فهرست مطالب a. shanei

Bystander (B.s) effect can influence non-irradiated cells and affect the desired effect in cancer treatment. This study was conducted to assess this effect on simultaneous administration of ultrasound (US) and Gold nanoparticles as a sonodynamic therapy (SDT) which is an important newly stimuli-responsive method in cancer treatment.

Firstly, the appropriate concentration of Gold nanoparticles (GNPs) and US intensity for SDT on melanoma cancer cells (A375) were evaluated. After treatments, the target cell culture was transferred to the bystander cells and the induced bystander effects including cell viability, apoptosis, expression of P53 (a promoter of apoptosis gene) and HO-1 (an inhibitor of apoptosis gene) were examined.

According to the MTT results, 50 µg/ml concentration of GNPs and 1.5 W/cm2 intensity of US wave were selected. Our results revealed that SDT induced B.s effect can alter the cell viability and apoptosis up to 20% and 51.61%, respectively. Moreover, a 2.9-fold increase in p53 gene expression and a decrease in OH-1 gene expression to 0.181-fold in comparison to the control groups were observed.

These results confirmed that B.s effect of sonodynamic can reduce the cancerous cell viability. Our finding showed that this treatment can potentially be an alternative to traditional treatment modalities.

Small photon beams are increasingly used in modern radiotherapy modalities. In small photon fields, the dosimetric field size will deviate from the nominal field size. An effective field size (FSeff) for use in small field dosimetry has been defined to overcome this issue. The present study aims to investigate the suitability of two ionization chambers and two semiconductor diodes in the measurement of 6MV photon beam profiles and to analyze the variations of FSeff in smaller fields.

Measurements were made at 6 MV photon beams of a Siemens Artiste linear accelerator and transverse profiles were acquired for nominal square field sizes of side 1×1 to 10×10 cm2 via the irradiation of detectors and radiochromic film. Full width at half maximum (FWHM) at the 50% isodose level was used to calculate FSeff.

The uncertainty of the FWHM values derived from the in-plane and cross-plane profiles (ΔFWHM%) were below 6% for all the detectors were below 6% except for Semiflex in the 1×1 field size. In small field sizes (less than 3 × 3 cm2), larger differences occurred between the dosimetric and nominal field sizes in all detectors. No significant differences between nominal and effective field sizes were observed in a field rage of 4×4 - 10×10 cm2.

In the acquisition of small field profiles, selection of an appropriate detector is influential in accurate measurements. The findings of present study support the argument that both the size and composition of detectors affect the small field profile measurements.

The induction of bystander effect via ionizing radiation has been well proven. However, few studies have investigated the bystander effect following non-ionizing radiation, such as ultrasound waves. Here, the bystander effect after different sonication times on human melanoma cell line (A375), is evaluated by assessing cell viability and apoptosis.

The cells were divided into two main target and bystander groups. Target cells were exposed to 1 MHz ultrasound at 2 W/cm² intensity for 1, 2, 5 and 10 min with an ultrasound unit. Then, bystander cells received the cell culture medium of target cells. MTT and flow cytometry assays were used to determine the cell’ viability at different times after exposure and medium transfer, as well as the detection of apoptosis.

The cell’ viability in ultrasound-exposed target cells was less than 75% for 24 and 48 h incubation. Furthermore, bystander cell’ viability was not significantly different from the control group 1 and 12 h after receiving the culture medium of target cells. However, bystander cells viability 24 and 48 h after target cells medium transfer was significantly decreased (P=0.01). The apoptosis rate of bystander cells, 24 and 48 h after receiving the cell culture medium of target cells, showed significant differences from the control group.

This research results revealed that the ultrasound waves could induce a biological effect in A375 bystander cells which were not directly exposed to direct ultrasound.

Acoustic cavitation which occurs at high intensities of ultrasound waves can be fatal for tumor cells; however, it can be used to destroy cancer cells as an efficient therapeutic method. On the other hand, it is known that the existence of nanoparticles in a liquid decreases the acoustic cavitation onset threshold.

In this work, the combined effects of therapeutic ultrasound and gold nanoparticles (GNPs) on a breast carcinoma tumour model in BALB/c mice were studied. The tumour-bearing mice were divided into 4 groups (1) Control, (2) GNPs, (3) Ultrasound alone and (4) Ultrasound in the presence of GNPs. In groups 2 and 4, GNPs were injected into tumours. Therapeutic effects on tumours were evaluated by measuring relative tumour volume (RTV), doubling time (T2) and 5-folding time (T5) for tumours volume.

The T5 showed a significant difference between ultrasound in the presence of GNPs group and the other groups. The maximum T2 and T5 were found in the ultrasound in the presence of GNPs group.

Combined effects of ultrasound and GNPs can be used as a method for increasing the therapeutic efficiency on tumor cells.

The current study aimed to compare the tumor control probability (TCP) and normal tissue complication probability (NTCP) of three-dimensional conformal radiation therapy (3D-CRT) and intensity-modulated radiation therapy (IMRT) for left-sided breast cancer using radiobiological models.

This study was conducted on 30 patients with left-sided breast cancer, who were planned for 3D-CRT and 6-9 fields IMRT treatments using the PROWESS treatment planning system.  The planning target volume (PTV) dose of 50 Gy was administered for the 3D-CRT and IMRT plans, respectively.  The Niemierko’s equivalent uniform dose (EUD) model was utilized for the estimation of tumor control probability (TCP) and normal tissue complication probability (NTCP). 

According to the results, the mean TCP values for 3D-CRT, 6-fields IMRT, and 9-fields IMRT plans were 99.07 ±0.07, 99.24 ±0.05 and 99.28 ±0.04, respectively, showing no statistically significant difference. The NTCPs of the lung and heart were considerably lower in the IMRT plans, compared to those in the 3D-CRT plans.

From the radiobiological point of view, our results indicated that 3D-CRT produces a lower NTCP for ipsilateral lung. In contrast, for TCP calculations, there was a higher gain with IMRT plans compared to 3D-CRT plans.