Comparison of Radiation Exposure during Fluoroscopy-Guided Transforaminal Epidural Steroid Injections at Different Vertebral Levels

Objective

To estimate and compare radiation exposure during transforaminal fluoroscopy-guided epidural steroid injection (TFESI) at different vertebral levels.

Materials and Methods

Fluoroscopy-guided TFESI was performed in 181 patients. The patients were categorized into three groups according to the injected lumbosacral nerve level of L2-4, L5, or S1. Fluoroscopy time (FT) and dose area product (DAP) were recorded for all patients; correlations between FT and DAP were determined at each level, and both FT and DAP were compared between the different vertebral levels.

Results

The numbers of patients who received ESI at L2-4, L5, and S1 were 29, 123, and 29. Mean FT was 44 seconds at L2-4, 33.5 seconds at L5, and 37.7 seconds at S1. Mean DAP was 138.6 µGy·m² at L2-4, 100.6 µGy·m² at L5, and 72.1 µGy·m² at S1. FT and DAP were positively correlated in each group (p values < 0.001). FT was significantly shorter at L5 than that at L2-4 (p = 0.004) but was not significantly different between S1 and L2-4 or L5 (p values = 0.286 and 0.532, respectively). DAP was significantly smaller at L5 and S1 than that at L2-4, but L5 and S1 were not significantly different. After correcting for FT, DAP was significantly smaller at S1 than that at either L2-4 or L5 (p values = 0.001 and 0.010).

Conclusion

The radiation dose was small during a single procedure of ESI and showed differences between different lumbosacral spine levels.     

Dosimetry of a cone beam CT device for oral and maxillofacial radiology using Monte Carlo techniques and ICRP adult reference computational phantoms

Objectives:

The aim of this study was to calculate organ and effective doses for a range of available protocols in a particular cone beam CT (CBCT) scanner dedicated to dentistry and to derive effective dose conversion factors.

Methods:

Monte Carlo simulations were used to calculate organ and effective doses using the International Commission on Radiological Protection voxel adult male and female reference phantoms (AM and AF) in an i-CAT CBCT. Nine different fields of view (FOVs) were simulated considering full- and half-rotation modes, and also a high-resolution acquisition for a particular protocol. Dose–area product (DAP) was measured.

Results:

Dose to organs varied for the different FOVs, usually being higher in the AF phantom. For 360°, effective doses were in the range of 25–66 μSv, and 46 μSv for full head. Higher contributions to the effective dose corresponded to the remainder (31%; 27–36 range), salivary glands (23%; 20–29%), thyroid (13%; 8–17%), red bone marrow (10%; 9–11%) and oesophagus (7%; 4–10%). The high-resolution protocol doubled the standard resolution doses. DAP values were between 181 mGy cm² and 556 mGy cm² for 360°. For 180° protocols, dose to organs, effective dose and DAP were approximately 40% lower. A conversion factor (DAP to effective dose) of 0.130 ± 0.006 μSv mGy⁻¹ cm⁻² was derived for all the protocols, excluding full head. A wide variation in dose to eye lens and thyroid was found when shifting the FOV in the AF phantom.

Conclusions:

Organ and effective doses varied according to field size, acquisition angle and positioning of the beam relative to radiosensitive organs. Good positive correlation between calculated effective dose and measured DAP was found.     

Radiation exposure of the interventional radiologist during percutaneous biopsy using a multiaxis interventional C-arm CT system with 3D laser guidance: a phantom study

Objective:

Evaluation of absolute radiation exposure values for interventional radiologists (IRs) using a multiaxis interventional flat-panel C-arm cone beam CT (CBCT) system with three-dimensional laser guidance for biopsy in a triple-modality, abdominal phantom.

Methods:

In the phantom, eight lesions were punctured in two different angles (in- and out-of-plane) using CBCT. One C-arm CT scan was performed to plan the intervention and one for post-procedural evaluation. Thermoluminescent dosemeters (TLDs) were used for dose measurement at the level of the eye lens, umbilicus and ankles on a pole representing the IRs. All measurements were performed without any lead protection. In addition, the dose–area product (DAP) and air kerma at the skin entrance point was documented.

Results:

Mean radiation values of all TLDs were 190 µSv for CBCT (eye lens: 180 µS, umbilicus: 230 µSv, ankle: 150 µSv) without a significant difference (p > 0.005) between in- and out-of-plane biopsies. In terms of radiation exposure of the phantom, the mean DAP was not statistically significantly different (p > 0.05) for in- and out-of-plane biopsies. Fluoroscopy showed a mean DAP of 7 or 6 μGym², respectively. C-arm CT showed a mean DAP of 5150 or 5130 μGym², respectively.

Conclusion:

In our setting, the radiation dose to the IR was distinctly high using CBCT. For dose reduction, it is advisable to pay attention to lead shielding, to increase the distance to the X-ray source and to leave the intervention suite for C-arm CT scans.

Advances in knowledge:

The results indicate that using modern navigation tools and CBCT can be accompanied with a relative high radiation dose for the IRs since detector angulation can make the use of proper lead shielding difficult.     

A method for measuring three-dimensional mandibular kinematics in vivo using single-plane fluoroscopy

Objectives

Accurate measurement of the three-dimensional (3D) motion of the mandible in vivo is essential for relevant clinical applications. Existing techniques are either of limited accuracy or require the use of transoral devices that interfere with jaw movements. This study aimed to develop further an existing method for measuring 3D, in vivo mandibular kinematics using single-plane fluoroscopy; to determine the accuracy of the method; and to demonstrate its clinical applicability via measurements on a healthy subject during opening/closing and chewing movements.

Methods

The proposed method was based on the registration of single-plane fluoroscopy images and 3D low-radiation cone beam CT data. It was validated using roentgen single-plane photogrammetric analysis at static positions and during opening/closing and chewing movements.

Results

The method was found to have measurement errors of 0.1 ± 0.9 mm for all translations and 0.2° ± 0.6° for all rotations in static conditions, and of 1.0 ± 1.4 mm for all translations and 0.2° ± 0.7° for all rotations in dynamic conditions.

Conclusions

The proposed method is considered an accurate method for quantifying the 3D mandibular motion in vivo. Without relying on transoral devices, the method has advantages over existing methods, especially in the assessment of patients with missing or unstable teeth, making it useful for the research and clinical assessment of the temporomandibular joint and chewing function.     

Low-Dose Three-Dimensional Rotational Angiography for Evaluating Intracranial Aneurysms: Analysis of Image Quality and Radiation Dose

ObjectiveThis study aimed to evaluate the image quality and dose reduction of low-dose three-dimensional (3D) rotational angiography (RA) for evaluating intracranial aneurysms.Materials and MethodsWe retrospectively evaluated the clinical data and 3D RA datasets obtained from 146 prospectively registered patients (male:female, 46:100; median age, 58 years; range, 19–81 years). The subjective image quality of 79 examinations obtained from a conventional method and 67 examinations obtained from a low-dose (5-seconds and 0.10-µGy/frame) method was assessed by two neurointerventionists using a 3-point scale for four evaluation criteria. The total image quality score was then obtained as the average of the four scores. The image quality scores were compared between the two methods using a noninferiority statistical testing, with a margin of -0.2 (i.e., score of low-dose group – score of conventional group). For the evaluation of dose reduction, dose-area product (DAP) and air kerma (AK) were analyzed and compared between the two groups.ResultsThe mean total image quality score ± standard deviation of the 3D RA was 2.97 ± 0.17 by reader 1 and 2.95 ± 0.20 by reader 2 for conventional group and 2.92 ± 0.30 and 2.95 ± 0.22, respectively, for low-dose group. The image quality of the 3D RA in the low-dose group was not inferior to that of the conventional group according to the total image quality score as well as individual scores for the four criteria in both readers. The mean DAP and AK per rotation were 5.87 Gy-cm² and 0.56 Gy, respectively, in the conventional group, and 1.32 Gy-cm² (p < 0.001) and 0.17 Gy (p < 0.001), respectively, in the low-dose group.ConclusionLow-dose 3D RA was not inferior in image quality and reduced the radiation dose by 70%–77% compared to the conventional 3D RA in evaluating intracranial aneurysms.     

Development of a low-dose protocol for cone beam CT examinations of the anterior maxilla in children

Objective:

The aim of this study was to develop a low-dose protocol suitable for cone beam CT (CBCT) examination of an impacted maxillary canine in children by using a combination of dosimetry with subjective and objective image quality assessment.

Methods:

Radiation dose and image quality measurements were made using a dental CBCT machine. An image quality phantom was used to investigate the relationship between objective image quality and dose–area product (DAP) for a broad range of exposure settings. Subjective image quality assessment was achieved using a paediatric skull phantom submerged in a water bath for the same range of exposure settings. Eight clinicians assessed each CBCT data set for nine aspects of image quality using a five-point rating scale of agreement.

Results:

Acceptable image quality, defined using subjective judgements by the clinicians of the skull phantom images, was achievable with DAP values of 127 mGy cm² or greater and a polytetrafluoroethylene (PTFE) contrast-to-noise ratio (CNR) of 4.8 or greater. A cautious choice was made to recommend a low-dose protocol of 80 kV and 3 mA for implementation into clinical practice, corresponding to a DAP value of 146 mGy cm² and a PTFE CNR of 5.0.

Conclusion:

A low-dose protocol for this particular CBCT machine was established which represents as much as a 50% reduction compared with manufacturer''s recommendations.

Advances in knowledge:

To the authors'' best knowledge, this is the first study that addresses dose optimization in paediatric clinical protocols in dental CBCT. Furthermore, this study explores the relationship between radiation dose, objective and subjective image quality.     

Evaluation of the effective dose of cone beam CT and multislice CT for temporomandibular joint examinations at optimized exposure levels

Objectives:

To compare the effective dose to patients from temporomandibular joint examinations using a dental CBCT device and a multislice CT (MSCT) device, both before and after dose optimization.

Methods:

A Promax^® 3D (Planmeca, Helsinki, Finland) dental CBCT and a LightSpeed VCT^® (GE Healthcare, Little Chalfont, UK) multislice CT were used. Organ doses and effective doses were estimated from thermoluminescent dosemeters at 61 positions inside an anthropomorphic phantom at the exposure settings in clinical use. Optimized exposure protocols were obtained through an optimization study using a dry skull phantom, where four observers rated image quality taken at different exposure levels. The optimal exposure level was obtained when all included criteria were rated as acceptable or better by all observers.

Results:

The effective dose from a bilateral examination was 184 µSv for Promax 3D and 113 µSv for LightSpeed VCT before optimization. Post optimization, the bilateral effective dose was 92 µSv for Promax 3D and 124 µSv for LightSpeed VCT.

Conclusions:

At optimized exposure levels, the effective dose from CBCT was comparable to MSCT.     

3′-Deoxy-3′-[18F]fluorothymidine and O-(2-[18F]fluoroethyl)-L-tyrosine PET in Patients with Suspicious Recurrence of Glioma after Multimodal Treatment: Initial Results of a Retrospective Comparative Study

Purpose

The purpose of this study was to compare the uptakes and diagnostic accuracies between 3′-deoxy-3′-[¹⁸F]fluorothymidine (FLT) and O-(2-[¹⁸F]fluoroethyl)-L-tyrosine (FET) PET in patients with a clinical suspicion of having a recurrence of glioma after multimodality treatment.

Methods

Thirty-two patients who underwent FLT and FET PET due to abnormal enhancement on magnetic resonance (MR) images were included. According to surgical confirmation or follow-up results, patients were divided into those with therapy-related benign changes (TRBCs) and those with recurrence. Recurrences were divided again into initial low-grade glioma (LGG) and high-grade glioma (HGG). The uptakes of FLT and FET were compared with the maximum standardized uptake value (SUVmax) and lesion-to-normal ratio (LNR). The diagnostic accuracies were compared via a receiver-operating-characteristic (ROC) curve analysis.

Results

The LNRs of FLT in recurrences with initial HGG (8.26 ± 5.02) were significantly higher than those in recurrences with initial LGG (3.43 ± 2.14) and TRBC (1.81 ± 0.60). The LNRs of FET in recurrence with initial HGG (2.70 ± 0.48) and LGG (3.03 ± 1.32) were significantly higher than those in the TRBC (1.60 ± 0.47). The areas under the ROC curve (AUCs) of FLT and FET for initial LGG were 0.768 and 0.893, respectively. The AUCs of FLT and FET for initial HGG were 1.000 and 0.964. However, there were no statistical significances. The results for comparing with SUVmax were the same as those with LNR.

Conclusions

Uptakes of FLT were different according to initial grade in patients with recurrent glioma, but those of FET were not. However, there were no statistical significances in the diagnostic accuracies according to initial grade between the two tracers in this study.     

Is Diffusion-Weighted MRI Useful for Differentiation of Small Non-Necrotic Cervical Lymph Nodes in Patients with Head and Neck Malignancies?

Objective

To evaluate the usefulness of measuring the apparent diffusion coefficient (ADC) in diffusion-weighted magnetic resonance imaging to distinguish benign from small, non-necrotic metastatic cervical lymph nodes in patients with head and neck cancers.

Materials and Methods

Twenty-six consecutive patients with head and neck cancer underwent diffusion-weighted imaging (b value, 0 and 800 s/mm²) preoperatively between January 2009 and December 2010. Two readers independently measured the ADC values of each cervical lymph node with a minimum-axial diameter of ≥ 5 mm but < 11 mm using manually drawn regions of interest. Necrotic lymph nodes were excluded. Mean ADC values were compared between benign and metastatic lymph nodes after correlating the pathology.

Results

A total of 116 lymph nodes (91 benign and 25 metastatic) from 25 patients were included. Metastatic lymph nodes (mean ± standard deviation [SD], 7.4 ± 1.6 mm) were larger than benign lymph nodes (mean ± SD, 6.6 ± 1.4 mm) (p = 0.018). Mean ADC values for reader 1 were 1.17 ± 0.31 × 10^-3 mm²/s for benign and 1.25 ± 0.76 × 10^-3 mm²/s for metastatic lymph nodes. Mean ADC values for reader 2 were 1.21 ± 0.46 × 10^-3 mm²/s for benign and 1.14 ± 0.34 × 10^-3 mm²/s for metastatic lymph nodes. Mean ADC values between benign and metastatic lymph nodes were not significantly different (p = 0.594 for reader 1, 0.463 for reader 2).

Conclusion

Measuring mean ADC does not allow differentiating benign from metastatic cervical lymph nodes in patients with head and neck cancer and non-necrotic, small lymph nodes.     

Transthoracic needle biopsy using a C-arm cone-beam CT system: diagnostic accuracy and safety

Objective

The purpose of this study was to evaluate the diagnostic accuracy and safety of performing transthoracic needle biopsy (TNB) under combined fluoroscopy and CT guidance using a C-arm cone-beam CT (CBCT) system.

Methods

We evaluated the diagnostic accuracy and safety of performing TNB using a C-arm CBCT system. We retrospectively evaluated 99 TNB cases performed in 98 patients using a C-arm CBCT system with an 18-gauge automated cutting needle. We reviewed the diagnostic accuracy according to the size and depth of the lesion, incidence of complications, additional treatment for complications, procedure time, number of needle passes per biopsy and radiation dose.

Results

The final diagnoses revealed 72 malignant and 27 benign lesions. The overall malignancy sensitivity, malignancy specificity and diagnostic accuracy were 95.8%, 100% and 97.0%, respectively, and those for small pulmonary nodules <20 mm in size were 94.1%, 100% and 96.6%, respectively. There was no significant difference in the correct diagnosis of malignancy according to lesion size (p=0.634) or depth (p=0.542). For benign lesions, a specific diagnosis was obtained in 14 cases (51.9%). TNB induced complications in 19 out of 99 procedures (19.2%), including pneumothorax (16.2%), immediate haemoptysis (2.0%) and subcutaneous emphysema (1.0%). Among these, four patients with pneumothorax required chest tube insertion (2.0%) or pig-tail catheter drainage (2.0%). The mean procedure time, number of needle passes and radiation doses were 11.9±4.0 min, 1.2±0.5 times and 170.0±67.2 mGy, respectively.

Conclusion

TNB using a C-arm CBCT system provides high diagnostic accuracy with a low complication rate and a short procedure time, particularly for small pulmonary nodules.Transthoracic needle biopsy (TNB) under image guidance is a well-known procedure for evaluating thoracic mass lesions, with a high diagnostic accuracy and a relatively low complication rate [1-5]. TNB can be performed under various types of image guidance, including fluoroscopy, CT and ultrasonography. The decision regarding which technique to use usually depends on the characteristics of the pulmonary lesions, such as size, location, the radiologist''s preference and the accessibility of imaging systems.Currently, CT or CT fluoroscopy is the most preferred method of image guidance for TNB. CT fluoroscopy provides real-time guidance of the biopsy needle in addition to the advantages of CT guidance, decreasing the procedure time and number of needle passes compared with CT-guided procedures [1]. However, significant radiation exposure to the operator''s hands is one limitation of this procedure.The C-arm cone-beam CT (CBCT) system is a form of flat-panel volume CT in which a cone-beam X-ray tube and a flat-panel detector are integrated within a C-arm gantry. This provides both CT and real-time fluoroscopic guidance for TNB [6].The purpose of this study was to evaluate the diagnostic accuracy and safety of performing TNB under combined fluoroscopy and CT guidance using a C-arm CBCT system.     

The Clinical Usefulness of 99mTc HMPAO Leukocyte/99mTc Phytate Bone Marrow Scintigraphy for Diagnosis of Prosthetic Knee Infection: A Preliminary Study

Purpose

The preferred radionuclide imaging procedure for diagnosing prosthetic joint infection is combined radiolabeled leukocyte/^99mTc sulfur colloid bone marrow scintigraphy, which has an accuracy of over 90 %. Unfortunately, sulfur colloid is no longer available in South Korea. In this study, we evaluated the usefulness of ^99mTc phytate, a substitute for ^99mTc sulfur colloid, when combined with radiolabeled leukocyte scintigraphy in suspected prosthetic knee infections.

Methods

Eleven patients (nine women, two men; mean age 72 ± 6 years) with painful knee prostheses and a suspicion of infection underwent both ^99mTc HMPAO leukocyte scintigraphy (LS) and ^99mTc phytate bone marrow scintigraphy (BMS). The combined images were interpreted as positive for infection when radioactivity in the LS at the site of clinical interest clearly exceeded that of the BMS (discordant); they were interpreted as negative when the increased activity in the LS was consistent with an increased activity in the BMS (concordant). The final diagnosis was made with microbiological or intraoperative findings and a clinical follow-up of at least 12 months.

Results

Five of eleven patients were diagnosed as having an infected prosthesis. The overall sensitivity, specificity, positive predictive value (PPV), negative predictive value (NPV), and diagnostic accuracy of the combined LS/BMS were 100 %, 83 %, 83 %, 100 % and 91 %, respectively.

Conclusion

We find that combined ^99mTc HMPAO LS/^99mTc phytate BMS shows comparable diagnostic performance to other studies utilizing sulfur colloid. Combined ^99mTc HMPAO LS/^99mTc phytate BMS is therefore expected to be an acceptable alternative to combined radiolabeled LS/^99mTc sulfur colloid BMS for diagnosing prosthetic knee infections.     

Effective dose span of ten different cone beam CT devices

Objectives:

Evaluation and reduction of dose are important issues. Since cone beam CT (CBCT) has been established now not just in dentistry, the number of acquired examinations continues to rise. Unfortunately, it is very difficult to compare the doses of available devices on the market owing to different exposition parameters, volumes and geometries. The aim of this study was to evaluate the spans of effective doses (EDs) of ten different CBCT devices.

Methods:

48 thermoluminescent dosemeters were placed in 24 sites in a RANDO^® head phantom. Protocols with lowest exposition parameters and protocols with highest exposition parameters were performed for each of the ten devices. The ED was calculated from the measured energy doses according to the International Commission on Radiological Protection 2007 recommendations for each protocol and device, and the statistical values were evaluated afterwards.

Results:

The calculation of the ED resulted in values between 17.2 µSv and 396 µSv for the ten devices. The mean values for protocols with lowest and highest exposition parameters were 31.6 µSv and 209 µSv, respectively.

Conclusions:

It was not the aim of this study to evaluate the image quality depending on different exposition parameters but to define the spans of EDs in which different CBCT devices work. There is a wide span of ED for different CBCT devices depending on the selected exposition parameters, required spatial resolution and many other factors.     

Preparation and Evaluation of 68Ga-ECC as a PET Renal Imaging Agent

Purpose

Development of a gallium-68-labeled renal tracer can be a good substitute for Tc-99m, a known SPECT tracer. In this study, effort was made to develop ⁶⁸Ga-ethylenecysteamine cysteine (⁶⁸Ga-ECC).

Methods

Ga-ECC was prepared using generator-based ⁶⁸GaCl₃ and ethylenecysteamine cysteine (ECC) at optimized conditions. Stability of the complex was checked in human serum followed by partition coefficient determination of the tracer. The biodistribution of the tracer in rats was studied using tissue counting and PET/CT imaging up to 120 min.

Results

Ga-ECC was prepared at optimized conditions in 15 min at 90 °C (radiochemical purity ≈97 ± 0.88 % ITLC, >99 % HPLC, specific activity: 210 ± 5 GBq/mM). ⁶⁸Ga-ECC was a water-soluble complex based on partition coefficient data (log P; −1.378) and was stable in the presence of human serum for 2 h at 37 °C. The biodistribution of the tracer demonstrated high kidney excretion of the tracer in 10–20 min. The SUV_max ratios of the liver to left kidney were 0.38 and 0.39 for 30 and 90 min, respectively, indicating high kidney uptake.

Conclusion

Initial biodistribution results showed significant kidney and urinary excretion of the tracer comparable to that of the homologous ^99mTc compound. The complex could be a possible PET kidney imaging agent with a fast imaging time.     

Diagnostic Performance of Three-Phase Bone Scan for Complex Regional Pain Syndrome Type 1 with Optimally Modified Image Criteria

Purpose

Although the three-phase bone scan (TBPS) is one of the widely used imaging studies for diagnosing complex regional pain syndrome type I (CRPS-1), there is some controversy regarding the TPBS image criteria for CRPS-1. In this study, we modified the image criteria using image pattern and quantitative analysis in the patients diagnosed using the most recent consensus clinical diagnostic criteria.

Materials and Methods

The study included 140 patients with suspected CRPS-1 (CRPS-1, n = 79; non-CRPS, n = 61; mean age 39 ± 15 years) who underwent TPBS. The clinical diagnostic criteria for CRPS-1 revised by the Budapest consensus group were used for confirmative diagnosis. Patients were classified according to flow/pool and delayed uptake (DU) image patterns, and the time interval between the initiating event and TPBS (TI_event-scan). Quantitative analysis for lesion-to-contralateral ratio (LCR) was performed. Modified TPBS image criteria were created and evaluated for optimal diagnostic performance.

Results

Both increased and decreased periarticular DU were significant image findings for CRPS-1 (CRPS-1 positive-rate = 73% in the increased DU group, 75% in the decreased DU group). The TI_event-scan did not differ significantly between the different image pattern groups. Quantitative analysis revealed an LCR of 1.43 was the optimal cutoff value for CRPS-1 and diagnostic performance was significantly improved in the increased DU group (area under the curve = 0.732). Given the modified image criteria, the sensitivity and specificity of TPBS for diagnosing CRPS-1 were 80% and 72%, respectively.

Conclusions

Optimally modified TPBS image criteria for CRPS-1 were suggested using image pattern and quantitative analysis. With the criteria, TPBS is an effective imaging study for CRPS-1 even with the most recent consensus clinical diagnostic criteria.     

Interpretation of Digital Chest Radiographs: Comparison of Light Emitting Diode versus Cold Cathode Fluorescent Lamp Backlit Monitors

Objective

To compare the diagnostic performance of light emitting diode (LED) backlight monitors and cold cathode fluorescent lamp (CCFL) monitors for the interpretation of digital chest radiographs.

Materials and Methods

We selected 130 chest radiographs from health screening patients. The soft copy image data were randomly sorted and displayed on a 3.5 M LED (2560 × 1440 pixels) monitor and a 3 M CCFL (2048 × 1536 pixels) monitor. Eight radiologists rated their confidence in detecting nodules and abnormal interstitial lung markings (ILD). Low dose chest CT images were used as a reference standard. The performance of the monitor systems was assessed by analyzing 2080 observations and comparing them by multi-reader, multi-case receiver operating characteristic analysis. The observers reported visual fatigue and a sense of heat. Radiant heat and brightness of the monitors were measured.

Results

Measured brightness was 291 cd/m² for the LED and 354 cd/m² for the CCFL monitor. Area under curves for nodule detection were 0.721 ± 0.072 and 0.764 ± 0.098 for LED and CCFL (p = 0.173), whereas those for ILD were 0.871 ± 0.073 and 0.844 ± 0.068 (p = 0.145), respectively. There were no significant differences in interpretation time (p = 0.446) or fatigue score (p = 0.102) between the two monitors. Sense of heat was lower for the LED monitor (p = 0.024). The temperature elevation was 6.7℃ for LED and 12.4℃ for the CCFL monitor.

Conclusion

Although the LED monitor had lower maximum brightness compared with the CCFL monitor, soft copy reading of the digital chest radiographs on LED and CCFL showed no difference in terms of diagnostic performance. In addition, LED emitted less heat.     

Evaluation of current clinical target volume definitions for glioblastoma using cell-based dosimetry stochastic methods

Objective:

Determination of an optimal clinical target volume (CTV) is complex and remains uncertain. The aim of this study was to develop a glioblastoma multiforme (GBM) model to be used for evaluation of current CTV practices for external radiotherapy.

Methods:

The GBM model was structured as follows: (1) a Geant4 cellular model was developed to calculate the absorbed dose in individual cells represented by cubic voxels of 20 μm sides. The system was irradiated with opposing 6 MV X-ray beams. The beams encompassed planning target volumes corresponding to 2.0- and 2.5-cm CTV margins; (2) microscopic extension probability (MEP) models were developed using MATLAB^® 2012a (MathWorks^®, Natick, MA), based on clinical studies reporting on GBM clonogenic spread; (3) the cellular dose distribution was convolved with the MEP models to evaluate cellular survival fractions (SFs) for both CTV margins.

Results:

A CTV margin of 2.5 cm, compared to a 2.0-cm CTV margin, resulted in a reduced total SF from 12.9% ± 0.9% to 3.6% ± 0.2%, 5.5% ± 0.4% to 1.2% ± 0.1% and 11.1% ± 0.7% to 3.0% ± 0.2% for circular, elliptical and irregular MEP distributions, respectively.

Conclusion:

A Monte Carlo model was developed to quantitatively evaluate the impact of GBM CTV margins on total and penumbral SF. The results suggest that the reduction in total SF ranges from 3.5 to 5, when the CTV is extended by 0.5 cm.

Advances in knowledge:

The model provides a quantitative tool for evaluation of different CTV margins in terms of cell kill efficacy. Cellular platform of the tool allows future incorporation of cellular properties of GBM.     

Radiosynthesis of 99mTc(CO)3-Clinafloxacin Dithiocarbamate and Its Biological Evaluation as a Potential Staphylococcus aureus Infection Radiotracer

Background

Clinafloxacin dithiocarbamate (CNND) was radiolabeled with technetium-99m (^99mTc) using [^99mTc(CO)₃(H₂O)₃]⁺ and assessed for its radiochemical stability in saline and serum, its in vitro binding with methicillin-resistant Staphylococcus aureus (MRSA) and biodistribution in female nude mice (FNM) artificially infected with live and heat-killed MRSA.

Methods

In normal saline (NS) the ^99mTc(CO)₃-clinafloxacin dithiocarbamate (^99mTc(CO)₃-CNND) showed radiochemical stability with a maximum value of 99.10 ± 0.20% and remained stable up to 4 h (92.65 ± 0.18%).

Results

In human serum at 37°C within 16 h of incubation, 14.85% side products as a result of de-tagging developed. Incubation with MRSA gave saturated binding with a maximum value of 72.75 ± 1.20%. Almost six-fold higher uptake was seen in the infected muscle of the FNM as compared to the inflamed and normal muscle. The ^99mTc(CO)₃-CNND complex showed a normal route of excretion from the body of the FNM model.

Conclusion

The higher stability in NS, HS, saturated in vitro binding with a live strain of MRSA and six-fold higher uptake in the target organ showed the ^99mTc(CO)₃-CNND complex to be a potential MRSA infection radiotracer.     

Gemstone spectral imaging reduced artefacts from metal coils or clips after treatment of cerebral aneurysms: a retrospective study of 35 patients

Objective:

This study aimed to evaluate the effect of gemstone spectral imaging (GSI) for metal artefact reduction in cerebral artery CT angiography (CTA) after metal coils or clips treatment.

Methods:

35 patients with cerebral aneurysms were treated with metal coils or clips and underwent CTA using gemstone spectral CT between February and December 2013. The data were reconstructed into three image groups including Group A (quality check images with 140 kVp), Group B (monochromatic image sets in the range of 40–140 keV) and Group C [monochromatic image sets with metal artefacts reduction software (MARS GE Medical Systems, Waukesha, WI)]. CT attenuation value of cerebral artery, contrast-to-noise ratio (CNR), signal-to-noise ratio (SNR) and the subjective score of all images were measured and compared statistically.

Results:

CT attenuation value of cerebral artery decreased in Groups B and C as the photon energy increased. The average energy levels of 60.05 ± 5.37 and 59.93 ± 5.57 keV presented the best CNR in Groups B and C, respectively. CNR values, SNR values and the subjective scores of the image quality of the two sets were higher than those of Group A.

Conclusion:

GSI reduced metal artefact and improved the image quality of CTA after metal coils or clips treatment in patients with cerebral aneurysm. The monochromatic images at the average energy level of 60.05 ± 5.37 keV with MARS and 59.93 ± 5.57 keV without MARS were suggested to be the optimal parameters.

Advances in knowledge:

GSI could reduce metal artefact after metal coils or clips treatment in patients with cerebral aneurysm.     

Monopolar Radiofrequency Ablation Using a Dual-Switching System and a Separable Clustered Electrode: Evaluation of the In Vivo Efficiency

Objective

To determine the in vivo efficiency of monopolar radiofrequency ablation (RFA) using a dual-switching (DS) system and a separable clustered (SC) electrode to create coagulation in swine liver.

Materials and Methods

Thirty-three ablation zones were created in nine pigs using a DS system and an SC electrode in the switching monopolar mode. The pigs were divided into two groups for two experiments: 1) preliminary experiments (n = 3) to identify the optimal inter-electrode distances (IEDs) for dual-switching monopolar (DSM)-RFA, and 2) main experiments (n = 6) to compare the in vivo efficiency of DSM-RFA with that of a single-switching monopolar (SSM)-RFA. RF energy was alternatively applied to one of the three electrodes (SSM-RFA) or concurrently applied to a pair of electrodes (DSM-RFA) for 12 minutes in in vivo porcine livers. The delivered RFA energy and the shapes and dimensions of the coagulation areas were compared between the two groups.

Results

No pig died during RFA. The ideal IEDs for creating round or oval coagulation area using the DSM-RFA were 2.0 and 2.5 cm. DSM-RFA allowed more efficient RF energy delivery than SSM-RFA at the given time (23.0 ± 4.0 kcal vs. 16.92 ± 2.0 kcal, respectively; p = 0.0005). DSM-RFA created a significantly larger coagulation volume than SSM-RFA (40.4 ± 16.4 cm³ vs. 20.8 ± 10.7 cm³; p < 0.001). Both groups showed similar circularity of the ablation zones (p = 0.29).

Conclusion

Dual-switching monopolar-radiofrequency ablation using an SC electrode is feasible and can create larger ablation zones than SSM-RFA as it allows more RF energy delivery at a given time.     

Are pitch and roll compensations required in all pathologies? A data analysis of 2945 fractions

Objective:

New linear accelerators can be equipped with a 6D robotic couch, providing two additional rotational motion axes: pitch and roll. These shifts in kilo voltage–cone beam CT (kV-CBCT) image-guided radiotherapy (IGRT) were evaluated over the first 6 months of usage of a 6D robotic couch-top, ranking the treatment sites for which the two compensations are larger for patient set-up.

Methods:

The couch compensations of 2945 fractions for 376 consecutive patients treated on the PerfectPitch™ 6D couch (Varian^® Medical Systems, Palo Alto, CA) were analysed. Among these patients, 169 were treated for brain, 111 for lung, 54 for liver, 26 for pancreas and 16 for prostate tumours. During the set-up, patient anatomy from planning CT was aligned to kV-CBCT, and 6D movements were executed. Information related to pitch and roll were extracted by proper querying of the Microsoft^® SQL server (Microsoft Corporation, Redmond, WA) ARIA database (Varian Medical Systems). Mean values and standard deviations were calculated for all sites. Kolmogorov–Smirnov (KS) test was performed.

Results:

Considering all the data, mean pitch and roll adjustments were −0.10° ± 0.92° and 0.12° ± 0.96°, respectively; mean absolute values for both adjustments were 0.58° ± 0.69° and 0.69° ± 0.72°, respectively. Brain treatments showed the highest mean absolute values for pitch and roll rotations (0.73° ± 0.69° and 0.80° ± 0.78°, respectively); the lowest values of 0.36° ± 0.47° and 0.49° ± 0.58° were found for pancreas. KS test was significant for brain vs liver, pancreas and prostate. Collective corrections (pitch + roll) >0.5°, >1.0° and >2.0° were observed in, respectively, 79.8%, 61.0% and 29.1% for brain and 56.7%, 39.4% and 6.7% for pancreas.

Conclusion:

Adjustments in all six dimensions, including unconventional pitch and roll rotations, improve the patient set-up in all treatment sites. The greatest improvement was observed for patients with brain tumours.

Advances in knowledge:

To our knowledge, this is the first systematic evaluation of the clinical efficacy of a 6D Robotic couch-top in CBCT IGRT over different tumour regions.