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Interstitial implants for brain tumours with removable iridium-192 radioactive seeds have been performed using a Brown-Roberts-Wells stereotactic frame. A simple and accurate computed-tomography-guided dosimetry pre-planning technique and procedure prior to implant have been developed and are discussed.
A 2 1/2-year-old girl with a history of bilateral retinoblastoma underwent primary enucleation of the right eye and was referred for further management of persistent tumor in the fellow eye. Previous treatment of the left eye included external beam radiotherapy, systemic chemotherapy, laser photocoagulation, cryotherapy, and direct scleral application of a bare iridium-192 radioactive seed. Examination revealed focal full-thickness necrosis of the left upper and lower eyelid and a large inferonasal viable retinoblastoma tumor with overlying retinal detachment. Systemic chemotherapy and direct laser photocoagulation were administered. Four months after presentation, the patient developed focal scleral necrosis with 360 degrees hemorrhagic choroidal detachment. Enucleation was performed and histopathologic examination demonstrated full-thickness scleral necrosis with adjacent viable retinoblastoma tumor cells. Follow-up examinations showed no evidence of recurrent or metastatic tumor. This case is the first report of scleral necrosis following combined modality treatment of retinoblastoma.
We present a uniform method for selecting an optimum implant geometry by presenting techniques for evaluating the therapeutically significant maximum dose rate (herein referred to as the "maximum dose rate"), the reference isodose (85% of the maximum dose rate), and the area enclosed by the reference isodose contour. The therapeutic performances of planar iridium implants may be compared by evaluating their respective maximum dose rates, reference isodoses , and areas within the reference isodose contours. Because these parameters are mathematically defined, they reproducibly describe each implant geometry. We chose a small microcomputer to develop these comparison algorithms so that the radiotherapist need not have large, expensive computer facilities available to conduct his own studies. The development of these algorithms led to some significant conclusions and recommendations regarding the placement of interstitial implants. Using seeds that are centrally located in the array to evaluate the maximum dose contour avoids underestimating the array's maximum dose rate. This could occur if edge or corner seeds were used. Underestimating the maximum dose rate (and hence the reference isodose contour area) may have a serious therapeutic outcome, because the actual total treatment dosage may be excessive. As ribbon spacing is increased, there is a point beyond which the reference isodose contours become decoupled. At this point, a single relatively uniform reference isodose contour separates into several contours. This effect not only complicates the planimetry calculations, but it also adversely affects the therapeutic efficacy of the implant by producing therapeutically "cold" regions.
Available statistics on breast cancer indicate a high frequency of positive internal mammary nodes, which is associated with decreased five-year survival rates. The close proximity of the majority of internal mammary nodes (87 percent within 1 cm) to the internal mammary vessels makes them easily accessible to high-dose intravascular continuous irradiation by afterloading radioactive ribbons (iridium 192) in the internal mammary vessels that are surgically exposed. This is a simple technique that can be carried out at the time of mastectomy or as a separate procedure, either as a primary radiation modality, for post-XRT recurrence, or as a boost in combination with conventional parasternal radiation therapy. The step-by-step technique, indications, need for revival, and future implications are presented.
A radioactive mold for treating skin was constructed by embedding ribbons of iridium-192 seeds in bolus material. The mold was designed to match the treatment area outlined on the patient's skin. Computer-assisted pre-planning was performed to optimize the seed strength, number of seeds, and spacing of ribbons. An outline of the treatment area was transferred to the surface of a uniform slab of tissue-equivalent bolus material 1.3 to 1.4 cm thick and planned locations for the ribbons were marked. Seeds were loaded into the bolus material at a depth to place the sources approximately 1.0 cm from the skin. The resulting mold was flexible enough to conform to the patient's skin and the seeds were so tightly confined within the bolus that there was no possibility of loss. Isodose distributions for the mold on a flat surface agreed well with preplans. A velcro strap and neck collar were used to attach the mold to the anterior portion of the patient's neck. For situations in which radioactive surface applicators are desirable, the use of iridium-192 seeds offers uniform dose within a highly individualized treatment area.
Radiation-induced carcinogenesis of the rat liver using iridium-192 seeds as an intrahepatic radioactive source was studied by enzyme histochemical means. Rats were divided into six groups according to various combinations of one or two iridium-192 or stainless steel seeds and whether they were given a diet containing 0.05% phenobarbital (PB) or a basal diet (BD). Each group were sacrificed at 20, 40, and 60 weeks after intrahepatic insertion of the iridium-192 or stainless steel seeds. gamma-Glutamyl transpeptidase (GGT), glucose-6-phosphatase (G6Pase), and adenosine triphosphatase (ATPase) were stained in the liver tissues, and GGT-positive foci were quantified. Liver neoplasm was not evident, but enzyme-altered foci (EAF) were induced by gamma-ray irradiation. At every point (20, 40, and 60 weeks) after the insertion of the seeds, the GGT-positive area was larger in the rats given than those given BD. Moreover, despite the iridium-192 radioactivity decay, EAF developed continuously in the rats given PB, and persisted in those given BD from 40 to 60 weeks after insertion. These results indicated that phenobarbital promotes the development of EAF initiated by irradiation, as it promotes the process of chemical carcinogenesis in the rat liver.
A patient with a small-sized pulmonary adenocarcinoma was successfully treated by percutaneous high dose rate interstitial brachytherapy alone. The patient, who had an adenocarcinoma with 12-mm diameter in the lingular lobe of left lung, was judged to be inoperable because of poor pulmonary function due to emphysema and extensive pleural adhesion. The tumor was punctured with a 21-gauge fine applicator needle followed by the introduction of an iridium 192 (192Ir) radioactive source through the applicator needle using a remote afterloader. The tumor was irradiated for 225.1 s in one fraction. The tumor was in the inside of the iso-dose line of 40 Gy. The delivered doses calculated at nine reference points, which were 12.5 mm distant from the center of the tumor, distributed between 19.225 and 32.169 Gy, with a mean of 24.8 Gy. No apparent side effect including pneumothorax and hemoptysis was observed. The tumor shrank and showed no increment of the size for about 2 years.
Endovascular brachytherapy with gamma-radioactive source ((192)iridium ) significantly reduces the restenosis after femoropopliteal angioplasty for both de novo and recurrent lesions. Increased arterial patency after additional stenting and brachytherapy was also achieved with the same approach. This was found as a result of single-center studies performed in Frankfurt, Germany, Vienna, Austria, and Bern, Switzerland. However, until recently, only one multicenter investigation was published that also underlined this positive effect of brachytherapy. A definitive role of radiotherapy in restenosis prevention should be established after the results of three multicenter, phase III trials (ie, Paris, Vienna-3, and Swiss) are presented in early 2003. These investigations recruited approximately 630 patients with recurrent and de novo lesions without stent placement. Another important phase III study, the results of which are also expected at the beginning of 2003, is the Vienna-5 trial. This study had the same inclusion criteria as the Paris and Vienna-3 trials, but angioplasty was combined in all patients with stenting. The patients were then randomized for brachytherapy or sham irradiation. Endovascular brachytherapy has shown to be a safe treatment modality. The only clinically relevant impediment was the late sudden thrombosis or occlusion that occurred after stenting and radiation. These events can present up to 1 year after brachytherapy, and in some cases even later. Prolonged antiplatelet medication with clopidogrel (at least 12 months) has solved this problem completely. No other major adverse effects were seen. If gamma radiation is used, the patients must be transported after intervention to the brachytherapy suite, owing to radiation safety regulations. Although no negative consequences during transportation were observed in all performed studies, this represents an additional risk. To shorten the whole procedure, studies using beta sources ((32)phosphorus, (90)strontium) are ongoing, whereas those with beta-radioactive sources of brachytherapy can be performed in the catheterization laboratory. Emerging approaches using drug-eluting stents with antiproliferative substances such as rapamycin and paclitaxel are being investigated as well; however, the safety and efficacy for restenosis prophylaxis must be proven in large clinical trials.
This study describes a method for the quantitation of macrophage phagocytosis by measuring the uptake of small particles of the radioactive inert metal, iridium (192Ir). It is shown that macrophage labeling with 192Ir was uniform, and the label was retained by the macrophages up to 21 days post-plating (when all cultures were terminated). 192Ir labeled macrophages were able to phagocytose other particles such as sheep red blood cells and were able to be activated to become tumorcidal in vitro 21 days following initial 192Ir uptake. Therefore, 192Ir could be a useful tool for the quantitative analysis and correlation of phagocytosis, tumor cytotoxicity and other macrophage functions.
The use of radioactive Iodine, Ruthenium, Iridium and Cobalt plaques of varying dimensions to treat choroidal and ciliochoroidal melanomas is discussed and placed in perspective with other treatment modalities. The regression pattern following plaque treatment appears to be more rapid for tumours that are more poorly differentiated. The visual results following plaque brachytherapy compare very favourably with those following local resection and external beam radiation. Ocular complications are significantly greater for tumours whose initial thickness exceeds 8 mm. The survival rater after plaque treatment is compared with that for patients who have had primary enucleation for equivalent-sized tumours.
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The authors report a rare case of a cystic metastasis in the midbrain that was successfully treated by brachytherapy following stereotactic biopsy and aspiration of the intratumoral cyst. Stereotactic aspiration of cystic lesions can lead to clinical improvement and brachytherapy prevents cyst recurrence. A 46-year-old man was referred to the authors' institution with a 2-month history of a left hemisensory disturbance and a 1-month history of progressive hemiparesis. Magnetic resonance (MR) imaging revealed a ring-enhancing cystic mass in the midbrain. On the basis of this imaging study, a differential diagnosis that included brainstem abscess, glioma, and metastatic tumor was made. Magnetic resonance imaging-guided stereotactic biopsy and aspiration of the intratumoral cyst were performed, yielding 5 ml of yellowish-white fluid. Histological examination provided a diagnosis of adenocarcinoma. During the surgery, a catheter through which brachytherapy would be delivered was inserted at a predetermined target. The patient's left hemiparesis and sensory disturbance were markedly improved and brachytherapy was begun 2 days postoperatively. Three radioactive isotopes composed of iridium-192 were implanted to irradiate the tumor tissue. The total dose at the tumor periphery was 30 Gy, which was administered over 100 hours. External-beam radiotherapy (20 Gy) was added after completion of the brachytherapy. At discharge from the hospital, the patient was alert and all his neurological symptoms had resolved. Follow-up MR imaging revealed stabilization of the cyst and no recurrence of the tumor. The patient is alive and well 18 months following the brachytherapy. This case suggests that brachytherapy can delay cyst recurrence, suppress tumor growth, and prolong survival in patients with cystic brainstem metastasis.
Special side effects which relate to specific areas are discussed. Head and neck radiation produces acute problems related to swallowing, dry mouth, sore throat and thickened saliva which all require medication. Alteration of taste may last for months after radiation is completed. Radiation to lungs may cause worsening breathlessness and coughing which may necessitate interruption of treatment. Radiation to pelvis and abdomen result in nausea and diarrhoea which usually respond to treatment. Proctitis, vaginal discharge and urinary problems all need attention. With cranial radiation, hair loss is a major problem and unlike chemotherapy induced alopecia, there is poor recovery. Patients must be informed that their condition will improve when radiation ceases, and not attribute all symptoms to underlying disease. Protection in this country is in line with international standards and strict adherence protects the work force. Patients with radioactive sources in situ e.g. radium or implants such as gold seeds, iridium wires, or being treated by radioactive iodine all require special nursing and are nursed in a protected ward. Staff wear film badges to detect radiation absorbed. If in doubt about safety measures contact superiors or radiophysics department of hospital. Patients already isolated from visitors must not be neglected and nurses must observe instructions and then proceed with safety.
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The first X-ray treatment ever given to a patient was done by Victor Despeignes of Lyon, five months after Roentgen's discovery. The first brachytherapies with radium emanation (radon) were performed a few years after the discovery (March 1st, 1896) of natural radioactivity by Becquerel and that of radium by the Curies (December 28, 1898). Marie Curie organised the Radium Institute and personally calibrated more than five thousand sources of radium disseminated in various French cancer departments. Bergonie and Tribondeau discovered (1906) the basic laws of tissular radiosensitivity. Since the work of Regaud and Coutard, published in 1925, fractionation has become the widely accepted mode of external radiation therapy. Mallet discovered the Cerenkov effect in 1926 and the Joliot-Curies artificial radioactivity in 1934. After the golden age of 200 kV X-rays and radium applications, the megavoltage era with imported telecobaltherapy units and betatrons began in 1954. Then the first french linear accelerator was manufactured. Recently the national manufacturer of linear accelerators (CGR-MeV) became a branch of General Electric Medical Systems. The French Atomic Energy Commission produces radioactive cobalt, cesium and iridium sources. In France, one century after the discovery of X rays, 326 megavoltage units are operating in 185 cancer centers, 18 university hospital radiotherapy departments, 20 comprehensive cancer centers including the Curie and the Gustave Roussy Institutes, 51 general public hospitals and 96 private clinics for a population of 58 millions inhabitants.