Iranian Journal of Medical Physics
Volume:20 Issue: 2, Mar-Apr 2023

Hassan Ali Nedaie et al., recently have published “Assessment of Radiation-induced Secondary Cancer Risks in Breast Cancer Patients Treated with 3D Conformal Radiotherapy” paper in Iranian journal of Medical Physics [1]. The aim of this study was to evaluate the secondary cancer risk in organs at risk for breast cancer radiotherapy by the 3D-CRT technique. The authors used BEIR VII model for measuring of excess absolute risk (EAR) and excess relative risk(ERR). This model was basically used for organs that received low dose (below 1-2 Gy) [2].     Based on the same paper, it’s clear that organs like contralateral breast and ipsilateral lung, and heart received a high dose, about several Gy [3-5]. In Nedaie et al. paper, authors reported mean dose for thyroid, heart, contralateral breast and ipsilateral lung are ranged from 3.73 to 15.99, since BEIR VII model is not appropriate for high dose, hence, cancer risk estimation encounters an error. On the other hand, received dose for organs in field is inhomogeneously distributed, for changing inhomogeneously distributed dose to a homogeneous dose, the concept of organ equivalent dose (OED) has been applied. The OED was calculated using the Schneider paper, this model considered repair cells after radiotherapy, dose fractionation, dose–response curve, etc. Therefore, for estimating secondary cancer risk of organs in field that receive high dose, we should use OED model [6].    In addition to received dose, some risk factors like smoking can increase lung cancer risk, therefore adding smoking factor on calculation of baseline risk will estimate EAR accurately [7]. Also, during radiation therapy of breast cancer, heart has been irradiated, Exposure of the heart to ionizing radiation increases heart diseases like coronary diseases, myocardial infarction, and etc. [8], also smoking, parental history of myocardial infarction, and blood factors like blood pressure, high-sensitivity C-reactive protein, total cholesterol, high-density lipoprotein cholesterol, hemoglobin are involved in cardiovascular risk in women [9]. Therefore, nominated factors are able to increasing lung cancer and heart disease after radiation therapy for breast cancer.    The first shortcoming of this paper comes from using BEIR VII Model instead of OED model for organs in field that received high dose. Using this model to calculate cancer risk is resulted to have uncertainties in estimating the secondary cancer risk for organs in field that received high dose [10].  The second shortcoming of this paper comes from lack of considering smoking, parental history of myocardial infarction, and blood factors for estimating EAR of heart disease. The third shortcoming comes from using OED model for estimation secondary cancer risk of lungs without considering effects of smoking on lung cancer risk. It should be noted that for accurate estimation of lung cancer and heart disease after radiation therapy of breast, below formula is appropriate [11].Which   is linearity of the rate of heart disease and lung cancer with increasing mean organ dose [8,12]  and baseline risk obtains by Reynolds risk score which is including effects of blood factors, smoking, and parental history of myocardial infarction [9]. I hope that my comments help the better understand the usage of an appropriate model for estimation lung cancer and heart diseases risk in radiation therapy.

The large aperture concave spherical focused ultrasonic transducer has stronger acoustic focusing effect and can obtain good temperature rise effect. The purpose of this study was to explore the effect of different frequency, duty cycle and inner radius parameters on temperature rise of multi-layer biological tissue.
The simulation model of high-intensity focused ultrasound (HIFU) irradiated multi-layer biological tissue was constructed. By changing the irradiation frequency, duty cycle and inner radius of large aperture concave spherical focused ultrasonic transducer, the sound field and temperature field of multi-layer biological tissue were simulated and calculated by using Westervelt nonlinear acoustic wave equation and Pennes biological heat conduction equation, respectively.
The intensity of sound field increased with the increase of frequency, while it decreased with the increase of inner radius, but the duty cycle almost had no effect on the intensity of sound field. The focal temperature increased with the increase of frequency and duty cycle, but decreased with the increase of inner radius.
By selecting appropriate parameters of transducer, the optimum temperature rise in the target area of biological tissue can be obtained by using a large aperture concave spherical focused ultrasonic transducer.

Until now, the gravitational stress effect on the time domain and frequency heart parameters has been well-documented. However, cardiac signal dynamics have not been studied adequately under the influence of postural changes. In addition, the effect of body positions on the bio-signals has been investigated only from the aspect of feature extraction and the classification problem has not been considered. Among the physiological signals, the heart rate (HR) becomes an emerging modality that captured the attention of many researchers due to its noninvasive recording and its ability to assess autonomic tone modulation. This study attempted to classify cardiac dynamics concerning postural changes by evaluating different entropy algorithms. In this study, the ECG signals of 10 participants (five women and five men with a mean age of 28.7±1.2 years) were designated from the database available at Physionet. First, the RR-intervals of electrocardiograms complying with the Pan-Tomkins procedure were estimated. Second, several entropy measures, including Shannon, log energy, sample, differential, Tsallis, Renyi, and approximate entropy, were calculated while participants were in supine rest, in two rapid head-up tilts, two stand-ups, and two slow head-up tilts. Then, we applied the support vector machine to classify different postures using one group vs. all other remaining groups (OVA) and one body posture vs. the resting supine position (BVR) in a k-fold cross-validation scheme. Empirical results showed that using the entropy measure in a BVR scheme leads to higher of accuracy rates up to 100%. This framework opens an avenue of research for different gravitational stress-based conditions in a broad range of applications like disease management, sports, and astronautics.

The purpose of this study was to establish of diagnostic reference level (DRL) and to compare radiation dose between single phase and unjustified double phase abdominopelvic CT imaging.
A total of 163 patients, 85 patients with single phase and 78 patients with unjustified double phase abdominopelvic CT scans, were included in this retrospective study. Volumetric CT dose index (CTDIvol) and dose length product (DLP) were obtained from the CT console. The third quartile of CTDIvol and DLP were determined for diagnostic reference level (DRL). Effective dose (E) and organ dose were obtained using CT-Expo software (version 2.2). Single phase and double phase scans were compared in terms of CTDIvol, DLP, size-specific dose estimate (SSDE), E and organ doses.
The institutional DRLs using CTDIvol and DLP for abdominopelvic CT were 9.8 mGy and 571 mGy.cm, respectively. The mean value of E was 5.4 ± 1.8 and 10.3 ± 3.4 for single phase and double phase imaging, respectively, resulting in 4.9 mSv excess dose per patient. Mean value of the DLP was 396.9 ± 142.7 and 759.0 ± 250.7 for single phase and double phase imaging, respectively. E was significantly higher in female compared to male (p < 0.05). Bladder has a highest lifetime attributed risk of cancer incidence among other organs. Also, the cancer risk incidence was higher for female than male.
The awareness of physicians about the correct indications of abdominopelvic CT should be increased by using associated reliable guidelines

It is important that estimated doses from patients administered radiopharmaceuticals in nuclear medicine by hospital staff but other people in connection to patients need radiation protection. The purpose of this study was to measure the dose rate with increasing distance from patients to estimate the average effective dose in hospital staff and companions of patients.

Myocardial perfusion scanning was performed using Technetium 99m-methoxy isobutyl isonitrile (99mTc-MIBI) (in 2 groups of stress and rest). We measured the external dose rate for 48 patients (23 men and 25 women) at 4 distances and 5 times. Doses are estimated for a range of scenarios, in hospital staff, public transportation, and family contacts. Finally, the obtained data were compared to the trigger level introduced by the International Commission on Radiological Protection 53 and 62 (ICRP). Data analysis was performed using SPSS version 24.

The distance of the times when patients need family or hospital staff to be with them was divided into 4 categories (injection to scanning, using public transport, emergency patients during injection to scanning, and emergency patients after finishing medical procedures). 

In all scenarios, effective doses were obtained at less than 100 µSv according to ICRP guidelines. Due to the significant increase of the uptake in the heart and skeleton, after injection, the dose rate per MBq in the stress rate before 1hr decreases more slowly than the rest test, and the effective dose of hospital staff in stress procedure is more than rest procedure.

Gliomas represent a considerable percentage of all diagnosed primary central nervous system tumors. A non-invasive access method, like magnetic resonance spectroscopy (MRS), is required for preoperative evaluation. So, the present study aimed to evaluate the application of Multivoxel 1H-MR Spectroscopy in the differentiation of high-grade from low-grade gliomas. 13 patients suspected of Cerebral Glioma, which already had been selected for brain surgery or biopsy, underwent a Multivoxel 1H-MR Spectroscopy. After the MRS exam, the pathology tests on specimens confirmed the grade of tumors. Then results were compared and represented as receiver operating characteristic (ROC) curves to show their sensitivity and specificity as well. Choline to creatine (Cho/Cr) and choline to N-acetyl-aspartate (Cho/NAA) were statistically lower in the low-grade group than in high-grade (p=0.007 and p=0.027, respectively) and N-acetyl-aspartate to creatine (NAA/Cr) was statistically higher in the high-grade group (p=0.037). But in border regions, only Cho/Cr and Cho/NAA were significant (P values= 0.19 and 0.22, respectively). With receiver operating characteristic (ROC) curves analysis, Cho/Cr had the best sensitivity and specificity in the differentiation of high-grade from low-grade gliomas in tumor area (92.86% sensitivity and 85.71% specificity) and this ratio had the best sensitivity and specificity in border regions of tumor (92.86% sensitivity and 78.43% specificity). Metabolite ratios of low and high-grade gliomas (HGG) were significantly different from each other. Cho/Cr and Cho/NAA ratios can use as an internal reference for grading the glioma non-invasively in the tumor area and the border area of the tumor.

In head and neck cancer (HNC) radiotherapy, parotid, submandibular, and minor salivary glands are often incidentally irradiated. Hence, Xerostomia is the most significant disabling side-effect, to improve the quality of life, it should be reduced. The study was to evaluate the parotid dose and PTV coverage in post operated Oral cancer patients using Volumetric Modulated Arc Therapy (VMAT) technique. The authors generated VMAT plans for 14 post operated oral cancer patients, where primary disease crossed midline or nodal stage ≥ 2. The doses to the moderate high-risk volume of the clinical target volume (CTV) and planning target volume (PTV) were 60Gy in 30 fractions. The low-risk volume received a dose to the CTV and PTV of 54Gy in 30 fractions. Plans were made for each patient, and the dose to D95 and D98 of target volumes was analyzed. The mean dose of the parotid and parotid minus PTV volumes were analyzed and compared with target doses (D98 & D95).  Median dose to the ipsilateral parotid gland was 54.45Gy and to the ipsilateral parotid gland minus PTV was 45.60Gy while to the contralateral parotid gland median dose was 16.31Gy, (mean is ranging from 14.01 to 17.06Gy) and to the contralateral parotid gland minus PTV was 14.92 (mean is ranging from 12.42 to 15.18Gy) after achieving the 95% coverage of PTV. Better sparing of contralateral parotid glands with the help of VMAT technique in post-operative HNC patients is possible, which can prevent xerostomia in most patients.

The present study demonstrated role of overall treatment time when estimating tumor control probability (TCP) and normal tissue complication probability (NTCP) for moderately hypofractionated and accelerated fractionation schedules in head & neck treatment plans. Repopulation effect in the squamous cell carcinoma is an influencing factor that should be considered when evaluating TCP and NTCP in early responding tissue. This effect can be incorporated by the means of overall treatment time in days.
The proposed study separated in two parts. In the first case, we assumed four moderately hypofractionated schedules for demonstration, including conventional fractionation schedule (CFS) (70Gy/35 #), fractionation schedule 1 (66Gy/30#), fractionation schedule 2 (60Gy/24#) & fractionation schedule 3 (55Gy/20#). Four independent volumetric modulated arc treatment plans were generated at different fractionation schedules for 15 patient’s data set and therefore led to a total of 60 treatment plans. The treatment plan created for CFS is the reference plan for comparison of calculated TCP & NTCP amongst the four plans. The rest three plans for each patient were created simply by changing the dose prescription for FS1, FS2 & FS3, the mean total dose and dose per fraction. In the second scenario, conventional fractionation schedule (66Gy/33# with five fractions per week) compared against accelerated fractionation schedule (66Gy/33# with six fractions per week). The cumulative dose volume histogram for all treatment plans were used for TCP/NTCP estimation by Niemierko EUD, Poisson model and LKB model. The TCP/NTCP calculated in two different way for tumor & oral mucosa of head & neck site. Contrary to the second case, the overall treatment time (OTT) in days not accounted in the first case.
It was statistically significant difference (p<0.05) obtained between calculated TCP/NTCP in both moderately hypofractionated and accelerated fractionation schedules.
There is significant impact of OTT and it should be considered when evaluating TCP/NTCP for early responding tissue.

Breast cancer is one of the most prevalent diseases around the world. Breast cancer patients treated with radiation may face Side effects as well as cancer recurrence. Some polyphenols exhibit antioxidant effects. Citrus and Orthosiphon Stamineus have source of methylated flavone called Sinensetin (SIN). In this research, we designation of Sinensetin as increasing radiation sensitivity.

The cytotoxic effect of Sinensetin was examined in MDA-MB-231 and T47D by MTT assay. As well as, the clonogenic ability of cells were Assessmented in the presence of Sinensetin and combination with radiation. To quantify expression alterations of apoptosis related genes, utilized Real-Time PCR method.

In a dose and time-dependent manner, Sinensetin decreased the viability of MDA-MB-231 and T47D. The survival fraction was decreased in cells treated with Sinensetin (SIN) prior to X-irradiation compared to cells treated with X-ray only. More ever, expression level of, Bcl-2, STAT3, and increased P53 via treated cells with Sinensetin (SIN) and X-ray.

Due to the results, Sinensetin (SIN) can be mentioned as a novel radiosensitizer and its effects may considered increasing apoptosis following DNA damage induced by irradiation.