Feasibility of Acquiring Radiotherapy Linac Commissioning Data with a Three-Dimensional Cubic Electronic Detector Array

PURPOSE/OBJECTIVE(S)

Linac commissioning data acquisition consists of measurements of PDDs/TMRs, profiles, and dosimetric factors done in water and lasting several weeks to complete. Data collected with an early prototype 3D cubic electronic detector suggests faster, reliable, accurate, and a cost-effective option for commissioning data collection in the future.

MATERIALS/METHODS

A 10 × 10 × 15 cm3 3D cubic electronic detector array prototype of acrylic, silicon rubber, and five 10 × 10 × 0.2 cm3 planar active matrices at 2.0, 4.0, 6.0, 8.0, and 10 cm depths, was constructed. Each active matrix has 25 pixels (diode, capacitor, MOSFET) of 2.0 cm separation in a 10 × 10 cm2 active area resulting in 125 pixels in the array. Data readout consists of a multiplex connectivity configuration where one channel provides data input/output to multiple pixels rather than one channel per pixel. Simultaneous absolute depth-dose (ADD) and profile measurements were performed using a 6 MV photon beam, 100 cm SSD, 10 × 10 cm2 open field, 100 MU, and 400 MU/min, without scanning. Also, ADDs and profiles were measured with 15-, 30- and 45-deg wedges. Data processing for these measurements, and 2D and 3D DD and profile displays, were done in a programming environment, and results were compared to calculated data in acrylic.

RESULTS

Table with ADD and profile results for the 10 × 10 cm2 open field. ADD and profiles with wedges showed similar results.

CONCLUSION

Absolute depth-dose and profile data acquired with an early prototype agreed within ±4 % of calculated values. This suggests that an improved 3D cubic electronic detector array could be used for commissioning data collection. If realized, it could reduce commissioning time from weeks to hours saving cost, staff time, and leveraging a new Linac into clinical operations sooner.

Activated recombinant human coagulation factor VII (rFVIIa) therapy for abdominal bleeding in patients with inhibitory antibodies to factor VIII

Eight patients with inhibitors to factor VIII (4 hemophilia A and 4 nonhemophilic) were treated with recombinant activated factor VII (rFVIIa) to control severe abdominal bleeding. The recombinant factor was supplied under an open-label, emergency-use program to patients previously unresponsive to one or more alternative therapies. Therapy with rFVIIa was administered for nine separate bleeding events; one patient was treated for two separate bleeding episodes. Patients were treated for an average of 9 days and received a mean total dose of 5.2 mg of rFVIIa for control of bleeding. Treatment was considered successful and hemostasis adequate in 7 of the 9 episodes (78%). Treatment with rFVIIa was partially successful in one other episode. Four patients in this series experienced serious adverse events; all the adverse events were considered unrelated to rFVIIa therapy. The results of this limited series indicate that rFVIIa is an effective means of managing life-threatening abdominal bleeding in individuals with hemophilia or acquired antibodies to factor VIII.