Full Answer
What is the role of iridium 192 in the treatment of prostate cancer?
Temporary implants with high-dose-rate iridium 192 (192 Ir) are usually combined with EBRT for the treatment of patients with intermediate- to high-risk prostate cancer.
What is the half life of ir192?
Iridium 192. Iridium 192 (Ir192) is the most commonly used source, has a half-life of 74.2 days, and emits an average photon energy of 0.38 MV, which allows for feasible shielding against radiation exposure for personnel.
What is the de-excitation of 192Pt?
For the β − decay channels, de-excitation of 192 Pt* to 192 Pt (ground state) proceeds mainly via gamma emission and in a smaller fraction by internal conversion. Gamma rays of 0.296, 0.309, 0.317, and 0.468 MeV are the most probable (29% to 83%).
Problem 29 Medium Difficulty
Cancer Therapy with Iridium Metal When iridium-192 is used in cancer treatment, a small cylindrical piece of 192 I, 0.6 m m in diameter and 3.5 m m long, is surgically inserted into the tumor. If the density of iridium is 22.42 g / c m 3, how many iridium atoms in the sample?
Video Transcript
once a couple of the number of atoms in. So you know what for? Two grams. So you have to be work backwards to find 20 to 40 course to, um, basically, millimeters says your 0.667 meters on your way is your point 41267 years. And then that's our electric.
What is brachytherapy iridium 192?
Endobronchial brachytherapy using iridium-192 is an established method of treating tumors in the main bronchi. It involves bronchoscopy and insertion of a small catheter, which is connected to a device that sends the radioactive source to prespecified positions along the tube that correspond to the location of the tumor; the radioactive sources remain in prespecified positions for a few minutes, as needed to deliver the prescribed dose of radiation. The advantage of this technique is that a high dose can be delivered locally to the tumor but it is not effective if there is bulky extraluminal tumor or complete obstruction of the bronchus.
What is 192 Ir?
Temporary implants with high-dose-rate iridium 192 (192 Ir) are usually combined with EBRT for the treatment of patients with intermediate- to high-risk prostate cancer. The procedure is similar to that for permanent implants in that temporary afterloading needles are placed transperineally into the prostate under sonographic guidance. 276,277 A pretreatment plan may be used, but real-time planning in the operating room has been used to optimize needle placement. 278 High-dose-rate 192 Ir implants are more forgiving than are 125 I or 103 Pd permanent implants; CT planning for the high-dose-rate treatment is done before the sources are placed, and the time at which the source dwells at particular points can be adjusted to optimize the dose distribution. The dose of each high-dose-rate fraction, the intervals between those fractions, and the sequencing with EBRT have varied greatly among investigators. Dosing schemes have ranged from 3.0 to 4.0 Gy in 4 fractions over 40 hours 276 to 9.5 Gy in 2 fractions over 2 weeks, 278 and the high-dose-rate 192 Ir seeds have been implanted before, during, and after the EBRT. 276,278-280
What is brachytherapy used for?
Brachytherapy, especially using manually afterloaded iridium-192, has been widely used to treat head and neck cancers. HDR brachytherapy has been used in selected cases to reduce radiation exposure and permit optimization as summarized in Table 14-17. 219-232 However, these advantages are offset by the need for multiple fractionation, since the critical structures of the head and neck area do not tolerate high doses per fraction. The nasopharynx is a site within the head and neck area that is easily accessed by an intracavitary HDR applicator. 233- 234 Leung et al. reported in 2008 their results from 145 patients with nasopharyngeal carcinoma treated with 66 Gy EBRT followed by two fractions of 10 to 12 Gy each via HDR. 231 Five-year local failure–free survival was reported to be 95.8% with a 5-year major complication-free survival rate of 89.5%. Moreover, thin residual tumors (<10 mm) following EBRT and chemotherapy may be more suitable candidates. 219 Additionally, recent results with the use of HDR brachytherapy in patients with recurrent and previously irradiated head neck tumors is promising. 235-238
How many catheters are placed on the inner vestibule?
With tumors of the lateral part of the vestibule, two catheters are placed on the inner aspects of the nasal vestibule. For medially localized tumors, catheters are placed on both sides of the vestibule. Following an EBRT dose of 50 Gy in 4 weeks, high-dose-rate brachytherapy is delivered in week 6.
How is 192 ir produced?
192 Ir is produced in the nuclear reactor in the reaction 191 Ir (n,γ) 192 Ir. 191 Ir composes 37.3% of natural iridium, 193 Ir making 62.7%. The material can be enriched so as to reduce the contamination of radioactive 194 Ir from 193 Ir and increase 192 Ir production. Interestingly, 192 Ir has a high neutron capture cross section, allowing double-neutron capture by 191 Ir into 193 Ir. Hence, the production rate of 192 Ir is limited by its own decay and by its transformation into 193 Ir.
How many IR wires are there in the Paris system?
The Paris system originated mainly for use with 192 Ir wires, hairpins (sources with a loop or curved aspect) and wire ( Gillin and Mourtada, 2005 ). There are three principle rules ( Gillin and Mourtada, 2005; Gillin et al., 1995 ): 1.