radiation therapy most often utilizes which imaging modality for treatment planning?

Full Answer

Which imaging modalities are used in the treatment-planning process?

Newer image modalities, such as magnetic resonance (MR) imaging and positron emission tomography (PET), are also used secondarily in the treatment-planning process. MR, with its better tissue contrast and resolution than those of CT, improves tumor definition compared with CT planning alone.

What are the different therapeutic modalities of radiation therapy?

Therapeutic modalities: radiation therapy 1 Goals of radiation therapy. The goal of definitive or curative radiation therapy is eradication of all viable tumor cells within the patient. 2 Normal tissue response. ... 3 Pre-radiation imaging. ... 4 Tumor-specific radiation considerations. ... 5 Newer technologies. ...

Why would radiation therapy be used as a treatment option?

-If tumor cannot be removed surgically (tumor is not solid or is in a difficult spot to remove, or patient condition makes them unable) -reduce tumor bulk so that surgery can be done -use as a adjunct (in addition to...) with surgery or chemotherapy List some reasons why radiation therapy would be used as a treatment option chemotherapy

Why do we use multiple doses of radiation for treatment?

a treatment radiation dose is broken down into multiple exposures over several weeks to minimize side effects - allows normal tissue to recover, while less efficient repair takes place in tumor cells -allows us to treat cells in multiple phases of radiosensitivity (mitosis is most sensitive phase cause of rapid division)

What imaging modalities are used in radiation therapy?

Imaging technologies used in IGRT include x-rays, computed tomography (CT), 3-D body surface mapping, magnetic resonance imaging (MRI) and ultrasound (US).

What is the most common imaging modality used for designing a radiation therapy treatment plan?

Despite its limitations, for several reasons CT is currently the only 3D imaging method accepted for treatment planning. Most treatment-planning algorithms were developed specifically for CT as it was the first available 3D imaging modality and CT scanners are more commonly used than MR or PET.

Why is CT used for radiation therapy planning?

You usually have a planning CT scan in the radiotherapy department. The scan shows the cancer and the area around it. You might have had other types of scans or x-rays before this appointment to help diagnose or stage your cancer. Your treatment team might also use these scans to plan your radiotherapy.

What is radiotherapy planning method?

Four different planning techniques were used for each patient including a standard 2D-tangential plan (Tan), forward-planned IMRT (fIMRT), inverse-planned IMRT (iIMRT) and VMAT.

Which is better IMRT or IGRT?

IGRT uses imaging with the therapy to increase the efficiency by improving the precision and accuracy of the treatment procedure. The IMRT therapy uses high-edged software and sophisticated hardware to vary the intensity and shape of radiation used for different parts of the treatment area.

What is an IMRT for radiation therapy?

Overview. Intensity-modulated radiation therapy (IMRT) is an advanced type of radiation therapy used to treat cancer and noncancerous tumors. IMRT uses advanced technology to manipulate photon and proton beams of radiation to conform to the shape of a tumor.

Is a CT scan radiation therapy?

Most patients have a CT before starting radiation treatments as part of the simulation procedure. The scan utilizes a low radiation dose protocol and often does not involve contrast in the bloodstream.

What do PET scans show?

The PET scan uses a radioactive drug (tracer) to show both normal and abnormal metabolic activity. A PET scan can often detect the abnormal metabolism of the tracer in diseases before the disease shows up on other imaging tests, such as computerized tomography (CT) and magnetic resonance imaging (MRI).

How is PET used in radiation therapy?

PET-CT in the planning of lung tumour radiotherapy PET-CT significantly changes lymph node staging in the thorax, usually by showing more positive lymph nodes than CT. In cases with atelectasis, PET-CT helps to define the border between tumour and atelectasis, allowing a smaller volume of lung to be treated.

What is 2D planning in radiotherapy?

Conventional (2D) radiation therapy refers to the old techniques of radiation therapy where treatments would be planned by defining a limited number of beams with the boundaries delineated on orthogonal x-rays of the patient.

What machines are used in radiation therapy?

A medical linear accelerator (LINAC) is the device most commonly used for external beam radiation treatments for patients with cancer. It delivers high-energy x-rays or electrons to the region of the patient's tumor.

What is RTP scan?

In radiotherapy, radiation treatment planning (RTP) is the process in which a team consisting of radiation oncologists, radiation therapist, medical physicists and medical dosimetrists plan the appropriate external beam radiotherapy or internal brachytherapy treatment technique for a patient with cancer.

What is the most effective way to increase radiation protection?

Therefore, maintaining a greater distance from the X-ray generator is a very effective method for radiation safety. In a previous study of radiographers, two steps behind the mobile support structure can decrease the exposure of the radiographer by about 80% [4].

What can radiotherapy be used for?

Radiation therapy (also called radiotherapy) is a cancer treatment that uses high doses of radiation to kill cancer cells and shrink tumors. At low doses, radiation is used in x-rays to see inside your body, as with x-rays of your teeth or broken bones.

What is the goal of radiation therapy?

Its intent is to cure the patient whenever possible and to prolong survival as long as possible. 18 Palliative radiation is playing a larger role in veterinary oncology as owners increasingly seek to improve quality of life, decrease pain, and minimize hospitalization of their pets rather than achieving a cure. Most palliative protocols use lower total radiation doses and a higher dose-per-fraction to accomplish these goals.

What are the factors that affect the response to radiation?

Factors affecting acute response to radiation in normal tissue include total dose, overall treatment time (dose intensity), and volume of tissue irradiated. Acute effects in healthy tissue are to be expected and will occur if curative doses are administered, but will resolve with time and supportive care.

What are the disadvantages of preoperative radiation?

Potential disadvantages include increased wound complications and delayed surgical extirpation. Preoperative radiation is not used in every situation. The decision to do so is based on tumor location, surgeon preference, and risk of wound complication.

What are the effects of radiation on the body?

These effects are related to damage to the vascular and connective (stromal) tissue in non- or slowly-proliferating tissue such as the brain, spinal cord, muscle, bone, kidney, and lung.

What tissues are affected by radiation?

Within the first few wk after the start of radiation, acute effects are typically seen in normal tissues such as bone marrow, epidermis, gastrointestinal cells, and mucosa as well as in neoplastic cells. Factors affecting acute response to radiation in normal tissue include total dose, overall treatment time ...

What is a pet radiology center?

Pet radiology centers are available to veterinarians who wish to refer their oncology patients for radiotherapy. In addition to other resources, the Veterinary Cancer Society provides an online list (vetcancersociety.org) of veterinary radiation therapy centers, including contact information, in 30 states throughout the United States.

Do you need a CT for radiation?

Patients with tumors in complex anatomical locations (e.g., head, neck, body wall) may require CT imaging for planning purposes prior to radiation. Patients treated with palliative courses of radiation may not require computer-based planning depending on tumor size and location. Hemoclips placed at surgery aid in delineating the tumor bed.19 Patient positioning during radiotherapy should attempt to exactly duplicate the patient position at the time of CT.

What is the most common type of radiation used in therapeutics?

Various types and energies of radiation can be delivered in this way, including electromagnetic radiation such as X-rays and γ-rays, or particles such as electrons and protons.

How long has radiation therapy been used?

Radiation therapy has been used as a treatment for cancer for more than 100 years, with its earliest roots dating back to the discovery of X-rays in 1895. Its development in the early 1900s is largely due to the work of Marie Curie (1867–1934), who discovered the radioactive elements polonium and radium in 1898. Despite these distant origins, radiotherapy remains at the forefront of the treatment for cancer. Approximately 60% of cancer patients currently receive radiation therapy at some stage during their illness with 75% of these treated with curative intent. 1 Despite major advances in drug treatments for cancer, there has continued to be a steady annual increase in radiotherapy treatment that is unlikely to change within the next 10–20 years. 2

What is IMRT in radiotherapy?

IMRT represents a further step in the development of high-precision radiotherapy delivery. The term refers to a variety of techniques in which the radiation beams are not only shaped and orientated to conform to the tumour volume but also the intensity of radiation is modulated across each treatment beam. This technique can produce dose distributions that conform highly to complex shapes, including treatment volumes that wrap around sensitive normal structures such as the spinal cord ( Fig. 73-6 ), enabling high-dose delivery to the tumour volume whilst sparing dose to the normal structures.

What is brachytherapy in a uterus?

Brachytherapy refers to a situation in which a radioisotope is placed onto or inside the patient. The radiation source is sealed in a protective capsule or wire which prevents the radioisotope from moving or dissolving in body fluids but allows the emission of ionising radiation (in the form of α, β, γ or X-radiation) to the surrounding tissues. The source can be placed into the target tissues or tumour itself such as the prostate or breast (interstitial brachytherapy), into a body cavity such as the uterine cavity, oesophagus or bronchus (intracavitary/intraluminal brachytherapy) or onto the skin surface to treat a cutaneous malignancy.

What is conventional radiotherapy?

Conventional radiotherapy refers to techniques in which the treatment volume is defined by simple geometric parameters. In general, no attempt is made to delineate the tumour outline or to shape the radiation dose distribution to conform to the tumour volume.

What is external beam radiation?

External beam radiotherapy refers to any situation where the source of the radiation is located at a distance from the patient and the beam of radiation is then directed towards a defined treatment area. Approximately 85% of all therapeutic radiation exposures are delivered using external beam techniques. Various types and energies of radiation can be delivered in this way, including electromagnetic radiation such as X-rays and γ-rays, or particles such as electrons and protons. Higher energies of radiation penetrate deeper into body tissues. As a result low-energy X-rays (60–300 keV) are reserved for the treatment of skin cancers and superficial subcutaneous tumours. Most external beam radiotherapy treatments utilise megavoltage X-rays or electrons (6–18 MeV) generated by a linear particle accelerator ( Fig. 73-2 ).

What is tomotherapy?

Tomotherapy is essentially a combination of spiral CT and intensity-modulated radiation therapy technology. As with a CT unit, the patient moves through the unit, but instead of a kilovoltage diagnostic X-ray, hundreds of pencil beams of megavoltage therapeutic X-ray radiation spirally rotate around the patient.

What is radiation therapy?

There are two, general classes of radiation therapy: brachytherapy and teletherapy. “Brachy,” a Greek word, means short distance and “tele” means long distance. Brachytherapy is treatment performed by placing the radioactive source near or in contact with a tumor, that is, the use of intracavitary or intraluminal placement of the treatment source.

What is the use of ionizing radiation for cancer?

The use of ionizing radiation for cancer treatment has undergone extraordinary development during the past hundred years. The advancement of medical imaging has been critical in helping to achieve this change. The invention of computed tomography (CT) was pivotal in the development of treatment planning.

What is fusion imaging?

In medical applications, these points are the same anatomical regions of the body, such as bone and organs, for the same patient. Fusion is the ability to display different types of registered images anatomically overlain on one another in a single, composite image [ 33#N#A. Ardeshir Goshtasby and S. Nikolov, “Image fusion: advances in the state of the art,” Information Fusion, vol. 8, no. 2, pp. 114–118, 2007. View at: Publisher Site | Google Scholar#N#See in References#N#]. Fusion provides the best information for each image, that is, geometric definition and tissue density from the CT image, soft-tissue contrast from the MR image, and metabolic information from the PET image. The combined information reduces the uncertainty regarding the tumor definition for geometric localization as well as determining the size and spread of the disease. By improving the accuracy of the target definition, image fusion can potentially improve the treatment outcome and decrease complications as less normal tissue is irradiated.

How does image fusion improve radiation treatment?

By improving the accuracy of the target definition, image fusion can potentially improve the treatment outcome and decrease complications as less normal tissue is irradiated. Currently, most radiation treatment planning systems support image registration and fusion. There are several fusion algorithms.

What are the three main aspects of cancer treatment?

The three most important aspects of cancer treatment are surgery, chemotherapy (in earlier times referred to simply as medicine), and radiation therapy . Of these, surgery is the oldest with records discovered by Edwin Smith, an American Egyptologist, and describing the surgical treatment of cancer in Egypt circa 1600 B.C. [ 1#N#R. E. Pollock and D. L. Morton, “Principles of surgical oncology,” in Cancer Medicine, D. W. Kufe and R. E. Pollock, Eds., B. C. Decker, Hamilton, Ontario, Canada, 2000. View at: Google Scholar#N#See in References#N#]. Medicines were also used in ancient Egypt at the time of the pharaohs, although the use of chemotherapy in cancer was first used in the early 1900s by the German chemist, Paul Ehrlich [ 2#N#V. T. de Vita Jr. and E. Chu, “A history of cancer chemotherapy,” Cancer Research, vol. 68, no. 21, pp. 8643–8653, 2008. View at: Publisher Site | Google Scholar#N#See in References#N#]. In contrast, radiation therapy, the therapeutic use of ionizing radiation, is by far the most recent technique used to treat cancer. X-rays, a kind of ionizing radiation, were discovered in 1895 by Wilhelm Roentgen and within months were used to treat tumors. This use of ionizing radiation has undergone extraordinary development during the past century. As we will discuss, the advancements in medical imaging have been critical to the evolution of modern radiation therapy.

Why is treatment planning important?

The primary goal of treatment planning is to precisely calculate the radiation dose to the tumor in order to improve the outcome and reduce toxicity. The future of imaging in radiation therapy treatment planning is promising, and other advances will contribute to better target definition.

When was X-rays first used?

X-rays, a kind of ionizing radiation, were discovered in 1895 by Wilhelm Roentgen and within months were used to treat tumors. This use of ionizing radiation has undergone extraordinary development during the past century. As we will discuss, the advancements in medical imaging have been critical to the evolution of modern radiation therapy.

Goals of Radiation Therapy

Normal Tissue Response

Pre-Radiation Imaging

• Patients with tumors in complex anatomical locations (e.g., head, neck, body wall) may require CT imaging for planning purposes prior to radiation. Patients treated with palliative courses of radiation may not require computer-based planning depending on tumor size and location. Hemoclips placed at surgery aid in delineating the tumor bed.19 Patien...

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Tumor-Specific Radiation Considerations

Newer Technologies