with volumes between 10 to 15 cm3, as compared with 25% for AVMs with a volume of more than 15 cm3. In the latter, the obliteration rate had increased to 58% at 50 months. The follow-up MR images revealed that large-volume AVMs had higher incidences of postradiosurgical edema, petechiae, and hemorrhage. The bleeding rate before cure was 9.2% (seven of 76) for AVMs with a volume exceeding 10 cm3, and 1.8% (three of 164) for AVMs with a volume less than 10 cm3. Although focal edema was more frequently found in large AVMs, most of the cases were reversible. Permanent neurological complications were found in 3.9% (three of 76) of the patients with an AVM volume of more than 10 cm3, 3.8% (three of 80) of those with AVM volume of 3 to 10 cm3, and 2.4% (two of 84) of those with an AVM volume less than 3 cm3. These differences in complications rate were not significant. Conclusions. Recent improvement of radiosurgery in conjunction with stereotactic MR targeting and multiplanar dose planning has permitted the treatment of larger AVMs. It is suggested that gamma knife radiosurgery is effective for treating AVMs as large as 30 cm3 in volume with an acceptable risk.

Factors related to complete occlusion of arteriovenous malformations after gamma knife radiosurgery

2000 ◽  
Vol 93 (supplement_3) ◽  
pp. 96-101 ◽  
Author(s):  
Jong Hee Chang ◽  
Jin Woo Chang ◽  
Yong Gou Park ◽  
Sang Sup Chung
Keyword(s):  
Gamma Knife ◽  
Arteriovenous Malformations ◽  
Gamma Knife Radiosurgery ◽  
Maximum Diameter ◽  
Content Type ◽  
Complete Occlusion ◽  
Factors Associated ◽  
Martin Grade ◽  
Fine Print

Object. The authors sought to evaluate the effects of gamma knife radiosurgery (GKS) on cerebral arteriovenous malformations (AVMs) and the factors associated with complete occlusion. Methods. A total of 301 radiosurgical procedures for 277 cerebral AVMs were performed between December 1988 and December 1999. Two hundred seventy-eight lesions in 254 patients who were treated with GKS from May 1992 to December 1999 were analyzed. Several clinical and radiological parameters were evaluated. Conclusions. The total obliteration rate for the cases with an adequate radiological follow up of more than 2 years was 78.9%. In multivariate analysis, maximum diameter, angiographically delineated shape of the AVM nidus, and the number of draining veins significantly influenced the result of radiosurgery. In addition, margin radiation dose, Spetzler—Martin grade, and the flow pattern of the AVM nidus also had some influence on the outcome. In addition to the size, topography, and radiosurgical parameters of AVMs, it would seem to be necessary to consider the angioarchitectural and hemodynamic aspects to select proper candidates for radiosurgery.

Gamma knife radiosurgery in the management of cavernous sinus meningiomas

2000 ◽  
Vol 93 (supplement_3) ◽  
pp. 68-73 ◽  
Author(s):  
Pierre-Hugues Roche ◽  
Jean Régis ◽  
Henry Dufour ◽  
Henri-Dominique Fournier ◽  
Christine Delsanti ◽  
...  
Keyword(s):  
Mr Imaging ◽  
Tumor Growth ◽  
Gamma Knife ◽  
Cavernous Sinus ◽  
Gamma Knife Radiosurgery ◽  
Surgical Removal ◽  
Content Type ◽  
Cavernous Sinus Meningioma ◽  
The Mean ◽  
Fine Print

Object. The authors sought to assess the functional tolerance and tumor control rate of cavernous sinus meningiomas treated by gamma knife radiosurgery (GKS). Methods. Between July 1992 and October 1998, 92 patients harboring benign cavernous sinus meningiomas underwent GKS. The present study is concerned with the first 80 consecutive patients (63 women and 17 men). Gamma knife radiosurgery was performed as an alternative to surgical removal in 50 cases and as an adjuvant to microsurgery in 30 cases. The mean patient age was 49 years (range 6–71 years). The mean tumor volume was 5.8 cm3 (range 0.9–18.6 cm3). On magnetic resonance (MR) imaging the tumor was confined in 66 cases and extensive in 14 cases. The mean prescription dose was 28 Gy (range 12–50 Gy), delivered with an average of eight isocenters (range two–18). The median peripheral isodose was 50% (range 30–70%). Patients were evaluated at 6 months, and at 1, 2, 3, 5, and 7 years after GKS. The median follow-up period was 30.5 months (range 12–79 months). Tumor stabilization after GKS was noted in 51 patients, tumor shrinkage in 25 patients, and enlargement in four patients requiring surgical removal in two cases. The 5-year actuarial progression-free survival was 92.8%. No new oculomotor deficit was observed. Among the 54 patients with oculomotor nerve deficits, 15 improved, eight recovered, and one worsened. Among the 13 patients with trigeminal neuralgia, one worsened (contemporary of tumor growing), five remained unchanged, four improved, and three recovered. In a patient with a remnant surrounding the optic nerve and preoperative low vision (3/10) the decision was to treat the lesion and deliberately sacrifice the residual visual acuity. Only one transient unexpected optic neuropathy has been observed. One case of delayed intracavernous carotid artery occlusion occurred 3 months after GKS, without permanent deficit. Another patient presented with partial complex seizures 18 months after GKS. All cases of tumor growth and neurological deficits observed after GKS occurred before the use of GammaPlan. Since the initiation of systematic use of stereotactic MR imaging and computer-assisted modern dose planning, no more side effects or cases of tumor growth have occurred. Conclusions. Gamma knife radiosurgery was found to be an effective low morbidity—related tool for the treatment of cavernous sinus meningioma. In a significant number of patients, oculomotor functional restoration was observed. The treatment appears to be an alternative to surgical removal of confined enclosed cavernous sinus meningioma and should be proposed as an adjuvant to surgery in case of extensive meningiomas.

Combined stereotactic split-course fractionated gamma knife radiosurgery and conventional radiation therapy for unfavorable gliomas: a phase I study

2000 ◽  
Vol 93 (supplement_3) ◽  
pp. 37-41 ◽  
Author(s):  
William F. Regine ◽  
Roy A. Patchell ◽  
James M. Strottmann ◽  
Ali Meigooni ◽  
Michael Sanders ◽  
...  
Keyword(s):  
Radiation Therapy ◽  
Disease Progression ◽  
Gamma Knife ◽  
Gamma Knife Radiosurgery ◽  
External Beam Radiation ◽  
Low Grade ◽  
Beam Radiation ◽  
Content Type ◽  
Group B ◽  
Fine Print

Object. This investigation was performed to determine the tolerance and toxicities of split-course fractionated gamma knife radiosurgery (FSRS) given in combination with conventional external-beam radiation therapy (CEBRT). Methods. Eighteen patients with previously unirradiated, gliomas treated between March 1995 and January 2000 form the substrate of this report. These included 11 patients with malignant gliomas, six with low-grade gliomas, and one with a recurrent glioma. They were stratified into three groups according to tumor volume (TV). Fifteen were treated using the initial FSRS dose schedule and form the subject of this report. Group A (four patients), had TV of 5 cm3 or less (7 Gy twice pre- and twice post-CEBRT); Group B (six patients), TV greater than 5 cm3 but less than or equal to 15 cm3 (7 Gy twice pre-CEBRT and once post-CEBRT); and Group C (five patients), TV greater than 15 cm3 but less than or equal to 30 cm3 (7 Gy once pre- and once post-CEBRT). All patients received CEBRT to 59.4 Gy in 1.8-Gy fractions. Dose escalation was planned, provided the level of toxicity was acceptable. All patients were able to complete CEBRT without interruption or experiencing disease progression. Unacceptable toxicity was observed in two Grade 4/Group B patients and two Grade 4/Group C patients. Eight patients required reoperation. In three (38%) there was necrosis without evidence of tumor. Neuroimaging studies were available for evaluation in 14 patients. Two had a partial (≥ 50%) reduction in volume and nine had a minor (> 20%) reduction in size. The median follow-up period was 15 months (range 9–60 months). Six patients remained alive for 3 to 60 months. Conclusions. The imaging responses and the ability of these patients with intracranial gliomas to complete therapy without interruption or experiencing disease progression is encouraging. Excessive toxicity derived from combined FSRS and CEBRT treatment, as evaluated thus far in this study, was seen in patients with Group B and C lesions at the 7-Gy dose level. Evaluation of this novel treatment strategy with dose modification is ongoing.

New dosimetric approach for multidimensional dose evaluation in gamma knife radiosurgery

2000 ◽  
Vol 93 (supplement_3) ◽  
pp. 239-242 ◽  
Author(s):  
R. Foroni ◽  
G. Gambraini ◽  
U. Danesi ◽  
M. Mauri ◽  
E. Pompilio ◽  
...  
Keyword(s):  
Gamma Knife ◽  
Metal Ion ◽  
Light Transmission ◽  
Xylenol Orange ◽  
Ferrous Sulphate ◽  
Gamma Knife Radiosurgery ◽  
Absorbed Dose ◽  
Content Type ◽  
3D Representation ◽  
Fine Print

✓ During the past two decades, the progress in computerized treatment planning systems has led to more accurate imaging and therapy by using the gamma knife, especially with the smallest collimators (4 mm). However, the ionization chambers that have been used to calibrate the gamma knife are not useful with the smallest collimators because the chambers are too big compared with the irradiated volume. Therefore, it is important to develop more suitable dosimeters. This study proposes a new dosimeter method. The FriXyGel method proposed here is based on a phantom dosimeter, an acquisition chain, and dedicated software. This dosimeter uses an agarose gel into which a ferrous sulphate solution (Fricke solution) and a metal ion indicator (xylenol orange) are incorporated. The absorbed dose is detected through measurements of visible light transmission, imaged by means of a charge-coupled device camera provided with a suitable optical filter. Gel layers are imaged before and after irradiation, and the differences in light absorption are related to the absorbed dose. By choosing convenient thickness of gel layers and by building up a phantom with different gel slices, it is possible to obtain a three-dimensional (3D) representation of the absorbed dose. The final 3D representation is reached after several mathematical processes have been applied to the images. The first step identifies and reduces all factors that could alter the original data, such as nonuniformity in illumination. Then, after calibration procedures, it is possible to obtain absorbed dose values and to discover their 3D representation. This goal has been reached by developing appropriate software that performs all the calculations necessary for spatial representation routines and prompt comparison with theoretical calculations.

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