Several methods are used to deliver<unk> .<unk>  can be delivered using electron beams (electron<unk> , orthovoltage (250-300 kV) x-rays (X-ray<unk> , high-dose-rate brachytherapy (HDR-IORT), or low-energy (50 kV) x-rays (low-energy<unk> . Electron<unk>  While<unk>  was first used in clinical practice in 1905, the modern era of<unk>  began with the introduction of electron<unk>  in the mid-1960s by transporting patients from the OR after the tumor was removed to the<unk>  department to receive their electron<unk> . Electron<unk>  has the advantages of being able to carefully control the depth of<unk>  penetration while providing a very uniform dose to the tumor bed. Applied with energies in the range of 3 MeV to 12 MeV, electron<unk>  can treat to depths of up to 4 cm over areas as large as 300 cm² (i.e. a 10 cm diameter circle) and takes only 1–3 minutes to deliver the prescribed<unk>  dose. A few hospitals built shielded operation rooms in which a conventional linear accelerator was installed to deliver the<unk><unk> . This eliminated the complex logistics involved with patient transportation, but was so costly that only a few hospitals were able to use this approach. The breakthrough came in 1997, with the introduction of a miniaturized, self-shielded, mobile linear accelerator (Mobetron, IntraOp Corporation, US) and a mobile but unshielded linear accelerator (Novac, Liac–SIT, Italy). More than 75,000 patients have been treated with electron<unk> , almost half of them since the introduction of mobile electron<unk>  technology. X-ray<unk>  Early practitioners of<unk>  treated primarily abdominal malignancies using superficial x-rays (75-125 kV) and later orthovoltage x-rays (up to 300 kV in energy) prior to the advent of technology that enabled high-energy electrons. For the first 75 years, X-ray<unk>  was used mostly for palliation, but there were a few anecdotal reports of long-term survivors. In the early 1980s, when the use of electron<unk>  was increasing and showed promising results for certain indications, a handful of hospitals installed othovoltage units in lightly shielded ORs to see if this lower cost approach could achieve comparable results to that of electron<unk> . This approach was less costly than building a shielded OR for an electron<unk>  unit and eliminated the logistics involved with patient transportation. However, it had a number of problems that limited its appeal. X-ray<unk>  has a poor uniformity of dose as a function of depth of penetration, the<unk>  does not stop at a pre-defined depth but continues to deposit<unk>  to underlying structures, and can do damage to boney structures if too high a dose is delivered. Despite its long use (since the 1930s), fewer than 1000 patients have been treated with this approach, and it is no longer offered at most centers. HDR-IORT This technique was developed in the late-1980s in an attempt to combine the dosimetric advantages of high-dose rate brachytherapy with the challenges of treating some complex anatomic surfaces with<unk> . It has the advantage of being lower cost than dedicated electron<unk>  systems, since many<unk>  centers already have an HDR system that can be transported to the OR when HDR-IORT is needed. HDR-IORT can also treat very large and convoluted surfaces. However, it does require a shielded OR or a shielded room in the OR complex to deliver the HDR-IORT. The depth of penetration is very limited, typically either ½ cm to 1 cm depth, sometimes requiring extensive surgery due to the limited penetration of the<unk> . Treatments tend to be 40 minutes or longer, resulting in greater OR time, more anesthesia and greater blood loss when compared to electron<unk> . There are about 10 to 20 active centers using HDR-IORT for locally advanced and recurrent disease, and approximately 2000 patients have received this treatment, mostly for colorectal cancer, head and neck cancer, and gynecologic cancer. Low-energy<unk>  (50 kV) Intrabeam, (Carl Zeiss AG, Germany) received FDA and CE approval in 1999 and is a miniature mobile X-ray source which emits low-energy X-ray<unk>  (max. 50 kV) in isotropic distribution. Due to the higher ionization density caused by soft X-ray<unk>  in the tissue, the relative biological effectiveness (RBE) of low-energy X-rays on tumor cells is higher when compared to high-energy X-rays or gamma rays which are delivered by linear accelerators. The<unk>  which is produced by low-energy mobile<unk>  systems has a limited range. For this reason, conventional walls are regarded sufficient to stop the<unk>  scatter produced in the operating room and no extra measures for<unk>  protection are necessary. This makes<unk>  accessible for more hospitals. Targeted<unk>  radiotherapy is a low-energy<unk>  technique. Evaluation of the long-term outcomes in patients who were treated with TARGIT-IORT for breast cancer confirmed that it is as effective as whole breast external beam radiotherapy in controlling cancer, and also reduces deaths from other causes as shown in a large international randomised clinical trial published in the British Medical Journal.
Intraoperative radiation therapy
Intraoperative electron radiation therapy
Neoadjuvant therapy
Targeted intra-operative radiotherapy
Adjuvant therapy
Nerve-sparing surgery
Selective internal radiation therapy
Prostate brachytherapy