Effect of radioprotective curtain length on the scattered dose rate distribution and endoscopist eye lens dose with an over-couch fluoroscopy system.

Sufficient dose reduction may not be achieved if radioprotective curtains are folded. This study aimed to evaluate the scattered dose rate distribution and physician eye lens dose at different curtain lengths. Using an over-couch fluoroscopy system, dH*(10)/dt was measured using a survey meter 150 cm from the floor at 29 positions in the examination room when the curtain lengths were 0% (no curtain), 50%, 75%, and 100%. The absorbed dose rates in the air at the positions of endoscopist and assistant were calculated using a Monte Carlo simulation by varying the curtain length from 0 to 100%. The air kerma was measured by 10 min fluoroscopy using optically stimulated luminescence dosimeters at the eye surfaces of the endoscopist phantom and the outside and inside of the radioprotective goggles. At curtain lengths of 50%, 75%, and 100%, the ratios of dH*(10)/dt relative to 0% ranged from 80.8 to 104.1%, 10.5 to 61.0%, and 11.8 to 24.8%, respectively. In the simulation, the absorbed dose rates at the endoscopist's and assistant's positions changed rapidly between 55 and 75% and 65% and 80% of the curtain length, respectively. At the 0%, 50%, 75%, and 100% curtain lengths, the air kerma at the left eye surface of the endoscopist phantom was 237 ± 29, 271 ± 30, 37.7 ± 7.5, and 33.5 ± 6.1 µGy, respectively. Therefore, a curtain length of 75% or greater is required to achieve a sufficient eye lens dose reduction effect at the position of the endoscopist.

Basic characteristics of Vision badge and its performance as an eye lens dosimeter for endoscopists.

Vision badge is an eye lens dosimeter to measureHp(3). This study aimed to evaluate the basic characteristics of the Vision badge and its performance as an eye lens dosimeter for endoscopists by phantom study. Energy dependence was evaluated by changing the tube voltage to 50 kV (effective energy of 27.9 keV), 80 kV (32.2 keV), and 120 kV (38.7 keV). Dose linearity was evaluated by changing the number of irradiation to 1, 5, and 40 times, which corresponded to 0.53, 5.32, and 21.4 mGy. Batch uniformity was evaluated by calculating the coefficient of variation ofHp(3) obtained from 10 Vision badges. Angular dependence was evaluated at 0° (perpendicular to the incident direction of x-rays), 30°, 60°, 75°, and 90°. The Vision badge and optically stimulated luminescence (OSL) dosimeter were attached to the inside of the radioprotective glasses, worn on the endoscopist phantom, and theHp(3) obtained from both dosimeters were compared. TheHp(3) obtained from the Vision badge with 38.7 keV was 3.8% higher than that with 27.9 keV. The Vision badge showed excellent linearity (R2= 1.00) with the air kerma up to 21.4 mGy. The coefficient of variation of theHp(3) for 10 Vision badges was 3.47%. The relative dose of the Vision badge decreased as the angle increased up to 75°, but increased at 90°. TheHp(3) obtained by the OSL dosimeter and the Vision badge were decreased as the endoscopist phantom was turned away from the patient phantom. TheHp(3) that was obtained by the Vision badge was 35.5%-55.0% less than that obtained by the nanoDot. In conclusion, the Vision badge showed specific angular dependence due to its shape, but satisfactory basic properties were exhibited for all characteristics. In phantom study, the Vision badge showed generally similar trends with the OSL dosimeter.

Half-value layer measurements using solid-state detectors and single-rotation technique with lead apertures in spiral computed tomography with and without a tin filter.

Solid-state detectors (SSDs) may be used along with a lead collimator for half-value layer (HVL) measurement using computed tomography (CT) with or without a tin filter. We aimed to compare HVL measurements obtained using three SSDs (AGMS-DM+ , X2 R/F sensor, and Black Piranha) with those obtained using the single-rotation technique with lead apertures (SRTLA). HVL measurements were performed using spiral CT at tube voltages of 70-140 kV without a tin filter and 100-140 kV (Sn 100-140 kV) with a tin filter in increments of 10 kV. For SRTLA, a 0.6-cc ionization chamber was suspended at the isocenter to measure the free-in-air kerma rate ( K ˙ air ) values. Five apertures were made on the gantry cover using lead sheets, and four aluminum plates were placed on these apertures. HVLs in SRTLA were obtained from K ˙ air decline curves. Subsequently, SSDs inserted into the lead collimator were placed on the gantry cover and used to measure HVLs. Maximum HVL differences of AGMS-DM+ , X2 R/F sensor, and Black Piranha with respect to SRTLA without/with a tin filter were - 0.09/0.6 (only two Sn 100-110 kV) mm, - 0.50/ - 0.6 mm, and - 0.17/(no data available) mm, respectively. These values were within the specification limit. SSDs inserted into the lead collimator could be used to measure HVL using spiral CT without a tin filter. HVLs could be measured with a tin filter using only the X2 R/F sensor, and further improvement of its calibration accuracy with respect to other SSDs is warranted.

Energy-based Hp(3) measurement using solid-state detector.

This study aimed to develop an energy-based Hp(3) measurement method using a solid-state detector (SSD). Incident and entrance surface air kerma were measured using an ionization chamber placed free-in-air and in front of an anthropomorphic or slab phantom. Subsequently, three SSDs were placed free-in-air, and half-value layer and readings were obtained. After measurements, an X-ray beam quality correction factor $\left ({{k}}_{{Q},{{Q}}_{\mathbf{0}}}^{{SSD}}\right)$, backscatter factor (BSF) and conversion factor from incident air kerma to Hp(3) (C3) were determined. Then, the incident air kerma by SSD $\left ({{K}}_{{a},{i}}^{{SSD}}\right )$, Hp(3) and Hp(3)/${{K}}_{{a},{i}}^{{SSD}}$ were calculated. The ${{k}}_{{Q},{{Q}}_{\mathbf{0}}}^{{SSD}}$ was almost consistent for all SSDs. The C3 and BSF were found to increase as tube potential increased. The Hp(3)/${{K}}_{{a},{i}}^{{SSD}}$ calculated with the anthropomorphic and slab phantoms were consistent within 2.1% and 2.6% for all SSDs, respectively. This method improves the energy dependence of Hp(3) measurement and can estimate the Hp(3) measurement error for dedicated Hp(3) dosemeters.

Reducing stray radiation with a novel detachable lead arm support in percutaneous coronary intervention.

BACKGROUND: Placing radioprotective devices near patients reduces stray radiation during percutaneous coronary intervention (PCI), a promising technique for treating coronary artery disease. Therefore, lead arm support may effectively reduce occupational radiation dose to cardiologists. PURPOSE: We aimed to estimate the reduction of stray radiation using a novel detachable lead arm support (DLAS) in PCI. MATERIALS AND METHODS: A dedicated cardiovascular angiography system was equipped with the conventional 0.5-mm lead curtain suspended from the table side rail. The DLAS was developed using an L-shaped acrylic board and detachable water-resistant covers encasing the 0.5-, 0.75-, or 1.0-mm lead. The DLAS was placed adjacent to a female anthropomorphic phantom lying on the examination tabletop at the patient entrance reference point. An ionization chamber survey meter was placed 100 cm away from the isocenter to emulate the cardiologist's position. Dose reduction using the L-shaped acrylic board, DLAS, lead curtain, and their combination each was measured at five heights (80-160 cm in 20-cm increments) when acquiring cardiac images of the patient phantom with 10 gantry angulations, typical for PCI. RESULTS: Median dose reductions of stray radiation using the L-shaped acrylic board were 9.0%, 8.8%, 12.4%, 12.3%, and 6.4% at 80-, 100-, 120-, 140-, and 160-cm heights, respectively. Dose reduction using DLAS with a 0.5-mm lead was almost identical to that using DLAS with 0.75- and 1.0-mm leads; mean dose reductions using these three DLASs increased to 16.2%, 45.1%, 66.0%, 64.2%, and 43.0%, respectively. Similarly, dose reductions using the conventional lead curtain were 95.9%, 95.5%, 83.7%, 26.0%, and 19.6%, respectively. The combination of DLAS with 0.5-mm lead and lead curtain could increase dose reductions to 96.0%, 95.8%, 93.8%, 71.1%, and 47.1%, respectively. CONCLUSIONS: DLAS reduces stray radiation at 120-, 140-, and 160-cm heights, where the conventional lead curtain provides insufficient protection.

Determination of geometric information and radiation field overlaps on the skin in percutaneous coronary interventions with computer-aided design-based X-ray beam modeling.

PURPOSE: This study aimed to develop a method for the determination of the source-to-surface distance (SSD), the X-ray beam area in a plane perpendicular to the beam axis at the entrance skin surface (Ap ), and the X-ray beam area on the actual skin surface (As ) during percutaneous coronary intervention (PCI). MATERIALS AND METHODS: Male and female anthropomorphic phantoms were scanned on a computed tomography scanner, and the data were transferred to a commercially available computer-aided design (CAD) software. A cardiovascular angiography system with a 200 × 200 mm flat-panel detector with a field-of-view of 175 × 175 mm was modeled with the CAD software. Both phantoms were independently placed on 40 mm thick pads, and the examination tabletop at the patient entrance reference point. Upon panning, the heart center was aligned to the central beam axis. The SSD, Ap , and As were determined with the measurement tool and Boolean intersection operations at 10 gantry angulations. RESULTS: The means and standard deviations of the SSD, Ap , and As for the male and female phantoms were 573 ± 15 and 580 ± 15 mm, 8799 ± 1009 and 9661 ± 1152 mm2 , 10495 ± 602 and 11913 ± 600 mm2 , respectively. The number of As overlaps for the male and female phantoms were 15/45 and 21/45 view combinations, respectively. CONCLUSIONS: CAD-based X-ray beam modeling is useful for the determination of the SSD, Ap , and As . Furthermore, the knowledge of the As distribution helps to reduce the As overlap in PCI.

Effect of equalization filters on measurements with kerma-area product meter in a cardiovascular angiography system.

PURPOSE: This study aimed to evaluate the effect of equalization filters (EFs) on the kerma-area product ( K A P Q K M ) and incident air-kerma ( K a , i , Q K M ) using a kerma-area product (KAP) meter. In addition, potential underestimations of the K a , i , Q K M values by EFs were identified. MATERIALS AND METHODS: A portable flat-panel detector (FPD) was placed to measure the X-ray beam area (A) and EFs dimension at patient entrance reference point (PERP). Afterward, a 6-cm3 external ionization chamber was placed to measure incident air-kerma ( K a , i , Q e x t ) at PERP instead of the portable FPD. KAP reading and K a , i , Q e x t were simultaneously measured at several X-ray beam qualities with and without EFs. The X-ray beam quality correction factor by KAP meter ( k Q , Q 0 K M ) was calculated by A, K a , i , Q e x t and KAP reading to acquire the K A P Q K M and K a , i , Q K M . Upon completion of the measurements, K A P Q K M , K a , i , Q K M , and K a , i , Q e x t were plotted as functions of tube potential, spectral filter, and EFs dimension. Moreover, K a , i , Q K M / K a , i , Q e x t values were calculated to evaluate the K a , i , Q K M underestimation. RESULTS: The k Q , Q 0 K M values increased with an increase in the X-ray tube potential and spectral filter, and the maximum k Q , Q 0 K M was 1.18. K A P Q K M and K a , i , Q K M decreased as functions of EFs dimension, whereas K a , i , Q e x t was almost constant. K a , i , Q K M / K a , i , Q e x t decreased with an increase in EFs dimension but increased with an increase in tube potential and spectral filter, and the range was 0.55-1.01. CONCLUSIONS: K a , i , Q K M value was up to approximately two times lower than the K a , i , Q e x t values by EFs. When using the K a , i , Q K M value, the potential K a , i , Q K M underestimation with EFs should be considered.

Measurement of the half-value layer for CT systems in a single-rotation technique: Reduction of stray radiation with lead apertures.

PURPOSE: This study aimed to compare two methods of assessing the half-value layer (HVL) for computed tomography scanners in a single-rotation technique with and without lead apertures (SRTLA / SRT). METHODS: A 0.6 cc real-time ionization chamber was suspended freely in the air at the isocenter, and six sheets of lead (130 × 170 × 2 mm) were placed at the bottom of the gantry cover, forming five apertures each having a width of 16 mm (SRTLA geometry). Four aluminum plates (100 × 100 mm2; 2.0, 4.0, 6.0, and 8.0 mm thick) were placed on these apertures. Air-kerma rate profiles (K̇air) in the spiral mode were measured at tube potentials of 80, 100, 120, and 135 kVp, a tube current of 100 mA, a nominal beam width of 32.0 mm, and a rotation time of 1.5 s. Thereafter, all lead sheets were removed, and these same measurements were taken to investigate the errors of the HVLs (SRT geometry). HVLs using the SRTLA and SRT were compared with those obtained through a conventional localization technique. RESULTS: The HVLs measured in the SRTLA/SRT at 80, 100, 120, and 135 kVp were 3.37/3.50, 4.24/4.47, 5.22/5.44, and 5.90/6.17 mm, respectively. The differences between these values and those obtained through the conventional technique were 0.09/0.22, 0.02/0.25, 0.05/0.27, and -0.01/0.26 mm, respectively. CONCLUSIONS: The accuracies of the HVLs of the SRTLA were similar to those of the conventional technique. The lead apertures under the aluminum plates would help reduce the number of inaccurate HVL measurements.

[Measurement Accuracy of CT Beam Width with a Portable Flat-panel Detector].

PURPOSE: X-ray film or computed radiography (CR) system has been employed in clinical setting, and these devices are gradually replaced by portable flat-panel detector (FPD) systems. They may be employed to measure the beam width instead of the traditional CR system. In this study, we estimated the accuracy of beam width measured by the portable FPD system. METHOD: A CR cassette and FPD were placed at the isocenter, and the pixel values were measured in a single axial CT scanning at a tube potential of 80 kVp, tube currents of 10-40 mA (5 mA steps), and tube rotation time of 0.5 s. Then, the FPD was sandwiched between 0.5 mm copper plate and 2 mm lead plate to avoid the pixel saturation and artifact from the FPD electronic substrates. The beam widths were measured at selected nominal beam widths (40, 80, 120 and 160 mm) using a double exposure technique (tube currents of 10 and 20 mA). RESULT: Log-linear relationships for two systems were obtained between the pixel value and radiation exposure for parameters less than or equal to 12.5 mAs. A test for the equivalence with confidence intervals showed that the measurement accuracy of the CR and FPD systems was equivalent. CONCLUSION: The portable FPD system could be utilized for the measurement of the CT beam width as well as CR system.

Estimation of primary radiation output for wide-beam computed tomography scanner.

PURPOSE: To estimate in-air primary radiation output in a wide-beam multidetector computed tomography (CT) scanner. MATERIALS AND METHODS: A 6-cc ionization chamber was placed free-in-air at the isocenter, and two sheets of lead (1-mm thickness) were placed on the bottom of the gantry cover, forming apertures of 40-80 mm in increments of 8 mm. The air-kerma rate profiles were measured with and without the apertures ( K ˙ w - A , K ˙ w / o - A ) for 4.8 s at tube potentials of 80, 100, 120, and 135 kVp, tube current of 50 mA, and rotation time of 0.4 s. The nominal beam width was varied from 40 to 160 mm in increments of 40 mm. Upon completion of data acquisition, the K ˙ w / o - A were plotted as a function of the measured beam width, and the extrapolated dose rates ( K ˙ 0 - w / o - A ) at zero beam width were calculated by second-order least-squares estimation. Similarly, the K ˙ w - A were plotted as a function of the radiation field (measured beam width × aperture size at the isocenter), and the extrapolated dose rates ( K ˙ 0 - w - A ) were compared with the K ˙ 0 - w / o - A . RESULTS: The means and standard errors of the K ˙ w / o - A with 40-, 80-, 120-, and 160-mm nominal beam widths at 120 kVp were 10.94 ± 0.01, 11.13 ± 0.01, 11.22 ± 0.01, and 11.31 ± 0.01 mGy/s, respectively, and the K ˙ 0 - w / o - A was reduced to 10.67 ± 0.02 mGy/s. The K ˙ 0 - w - A of 40-, 80-, 120-, and 160-mm beam widths were reduced to 10.6 ± 0.1, 10.6 ± 0.2, 10.5 ± 0.1, and 10.6 ± 0.1 mGy/s and were not significantly different from the K ˙ 0 - w / o - A . CONCLUSIONS: A method for describing the in-air primary radiation output in a wide-beam CT scanner was proposed that provides a means to characterize the scatter-to-primary ratio of the CT scanner.

[Evaluation of Radiation Dose and Image Quality for Angiographic System with Spectral Shaping Filter].

Complex procedures for interventional radiology can result in high radiation doses to patients and physicians. A spectral shaping filter (SSF) has recently been developed and equipped with angiographic systems to modulate the X-ray beam spectrum. In our feasibility study, the radiation doses to patients and physicians, air kerma rate at image receptor, and image quality were evaluated when SSF was applied in fluoroscopy. Polymethyl methacrylate (PMMA) phantom, a catheter attached on the bottom was placed on the examination table. The entrance air kerma rate at patient entrance reference point, H* (10) rate at a distance of 100 cm from the center of PMMA, air kerma rate at image receptor and the fluoroscopic catheter images were recorded as a function of PMMA thickness. Contrast-to-noise ratio (CNR) was used for the objective image quality. As a subjective image quality evaluation, three physicians (cardiologist, neurologist, and radiologist) rated the catheter images by a Likert scale. With SSF, the entrance air kerma rate and H* (10) rate reduced by about 34 and 21%, respectively. The air kerma rate at image receptor in conventional filter mode increased when the PMMA was up to 10 cm and then CNR was also improved. However, no significant differences were found in the subjective image qualities. In conclusion, SSF was contributed to the reduction of the radiation doses to patients and physicians while the subjective image quality was not affected.

[Introduction and Applications of 3D Printing in Radiological Technology].

A 3D printing emerges as a common procedure in clinical radiology practice after installation of a module that converts the digital imaging and communications in medicine (DICOM) dataset into stereolithography (STL) data on medical workstations. However, they did not conventionally provide the appropriate filtering, sculpting, hollowing out, and Boolean (subtraction) operations on STL data. These functions are indispensable to handle the STL data to fabricate the smooth, low-cost, and sophisticated models. Here are some tips for handling the 3D data with three software packages through making a sample lumbar spine model. Because they are all free- and open-source software with the exception of Boolean operations, they could make it easy for anyone to fabricate their 3D model imaged by CT or MRI. We tested the loop subdivision surface algorithms for the smoothing, the sculpting function for removing a sharp prick, and the hollowing function to save the cost. Computer-aided design (CAD) is also used to fabricate the devices in medical research. We designed and developed a cap attached to a glass dosimeter to show the effectiveness of CAD in radiological research. Lastly, we discuss the important matters for 3D printing and examples of the clinical applications.

Does gantry rotation time influence accuracy of volume computed tomography dose index (CTDIvol) in modern CT?

PURPOSE: The purpose of this study was to develop a gantry overrun corrected CTDIvol (cCTDIvol) dosimetry and evaluate the differences between the displayed CTDIvol (dCTDIvol), measured CTDIvol (mCTDIvol), and the cCTDIvol. METHODS AND MATERIALS: The each 8 rotation times between 275 and 1000ms of two CT scanners were investigated. Rotation time (Trot) and the beam-on time (Tbeam) in axial scanning were measured accurately to determine the gantry overrun time (Tover) as Tbeam-Trot. Subsequently, mCTDIvol was measured by using a 100mm ionization chamber and CTDI phantoms. Furthermore, we introduced a gantry overrun correction factor (Co=Trot/Tbeam) to obtain cCTDIvol. Upon completion of the data acquisition, the dCTDIvol and mCTDIvol were compared with the cCTDIvol. RESULTS: The discrepancies of Trot were 0.2±0.2ms as compared to the preset rotation times, and Tover was machine-specific and almost constant (22.4±0.5ms or 45.1±0.3ms) irrespective of the preset rotation time. Both dCTDIvol and mCTDIvol were increasingly overestimated compared to cCTDIvol as the faster the preset rotation time was selected (1.7-23.5%). CONCLUSION: The rotation time influences the accuracy of CTDIvol in modern CT, and should be taken into consideration when assessing the radiation output in modern CT.