Equivalent uniform dose concept evaluated by theoretical dose volume histograms for thoracic irradiation.

BACKGROUND AND PURPOSE: The goal of our study was to quantify the limits of the EUD models for use in score functions in inverse planning software, and for clinical application. MATERIALS AND METHODS: We focused on oesophagus cancer irradiation. Our evaluation was based on theoretical dose volume histograms (DVH), and we analyzed them using volumetric and linear quadratic EUD models, average and maximum dose concepts, the linear quadratic model and the differential area between each DVH. RESULTS: We evaluated our models using theoretical and more complex DVHs for the above regions of interest. We studied three types of DVH for the target volume: the first followed the ICRU dose homogeneity recommendations; the second was built out of the first requirements and the same average dose was built in for all cases; the third was truncated by a small dose hole. We also built theoretical DVHs for the organs at risk, in order to evaluate the limits of, and the ways to use both EUD(1) and EUD/LQ models, comparing them to the traditional ways of scoring a treatment plan. For each volume of interest we built theoretical treatment plans with differences in the fractionation. CONCLUSION: We concluded that both volumetric and linear quadratic EUDs should be used. Volumetric EUD(1) takes into account neither hot-cold spot compensation nor the differences in fractionation, but it is more sensitive to the increase of the irradiated volume. With linear quadratic EUD/LQ, a volumetric analysis of fractionation variation effort can be performed.

Esophageal cancer: determination of internal target volume for conformal radiotherapy.

BACKGROUND AND PURPOSE: To evaluate esophageal tumor and OAR movement during the respiratory cycle in order to obtain optimal values for ITV and PRV. To correlate tumor motion with chest wall displacement - information of value in the free-breathing gating system. MATERIAL AND METHOD: Inclusion criteria were: histologically proven squamous-cell carcinoma (SCC) or adenocarcinoma at stage T3 - T4 NX or TX N1 M0 according to the UICC 1997 classification. Two spiral scans were performed with breath-hold respiration under spirometric control: one at end expiration (EBH) and the other at end inspiration (IBH). Displacements between exhalation and inhalation were calculated according to ICRU report 42 recommendations. For the correlation study, CT-scan acquisition was performed at the isocenter over a 20 - 40 s period. After Fourier Transform, frequency spectra for amplitude and phase of tumor and chest wall motions were performed for each patient. RESULTS: Cumulative distribution of CTV motion in absolute values showed that 95% of data ranged from 0 to 1 cm. Cumulative distribution of GTV motion in absolute values showed that 95% of data ranged from 0 to 0.8 cm. The correlation study demonstrated no specific relationship between respiratory and esophageal motions. CONCLUSION: The ITV margin for 3D conformal radiotherapy in esophageal cancer was 1 cm when 95% of motions were taken into account in this clinical study involving eight patients. Before using a free-breathing gating system, the correlation between external markers and target displacement during irradiation must be established for each patient.

[The French preliminary experience of the use of a seed-projector for exclusive iodine 125 prostate brachytherapy: feasibility and acute toxicity]. / L'expérience française de l'utilisation d'un projecteur de source pour la curiethérapie prostatique exclusive par implants permanents d'iode radioactif: faisabilité et données de toxicité aiguë.

PURPOSE: To analyse a new technique for prostate brachytherapy with permanent Iodine implants characterized by the use of a seed projector after a 3D dosimetric peroperative treatment planning (FIRST technique). PATIENTS AND METHOD: 395 patients have been treated in France with this technique in six radiotherapy centres between November 2002 and December 2005 for a localized prostate cancer. RESULTS: Thirteen patients (3.3%) developped a urinary retention, and respectively 7.8 and 26.5% an acute RTOG grade 3 and 2 toxicity. The 6-weeks IPSS score was equal or lower to 15 in 73% with a 11 median IPSS value. A failure of the loading with the seed-projector, leading to a manual loading of the seeds, occurred in 9 patients (2.3%) in two centres, directly related to the loading procedure with the seed-projector in 5 cases. The median duration of the procedure was reduced by 30 minutes for the patients treated in 2005. CONCLUSIONS: This multicenter study establishes the feasibility of the routine use of a seed projector for permanent iodine 125 prostate implants with an initial tolerance similar to the best results published for other implants techniques.

Dosimetric consequences of breath-hold respiration in conformal radiotherapy of esophageal cancer.

The objective of this paper is to study the dosimetric impact of respiratory gated radiotherapy in locally advanced esophageal carcinomaand to define the optimal respiratory phase for this treatment. The study included 8 consecutive patients with squamous-cell carcinoma (SCC) or histologically proved adenocarcinoma, for both at least T3-T4 NX or TX N1 M0 stage. Informed consent was obtained before beginning the study. Three spiral scans were performed in breath-hold respiration: one acquisition in end expiration (EBH), one in end inspiration (IBH) and one in deep inspiration breathhold (DIBH); and one acquisition was performed in Free Breathing (FB). A 3 mm-margin was defined as Internal Target Volume (ITV) on FB CT-scan. No ITV was applied on EBH, IBH and DIBH CT-scan. Target volumes were analyzed and we performed dosimetric comparisons on DVH data of each CT-scan for PTV and Organs at Risk (OAR) (Conformity Index, V(dose), D(mean), Equivalent Uniform Dose). DIBH and IBH correlated with a 32% (p=0.77) and 20% (p=0.52) decrease in lung V(20) respectively as compared to FB (13.5%and 15.6% respectively versus 19.9%). DIBH and IBH correlated with a 25% (p=0.25) and 17% (p=0.39) decrease in cardiac V(40) respectively, as compared with FB (16.9% and 18.9% respectively versus 22.7%). For spinal cord irradiation, the minimum dose was obtained in IBH (36.5 Gy). Conformal radiotherapy with respiratory gating for esophageal cancer decreases the irradiated dose to OAR. We suggest that DIBH technique should be used when irradiation is performed using the spirometric system. In the Tidal Volume, the inspiration phase is the most favourable and should be chosen for irradiation with a free breathing gating system.

The study of tumoral, radiobiological, and general health factors that influence results and complications in a series of 448 oral tongue carcinomas treated exclusively by irradiation.

PURPOSE: Our aim was to study the different factors that influence the results and complications in a series of 448 carcinomas of the oral tongue treated from January 31, 1972 to December 31, 1986, by brachytherapy (Br) +/- neck dissection (181 cases) or combination of external beam irradiation and brachytherapy (EBI + Br) (267 cases). METHODS AND MATERIALS: The patients distribution (TNM classification 1979) was: 125 T1, 186 T2, 128 T3, 9 T4Tx, 78% N0, and 22% N+. We used guide gutter or plastic tubes technique (Paris system dosimetry). Results at 5 and 10 years are: local control 68% and 64%, locoregional control 58% and 53%, specific survival 45% and 39%, and overall survival 44% and 27%. RESULTS: In the univariate analysis for local control (LC) and overall survival (OS), we considered the tumoral factors. At 5 years, the LC for T1, T2, T3 are 93%, 65%, and 49%, and the OS 69%, 41%, and 25%, respectively (p < 0.002). The lesions of the undersurface of the tongue have a better LC (77%) than other localizations (64%) (p = 0.02). For general factors, the index of general health condition, age, and sex were not significant for LC, but proved significant for OS (p = 0.01). Significant radiobiological factors: the safety margin (expressed by the ratio treated surface on tumoral surface > or = 1.2) is significant for LC and OS. This is the same if the interval between EBI and Br is < or = 20 days. Neither the dose rate, the spacing between the sources, the total dose, nor Br dose were significant, but the last two were adapted according to the infiltration. In the univariate study for grade 2 and 3 complications (tissue and bone), the surface treated (> 12 cm2), and the dose rate > 0.7 Gy/h were significant. CONCLUSION: The multivariate study showed that the small size of the lesion is the most important factor for local control, with brachytherapy alone for T1T2N0 and the number of days between EBI and brachytherapy < or = 20 days. For the complications, the most important factors are the total dose > 80 Gy and a treated surface > 12 cm2.

Salvage irradiation by brachytherapy of velotonsillar squamous cell carcinoma in a previously irradiated field: results in 73 cases.

PURPOSE: The salvage brachytherapy performed in patients presenting velotonsillar carcinoma in a previously irradiated field is evaluated in terms of local control, complications and survival. METHODS AND MATERIALS: Between 1976 and 1990, 73 patients presenting with velotonsillar squamous cell carcinoma in a previously irradiated area were treated at Center Alexis Vautrin with brachytherapy along using an 192Ir implant (afterloading technique) with curative intent. According to the UICC 1987 TNM classification, there were 45 T1 N0, 20 T2 N0, one T3 NO, one T3 N2 and six Tx Nx. RESULTS: The 5-year actuarial local control for T1 N0 and T2 N0 are 80% and 67% respectively. The regional relapse rate was 10% in both groups. Grade 2 complications occurred in 13% of patients and these were neither related to the volume treated nor the dose rate. There were no Grade 3 or 4 complications. The 5-year specific survival is 64%, with a plateau after the 5th year, but the 5-year overall survival is only 30%. Fourty-two percent of the patients in this series died from another carcinoma. All but two of these were related to continued alcohol and tobacco intoxication. CONCLUSION: We conclude that brachytherapy alone (60 Gy) is optimal treatment for patients presenting with velontonsillar carcinoma in a previously irradiated field. The greatest challenge is the screening of these patients and the prevention of subsequent head and neck cancers. Recognizing the fact that these patients are at high risk for subsequent malignancies of upper aerodigestive tract, lung and esophagus, close surveillance is necessary for: (a) early diagnosis and prompt treatment; and (b) development of prevention strategies of field cancerization.

Velotonsillar squamous cell carcinoma: 277 cases treated by combined external irradiation and brachytherapy--results according to extension, localization, and dose rate.

From 1977 to 1987, 277 patients with velotonsillar cancer (oropharyngeal cancer excluding base of tongue and valleculae) were treated by brachytherapy either alone (14 patients) or combined with external beam irradiation (263 patients) using a new afterloading Iridium-192 technique. The distribution of patients according to the localisation was as follows: 106 tonsillar region, 98 soft palate, 45 anterior pillar, 8 posterior pillar and 20 pharyngoglossal sulcus. According to the UICC TNM classification of 1979, the patients were staged as follows: 65 T1, 103 T2, 101 T3, 8 TX. 172 patients were NO, 74 N1, 3 N2, 20 N3 et 8 NX. According to the tumor extension, the 5 year actuarial local control, locoregional control, specific survival and overall survival by T stage (T1 [65 pts], T2 [103 pts.], T3 [101 pts]) were respectively: local control: 89%, 86%, 69%; locoregional control: 84%, 80%, 67%; specific survival (excluding patients dead with intercurrent disease or second cancer): 78%, 62%, 46%; overall survival: 62%, 53%, 43%. No local recurrence was detected after 3 years. According to the localization, the tumors arising from the tonsillar region, the soft palate and the posterior pillars (A Group) had a better prognosis than the tumors arising from the anterior pillars and glossotonsillar sulcus (B Group). The complications were classified into four grades according to their extension and duration: Grade 1 (minor) with very small tissue ulcer which healed within 2 months with medical treatment (20%). Grade 2 (moderate) (5%), grade 3 (severe) (1.4%), grade 4 (fatal) (0.4%). The dose rate seemed to be relatively higher in patients with grade 2 and 3 complications (70 cGy per hour on average) versus the dose rate of patients without complications (50 cGy per hour) but the difference was not significant. In conclusion, the brachytherapy boost after external irradiation can be performed under favourable conditions with an acceptable rate of complications. It was set out in order to attempt to improve the local control of the tumor while preserving the salivary function and lessening the muscular fibrosis. It shows how experienced the team is, however only a randomized study would allow to state whether this technique brings about a real improvement especially as for tumors T2 or T3.

Conservative treatment by irradiation of epidermoid cancers of the anal canal: prognostic factors of tumoral control and complications.

UNLABELLED: We analyzed in a retrospective series of patients treated by conservative irradiation for an epidermoid cancer of the anal canal (ECAC) the prognostic factors of locoregional control (LRC), survival, late severe complications (LSC), and sphincter conservation (SC). METHODS AND MATERIALS: From 1976 until 1994, 118 patients presenting with an ECAC were conservatively treated (mean age, 65 years). According to the 1987 International Union Against Cancer (TNM) classification, they were: 19 T1, 70 T2, 22 T3, 7 T4, 94 N0, and 24 N1-3. The treatment started with external beam irradiation (EBI) (36 Gy in 3 weeks or 45 Gy in 5 weeks). Concomitant chemotherapy (5-fluorouracil and mitomycin C) was delivered to 31 patients. Two months later, a boost of 20 Gy was delivered by interstitial 192Ir brachytherapy to 101 patients and EBI in 5. Twelve other patients had an abdominoperineal resection (APR). The mean follow-up was 6 years. RESULTS: At 5 years the overall survival was 60%, and specific survival (SS) was 75%; it was 94% for T1, 79% for T2, 53% for T3, and 19% for T4. In multivariate analysis, tumor size (> or = 4 cm), node involvement, and no response to the EBI were factors of poor prognosis for SS. Thirty-two locoregional recurrences occurred of which 21 were local recurrences in the 106 patients treated by a conservative schedule. Only tumor size and response to the EBI were prognostic factors on multivariate analysis for local and LRC. A total of 17 patients presented with LSC (Grade 3, 16 patients; and Grade 4, 1 patient), which was treated by APR in 4 patients and colostomy in 11 (of which 7 were definitive). The only significant prognostic factor for LSC in the multivariate analysis was the total extrapolated response dose of irradiation. The definitive rate of SC after conservative treatment in cured patients was 100% for T1, 82% for T2, 58% for T3, and 100% for T4. Since 1989, improvements of the technique have allowed reduction of the LSC in maintaining the same local control. CONCLUSION: The results of this series are similar to those of the literature. The confirmation of pretherapeutic prognostic factors related to response to the treatment should allow us to adapt the therapeutic intensity for each case to obtain better tumor control, with as few sequelae as possible, to yield a better rate of SC.

Influence of tumoral, radiobiological, and general factors on local control and survival of a series of 361 tumors of the velotonsillar area treated by exclusive irradiation (external beam irradiation+brachytherapy or brachytherapy alone)

PURPOSE: To evaluate statistically the factors influencing the therapeutic results. METHODS AND MATERIALS: A statistical study was carried out concerning 361 patients treated from 1977 to 1991 for velotonsillar carcinoma. They received either brachytherapy alone (18) or a combination of external beam irradiation and brachytherapy (343 patients) using an afterloading iridium technique in plastic tubes. The distribution of patients according to the localization was: 128 tonsils, 134 soft palates, 9 posterior pillars, 63 anterior pillars, and 27 glossotonsillar sulcus. The patients were staged as follows: 90 T1, 141 T2, 119 T3, 2 T4, 9 Tx with 230 N0, 93 N1, 9 N2, 20 N3, and 9 Nx. RESULTS: The results at 5 and 10 years show: local control 80% and 74%, locoregional control 75% and 70%, overall survival 53% and 27%, specific survival 63% and 52%, respectively. The univariate study shows at 5 years a better local control for T1T2 (87%) compared with T3 (67%) with p = 0.00004. The locoregional control is better for N0 (80%) than for N+ (55%) with p = 0.002. This is the same for the overall survival (59% vs. 42%, p = 0.002). Tumors with an extension to the mobile tongue or the base have a poor prognosis (p < 0.002). The radiobiological factors show less recurrences if the total duration of the treatment is < 55 days, the number of days between External Beam Irradiation and brachytherapy is < 20. The security margin seems important also. CONCLUSIONS: For the combination external irradiation and brachytherapy, the multivariate study for local control shows that ony T, localization, and the total duration of treatment are significant. For complications, classified into four grades, only the dose rate is significant.

Complications following definitive irradiation for cancers of the oral cavity and the oropharynx (in a series of 1134 patients).

PURPOSE: To study the rate and severity of complications in a series of 1134 patients treated by definitive irradiation for tumors of the oral cavity (772 cases) or the oropharynx (361 cases). METHODS AND MATERIALS: Patients were staged as 29.5% T1, 42% T2, 26% T3, 2.5% T4-Tx, and 74.5% N0 tumors. We treated 364 patients with brachytherapy only (192Ir) for the primary lesion. External irradiation and brachytherapy were combined for 770 patients. RESULTS: The results included local control and survival. Out of 1134 patients, 330 had 376 complications. Grade 1 complications occurred in 20% of the patients, Grade 2 in 9%; Grade 3 in 4%; and Grade 4 in 0.2%. Of the Grade 1 complications, 78% were soft tissue and only 24% were bone complications. For the more severe grades (2, 3, and 4), there were 56 soft tissue complications and 90 bone complications out of 1340 patients. The statistical analysis included tumor-related factors and treatment-related factors. For the first two factors, only tumor location was significant. The treatment-related factors significant for complications were studied in univariate and multivariate study. This multivariate study confirmed that for soft tissue complications dose rate and volume treated were important (p < 0.001). It also confirmed that for bone complications, total dose > 80 Gy, dose rate > 0.7 Gy/h, and the absence of leaded protection of the mandible were all important factors. CONCLUSION: This statistical study should allow future reduction of severe complications (Grades 2, 3, 4), if treatment factors inducing them can be taken into account. This is not always possible for very large tumors.

Dose escalation with 3D-CRT in prostate cancer: French study of dose escalation with conformal 3D radiotherapy in prostate cancer-preliminary results.

PURPOSE: To evaluate the feasibility of dose escalation in a multi-institutional study in prostate cancer patients. METHODS AND MATERIALS: Between October 1995 and October 1998, 164 patients with localized adenocarcinoma of the prostate were treated with 3-dimensional conformal radiotherapy at one of five French institutions. The dose of radiation was escalated from 66 to 80 Gy (ICRU point). The maximum dose to the rectal wall was limited to 75 Gy. RESULTS: Results were compared in two groups, one (group 1) receiving the standard dose (n = 46 patients; 66 to 70 Gy) and the other (group 2) receiving the escalated dose (n = 118 patients; 74 to 80 Gy). There was no difference in the characteristics of patients between the two groups. The mean follow-up time was 32 months in group 1 and 17.5 months in group 2. No statistical difference between the two groups was observed in the incidence of late gastrointestinal and urinary toxicities. The probability of achieving a posttreatment prostate-specific antigen nadir of

Design of a non-docking intraoperative electron beam applicator system.

A development of a non-docking system is described which enables collimation of an electron beam for intraoperative radiation therapy. This system, adapted to a linear accelerator (SATURNE 43-CGR MeV), has been designed to minimize the mechanical, electrical and tumor visualization problems associated with a docking system. A number of dosimetric considerations and technical innovations have been used in the design of this system. Among them are the central axis of the beam alignment with the axis of the cone via a laser system and the clamping method of the intraoperative cone to the treatment couch by a rigid system. This collimation system can be adapted for different makes of linear accelerator. The dose distribution in this new design system shows a better homogeneity in the patient's target volume and small (thus accessable) leakage radiation dose to tissues outside the intraoperative cone. The design concept and dosimetric characteristics of this novel applicator system are presented in this paper.

Detection of errors in individual patients in radiotherapy by systematic in vivo dosimetry.

We report 5 years of systematic measurements of the dose delivered to each patient undergoing radiotherapy treatment with photon beams in order to detect any systematic error that may have escaped the different checks performed at each step of planning and calculation prior to the first treatment session, or may have arisen during the set-up or the treatment delivery. For each patient the target-absorbed dose is derived from the entrance and exit doses measured by silicon diodes, on the beam axis at the patient's skin. Depending on the discrepancies observed between the measured and expected doses we have set decision levels for the corrective actions to be taken. In addition these measurements allow us to obtain information on the overall accuracy or on the quality of a specific treatment. During 5 years, 7519 patients have been measured and 79 errors were detected. Half could have induced a variation of over 10% in the dose delivered. Seventy-eight out of 79 errors were of human origin. As part of an overall quality assurance programme, it is of the utmost importance to check the dose delivered for each patient undergoing radiotherapy treatment in order to avoid systematic underdosing or overdosing.

A semi-empirical method for calculating the effect of air gap space on output factors on electron beam dose distributions.

BACKGROUND: A simple approach to calculate the effect of air gap on output factors on electron beam dose distribution is presented. METHODS: The method accounts for variations of pencil beam parameters using a model developed by Bruinvis et al. [4,5]. The evaluation of this method is based on measurements of the output factors at various distances between the final collimating device and the phantom surface. RESULTS: Comparison of calculations and measurements of output factors for various cone sizes and 0, 2 and 4 cm air gaps show agreement to within approximately 1.5% for electron energies of 6-13.5 MeV and field sizes of 5.3-10 cm in diameter. CONCLUSION: The accuracy of this semi-empirical method can be considered clinically acceptable and reduces the amount of experimental work needed.

Iridium-192 brachytherapy in the management of 147 T2N0 oral tongue carcinomas treated with irradiation alone: comparison of two treatment techniques.

Our purpose is to analyse local control, complications relative to the proportion of total dose delivered by external beam irradiation versus interstitial implant in 147 patients with previously untreated T2N0 squamous cell carcinoma of the oral tongue, managed between 1973 and 1986 (UICC staging system). These T2N0 patients are part of a larger group of 430 patients with oral tongue carcinoma (T1, T2, T3) treated with irradiation alone. Of these 147 T2N0 patients, 70 were treated with interstitial implant alone and 77 with both external beam irradiation and implant. In the group treated with interstitial implant alone, the 5-year local control was 89.8% against 50.6% in those treated with external beam irradiation and interstitial implant (log-rank test, p = 0.00002); 67.6% versus 46.5% for locoregional control (p = 0.029); and 62.2% versus 34.7% for specific survival (p = 0.0015). Since 1980, all the patients treated by iridium implantation were protected with a leaded spacing device between the tongue and the mandible. Soft tissue necrosis and bone exposure following treatment were scored according to the following criteria: minor, moderate or severe. Seven moderate and one severe complications were recorded in the brachytherapy group. None of the patients required surgery. In the combined treatment group, six moderate and two severe complications were observed. Patients treated with interstitial implant alone, and showing moderate or severe complications had received an average brachytherapy dose of 7600 cGy. In the same group, the patients without complications had received an average dose of 6800 cGy.(ABSTRACT TRUNCATED AT 250 WORDS)

Indications, techniques and results of postoperative brachytherapy in cancer of the oral cavity.

PURPOSE/OBJECTIVE: We tried to reduce the number of local recurrences after surgery and external beam irradiation (EBI) in carcinoma of the oral cavity, when margins were positive or close. MATERIAL AND METHODS: From 1980 to 1992, we treated 97 cases of carcinomas of the oral cavity by postoperative brachytherapy. Surgery was combined with EBI+brachytherapy in 51 cases and with brachytherapy alone in 46 cases. We treated 29 T1, 34 T2, 30 T3T4 and four Tx (73% were N0 at first examination and 23% had positive nodes). The type of surgery is analysed. Brachytherapy was performed in one or two planes along the surgical scar. If the mandibular rim was resected, especially when the tongue or the remaining floor were sutured to the internal face of the inferior lip or to the buccal mucosa, the bridge technique was used. To decrease the dose to the inferior part of the mandible, the bridge was modified thanks to experimental dosimetry. RESULTS: At 5 years, the local control (LC) is 89%, the locoregional control (LRC) 82%, the specific survival (SS) 74% and the overall survival (OS) 67%. COMPLICATIONS: We noted 19% of grade 1 (minor), 12% of grade 2 (moderate) and 6% of grade 3 (major) complications. CONCLUSION: Compared with the results of the literature, we think that postoperative brachytherapy can improve classical radiosurgical results in selected cases with a risk of local recurrence.

Preprocessing of control portal images for patient setup verification during the treatments in external radiotherapy.

The main problem in processing the control portal images is their poor quality. We have developed a way of improving the image quality to allow a segmentation stage. Three items were studied for this purpose the background gradient of intensity correction, the noise reduction, and the image restoration. The background was corrected by subtracting a smoothed version of the image from the original. We tested 15 noise reduction methods. The most appropriate for control portal images was found to be the truncated average. Finally, four restoration techniques were compared. The maximum a posteriori (MAP) algorithm was the most efficient. The algorithms were tested over a wide range of conditions (image quality). They produced a great improvement in anatomic detail for all the imaging systems, energies, and anatomical zones tested. For example, the signal-to-noise ratio of a SRI-100 pelvis image, acquired with 4 monitor units (MU) at 10 MV (very low quality image), increased from 0.97 to 42.84 after preprocessing. We found that the improvement in image quality facilitated or even enabled segmentation of the control portal images. The percentage of segments belonging to a structure increased from 30% to 65% in the example cited. The preprocessing of control portal images is the first step in checking the patient setup.

The use of a microcomputer for non-linear optimisation of doses in external radiotherapy.

The study presents software for a microcomputer designed to determine the optimum dose distribution in external radiotherapy, either by calculating the doses delivered and the field width (in linear programming) or, in addition, by calculating the beam geometry (non-linear optimisation). Various optimisation criteria can be selected, namely the homogeneity, the concentration on the target and the total dose in a sensitive area. The article outlines an example.

Cardiac catheterization: dosimetry on patients.

Our study was made on 49 patients and we used capsules of lithium fluoride. The average fluoroscopy time was 32 min. and the average cinema film length was 76.5 metres. The relationship between the entry dose, the fluoroscopy time and the length of cinema film allowed us to calculate a fluoroscopy equivalent time (F.E.T) for each patient which was of 51 min. (32 min. + 76/4) as radiation dose of one minute fluoroscopy equal radiation dose of 4 metres of cinema film. The average heart dose was 0.70 X 10(-3) X FET (GY) or 70 mr/min. There was an absence of relation of the exit dosage to the diameter of the patient and a proportionality of the heart dose to the exit dose. Furthermore the maximum eye dose recorded was 200 mrads and the maximum gonadal dose was 350 mrads.

Role of interstitial brachytherapy in oral and oropharyngeal carcinoma: reflection of a series of 1344 patients treated at the time of initial presentation.

Our study focuses on a series of 1344 cases of carcinoma of the oral cavity and oropharynx treated between 1973 and 1992. Brachytherapy was always performed with iridium 192, either alone or in combination with external-beam irradiation or with surgery for the treatment of the primary tumor. For the oral cavity, we studied 565 cases of mobile tongue. The local control and overall survival rates, respectively, at 5 years are as follows: for T1, 92% and 70%; for T2, 62% and 42%; and for T3, 50% and 29%. For the subgroup T1T2NO, there was a better prognosis for treatment by brachytherapy of the primary lesion alone (p < 0.0001). Two hundred seven cases of floor-of-mouth carcinoma have been reported. The T3T4 patients were not considered surgical candidates. The local control and overall survival rates, respectively, at 5 years are as follows: for T1, 97% and 71%; for T2 72% and 42%; and for T3, 51% and 35%. Ninety-seven patients were treated by postoperative brachytherapy. These were patients for whom the margins after surgery were positive or narrow. A technique termed the modified bridge is described for lesions located in the mandible. Carcinomas of the buccal mucosa are rare in our country; only 42 cases were treated in this comparison of two techniques, and the overall survival rate was 48%. Epidermoid carcinomas of the oropharynx have nearly always been treated by a combination of external-beam irradiation and brachytherapy because of the bilateral node risk. Seventy-two patients with epidermoid cancers of the base of the tongue had an overall survival rate of 44%. The tonsil, soft palate, and pillars benefited from the use of the loop technique of brachytherapy combined with external-beam irradiation. Three hundred sixty-one patients were treated. Among these patients were two groups with different prognoses. Patients with tonsil, soft palate, and posterior pillar carcinomas had a local control rate of 84% and an overall survival rate of 57%. Conversely, the anterior pillar and the pharyngoglossal sulcus have a local control rate of only 65% and an overall survival rate of 38%. Statistical analysis revealed the prognostic factors for local control. The complications were classified into four grades: minor (20%), moderate (9%), major (4%), or inducing death (0.2%). The bone complications of grade 2 or 3 are more frequent for the floor of the mouth than for other locations.