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Hinduja Installs RPM System for Respiratory Gating & Motion Management

Treatments with the RPM system generally last 15 minutes

PD Hinduja National Hospital, Mumbai has recently installed Real-Time Position Management (RPM) System for treatment in radiation oncology, especially for patients suffering from tumours located in the abdomen and the thorax which move with respiration. The equipment from Varian Medical Systems has cost - $100,000.

The system's cameras track the position of a reflective, plastic marker block placed on the patient's chest or abdomen. As the cameras track the movement, the system learns the motion patterns for that particular area and alerts the clinician to any variations outside the norm

The respiratory gating radiotherapy 4DCT scanning is used and it helps in reducing the margins given around the tumor to 5-7mm from 15 to 25mm. Treatments with the RPM system generally last 15 minutes, although this can increase depending on the respiratory cycle. The RPM technology is particularly suited to large tumors in the abdomen and thorax. It is also popular for certain breast treatments. "Especially for a left-sided breast, one can cause damage to the heart with radiation therapy," said Dr V Kannan, Head, Radiation Oncology, Hinduja Hospital.

Recently introduced rapid multidetector CT scanners make it feasible to synchronise image data acquisition with the respiratory gating device according to the segment of the breathing cycle when each image is recorded. Thus, virtually 4-D images can be reconstructed from each respiratory phase data series to form a model of anatomic movement. This process minimises motion artifacts but reproduces great detail.

The RPM Respiratory Gating System automatically compensates for respiratory movement during chest and abdomen external beam cancer radiation therapy treatments. A non-invasive reflective marker affixed to the patient's chest allows an infrared video camera to track breath motion through several cycles while software processes the tracked movements to characterise the patient's normal respiratory pattern into a waveform. The resulting images are used to design a highly individual treatment plan, calculating dosage and delivery based on the patient's most natural breathing rhythm.

As the continuous signal is processed, the RPM computer initiates a beam-hold in the accelerator when the breath movement exceeds the parameters determined during treatment simulation. The gate can be programmed for inspiration, expiration, or breath-hold intervals. The software monitors total treatment time as well as individual beam impacts and rejections of unexpected motion patterns (eg, coughing or throat clearing).

Internal movement of critical organs can impact treatment. For example, kidney motion can affect treatment of adjacent pancreatic tumor. "If you were to design a radiation field for only the tumor itself and not take into account the kidney motion that could come directly into the radiation field, one may unnecessarily or inadvertently irradiate the kidneys and cause problems," said Dr Vivek J Anand, Consultant Radiation Oncologist at Hinduja Hospital.

EH News Bureau