brachytherapy is limited to a few ldr applications, due to risk of radiation exposure to clinical staff. in contrast, afterloading involves the accurate positioning of non-radioactive applicators in the treatment site, which are subsequently loaded with the radiation sources. in manual afterloading, the source is delivered into the applicator by the operator. remote afterloading systems provide protection from radiation exposure to healthcare professionals by securing the radiation source in a shielded safe. once the applicators are correctly positioned in the patient, they are connected to an 'afterloader' machine (containing the radioactive sources) through a series of connecting guide tubes. the treatment plan is sent to the afterloader, which then controls the delivery of the sources along the guide tubes into the pre-specified positions within the applicator. this process is only engaged once staff are removed from the treatment room. the sources remain in place for a pre-specified length of time, again following the treatment plan, following which they are returned along the tubes to the afterloader. on completion of delivery of the radioactive sources, the applicators are carefully removed from the body. patients typically recover quickly from the brachytherapy procedure, enabling it to often be performed on an outpatient basis. between 2003 and 2012 in united states community hospitals, the rate of hospital stays with brachytherapy (internal radiation therapy) had a 24.4 percent average annual decrease among adults aged 45–64 years and a 27.3 percent average annual decrease among adults aged 65–84 years. brachytherapy was the or procedure with the greatest change in occurrence among hospital stays paid by medicare and private insurance. radiation sources commonly used radiation sources (radionuclides) for brachytherapy. radionuclide type half-life energy cesium-131 (131cs) electron capture, ε 9.7 days 30.4 kev (mean) cesium-137 (137cs) β−- particles, γ-rays 30.17 years 0.512, 0.662 mev γ-rays cobalt-60 (60co) β−- particles, γ-rays 5.26 years 1.17, 1.33 mev γ-rays iridium-192 (192ir) γ-rays 73.8 days 0.38 mev (mean) iodine-125 (125i) electron capture, ε 59.6 days 27.4, 31.4 and 35.5 kev palladium-103 (103pd) electron capture, ε 17.0 days 21 kev (mean) ruthenium-106 (106ru) β−- particles 1.02 years 3.54 mev radium-226 (226ra) α- particles 1599 years history brachytherapy dates back to 1901 (shortly after the discovery of radioactivity by henri becquerel in 1896) when pierre curie suggested to henri-alexandre danlos that a radioactive source could be inserted into a tumour. it was found that the radiation caused the tumour to shrink. independently, alexander graham bell also suggested the use of radiation in this way. in the early twentieth century, techniques for the application of brachytherapy were pioneered at the curie institute in paris by danlos and at st luke's and memorial hospital in new york by robert abbe.: ch. 1 working with the curies in their radium research laboratory at the university of paris, american physicist william duane refined a technique for extracting radon-222 gas from radium sulfate solutions. solutions containing 1 gram of radium were "milked" to create radon "seeds" of about 20 millicuries each. these "seeds" were distributed throughout paris for use in an early form of brachytherapy named endocurietherapy. duane perfected this "milking" technique during his time in paris and referred to the device as a "radium cow". duane returned to the united states in 1913 and worked in a joint role as assistant professor of physics at harvard and research fellow in physics of the harvard cancer commission. the cancer commission was founded in 1901 and hired duane to investigate the usage of radium emanations in the treatment of cancer. in 1915 he built boston's first "radium cow" and thousands of patients were treated with the radon-222 generated from it. interstitial radium therapy was common in the 1930s.: ch. 1 gold seeds filled with radon were used as early as 1942 until at least 1958. gold shells were selected by gino failla around 1920 to shield beta rays while passing gamma rays. cobalt needles were also used briefly after world war ii.: ch. 1 radon and cobalt were replaced by radioactive tantalum and gold, before iridium rose in prominence.: ch. 1 first used in 1958, iridium is the most commonly used artificial source for brachytherapy today.: ch. 1 following initial interest in brachytherapy in europe and the us, its use declined in the middle of the twentieth century due to the problem of radiation exposure to operators from the manual application of the radioactive sources. however, the development of remote afterloading systems, which allow the radiation to be delivered from a shielded safe, and the use of new radioactive sources in the 1950s and 1960s, reduced the risk of unnecessary radiation exposure to the operator and patients. this, together with more recent advancements in three-dimensional imaging modalities, computerised treatment planning systems and delivery equipment has made brachytherapy a safe and effective treatment for many types of cancer today.: ch. 1 the word "brachytherapy" comes from the greek word βραχύς, brachys, meaning "short-distance" or "short". environmental hazard due to the small size of brachytherapy sources and low control in early decades, there is a risk that some of these have escaped into the environment to become orphaned sources. a radium needle was found in a prague playground in 2011, radiating 500 µsv/h from one metre away.