Background: Accurate dosimetry in cyberknife, is challenging because of the unavailability of suitable detectors to satisfy all the criteria of small-field dosimetry. In this work, eight different small-field detectors from PTW and IBA Dosimetry were used to determine the dosimetric parameters for twelve fixed collimators in the cyberknife® radiosurgery system. The scope of this work was to assist medical physicists in detector selection in small-field dosimetry. Materials and Methods: Dosimetric parameters such as the surface dose (Ds), dose buildup (DB), percentage dose at 100 mm (D100), percentage dose at 200 mm (D200), depth of dose maximum (Dmax), and total scatter factor (Scp) were compared and analyzed from the acquired Percentage Depth Dose(PDD). Results: Large variations in Ds were observed with different detectors for smaller collimator sizes. On analyzing the dose buildup, considerable differences were observed with all detectors from the surface to 6 mm depth for the smallest cone of 5 mm diameter. The D100 and D200 values obtained using ion chambers were higher than those using diodes, likely due to the volume averaging effect. The depth of dose maximum was found to increase with increase in the field size for most of the detectors. Considerable variation in Scp was noticed with all detectors in smaller field ranges. Conclusion: For small fields, the selection of detector is crucial, and awareness of the advantages, disadvantages and limitations of the detectors used is crucial. As in absolute dosimetry, the relative dosimetry in small fields is challenging and requires further studies and recommendations.

Introduction: Radical prostatectomy is an effective curative treatment option for organ-confined prostate cancer. There is a recent trend in offering curative treatment to patients with oligometastatic disease. More sensitive imaging modalities can identify oligometastatic disease that is not usually detected by conventional imaging techniques. Case presentation: We present a case in which a solitary left para-aortic metastatic lesion was ablated; using cyberknife image-guided stereotactic radiotherapy after robotic-assisted radical prostatectomy with negative margins and negative lymph node status. Conclusion: With the increasing number of patients diagnosed with oligometastatic prostate cancer, there is a paradigm shift towards its treatment with curative intent. The unusual sites of metastasis, can be cured effectively with Cyber Knife technology, whilst minimising adverse effects. Our report is an effort to highlight this technique as an effective treatment modality to be used and popularised as a standard option.

Background: Several high-precision stereotactic radiation therapy modalities are currently used in clinical settings. We aimed to evaluate whether the cyberknife (CK) or TrueBeam (TB) radiation treatment systems were more appropriate for treating targets of various morphologies according to the physical properties of each device. Materials and Methods: Spheres (diameter = 5– 50 mm), as well as triangular prisms and cubes (length of a side = 10– 50 mm), were used as virtual targets for each treatment delivery system. A phantom with dosimetry film was irradiated to evaluate the flatness and gradient of the radiation treatment from each modality. Results: The homogeneity index (HI) for the spherical targets was significantly higher (dose distribution was more homogeneous) using the TB than when using the CK (1. 9 vs. 1. 4; p = 0. 002). There were no significant differences between treatment modalities in the HI for more complex shapes. The HI increased monotonically as the virtual target diameter increased for the CK (p = 0. 048). The flatness parameter was lower for the TB than for the CK (1. 4 vs. 1. 1; p < 0. 001). Conclusion: The CK is particularly robust for delivering therapeutic radiation to small targets, while the TB is more suitable for targets with a simple shape or when the HI is a critical treatment factor.

Background: We assessed local control and survival in non-small cell lung cancer (NSCLC) patients with limited brain metastases (BM) who underwent stereotactic radiotherapy (SRT) using the cyberknife-M6 (CK-M6) system as well as the treatment efficacy. Materials and Methods: Twenty NSCLC patients with 40 BM were treated between 2018 and 2020. Median age was 61 years (46-80 years). Surgery was performed for nine lesions in eight cases. Median lesion size was 10 mm (2–38 mm). Resection cavities and intact metastases contoured as gross target volume. Planning target volume (PTV) was created with a margin of 0–2 mm. A median of 18 Gy (18–20 Gy) in one fraction was applied to 19 lesions, and 25 Gy/5 fractions (24–30 Gy/3–6 fx) to 21 lesions. Median treatment time was 20 min (13–35 min). Results: The median follow-up duration was nine months (1–15 months) in March 2021. Prescription isodose covering 95% of PTV was 85, 9% (80% –92, 7%). During the follow-up, local and intracranial control rates in evaluated patients were 88% (15/17) and 70, 5% (12/17), respectively. Asymptomatic radionecrosis was observed in 23. 5% (4/17) of patients at a median of 8 months (6–12 months). The median survival was 13 months (1–25 months). In univariate analysis, factors positively affecting survival were Karnofsky performance status, RPA, and DS-GPA classification (p < 0, 05). Conclusion: Promising local control and survival in patients and treatment time demonstrated that CK-M6 based SRT was effective, safe and comfortable in the treatment of NSCLC with BM.

Context: Lung cancer is one of the most common cancers worldwide with high mortality and short survival rate. Radiotherapy is one of the treatment modalities in patients who are non-surgery candidates or refuse surgery. Objectives: The current study aimed at evaluating the effectiveness and safety of this technique compared to similar ones for lung cancer treatment. Methods: In order to answer the research question and find the available evidence, after the development of the search strategy, Pubmed, Cochran, Ovid, Medline, and DARE databases were searched and related articles were selected based on the inclusion criteria. Then, we chose all studies that had the PICO acceptance criteria (Participants: adults with lung cancer; Intervention: tomotherapy; Comparisons: tomotherapy with cyberknife; Outcomes: local tumor control (LTC), survival rate (SR), complications, and degree of toxicity). The quality assessment of the studies was conducted using the CASP (Critical Appraisal Skills Programme) checklist. Two independent search engines evaluated the articles in terms of methodology, and information was extracted from the papers. Results: Overall, 12 retrospective studies with 616 patients were found examining the efficacy and safety of a certain technology. According to the results of the studies, the local tumor control (LTC) index varied from 63% to 100%. The two and five-year SRs were 73% and 56%, respectively. In addition, the mortality rate of patients until the completion of the treatment course was 34%, indicating the higher efficacy of tomotherapy than the efficacy of other similar techniques. The toxicity of tomotherapy was less than that of cyberknife, which indicates its more safety. Conclusions: According to the epidemiology of cancer, especially lung cancer, and due to aging of the population in Iran, and considering the higher efficacy and safety of tomotherapy in comparison with other similar technologies, i. e., cyberknife and Gamma Knife, tomotherapy is a superior technique in the control and treatment of lung cancer although other aspects, such as cost-efficacy, should be considered.

Purpose: This study was conducted to evaluate single collimator (SC) and double collimator (DC) plans with respect to dosimetric analysis, calculated dose delivery to OAR and treatment time in carcinoma prostate patients treated with cyberknife. Materials and Methods: A retrospective study was conducted among twenty low and intermediate risk carcinoma prostate previously treated with cyberknife. PTV was created and OARs were delineated. The prescribed dose was set as 37. 5 Gy in 5 fractions and a base plan (BP), followed by three reduction plans (time, beam and node) were generated for both single and double collimators with sequential optimization module. The SC and DC plans were compared for the above-said variables. The mean differences were compared using paired t-test. A p-value of <0. 05 was taken as statistically significant. Results: The median age of the patients was 63 years. DC plans had tighter isodose lines. The means of minimum doses did not vary significantly across the plans but the mean and maximum doses, PTV D2 and V95 means were significantly higher in single collimator plan. The mean CI and HI values were better in DC plans. The doses to OAR were comparable in both single and double collimator plans in terms of maximum doses. The mean doses received by OAR’ s were significantly lesser in DC plans. SC plans resulted in lesser beams, nodes, MU and treatment time. Conclusion: Double collimator plans were better in producing good dosimetric results and reduced OAR doses with lesser estimated treatment efficiency.

Background: To determine the basic physical and dosimetric properties of a new synthetic single-crystal diamond detector and its application for relative small field dosimetry. Materials and Methods: The pre-irradiation dose required to stabilize detector response, dose rate dependence, photon and electron energy dependence, temperature dependence and angular dependence of MicroDiamond detector response were evaluated. Output factors on Leksell Gamma Knife Perfexion and on cyberknife were measured to assess detector feasibility in small radiation field dosimetry. For all measurements, the detector was connected to Unidos electrometer set to 0 voltage. Results: Relative output factors measured on Leksell Gamma Knife Perfexion for 4 mm and 8 mm collimators were in agreement with Monte Carlo reference values from the manufacturer, with deviations of 0. 3% and 2. 1%, respectively. For cyberknife and fixed circular collimators, the difference in output factor values did not exceed 2% from vendor-supplied values, even for the smallest radiation field with a diameter of 5 mm. Conclusion: Our results indicate that the MicroDiamond detector is a promising tool for relative small field dosimetry. For output factor measurements on Leksell Gamma Knife Perfexion and cyberknife, the detector can be used with minimal response corrections applied (correction factors not larger than 2%).

Background: The aim of this study was to make a comparison of plan quality between MLC-based EDGE and the cone-based cyberknife systems in SBRT of localized prostate cancer. Materials and Methods: Ten patients with target volumes from 34. 65 to 82. 16 cc were included. Treatment plans were created for both systems using the same constraints. Dosimetric indices including target coverage, conformity index (CI), homogeneity index (HI), gradient index (GI) were applied for target, while the sparing of critical organs was evaluated with special dose-volume metrics and integral dose. Meanwhile, the delivery time and monitor units (MUs) were also estimated. The radiobiological indices such as equivalent uniform dose (EUD), tumor control probability (TCP) and normal tissue complication probability (NTCP) were also analyzed. Results: Both plans produced similar target coverage, HI and GI. For EDGE, more conformal dose distribution as well as reduced exposure of critical organs were obtained together with reduction of 91% delivery time and 72% MUs. EDGE plans also got lower EUD for bladder, rectum, urethra and penile bulk, which associated with reduction of NTCPs. However, higher values of EUD and TCP for tumor were obtained with CK plans. Conclusion: It indicated that both systems were capable of producing almost equivalent plan quality and can meet clinical requirements. cyberknife has higher target dose while EDGE system has more advantages in normal tissue sparing and delivery efficiency.