Optimized Cylindrical Diffuser Powers for Interstitial PDT Breast Cancer Treatment Planning: A Simulation Study

Purpose. It is well known that interstitial photodynamic therapy (iPDT) of large tumors requires effective planning to ensure efficient delivery of therapeutic dose to the target tumors. This should be achieved in parallel with minimal damage to the nearby intact tissues. To that end, clinical iPDT can be attained using cylindrical diffusing optical fibers (CDFs) as light sources. In this work, we optimize output CDF powers in order to deliver a prescribed light dose to a spherical volume such as a tumor node. Methods. Four CDFs are placed vertically inside the tumor node. The fluence rate is calculated using the diffusion equation. Therapeutic target dose is (20-50) J·cm-2. The optical properties (μa=0.085 cm−1, μs′=16 cm−1) of a breast tumor and the treatment time of 150 sec are used to calculate the fluence rate. Results. For four CDFs, the therapeutic target dose (20-50) J·cm-2 is delivered to more than 90%. This is the ratio of the total points that receive the target dose in proportion to the total points in the volume of the node of 3 cm in diameter, whereas, in larger nodes, the ratio is decreased to approximately 67%. Five CDFs are required to improve this ratio by more than 10%. Conclusion. Optimizing delivered powers enables the distribution of the therapeutic dose uniformly in the medium. In addition, this simulation study represents an essential part of a development dosimetry system for measuring and controlling the optical dose in the breast tumors

Using the MIRD5 Mathematical Phantom to calculate the absorbed dose in organs in case of brain and chest CT scan

Purpose: Simulate organs and calculate the absorbed dose in each organ for brain and chest CT scans.  Method and Materials: In this research; the mathematical phantom MIRD5 for adult men and women was used to calculate the absorbed dose in organs, in the case of brain and chest CT scans. Where; the mathematical phantom MIRD5 and MCNP code were used to simulate organs and calculate the absorbed dose in each organ for brain and chest CT scans, in Voltage (80 KVp, 100 KVp, 120 KVp). Results:  For chest scan, the maximum absorbed dose was in scapulae, rib cage, skin, arm bones, breasts, and lungs. For brain scan, the maximum absorbed dose was in the facial skeleton, skin, cranium, Brain, Spine, and scapulae. With the increase in the value of Voltage, the value of the absorbed dose increases, and the absorbed dose in men is greater than the dose in women. • For the man's phantom during chest imaging, we find: • For the woman's phantom during chest imaging, we find: • For the man's phantom during brain imaging, we find: • For the woman's phantom during brain imaging, we find: Conclusion: The difference in the dose values for men and women is due to the difference in the size of the organs, where the structure of the man is larger than the structure of the woman and therefore the values of the dose for the man are larger.  As a result, for CT chest scan and brain scan, it is necessary to consider all means necessary to reduce the patient's dose such as: lead shielding of healthy organs not subject to scan, and setting voltage and current to low values without reducing image quality