POSSIBILITY OF EYE OVERDOSE DURING RADIATION THERAPY OF HEAD TUMORS

Session

Nursing and Medical Sciences

Description

Over 50% of all tumors, in Radiotherapy (Teletherapy), now and many years ago, start their treatment with Gamma rays and electrons. The success of the treatment is closely related to the accuracy of giving the dose in the tumoral volume (PTV-Planning Target Volume), localized by the doctor. It is known that the role of determining the exact area to be irradiated belongs to physics and the medical physicist. To guarantee successful radiation in this radiation zone, the patient must be correctly positioned according to the radiation plan. In this process, the patient, after lying on the bed of the accelerator, and before starting the radiation therapy, is given at least two X-ray exposures, from the angles usually combined by the accelerator, with gentry 0° and 270° or 90° and 180°, to see if the patient is positioned as required by the radiation plan.

Modern accelerators used in radiotherapy, at angles (Gentri) of 0° and 180° in their tube, use only energy in MV (Mega Volt), while at angles of 270° or 90° they use energy in kV (kilo Volt).

During radiotherapy of head tumors, when we analyze the dose received by the lens of the eye during tumor treatment, with these values of the energy received by the patient during positioning (Setup fields), it can often present a risk of overdosing the eyes and become in visual impairment measure. What dose is created by the use of MV energy with only 2 shots (2 MU - Monitor Units) and what from that kV, in this paper the measurement values are given, where it can be observed that despite the fact that lead filters with a thickness of 8 mm for eye protection, at the 0o angle to the MV energy source, the device records the dose of 1.3 mGy, while at the 90o angle with the kV energy source, the device records the dose of 0.29 mGy. Usually the doctor's request is not to exceed the limit of 5 Gy during therapy. The therapy energy that must be used to achieve the radiation effects will not have to be below 4.5 Gy. When the positioning energy is added to this energy, and when the monthly values are multiplied for how long the therapy lasts, it turns out that the patient who has cancer in the area of the brain near the eyes, can very easily overdose and damage the sight.

Considering that much more energy is produced from MV energy than with kV, in cases where it is possible, it is preferable to adjust the apparatus through the rotation of the angles so that the patient is subjected to as little MV energy as possible. In practice, it is more convenient to use the 0° angle with MV energy with eye protection through glasses and the 90° angle with kV energy.

For this purpose, as a suitable solution, it is recommended to manipulate the apparatus where kV energy is used at the 0o angle and MV energy is used at the 90o angle, in which case the possibility of overdose of the patient in the eye lens would be reduced.

This would take a few extra seconds in the process of the patient lying in the apparatus but would increase the chance of saving the patient from serious eye damage.

Keywords:

Head tumors, visual impairment, eye overdose.

Proceedings Editor

Edmond Hajrizi

ISBN

978-9951-550-95-6

Location

UBT Lipjan, Kosovo

Start Date

28-10-2023 8:00 AM

End Date

29-10-2023 6:00 PM

DOI

10.33107/ubt-ic.2023.207

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Oct 28th, 8:00 AM Oct 29th, 6:00 PM

POSSIBILITY OF EYE OVERDOSE DURING RADIATION THERAPY OF HEAD TUMORS

UBT Lipjan, Kosovo

Over 50% of all tumors, in Radiotherapy (Teletherapy), now and many years ago, start their treatment with Gamma rays and electrons. The success of the treatment is closely related to the accuracy of giving the dose in the tumoral volume (PTV-Planning Target Volume), localized by the doctor. It is known that the role of determining the exact area to be irradiated belongs to physics and the medical physicist. To guarantee successful radiation in this radiation zone, the patient must be correctly positioned according to the radiation plan. In this process, the patient, after lying on the bed of the accelerator, and before starting the radiation therapy, is given at least two X-ray exposures, from the angles usually combined by the accelerator, with gentry 0° and 270° or 90° and 180°, to see if the patient is positioned as required by the radiation plan.

Modern accelerators used in radiotherapy, at angles (Gentri) of 0° and 180° in their tube, use only energy in MV (Mega Volt), while at angles of 270° or 90° they use energy in kV (kilo Volt).

During radiotherapy of head tumors, when we analyze the dose received by the lens of the eye during tumor treatment, with these values of the energy received by the patient during positioning (Setup fields), it can often present a risk of overdosing the eyes and become in visual impairment measure. What dose is created by the use of MV energy with only 2 shots (2 MU - Monitor Units) and what from that kV, in this paper the measurement values are given, where it can be observed that despite the fact that lead filters with a thickness of 8 mm for eye protection, at the 0o angle to the MV energy source, the device records the dose of 1.3 mGy, while at the 90o angle with the kV energy source, the device records the dose of 0.29 mGy. Usually the doctor's request is not to exceed the limit of 5 Gy during therapy. The therapy energy that must be used to achieve the radiation effects will not have to be below 4.5 Gy. When the positioning energy is added to this energy, and when the monthly values are multiplied for how long the therapy lasts, it turns out that the patient who has cancer in the area of the brain near the eyes, can very easily overdose and damage the sight.

Considering that much more energy is produced from MV energy than with kV, in cases where it is possible, it is preferable to adjust the apparatus through the rotation of the angles so that the patient is subjected to as little MV energy as possible. In practice, it is more convenient to use the 0° angle with MV energy with eye protection through glasses and the 90° angle with kV energy.

For this purpose, as a suitable solution, it is recommended to manipulate the apparatus where kV energy is used at the 0o angle and MV energy is used at the 90o angle, in which case the possibility of overdose of the patient in the eye lens would be reduced.

This would take a few extra seconds in the process of the patient lying in the apparatus but would increase the chance of saving the patient from serious eye damage.