Supraclavicular Field Research Articles

A method for delivering accurate and uniform radiation dosages to the head and neck with asymmetric collimators and a single isocenter

To investigate the use of asymmetric collimators and a single isocenter for delivering a uniform, accurate dose of radiation to the head, neck, and supraclavicular lymph nodes. A linear accelerator with a pair of asymmetric collimators is required for this technique. An isocenter was placed at the junction of the lateral head and neck fields and the anterior supraclavicular field. The asymmetric collimators were set longitudinally, by collimator rotation if necessary. The collimators split the radiation beam to all portals. Dose uniformity was measured at the junction with films in solid-water phantoms. Film dosimetry showed a uniform dose at the junction without hot or cold regions. A digital display tolerance of +/- 1.0 mm for a field size maintained an acceptable uniform dose (+/- 5% dose variation) at the junction. The single isocenter and asymmetric collimators reduced field setup time by half. No table rotation was required to match fields. The asymmetric collimators lead to easy and accurate patient setup. The absence of the trapezoid effect resulted in the complete coverage of the submandibular and cervical nodes without any hot spots.

Radiotherapy technique, dose and fractionation in breast conserving treatment: current issues

Following a departmental review of alternative external beam irradiation techniques for treating carcinoma of the breast, it was determined to implement a technique based on two isocentrically arranged tangential fields and an abutting supraclavicular field.

Extended-field radiotherapy in favorable stage IA–IIA Hodgkin's disease (Prognostic role of stage)

Purpose : The study was undertaken to evaluate the long-term results in a favorable subset of patients with pathological Stage IA–IIA treated with irradiation alone. Methods and Materials : One hundred and forty-seven adults with laparotomy- Staged IA–IIA “favorable” Hodgkin's disease were treated with primary subtotal nodal irradiation. Patients with infradiaphragmatic presentation were irradiated through paraortic and inguino-iliac node chains (inverted Y field) followed by prophylactic mediastinal and supraclavicular fields. Results : Actuarial overall survival (OS) at 7 years (median follow-up 77 months) was: 93% for the whole series, 94% for Stage I, and 92% for Stage II. The freedom from first progression (FFP) (80% for the whole series) showed a statistically significant difference ( p = 0.008) between Stage I (88%) and Stage II (71%). By univariate analysis, stage alone had an independent prognostic significance for OS and FFP. Of the 29 relapsed patients, 8 were previously classified as Stage I and 21 as Stage II; 16 of 29 (55%) of the relapses occurred in the pelvis and 9 in extranodal sites. After salvage treatment with chemotherapy all patients achieved a second complete remission. Seven second malignancies (two acute nonlymphocytic leukemias, one preleukemic syndrome, and four solid tumors) have been detected so far. Hypothyroidism was observed in 16% of patients and a reversible pulmonary restrictive syndrome in 14% of cases, respectively. Conclusions : Within 7 years from radiation therapy, about one-quarter of the patients with Stage II disease will experience a relapse and need intensive salvage chemotherapy. This is not invariably successful and safe, for it may be complicated by either acute or potentially fatal long-term adverse effects, such as second malignancies and cardiac or pulmonary sequelae, in about 5% of patients. The high frequency of relapse in Stage IIA patients suggests a combined modality approach with relatively short-term chemotherapy not including alkylating agents.

Three-field breast irradiation technique using tangential quarter fields

We have developed and implemented in clinical practice an isocentric three-field breast irradiation technique using tangential quarter fields. In this technique, the same isocenter is used for the supraclavicular and the tangential breast fields. The superior-posterior corner of the tangential breast fields is placed at the central axis by asymmetric collimation of both the length and the width of the field. Consequently, the beam divergence at both the superior and posterior edges is eliminated, allowing a perfect geometric match between the posterior borders of both tangential breast fields and the supraclavicular field without table rotation. Compared to conventional techniques requiring table rotations, the present method produces a more uniform dose distribution in the target volume and requires significantly less simulation time.

A single isocenter three-field breast irradiation technique using an empiric simulation and asymmetric collimator

The treatment of abutting fields presents multiple difficulties, including problems of field overlaps or gaps, complexity of simulation, and the difficulties of daily setup and variation. Multiple techniques have been described for the treatment of the breast/chest wall and supraclavicular nodes using tangents and a matched supraclavicular field. The techniques described have used collimator angles, couch angles, and/or corner blocks in an attempt to match these fields with no overlap or gap. Some of these techniques required complex calculations or treatment devices to achieve a geometric match between fields. We describe a technique for treatment of breast and supraclavicular nodes that uses a single isocenter and requires asymmetric collimator jaws to give half-blocked fields. The simulation and setup are done empirically, with no complex calculations required. The daily setup and treatment can be done rapidly and reliably, with no extra equipment required. Custom blocks may be used to conform to the chest wall contour and decrease the amount of lung in the treatment fields.

Three-field isocentric breast irradiation using asymmetric jaws and a tilt board

Perfect abutment of medial and lateral tangential breast portals with the adjacent supraclavicular field may be achieved with ease. A simple and safe approach was developed using a tilt board and new technology that is standard on a popular linear accelerator. The patient is secured on a tilt board as a means to level the chest wall. Isocenter is placed at depth on the matchline, where asymmetric jaws are used to produce non-divergent field edges and a perfect abutment. This is done without the need for table or collimator rotations, beam-splitters, or vertical cephalad blocks. The dorsal beam edge of the tangents is made coplanar by rotating the gantry more than 180°. This procedure produces a dosimetrically sharp field edge and eliminates concern about block transmission and excess dose to the contralateral breast. Set-up is fast, and the steps involved are simple and few. Advantages and limitations of this technique are presented.

Expedient set-up of tangential breast fields with a simple gantry attachment

A novel technique for setting up tangential fields is described. The technique uses a simple device (Breast Aligner) which attaches to the collimator of the treatment unit. The function of the Breast Aligner is similar to conventional front and back pointers except that the beam edge rather than central ray is defined. By delineating beam entrance and exit points at the posterior field edge, the device greatly simplifies and expedites setup, and enhances precision of port alignment. Additional advantageous features include: (a) the ability to compensate for small inadvertent variations from the initial set-up position or for patient movement between the set-up of opposing ports, (b) the ability to visually check port alignment in the treatment position immediately before irradiation, and (c) decreased chance of human and equipment error by eliminating the need for measurements and calculations at the time of treatment. Our method can be used for SSD or SAD techniques and, with minor adjustment, is applicable for establishment of coplanar cephalad field borders as required at the junction of a supraclavicular field.

A Technique for Treating Local Breast Cancer Using a Single set-up Point and Asymmetric Collimation

Using both pairs of asymmetric jaws of a linear accelerator local-regional breast cancer may be treated from a single set-up point. This point is placed at the abutment of the supraclavicuhu fields with the medial and lateral tangential fields. Positioning the jaws to create a half-beam superiorly permits treatment of the supraclavicular field. Positioning both jaws asymmetrically at midline to define a single beam in the inferoanterior quadrant permits treatment of the breast from medial and lateral tangents. The highest possible matching accuracy between the supraclavicular and tangential fields is inherently provided by this technique. For treatment of all fields at 100 cm source to axis distance (SAD) the lateral placement and depth of the set-up point may be determined by simulation and simple trigonometry. We elaborate on the clinical procedure. For the technologists treatment of all fields from a single set-up point is simple and efficient. Since the tissue at the superior border of the tangential fields is generally firmer than in mid-breast, greater accuracy in day-to-day set-up is permitted. This technique eliminates the need for table angles even when tangential fields only are planned. Because of half-beam collimation the limit to the tangential field length is 20 cm. Means will be suggested to overcome this limitation in the few cases where it occurs. Another modification is suggested for linear accelerators with only one independent pair of jaws.

Definitive irradiation for intraductal carcinoma of the breast

During the period from 1978 to 1985, 51 women with intraductal carcinoma of the breast were treated with definitive irradiation following breast-conserving surgery. Surgical treatment of the primary tumor in all patients consisted of excisional biopsy or wide resection. In general, definitive irradiation consisted of conventional breast tangents to 4500–5000 cGy followed by a breast boost to a total dose of 6000–6600 cGy (median = 6000 cGy; range = 4200–6600 cGy). No patient was treated with radiation to a supraclavicular or axillary field. For the 51 patients, the median follow-up was 68 months (range = 25–126 months). The 5-year acturial rate of local failure was 6%. A total of five patients failed in the breast at 19, 35, 40, 79, and 119 months following definitive irradiation. Salvage treatment in these five patients consisted of mastectomy in all five patients plus adjuvant tamoxifen in one patient. All five of the patients with breast failures are alive and NED (no evidence of disease), although with limited follow-up (median = 12 months; range = 6–68 months). These results suggest that definitive irradiation is an acceptable alternative to conventional mastectomy for appropriately selected and staged patients with intraductal carcinoma of the breast. In view of the long natural history of this disease, prolonged and careful follow-up of these patients is required.

Treatment results and acute and late toxicity of radiation therapy for testicular seminoma

From 1977 to 1988, 215 patients with a diagnosis of testicular seminoma were referred to the University Hospital, Hamburg, West Germany, for radiation therapy (RT). In 15 patients a careful review of the histologic condition showed signs of embryonal cell carcinoma. Three patients refused completion of therapy. No patient was lost to follow-up. On this basis, a retrospective review of 197 patients was carried out. One hundred thirty-three patients were classified as Stage I (67%), 39 as Stage II (20%), 8 as Stage III (4%), and 17 as Stage IV (9%). One hundred eighty patients had classic seminoma and 17 had anaplastic seminoma. All patients underwent high inguinal orchiectomy before treatment. Seven patients with Stages III and IV received chemotherapy before RT. Patients with Stages I and II were treated with 40-Gy photons to paraaortic and parailiac fields. Ten patients with Stage III and IV seminoma received 30-Gy photons to mediastinal and supraclavicular fields as well. Sixty patients received additional inguinal RT. The overall 5-year survival rate (corrected for intercurrent death, except for treatment toxicity) was 100% for Stage I, 100% for Stage II, 87% for Stage III, and 87% for Stage IV. The mean follow-up time was 6.3 years (range, 0.6 to 11.9 years). An evaluation of all patients showed no difference according to histologic condition or prior chemotherapy. Mediastinal and supraclavicular irradiation showed no improvement in treatment results. Acute toxicity consisted of mild to moderate emesis, increased bowel frequency, erythema, and, in four cases leucopenia and thrombopenia (all World Health Organization [WHO] Grades I to II). However, one patient died of a pulmonary fibrosis 1 month after mediastinal irradiation and 2 months after polychemotherapy, and a gastroduodenal ulcer developed in another patient 1.5 months after paraaortic RT and prior polychemotherapy. Overall, the data suggest that to avoid overtreatment and consecutive treatment morbidity reduced doses of 30 Gy and a restrictive treatment planning adapted to the individual risk are sufficient for RT for testicular seminoma. An alternative to postoperative RT in Stage I (and possibly Stage II) seminoma could be no RT, but close follow-up instead.

A technique for treating local breast cancer using a single set-up point and asymmetric collimation

Using both pairs of asymmetric jaws of a linear accelerator local-regional breast cancer may be treated from a single set-up point. This point is placed at the abutment of the supraclavicular fields with the medial and lateral tangential fields. Positioning the jaws to create a half-beam superiorly permits treatment of the supraclavicular field. Positioning both jaws asymmetrically at midline to define a single beam in the inferoanterior quadrant permits treatment of the breast from medial and lateral tangents. The highest possible matching accuracy between the supraclavicular and tangential fields is inherently provided by this technique. For treatment of all fields at 100 cm source to axis distance (SAD) the lateral placement and depth of the set-up point may be determined by simulation and simple trigonometry. We elaborate on the clinical procedure. For the technologists treatment of all fields from a single set-up point is simple and efficient. Since the tissue at the superior border of the tangential fields is generally firmer than in mid-breast, greater accuracy in day-to-day set-up is permitted. This technique eliminates the need for table angles even when tangential fields only are planned. Because of half-beam collimation the limit to the tangential field length is 20 cm. Means will be suggested to overcome this limitation in the few cases where it occurs. Another modification is suggested for linear accelerators with only one independent pair of jaws.

The Tangential Breast Match Plane: Practical Problems and Solutions

The three-field breast set-up, in which tangential oblique opposed fields are joined to an anterior supraclavicular field, has been the method of choice for treatment of breast cancer for many years. In the last several years many authors have suggested refinements to the technique that improve the accuracy with which fields join at a match plane. The three-field breast set-up, using a rotatable half-beam block is the technique used at our institution. In instituting this procedure, several practical problems were encountered. Due to the small collimator rotation angles used it is possible to clinically reverse the collimator angle without observing an error noticeable on fluoroscopy. A second error can occur when the table base angle is used to compensate for the incorrect collimator rotation. These potential sources of error can be avoided if a programmable calculator or computer program is used to assist the dosimetrist during the simulation. Utilization of fluoroscopy, digital table position displays and a caliper provide accurate input for the computer program. This paper will present a hybrid procedure that combines practical set-up procedures with the mathematical calculation of ideal angles to result in an accurate and practical approach to breast simulation.

Spinal cord dose reduction using an anterior 13 MeV electron field situated between a split anterior 60Co Supraclavicular field

As part of the treatment for lymphoma, disease involving the supraclavicular region has been treated with megavoltage 60Co photons to a midline dose of 30 to 45 Gy through an anterior involved field and a supplementary posterior field when necessary. The spinal cord was shielded with a 5 cm lead block during treatment to the posterior field. A typical 40 Gy treatment results in a dose to the lower cervical and upper thoracic spinal cord in the range of 22 to 26 Gy, a level that could compromise subsequent mediastinal treatment in the event of a relapse. To reduce this cord dose, the midportion of the anterior supraclavicular 60Co field was replaced with a high-energy (13 MeV) electron port, which reduces the dose to the cord to below 6 Gy in the average adult patient. This modification of the routine supraclavicular treatment allows greater flexibility in future treatment in the event of a mediastinal relapse.

Matchline dosimetry of a three field technique for breast treatment using cobalt or 6 MV X rays.

The matchline dose distribution between the tangential and supraclavicular fields used for treatment of breast cancer was investigated using 60Co and 6 MV X rays. Techniques which allow minimum, moderate, and maximum overlap between the fields as well as a geometric alignment technique were studied. For a given technique, comparable matchline widths and doses were obtained with either machine. Average matchline doses were slightly greater with 6 MV X rays, however, more tissue was irradiated to higher dose levels with 60Co. Among the techniques which do not geometrically align the three fields, doses as high as 150% or as low as 70% were observed depending on the amount of overlap between the fields. Matching the tangents 3.5 cm medial and lateral to the supraclavicular field center yielded average maximum and minimum matchline doses within ten percent of those with geometric alignment techniques. However, these distributions will vary with patient size and matchline length. Geometric alignment techniques offer the advantages of matchline dose uniformity and reproducibility over the patient population with maximum matchline doses of only 110-115%.

A simple isocentric technique for irradiation of the breast, chest wall and peripheral lymphatics.

The major problem with the standard technique for irradiation of the breast or chest wall and peripheral lymphatics is field matching at the junction between the supraclavicular and tangential fields. Overdosing or under-dosing across the junctions is unavoidable because of beam divergence. Various techniques using a half-blocked supraclavicular field in conjunction with special tangential fields have been introduced recently to eliminate the junction problem; they are, however, complicated, involving couch motions and machine isocentre repositioning when changing from the supraclavicular to the tangential fields. The breast treatment technique which we have used over the past twelve months utilises a supraclavicular half-blocked field, two tangential half-blocked fields and an optional posterior axillary field. The technique is simple and easy to set up since the same machine isocentre is used for all treatment fields and no couch movement or patient repositioning is required. The same half-block collimator which is used to define the caudad border of the supraclavicular field is used to define the cephalad edges of the two tangential fields. The margin of error of treatment is reduced and the dose measurements demonstrate excellent dose homogeneity through the entire treatment volume with no overdose or underdose at the field junction.

Three-field technique for breast irradiation using tangential field corner blocks

A further modification of the three-field technique for the radiotherapy of the breast has been developed. Two isocentric opposing tangential fields encompass the breast, chest wall, and may include the internal mammary lymph nodes. The third, an anterior field, encompasses the axilla and supraclavicular areas. As with our previously reported techniques, the objectives of the present modification is to make the posterior edges of the tangential fields coplanar and to match the cephalad geometric edges of the tangential fields to the caudad geometric edge of the supraclavicular field. A half-beam block is used to shield the caudad half of the anterior field, thus producing a vertical transverse plane to which the tangential fields are matched. Small corner blocks are used on the cephalad edges of the tangential fields to produce the vertical edge necessary for matching to the anterior field. It is essential that the match between the tangential fields and the anterior field be geometrically correct to ensure both local control of disease and good cosmetic results. Two advantages of the present technique are the ease with which it can be carried out and the precision of the match plane without the use of cumbersome mechanical accessories.

Three-field technique for breast treatment using a rotatable half-beam block

A new three-field technique for the radiation therapy of breast cancer has been developed. Two opposing tangential fields treat the breast, chest wall, and ipsilateral internal mammary lymph nodes. The third, an anterior field, treats the axilla and supraclavicular area. The objective of the technique is to make the posterior geometric edges of the tangential fields coplanar, and also to make their cephalad geometric edges and the caudad geometric edge of the supraclavicular field coplanar. To effect the matching of fields, the technique utilizes a rotatable half-beam shielding block. To simplify the simulation procedure, an exact mathematical solution is given for the required treatment set-up parameters.

Mid-sagittal plane dosimetry in patients with extensive head and neck malignancy

Abstract This is a film dosimetry study in a phantom showing the mid-sagittal plane dose distribution when two opposed lateral fields are abutted on the skin to an anterior supraclavicular field, no correction for beam divergence is made, and the anterior midline block is omitted. A modification of this set-up is presented as an alternative to avoid the overlap created at the level of the spinal cord.

A modified three-field technique for breast treatment

Radiation therapy of breast cancer commonly uses three high-energy photon fields. The supraclavicular field and the two tangential fields are often matched on the skin. An analysis of the dose distribution in the matchline region shows a dose of up to 200% of the prescribed dose over the width of 8 mm at 3 cm depth. This is a result of the beam divergence and the complex geometry. A modification of the treatment technique has reduced the dose to less than 140% of the prescribed dose over approximately 4 mm. The modified technique uses a shielding block which covers the caudad half of the supraclavicular field and makes the caudad edge vertical. The cephalad edges of the two tangential fields are defined by a shielding block, which hangs vertically from the treatment head regardless of gantry and collimator position. This block obstructs a small portion of the radiation field and defines a vertical field edge. These three vertical field edges are brought into coincidence by adjustment of couch turntable angle and longitudinal couch position. The nearly perfect geometric match in three dimensions achieved in this manner further improves the cosmetic results after radiation treatment of breast cancer.

Field separation between lateral and anterior fields on a 6 MV linear accelerator

Field separations of 0, 2.5, 5, and 10 mm between lateral facial-cervical fields and anterior supraclavicular fields have been studied using thermoluminescent dosimeters in the Rando phantom. Measurement points were taken at three different depths in the midsagittal plane and at two locations out of that plane. The resultant radiation distribution for these points was measured at intervals of less than 1 mm. The measured dose distribution was compared to computer generated distributions. The field separation which resulted in the most ideal distribution for routine cases was determined. This agreed well with the field separation determined by the standard calculational approach, which may be used by modifying certain conditions. The application of the results of this data to the clinical situation is discussed.