An endocavitary rectal irradiation technique

An alternative to standard short target-skin distance (TSD) rectal irradiation techniques is presented. The proctoscopic rectal cone is linked outside of the patient to a superficial X ray tube operated at 50 kVp and 25 mA. The cone is rigidly held in place by a hydraulic clamp and linked to the X ray tube with an electromagnetic lock. The X ray beam is filtered by 0.3 mm of aluminum, giving a half-value-layer of 0.27 mm of aluminum and an exposure rate of 720 R/min. (0.186 C/kg-min.) at the treatment TSD of 22 cm. The physical aspects of the technique are described in detail.     

Characteristics of an MM 22 medical microtron 21 MV photon beam

Beam quality, surface doses, depths of maximum dose, peak dose rates, beam profiles, and central axis percentage depth doses of a medical microtron's 21 MV photon beam were measured. The half-value layer of lead was 1.35 cm, the half-value layer of water was 23 cm, and the nominal acceleration potential was 17.7 MV. For a 10 X 10 cm2 field at 100 cm SSD, the maximum dose occurred at a depth of 3 g X cm-2 and the surface dose was 18% of the maximum. The highest dose rate at isocenter was approximately 800 cGy X min-1. The worst horns on beam profiles occurred at a depth of 5 cm for the 35 X 35 cm2 field where the dose rate 4 cm from the edge of the beam was 3% higher than that on the central ray. No horns were apparent for fields 25 X 25 cm2 or smaller.     

Dosimetric evaluation of a variable energy superficial X-ray machine with applications for endocavitary radiotherapy techniques

This investigation presents the beam characteristics of a newly-marketed variable energy superficial X ray machine for radiotherapy. The X ray system hardware, including a high voltage generator, and console software allow for nine independent operator-selected X ray beams from 10-150 kVp. Filament current values are also independently variable; 1.0-13.0 mA for 90-150 kVp, and 1.0-30.0 mA for 10-90 kVp. The HVL's, effective energies, and radiation outputs for the nine combinations of kVp and mA are presented. In addition, percentage depth dose and beam uniformity results are presented as a function of cone size. Radiation output stability and reproducibility results are included. Discussion of adaptation of this X ray system to the Papillon technique for the treatment of rectal cancers is presented.     

Methods of bolusing the tracheostomy stoma

PURPOSE: The tracheostomy stoma is a potential site of recurrence for patients who have subglottic cancer or subglottic spread of cancer. In these patients, it is important that the anterior supraclavicular field does not underdose the posterior wall of the tracheostomy stoma when using a 6-MV anterior photon field. Conventionally, this problem is surmounted with placement of a plastic tracheostomy tube, which is uncomfortable for the patient, potentially traumatic, and can interfere with vocalization via a tracheal esophageal puncture. Our study was designed to investigate the dosimetry of this region and see if alternate methods would be effective. METHODS AND MATERIALS: A phantom was constructed using a No. 6 tracheostomy tube as the model for the tracheostomy curvature and size. Using the water-equivalent phantom, film dosimetry, and films oriented parallel to the en face field, we investigated the dose at the depth of the surface of the posterior wall of the phantom's tracheostomy stoma. Dose was measured both in space and at the tissue interface by scanning points of interest both horizontally and vertically. We measured doses with a No. 6 and No. 8 plastic tracheostomy tube, either 0.5 cm and 1.0 cm of bolus (1-cm airhole) with no tracheostomy tube, as well as 0.3 cm and 0.6 cm tissue-equivalent Aquaplast (Med-Tec Co., Orange City, Iowa) over the tracheostomy. Dosimetry at the posterior interface was confirmed using thermoluminescent dosimeters. RESULTS: Three mm and 6 mm of Aquaplast produced a posterior tracheal dose of 93% and 100%. CONCLUSION: There is no need for these patients to wear a temporary plastic tracheostomy tube during their external radiation therapy. Aquaplast should allow better position reproducibility, reduce trauma, not interfere with patient respiratory efforts, and be compatible with vocalization via a tracheal esophageal puncture.     

A case of advanced gastric cancer successfully treated with chemoradiotherapy targeting for recurrent lymph node metastasis

The patient was a 75-year-old male, who was diagnosed with type 3 advanced gastric cancer and bulky lymph node metastasis. Two courses of neoadjuvant chemotherapy (S-1, CDDP) which showed a partial remission and distal gastrectomy were performed. Although he received S-1 medication as adjuvant chemotherapy, lymph node recurrence appeared 6 months after the operation. Radiation therapy at a total dose of 65 Gy (10MV X ray, 2.5 Gy/day × 26 Fr) selectively targeting for recurrent lymph node metastasis with S-1 medication were applied. There were no adverse effects during chemoradiation therapy and the metastatic node showed regression (30 mm to 15 mm). Sixteen months passed from chemoradiation, and the patient remains alive with no signs of relapse without any treatment after the chemoradiation. Therefore, our case suggests that chemoradiation therapy could be an effective treatment for recurrent lymph nodes metastasis in gastric cancer.     

Mantle planning: Report of the Australasian Radiation Oncology Lymphoma Group film survey and consensus guidelines

The purpose of the present paper was to measure the variation in mantle planning in Australia and New Zealand. A chest X‐ray (CXR) of a patient in the supine position with a neck node marked by wire was sent to every radiation oncologist in Australia and New Zealand. They were to mark on the CXR the lung blocks that they would use to treat this patient, assuming that the patient had stage IA Hodgkin’s disease. These marks were compared with a small sample of radiologists who were asked to define the mediastinum on the same CXR. Radiation oncologists were also asked to complete a short questionnaire about other modifications to their treatment fields and their experience with this technique. One hundred and six films were sent out and 44 radiation oncologists replied. There was a maximum variation in the placement of their lung blocks of 6 cm. Half of the lung blocks were within a 2‐cm range. One respondent said they would not use a mantle field to treat this patient. Mediastinal coverage was inadequate in at least 50% of cases. There was a very large variation in mantle field planning practices within Australia and New Zealand. For this reason Australasian Radiation Oncology Lymphoma Group has produced consensus guidelines for mantle block design. These are appended to the present paper.     

锥形束断层CT对肺部肿瘤放射治疗摆位误差修正及其阈值的确定*

目的:采用锥形束CT（cone beam computed tomography ,CBCT）检测并修正肿瘤放射治疗摆位误差可以有效减少放射治疗边界,而CBCT图像引导治疗误差的修正范围受许多不确定因素影响,本研究目的是确定锥形束CT影像技术对肺部肿瘤放射治疗摆位误差修正阈值。方法:对30例肺部肿瘤放疗患者在每次照射前获取CBCT,通过系统的匹配功能,将获取的CBCT图像和计划CT图像匹配,获得左右（X）、头脚（Y）、前后（Z）三个方向的摆位误差。若任何方向误差>2mm,相应移动治疗床修正误差后再次获取CBCT图像,设定1mm、2mm、3mm和5mm调准阈值并分析相应调整后的残余摆位误差及其规律。结果:30例患者共进行CBCT扫描860 次。每次治疗开始前首次摆位CBCT 584 次,调整治疗床后再次CBCT扫描276 次,调整误差前胸部摆位误差在Y 轴最大,其误差≤1mm、2mm、3mm和5mm的百分率分别为15.0% 、26.0% 、48.7% 和63.7% ,调整后残余误差≤1、2、3、5mm的百分率分别为78.4% 、95.2% 、98.3% 和99.6% ;初次摆位最大系统误差和随机误差分别为4.2mm和5.0mm,其外放边界（Msetup）为6.9～13.8mm,根据1、2、3、5mm阈值调整获得的残余误差值分别为≤1.0mm、≤1.0mm、≤1.2mm和≤2.2mm,与之相对应的外放边界分别为≤2.2mm、≤2.2mm、≤3.1mm和≤4.4mm。结论:CBCT有助于检测和修正分次间摆位误差,采用2mm和3mm作为胸部肿瘤CBCT摆位误差的修正阈值是可行的。      

计算机辅助肺部小病灶穿刺定位系统的建立

目的：在“肺癌早期诊断立体定位仪”的基础上，利用计算机技术，研制一个新型的同步实时三维X线定位穿刺诊断系统，方法：该系统模拟利用两台X线机，从两个不同的角度同时获取图像，采用计算机图像处理和计算机视觉技术进行处理，以获得病灶和穿刺针的三维信息。结果：两台X线机可以较好地模拟一台双球管双C臂的X线机，完成两路图像的实时同步采集。实验表明两束X光在成像时相互之间没有干扰，系统的平均定位误差约为0．5mm，最大定位误差约为1．0mm，实时显示速度为4帧／秒，结论：实验结果表明，应用计算机技术研制一个新型同步实时三维立体定位系统，从理论和实践上是可行的。本系统无论是硬件配置，还是软件性能，都可以满足临床实用的需要。     

Design and characteristics of a facility for total-body and large-field irradiation

A facility for total-body X ray irradiation has been built using two 4 MV linear accelerators, one supported from the ceiling and one placed in a floor pit. The maximum distance between the sources is 410 cm. The patient lies supine on a light, movable support with a stretched-canvas top, halfway between the sources where the field size is 80 X 220 cm2. A special flattening filter maintains the doserate variation in air within +/- 3% over the central 70 X 200 cm2 of the field, but some quality variations within the beam are noticeable. The doserate at 205 cm distance from the sources is variable between 0.05 and 0.8 Gy/min (half from each source). To permit treatment of large fields at higher doserates, the accelerators can be moved vertically to place the sources at 120 cm or 160 cm from the patient's midplane. For this purpose, independently movable collimators are provided and the flattening filter is designed to provide two options, one for the large total-body field and the other with less filtration covering a smaller solid angle. At 120 cm distance, each beam can provide a doserate of up to 1.1 Gy/min.     

A method of radiation treatment for advanced neck node metastases

Thirty-one advanced cervical node metastases (staged N3 according the U.I.C.C. system; 4 N2A, 27N3A according the A.J.C. system) were treated using a particular schedule consisting in two courses: in the first, only the palpable tumor was irradiated with several low energy beams (3.3 mm Al HVL), using as X ray tube operated at 60 kV; in the second course, the whole lymphatic area was treated with 60 Co and conventional fractionation. Palpable disease received 7500 to 10,500 cGy in a overall time of 45-55 days. The local control rate was 87%, without any severe complication. The four (13%) failures were all related to the lowest dose levels.     

Preliminary report on the effects of localized head irradiation on the development of transplanted tumors in C3H/HeJ mice.

The growth rate, as measured by increases in volume of a transplanted tumor (adenocarcinoma), was compared in mice that were irradiated locally to the head and in nonirradiated mice. 6-month-old female C3H/HeJ mice were used, and those that were irradiated received dosages of 100 and 200 r from a Keleket 220 KVP 20 Ma X-ray machine. The dosages were delivered at 6.66 r/sec through a 0.25 cu/1.0 aluminium filter. The beam from the X-ray tube was then collimated through a series of lead shields before reaching the cranium of the mouse. 24 h after irradiation, some mice were transplanted into the left side of the axillary fold, with small pieces, approximately 2 mm3, of tumor tissue. Careful weekly examinations for 15 weeks after the initial transplantation revealed major differences in tumor volume between irradiated and nonirradiated animals.     

Characteristics of an intraoral cone for electron beam therapy with an 18 MeV linear accelerator

A 3.0 cm diameter X ray intraoral cone was attached to the end of a 4.0 cm × 4.0 cm electron beam applicator for an 18 MeV linear accelerator. The central axis depth dose, X ray contamination, field flatness, and isodose distributions were determined for this configuration at five electron beam energies with film, using ionization chamber measurements as a check on the dosimetry. These data indicated possible clinical advantages with the electron beam as compared to an X ray beam.     

Electron beam energy degradation by low density scattering material

Low density filters have been used successfully for many years to degrade the normally available electron beams from medical linear accelerators for the treatment of skin disorders and chest wall irradiation. In the former case the filter is generally far removed from the patient for whole body irradiation while in the latter case the filter is in contact with patient's skin. In the case of our 18 MeV accelerator', where the cones are 5 cm short of the isocenter, placing filters at the cone face leads to a reduction in beam homogeneity at the patient. The reduction has been found to be as high as 80 % in some cases and is a function of filter thickness, nominal beam energy and cone size. Placing filters at the collimator face, with the electron applicator attached, leads to acceptable field homogeneity but significantly reduces the electron output with a small increase in X ray contamination. In this study, high impact polystyrene and acrylic sheets have been used as filters to degrade the incident electron beam energies normally available on our accelerator. The effects of placing these filters at varous sites in the beam have been examined in detail. Our results show that electron beam energy degradation using filters is a trade off between homogeneity on the one hand and X ray contamination and output on the other.     

Stereotactic target point verification of an X ray and CT localizer

Stereotactic radiosurgery with a linear accelerator requires the accurate determination of a target volume and an accurate match of the therapeutic radiation dose distribution to the target volume. X ray and CT localizers have been described that are used to define the target volume or target point from angiographic or CT data. To verify the accuracy of these localizers, measurements were made with a target point simulator and an anthropomorphic head phantom. The accuracy of determining a known, high contrast, target point with these localizers was found to be a maximum of +/- 0.5 mm and +/- 1.0 mm for the X ray and CT localizer, respectively. A technique using portal X rays taken with a linear accelerator to verify the target point is also described.     

近距离治疗中^192Ir放射源的校准

叙述以参考空气比释动能率校准１９２Ｉｒ高剂量率放射源的刻度方法及对结果的分析。材料与方法使用ＮＥ０．６ｃｃ２５７１型石墨电离室和自行设计的测量支架。电离室及剂量仪经国家计量科学院校准，由于目前尚无１９２Ｉｒ刻度标准，一般对６０Ｃｏγ和２５０ＫＶＸ射线插值，以获得１９２Ｉｒ的校准因子。这一方法要求电离室具有较好的能响特性（１．０－２．０％），以及校准时有相同的室壁厚度。结果分别在１０ｃｍ和１５ｃｍ处刻度１９２Ｉｒ放射源，所得结果的差别小于１．０％。结论这一方法的系统误差，主要来自插值以获得１９２Ｉｒ的校准因子，由于使用的电离室能响较好及方法得当，插值的误差不会超过０．５％，而其他因子相对较小，对系统误差不会有较大影响，因此可以认为以参考空气比释动能率刻度１９２Ｉｒ剂量率的方法准确可行。     

Evidence and interdisciplinary consensus-based German guidelines: surgical treatment and radiotherapy of melanoma

The primary treatment of a melanoma is surgical excision. An excisional biopsy is preferred, and safety margins of 1 cm for tumor thickness up to 2 mm and 2 cm for higher tumor thickness should be applied either at primary excision or in a two-step procedure. When dealing with facial, acral or anogenital melanomas, micrographic control of the surgical margins may be preferable to allow reduced safety margins and conservation of tissue. The sentinel lymph node biopsy should be performed in patients whose primary melanoma is thicker than 1.0 mm and this operation should be performed in centers where both the operative and nuclear medicine teams are experienced. In clinically identified lymph node metastases, radical lymph node dissection is considered standard therapy. If distant metastases involve just one internal organ and operative removal is feasible, then surgery should be seen as therapy of choice. Radiation therapy for the primary treatment of melanoma is indicated only in those cases in which surgery is impossible or not reasonable. In regional lymph nodes, radiation therapy is usually recommended when excision is not complete (R1 resection) or if the nodes are inoperable. In distant metastases, radiation therapy is particularly indicated in bone metastases, brain metastases and soft tissue metastases.     

Three-dimensional internal mammary lymphoscintigraphy: implications for radiation therapy treatment planning for breast carcinoma

Conservative surgery combined with radiation therapy for the treatment of early breast carcinoma has been shown to achieve both a high rate of local tumor control and good cosmetic results with a minimum of complications. Whether the internal mammary lymph nodes (IMNs) should be included in the treatment volume is a topic of considerable controversy. Radionuclide internal mammary node lymphoscintigraphy (IMN-LS) can locate these nodes in three dimensions. We have analyzed the results of IMN-LS in 167 patients imaged at the Dana-Farber Cancer Institute and treated at the Joint Center for Radiation Therapy between 1977 and 1980. The location of the IMNs was found variable from patient to patient. At least one IMN was not included within tangential fields arbitrarily arranged to have a medial entrance point 3.0 cm across the midline in 17% of evaluable patients. However, 48% and 66% of patients had IMNs that could be adequately treated with fields positioned only 1.0 cm or 2.0 cm across midline, respectively. We conclude that when treatment of the IMNs is warranted, IMN-LS not only assures their complete coverage in the majority of patients but also may help reduce the amount of heart and lung irradiated.     

Improvement of small-field penumbra and dose distributions on a 4 MV accelerator

The penumbra and dose distributions for small X ray fields from a 4 MV accelerator, designed for 80 cm source-to-surface distance (SSD) but used at 100 cm SSD, were observed to be similar to those obtained from cobalt-60 units. Penumbra was reduced and flatter isodose curves were obtained by the addition of tungsten trimmers at a distance of 48 cm from the X ray source. This stratagem improves the definition of irradiation volume of small fields which are common in the treatment of lesions in the head and neck.     

Use of 10 MV spoiled x ray beam for treatment of head and neck tumors

The employment of a 10 MV X ray beam for treatment of head and neck tumors has been investigated. A 1.2 cm thick beam spoiler positioned 7 cm from the patient surface was used to achieve adequate dose to the superficial region. This technique provides at least 90% depth dose at 0.5 cm depth, which is clinically required for the treatment. For departments able to acquire only one megavoltage machine, the technique can provide an option to treat adequately both shallow as well as deep-seated tumors by choosing a high megavoltage machine; a low megavoltage machine cannot provide an equivalent option to treat deep-seated tumors.