Using advanced MRI techniques to improve the planning treatment for head-neck hyperthermia and radiotherapy

Advanced tumours in the head/neck region are usually treated with radiation
therapy, possibly supplemented by chemotherapy. This treatment does not always
lead to desired results and the side effects can be exhaustive. After
treatment, patients often experience loss of saliva production and loss of
swallowing function. For different types of tumours and different tumour
sites, it has shown that hyperthermia the tissue temperature increases to
39-45 ° C, the effects of radiotherapy and chemotherapy markedly improved and
barely contributes to the side effects. Until recently it was not possible to
heat the head/neck region deeper than 4 cm below the skin. With the recent
development of the Hyper Collar now tumours can be heated deeper than 4 cm
below the skin.

The Hyper Collar consists twelve antennas that can be independently controlled.
Optimal use of this device requires a patient-specific treatment planning by
using computer simulations.This process of treatment planning based on computer
simulations, is analogous to the procedure for radiotherapy, wherein for each
patient prior to the treatment planning such a treatment is made. On a Computed
Tomography (CT) scan the target area and the critical normal tissues (spinal
cord, brains, salivary glands) are visible and through a planning system the
optimal dose can be calculated. For hyperthermia treatment planning the same CT
will be used. However, the CT data deduce a a fully 3D patient model
consisting of different tissue structures. To these tissue structures,
allocated electromagnetic prope will be assigned. By the 3D model, the
patient's energy dose for the hyperthermia treatment can be calculated and
optimized.


The results of the present study (MEC 2010-318) show that the addition of an
MRI scan, in addition to the normal CT scan, provides a rapid and accurate
underwriting of the tissues in the head and neck region which the energy dose
distribution can be accurately predicted. However, for a good prediction of the
thermal dose, also detailed information about the cooling of the tissues is
required. For the calculation of the thermal dose for the hyperthermia
treatment planning, the thermal properties of the tissue is very important. In
particular, the presence of blood vessels and the blood flow in the tissue are
important, because the released heat removes through the blood and thereby it
provides cooling of the tissue. In calculation of the actual thermal dose is
assumed that the blood flow does not change from patient to patient.
Furthermore, there also is a homogeneous tissue blood supply assumed. However,
it is known that the blood flow in tissue is very heterogeneous, particular in
tumours. For example, a blood vessel through the tumour ensures that carry heat
away from the tumour, so that the temperature is much lower than expected and
so suboptimal temperatures can be achieved in the tumour. To specify and
accurate our thermal dose, it is important to map the vascular tree both as the
perfusion by using advanced MRI techniques.

Because of the combined radiotherapy and hyperthermia treatment the tumour
changes during the treatment series. This indicates changes in the
characteristics of the tumour, but also in the tissues surrounded region. It is
possible that the beginning of the treatment planning is no longer accurate at
the end of the treatment series. This means that the patient characteristics
may have to adjust to an accurate treatment for a maximal therapeutic effect.
To make the change for mapping the properties, we want three times during the
treatment series (assuming 35x2Gy, 6x/week diagram).


This information, makes it possible to use the blood flow in the tumour and the
surrounding tissue, that can be determined for each patient. Furthermore, with
the date we can determine whether blood flow during combined hyperthermia and
radiotherapy treatment series changes. With this information we can decide
whether it is necessary to adapt hyperthermia and radiotherapy treatment
planning during the treatment series.

The purpose of this study is to determine the thermal parameters by MRI scans
at different time points during head-neck radiotherapy combined with
hyperthermia treatment series.

The first MRI scan will preferably be scheduled on the same day as the planning
CT, which is the standard specification for radiotherapy treatment planning.
The 2nd and 3rd MRI scan will be respectively in the 2nd week and in the 5th
week of the treatment series (assuming 35x2Gy, 6x/week schedule) are planned.
These MRI scans will always be planned adjacent to radiotherapy and / or
hyperthermia treatment.

The MRI scan is harmless to health. The MRI scanner consists a strong magnet.
This means that some people are not allowed in the MRI scanner, namely people
with pacemakers, with some shunts with metal in their bodies. Prior to the MRI
the physician there will be a questionnaire to check whether it is safe to
undergo the MRI scan. Allergic reactions to the contrast are very rare, but can
not be administered in a poor kidney function.