I would like to recommend you to read the information contained in Treatment for Cancer - National Cancer Institute www.cancer.gov. It seems to me that x-ray is not an effective tool for cancer treatment.

Thank you Jorge Morales Pedraza. Can you please tell briefly in what way x-rays are not effective ? Does it mean to the matter of targeting ?

Dear Fredrick in my reply the words "in low doses" were missing.

In principle, X-ray, a type of high-energy electromagnetic radiation, is often used for cancer diagnosis and staging and in high doses for treatment.

An X-ray uses electromagnetic radiation to make images. The image is recorded on a film, called a radiograph. The images produced appear light or dark, depending on the absorption rates of the different tissues. For example, dense materials, such as bone, show up as white on a film, while fat and muscle appear as varying shades of gray.

An X-ray exam is fast and painless. In low doses, X-rays can be used to construct images of structures inside the body to detect and stage a tumor.

However, in higher doses X-rays can be used in radiation therapy to help destroy cancerous cells in the body.

It is a matter of interaction of radiation with matter. In brachytherapy beta or alpha emitters are used because they deliver much more energy to matter into a very small path (very high LET). This particles travel very small path into the body (this is the reason they are placed next to the tumor) and deliver very high dose. Using photons (lower LET) instead of heavier particles will deliver smaller dose and hence less effective treatment.

Dear Jorge Morales Pedraza thank you again. How this method of HDR radiation therapy is successful in differentiating the tumor cells from the healthy cells by means of target?  Will this be an good tool if this method is chosen to destroy them at the point of interest without any destruction to the neighbouring  healthy cells ? 

Thank you Jesús Silva-Rodriguez. Therefore you mean very High LET are more advantageous than lower LET ? So to what extent designing tools based on this will be helpful to treat cancerous patients. But providing high dose at a instant is not recommended I guess and will that not  commit lethal effects to the DNA in the nearby cells ? 

There are precise mathematical tools that are used by well experience professionals to focus the use of equipment such as cobalt-60 units, accelerators, etc.,  for cancer treatment in the cancerous cells without damaging the good ones or at least to reduce the possible damage of the healthy cells to the minimum. In my book  entitled The Use of the Ionizing Rdadiation Technique for Tissue Sterilization. The IAEA Experience" you can have additional information about the use of these equipments for sterilization purpose, but in a similar manner that they are used for cancer treatment.

Dear Jorge Morales Pedraza how can a mathematical tool majorly act on focusing and controlling the beam? Are they any special algorithm run for this kind ? else the mechanical structuring of the equipment is patterned such a way ?

Dear Frederick. There are mathematical software that can be used by competent professionals (called  Physical- Medical)  to calculate the exact doses to be given, the time of the treatment, the place where the focus of the X-ray should be given, etc. You cannot use equipment for cancer treatment without the proper use these mathematical tools. At the same time if you do not make a good use of these tools, then you can cause serious damage to the patient, including his/her death.

Just entered this question. Very good comments by Jorge. Of course you need therapy planning by modern software and dosimetric control of the radiation field.

But one small mistake about LET by Jesus. Betas have the same LET as photons from X-ray tubes at least for the normal energies in the beta spectra. The advantage of high LET of alphas is in most cases (radioactive sources) limited to a penetration depth of only some cell diameters

In radiotherapy, the dominant type of radiation used is photons, both for external beam radiotherapy and for brachytherapy.

In high dose rate (HDR) brachytherapy, Ir-192 is the most commonly used radioactive source; the photons from the decay are used therapeutically, the electrons (sort of a bother here) are mostly absorbed in the source encapsulation and the applicators.

There are miniature x-ray sources, designed for brachytherapy, commercially available.

Photons ( and electrons, protons etc.) can not distinguish between cancer cells and normal cells.

You can find some basic information also on the EMITEL web site, in the EMITEL encyclopaedia.

To be useful for brachytherapy, an X-ray tube construction must enable to enter its target (anode) inside the to-be-irradiated object. Besides, it must emit radiation isotropically into the whole 4 pi solid angle. Miniature X-ray source inserted into a flexible cooling catheter.50 kV operating potential, 300 μA current and Output: ~1 Gy/minute at 3 cm depth in water are used.

Thank you Inger-Lena Lamm. Can you explain how deep does x-rays and photon differ in application for brachytherapy ? According to your statement you mean x-rays can't be used ? 

Thank You Yousif Mohamed Y. Abdallah. How can the shielding be done and how will it influence the output at the catheter if it is inserted in to it ? 

Fredrick Johnson JOSEPH, there appear to be some misconceptions or miscommunications happening that I would like to clear up. First, x-rays are photons. Photons can have a variety of energies, from very low energy radio waves to high energy x-rays. Gamma rays are higher energy than x-rays, and the photons produced by linear accelerators (for so-called "external beam radiation therapy") are even higher energy so that they can penetrate deeply into the body to reach tumors. Brachytherapy typically uses radioactive sources that produce lower energy photons (through a variety of different radioactive decay processes depending on the particular element used) than those made with linear accelerators because in brachytherapy, the sources are placed very close to (or within) the tumor that you are trying to treat. That is how brachytherapy spares normal tissues...by placing the source of radiation within or very nearby the tumor, the photons produced deliver the majority of their dose to the tumor and spare normal tissues that are further away. Brachytherapy is VERY effective and usually safer than external beam radiation therapy...the difficulty is that in many locations in the body it is difficult if not impossible to deliver the sources of radiation into the tumor safely and effectively (it would require a surgical procedure or long needles that are difficult to place accurately). Also, it is uncomfortable for the patient to undergo the procedures, especially when multiple treatments are required (most HDR brachytherapy courses require multiple treatments over a period of several weeks).

Currently, brachytherapy is most commonly used in cervical and endometrial cancer (because it is easy to get the sources into the cervix or uterus...the treatment apparatus is inserted during a pelvic exam under mild to moderate sedation, the HDR source is inserted for a period of several minutes, then the radiation source and the treatment apparatus are removed and the patient goes home. The procedure is repeated 5-7 or so times.) and prostate cancer (because with LDR brachytherapy, the patient only requires a one day procedure and the seeds stay in the prostate afterwards constantly emitting radiation at a low dose rate for several months). Everywhere else, brachytherapy is difficult and not commonly used.

Hope this helps clear things up!