A Monte Carlo study comparing dead-time losses of a gamma camera between tungsten functional paper and lead sheet for dosimetry in targeted radionuclide therapy with Lu-177.

OBJECTIVE: Dead-time loss is reported to be non-negligible for some patients with a high tumor burden in Lu-177 radionuclide therapy, even if the administered activity is 7.4 GBq. Hence, we proposed a simple method to shorten the apparent dead time and reduce dead-time loss using a thin lead sheet in previous work. The collimator surface of the gamma camera was covered with a lead sheet in our proposed method. While allowing the detection of 208-keV gamma photons of Lu-177 that penetrate the sheet, photons with energies lower than 208 keV, which cause dead-time loss, were shielded. In this study, we evaluated the usefulness of tungsten functional paper (TFP) for the proposed method using Monte Carlo simulation. METHODS: The count rates in imaging of Lu-177 administered to patients were simulated with the International Commission on Radiological Protection (ICRP) 110 phantom using the GATE Monte Carlo simulation toolkit. The simulated gamma cameras with a 0.5-mm lead sheet, 1.2-mm TFP, or no filter were positioned closely on the anterior and posterior sides of the phantom. The apparent dead times and dead-time losses at 24 h after administration were calculated for an energy window of 208 keV ± 10%. Moreover, the dead-time losses at 24-120 h were analytically assessed using activity excretion data of Lu-177-DOTATATE. RESULTS: The dead-time loss without a filter was 5% even 120 h after administration in patients with a high tumor burden and slow excretion, while those with a lead sheet and TFP were 0.22 and 0.58 times less than those with no filter, respectively. The count rates with the TFP were 1.3 times higher than those with the lead sheet, and the TFP could maintain primary count rates at 91-94% of those without a filter. CONCLUSIONS: Although the apparent dead time and dead-time loss with the lead sheet were shorter and less than those with TFP, those with TFP were superior to those without a filter. The advantage of TFP over the lead sheet is that the decrease in primary count rates was less.

Outcome of immune checkpoint inhibitor treatment in non-small cell lung cancer patients with interstitial lung abnormalities: clinical utility of subcategorizing interstitial lung abnormalities.

Interstitial lung abnormalities (ILAs) are immune checkpoint inhibitor (ICI)-related pneumonitis (ICI-P) risk factors. However, the relationship between imaging patterns and immunotherapy outcomes, and treatment strategies remain unclear in patients with non-small cell lung cancer (NSCLC) and ILAs. We retrospectively evaluated patients with ILAs-complicated NSCLC who received ICI therapy. ILAs were subcategorized as non-subpleural, subpleural non-fibrotic, and subpleural fibrotic (SF) based on the 2020 position paper by the Fleischner Society. We investigated ICI-P incidence, ICI-P risk factors, lung cancer prognosis, and ILAs radiological progression. Of the 481 ICI-treated patients, 79 (16.4%) had ILAs (45 non-SF and 34 SF). The ICI-P cumulative incidence (hazard ratio, 4.57; 95% confidence interval [CI], 1.90-10.98; p = 0.001) and any grade and grade ≥ 3 ICI-P incidences were higher in patients with SF-ILAs than in those with non-SF-ILAs (all grades: 7/45 [15.6%)] vs. 18/34 [52.9%]; p < 0.001; grade ≥ 3: 1/45 [2.2%] vs. 10/34 [29.4%]; p = 0.001). According to multivariate analysis, SF-ILAs independently predicted ICI-P (odds ratio, 5.35; 95% CI 1.62-17.61; p = 0.006). Patients with SF-ILAs had shorter progression-free and overall survival and higher ICI-P-related respiratory failure death rates than those with non-SF-ILAs. Approximately 2.5 times more patients with SF-ILAs showed progression by the 2-year follow-up than those with non-SF-ILAs. SF-ILAs is an independent strong predictor of ICI-P development in patients with NSCLC, may increase ICI-P severity, worsen prognosis, and accelerate ILAs progression. ILAs subcategorization is an important treatment strategy for patients with lung cancer treated with ICIs.

Atractylodes lancea (Thunb.) DC. [Asteraceae] rhizome-derived exosome-like nanoparticles suppress lipopolysaccharide-induced inflammation in murine microglial cells.

Background: Exosome-like nanoparticles (ELNs) mediate interspecies intercellular communications and modulate gene expression. Hypothesis/Purpose: In this study, we isolated and purified ELNs from the dried rhizome of Atractylodes lancea (Thunb.) DC. [Asteraceae] (ALR-ELNs), a traditional natural medicine, and investigated their potential as neuroinflammatory therapeutic agents. Methods: ALR-ELN samples were isolated and purified using differential centrifugation, and their physical features and microRNA contents were analyzed through transmission electron microscopy and RNA sequencing, respectively. BV-2 microglial murine cells and primary mouse microglial cells were cultured in vitro, and their ability to uptake ALR-ELNs was explored using fluorescence microscopy. The capacity of ALR-ELNs to modulate the anti-inflammatory responses of these cells to lipopolysaccharide (LPS) exposure was assessed through mRNA and protein expression analyses. Results: Overall, BV-2 cells were found to internalize ALR-ELNs, which comprised three microRNAs (ath-miR166f, ath-miR162a-5p, and ath-miR162b-5p) that could have anti-inflammatory activity. Pretreatment of BV-2 cells with ALR-ELN prevented the pro-inflammatory effects of LPS stimulation by significantly reducing the levels of nitric oxide, interleukin-1ß, interleukin-6, and tumor necrosis factor-α. Notably, the mRNA levels of Il1b, Il6, iNos, ccl2, and cxcl10 in BV-2 cells, which increased upon LPS exposure, were significantly reduced following ALR-ELN treatment. Moreover, the mRNA levels of heme oxygenase 1, Irf7, ccl12, and Irg1 also increased significantly following ALR-ELN treatment. In addition, pretreatment of primary mouse microglial cells with ALR-ELN prevented the pro-inflammatory effects of LPS stimulation by significantly reducing the levels of nitric oxide. Conclusion: Our findings indicate that ALR-ELNs exhibit anti-inflammatory effects on murine microglial cells. Further validation may prove ALR-ELNs as a promising neuroinflammatory therapeutic agent.

Correlation between the thyroid computed tomography value and thyroid function in hyperthyroidism: a retrospective study.

OBJECTIVE: Radioiodine (I-131) therapy for hyperthyroidism is a well-established and safe treatment option. This study aimed to investigate the relationship between the computed tomography (CT) value and the function and volume of the thyroid gland by identifying the factors that induce changes in the CT value of patients with hyperthyroidism. METHODS: This retrospective study evaluated 38 patients with Graves' disease and 10 patients with Plummer disease. To obtain the mean CT value and volume of the thyroid gland, the entire thyroid gland was set as the region of interest. A test dose of 3.7 MBq I-131 was administered before initiating I-131 therapy, and the radioiodine uptake (RIU) rate was assessed after 3, 24, 96, and 168 h. An approximate curve was plotted based on the RIU values obtained, and the effective half-life (EHL) was calculated. The correlation between the mean CT value and the volume of the thyroid gland, 24-h RIU, EHL, and the free triiodothyronine (FT3), free thyroxine (FT4), thyroid-stimulating hormone (TSH), and TSH receptor antibody (TRAb) levels was evaluated. RESULTS: The CT value exhibited a significant positive correlation with EHL in patients with Graves' disease (r = 0.62, p < 0.0001) as well as patients with Plummer disease (r = 0.74, p < 0.05). However, it did not display any correlation with the remaining parameters. CONCLUSION: The CT value is significantly correlated with EHL, suggesting that it reflects thyroid function and is mainly related to the factors associated with iodine discharge.

Effective treatment of steroid-resistant immune checkpoint inhibitor pneumonitis with mycophenolate mofetil.

Insufficient evidence is available for treating steroid-resistant immune checkpoint inhibitor pneumonitis (CIP). Although guidelines recommend the use of immunosuppressants, the efficacy of mycophenolate mofetil (MMF) has not been sufficiently verified. We report two cases of steroid-resistant CIP treated with MMF. Both patients responded to initial treatment with prednisolone (PSL), but the CIP flared up repeatedly as the steroids were gradually tapered off. Upon receiving MMF in addition to PSL, their subjective symptoms improved, and the shadows gradually disappeared, allowing for a reduction in the steroid dose. Ultimately, no CIP recurrence was observed despite discontinuing PSL and MMF. Both cases were completely resolved by treatment with MMF. This indicates that MMF may be effective in treating steroid-resistant CIP. In the future, the effects and safety of MMF should be investigated in large-scale clinical trials targeting patients with steroid-resistant CIP.

A simple method to shorten the apparent dead time in the dosimetry of Lu-177 for targeted radionuclide therapy using a gamma camera.

BACKGROUND: The dead-time loss reportedly degrades the accuracy of dosimetry using a gamma camera for targeted radionuclide therapy with Lu-177; therefore, the dead-time loss needs to be corrected. However, the correction is challenging. In this study, we propose a novel and simple method to shorten the apparent dead time rather than correcting it through experiments and Monte Carlo simulations. METHODS: An energy window of 208 keV ± 10 % is generally used for the imaging of Lu-177. Lower-energy gamma photons and X-rays of Lu-177 do not contribute to image formation but lead to dead-time losses. In our proposed method, a thin lead sheet was used to shield gamma photons and X-rays with energies lower than 208 keV, while detecting 208 keV gamma photons that penetrated the thin sheet. We measured and simulated the energy spectra and count rate characteristics of a clinical gamma camera system using a cylindrical phantom filled with a Lu-177 solution. Lead sheets of 1.0- and 0.5-mm thicknesses were used as thin shields, and the dead-time losses in tumour imaging with consumed Lu-177 were simulated. RESULTS: The apparent dead times with lead sheets of 1.0- and 0.5-mm thicknesses and without a lead sheet were 1.7, 1.9, and 5.8 µs for an energy window of 208 keV ± 10 %, respectively. The dead-time losses could be reduced from 10 % to 1.3 % using the 1.0-mm thick lead sheet in the simulated imaging of tumour. CONCLUSION: Our method is promising in clinical situations and studies on Lu-177 dosimetry for tumours.

Posterior Papillary Muscle Suspension for Treating Systolic Anterior Motion in Hypertrophic Obstructive Cardiomyopathy.

Systolic anterior motion of the anterior mitral leaflet can persist after ventricular septal myectomy for obstructive hypertrophic cardiomyopathy, resulting in residual pressure gradients and mitral regurgitation. However, additional procedures for systolic anterior motion involving mitral valve leaflet suturing and resection may lead to future valve disease. Therefore, we adopted posterior papillary muscle suspension, a subvalvular procedure for functional mitral regurgitation, to treat systolic anterior motion without directly intervening in the mitral valve leaflets. Papillary muscle suspension toward the posterior mitral annulus moved the papillary muscles away from the interventricular septum and successfully eliminated the systolic anterior motion and midventricular pressure gradient. In terms of avoiding direct mitral interventions, this procedure is a viable option for systolic anterior motion, especially in cases of very mild mitral regurgitation.

Antipodoplanin antibody enhances the antitumor effects of CTLA-4 blockade against malignant mesothelioma by natural killer cells.

Combination immunotherapy with multiple immune checkpoint inhibitors (ICIs) has been approved for various types of malignancies, including malignant pleural mesothelioma (MPM). Podoplanin (PDPN), a transmembrane sialomucin-like glycoprotein, has been investigated as a diagnostic marker and therapeutic target for MPM. We previously generated and developed a PDPN-targeting Ab reagent with high Ab-dependent cellular cytotoxicity (ADCC) and complement-dependent cytotoxicity (CDC). However, the effects of anti-PDPN Abs on various tumor-infiltrating immune cells and their synergistic effects with ICIs have remained unclear. In the present study, we established a novel rat-mouse chimeric anti-mouse PDPN IgG2a mAb (PMab-1-mG2a ) and its core-fucose-deficient Ab (PMab-1-mG2a -f) to address these limitations. We identified the ADCC and CDC activity of PMab-1-mG2a -f against the PDPN-expressing mesothelioma cell line AB1-HA. The antitumor effect of monotherapy with PMab-1-mG2a -f was not sufficient to overcome tumor progression in AB1-HA-bearing immunocompetent mice. However, PMab-1-mG2a -f enhanced the antitumor effects of CTLA-4 blockade. Combination therapy with anti-PDPN Ab and anti-CTLA-4 Ab increased tumor-infiltrating natural killer (NK) cells. The depletion of NK cells inhibited the synergistic effects of PMab-1-mG2a -f and CTLA-4 blockade in vivo. These findings indicated the essential role of NK cells in novel combination immunotherapy targeting PDPN and shed light on the therapeutic strategy in advanced MPM.

Fenofibrate attenuates the cytotoxic effect of cisplatin on lung cancer cells by enhancing the antioxidant defense system in vitro.

Fenofibrate (FF) is a peroxisome proliferator- activated receptor (PPAR)-α agonist that is widely used for the treatment of hyperlipidemia. It has been shown to have pleiotropic actions beyond its hypolipidemic effect. FF has been shown to exert a cytotoxic effect on some cancer cells when used at higher than clinically relevant concentrations; on the other hand, its cytoprotective effect on normal cells has also been reported. The present study assessed the effect of FF on cisplatin (CDDP) cytotoxicity to lung cancer cells in vitro. The results demonstrated that the effect of FF on lung cancer cells depends on its concentration. FF at ≤50 µM, which is a clinically achievable blood concentration, attenuated CDDP cytotoxicity to lung cancer cells, whereas FF at ≥100 µM, albeit clinically unachievable, had an anticancer effect. The mechanism of FF attenuation of CDDP cytotoxicity involved PPAR-α-dependent aryl hydrocarbon receptor (AhR) expression, which in turn stimulated nuclear factor erythroid 2-related factor 2 (Nrf2) expression and antioxidant production, resulting in lung cancer cell protection from CDDP-evoked oxidative damage. In conclusion, the present study revealed that FF, at clinically relevant concentrations, attenuated CDDP cytotoxicity to lung cancer cells by enhancing the antioxidant defense system through activation of a pathway that involves the PPAR-α-PPAR response element-AhR xenobiotic response element-Nrf2-antioxidant response element. These findings suggested that concomitant use of FF with CDDP may compromise the efficacy of chemotherapy. Although the anticancer property of FF has recently attracted much attention, concentrations that exceed clinically relevant concentrations are required.

Development of a high-resolution two-dimensional detector-based dose verification system for tumor-tracking irradiation in the CyberKnife system.

We aim to evaluate the basic characteristics of SRS MapCHECK (SRSMC) for CyberKnife (CK) and establish a dose verification system using SRSMC for the tumor-tracking irradiation for CK. The field size and angular dependence of SRSMC were evaluated for basic characterization. The output factors (OPFs) and absolute doses measured by SRSMC were compared with those measured using microDiamond and microchamber detectors and those calculated by the treatment planning system (TPS). The angular dependence was evaluated by comparing the SRSMC with a microchamber. The tumor-tracking dose verification system consists of SRSMC and a moving platform. The doses measured using SRSMC were compared with the doses measured using a microchamber and radiochromic film. The OPFs and absolute doses of SRSMC were within ±3.0% error for almost all field sizes, and the angular dependence was within ±2.0% for all incidence angles. The absolute dose errors between SRSMC and TPS tended to increase when the field size was smaller than 10 mm. The absolute doses of the tumor-tracking irradiation measured using SRSMC and those measured using a microchamber agreed within 1.0%, and the gamma pass rates of SRSMC in comparison with those of the radiochromic film were greater than 95%. The basic characteristics of SRSMC for CK presented acceptable results for clinical use. The results of the tumor-tracking dose verification system realized using SRSMC were equivalent to those of conventional methods, and this system is expected to contribute toward improving the efficiency of quality control in many facilities.

Verification of morphological and physical properties for the development of a lung substitute phantom using microspheres.

This paper proposes a new concept of phantom development, along with the utilization of new materials that can reproduce lung morphology and density. A lung substitute phantom using microspheres was fabricated; then, its dosimetric utility in radiotherapy was investigated, during which the density was adjusted to closely resemble the morphology of the actual human lung. Microspheres were used to reproduce alveoli, which are the main components of the lung. By changing the ratio of urethane, which is commonly used in soft tissue phantoms, to microspheres, we reproduced the density change of the lungs due to respiration. Here, we fabricated two slab-like lung substitutes to emulate commercially used phantoms. Although there is room for improvement in terms of practicality, the substitutes were easy to fabricate. Microscopic observation of the cut surface of the phantoms showed that the morphology of the phantoms mimicked the alveoli more faithfully than commercial phantoms. Furthermore, to compensate for the energy-independent mass attenuation and mass collision inhibition ability required by the tissue substitute phantom, we examined the physical properties of the phantom and confirmed that there was negligible energy dependence.

Double-ring sign in granulocyte colony-stimulating factor-induced vasculitis.

The double-ring sign found in contrast-enhanced computed tomography, which reflects inflammatory changes in the adventitia and oedema of the intima, is thought to be characteristic of Takayasu arteritis; however, herein, it was also observed for granulocyte colony-stimulating factor-induced vasculitis.

Mouthpiece polymer-gel dosimeter for in vivo oral dosimetry during head and neck radiotherapy.

In this study, we developed a mouthpiece-type gel dosimeter to prevent the oral mucositis caused by the perturbation effect of dental alloys in the radiotherapy of the head and neck regions and to enable in vivo dosimetry. Understanding the dose distribution in the oral cavity during radiotherapy helps identify the possible site for oral mucositis during treatment. Here agarose, which has a higher melting point than gelatin, was added as a coagulant to stabilize the shape of the dosimeter. The strength and dose response of the dosimeter were investigated. The strength was measured at room temperature, 20°C-40 °C, which is higher than the intraoral temperature. The dose-response curves were obtained by magnetic resonance imaging with R2 ranging from 0 to 25 Gy. The strength and dose response of the mouthpiece-type gel dosimeter were approximately 4 and 2.1 times higher than those of polyacrylamide gel and tetrakis hydroxymethyl phosphonium chloride dosimeters commonly used in the prescribed doses per fraction of treatment. The dosimeter is composed of 4 wt% MgCl2 and 1.5 wt% agarose; thus, it can retain the water equivalence. Through in vivo oral dosimetry in three dimensions for head and neck radiotherapy with dental alloys using the mouthpiece-type gel dosimeter, we obtained three-dimensional dose distributions in the dosimeter. The properties of the dosimeter show that it can be used in the clinic, depending on the prescribed dose.

Bronchial artery hypertrophy-associated perioperative pulmonary hemorrhage in cardiovascular surgery: a case report.

BACKGROUND: Pulmonary hemorrhage is a life-threatening complication of cardiovascular surgery. Bronchial artery hypertrophy, a rare pathology associated with inflammatory and ischemic respiratory diseases, increases the risk of pulmonary hemorrhage; however, its involvement in cardiovascular surgery is not well known. We present two cardiovascular surgical cases in which embolization of the hypertrophied bronchial artery was effective in controlling perioperative pulmonary hemorrhage. CASE PRESENTATION: The first case was a 51-year-old man with chronic obstructive pulmonary disease who developed acute type A aortic dissection. After emergent surgery, his blood pressure suddenly dropped in the intensive care unit; computed tomography revealed a right hemothorax. Because a 4-mm dilated bronchial artery was identified on preoperative computed tomography, the hemothorax was suspected to be associated with bronchial artery hypertrophy. Selective bronchial arteriography was emergently performed and revealed a right pulmonary parenchymal blush. After subsequent coil embolization of the bronchial artery, the parenchymal blush disappeared, and his hemodynamic condition stabilized. The second case was a 66-year-old man with bronchiectasis who was referred for redo aortic valve replacement due to structural valve deterioration. A bioprosthesis was previously implanted to avoid permanent anticoagulation because the patient had repeated episodes of hemoptysis; however, he still had persistent hemosputum during admission for the redo aortic valve replacement. A dilated bronchial artery 3.7 mm in size was incidentally identified on preoperative computed tomography, and hence, the repeated hemosputum was suspected to be associated with bronchial artery hypertrophy. Bronchial arteriography revealed a right pulmonary parenchymal blush, and prophylactic embolization of the bronchial artery was performed. The hemosputum disappeared after the procedure, and redo aortic valve replacement was performed uneventfully 8 days later. CONCLUSION: In cardiovascular surgery, the risk of pulmonary hemorrhage associated with bronchial artery hypertrophy should be considered, especially in patients with inflammatory and ischemic respiratory diseases.

Orbital apex syndrome associated with intraorbital metastasis of lung cancer.

We present the case of a patient with lung adenocarcinoma stage IVB diagnosed as orbital apex syndrome (OAS) associated with intraorbital metastasis of lung cancer. When patients with lung cancer have diplopia, ptosis or ocular motility disorder, identifying OAS is important.

Chunnel debranching for hybrid repair of thoracoabdominal aortic aneurysm.

Hybrid repair of a thoracoabdominal aortic aneurysm comprising thoracic endovascular aortic repair and total renovisceral debranching is a feasible alternative to open repair, especially for high-risk patients. However, transperitoneal debranching is a relatively complicated procedure that requires deep dissection around vital abdominal organs. Therefore, we developed a new debranching technique called Chunnel debranching, which was characterized by transaortic tunneling using a covered stent between the target artery and the prosthetic graft anastomosed on the aneurysmal wall using an inclusion technique. This procedure increases the feasibility of renovisceral debranching with fewer dissections than conventional transperitoneal debranching.

Improved Prognostic Prediction by Combination of Early Initiation of Polymyxin B Hemoperfusion with Modified Gender-Age-Physiology Index in Acute Exacerbation of Idiopathic Pulmonary Fibrosis.

INTRODUCTION: Respiratory failure from acute exacerbation of idiopathic pulmonary fibrosis (AE-IPF) is associated with high mortality. Direct hemoperfusion with polymyxin B-immobilized fiber column (PMX-DHP) has been reported to have beneficial effects on patients with AE-IPF. Whether patient characteristics influence the extent of this benefit remains unclear. METHODS: We retrospectively examined the records of 30 patients with AE-IPF who underwent PMX-DHP. The favorable factors of survival were determined using Cox proportional hazards analyses. RESULTS: The 1- and 12-month survival rates after PMX-DHP were 70.0% and 50.0%, respectively. The multivariate analysis revealed that low modified Gender-Age-Physiology (GAP) index (≤8 points) (hazard ratio [HR] 0.317, p = 0.015) and PMX-DHP received within 48 h of steroid pulse (HR 0.289, p = 0.012) were favorable factors. Notably, even in the patients with high modified GAP index (>8 points), that is, more advanced IPF, those who received PMX-DHP within 48 h of steroid pulse had a better prognosis than those who did after 48 h of the steroid pulse (p = 0.032). CONCLUSIONS: Early PMX-DHP initiation in patients with AE-IPF, specifically within 48 h after the steroid pulse therapy, may improve prognosis regardless of the severity of chronic phase of IPF before AE-IPF.

Impact of sarcopenia on chemotherapy-triggered exacerbation of interstitial lung disease in patients with non-small cell lung cancer.

BACKGROUND: While recent evidence has suggested that sarcopenia could predict chemotoxicity, its association with chemotherapy-triggered interstitial lung disease (ILD) exacerbations has yet to be investigated. Thus, the present study sought to determine whether sarcopenia could predict ILD exacerbations and overall survival (OS) in patients with ILD-complicated non-small cell lung cancer (NSCLC). METHODS: From January 2010 to July 2020, 74 patients with ILD-complicated NSCLC who received chemotherapy were retrospectively investigated. After categorizing patients according to the presence or absence of sarcopenia based on the psoas muscle index, ILD exacerbation rates and OS were evaluated. RESULTS: Among the patients in the study, 39 were included in the sarcopenia group. Moreover, 17 (22.9%) patients developed ILD exacerbations, with the sarcopenia and nonsarcopenia groups having an exacerbation rate of 33.3% and 11.4%, respectively (p = 0.025). Multivariate analysis identified sarcopenia as an independent predictor of ILD exacerbations (p = 0.039). Furthermore, patients with sarcopenia demonstrated a significantly shorter median OS compared to those without the same (9.2 vs. 13.3 months; p = 0.029). CONCLUSIONS: Sarcopenia predicted chemotherapy-triggered ILD exacerbation and OS in patients with ILD-complicated NSCLC, suggesting its utility in determining treatment approaches.

Computed tomography imaging using split-bolus contrast injection with volume scan of aortic root and heart for preoperative evaluation of transcatheter aortic valve implantation.

The purpose of this study was to investigate using split-bolus contrast injection (SPBI) with volume scanning of the heart and aortic root with helical scanning of the access route, compared to single bolus contrast injection (SI) with variable helical pitch scanning (VHP) of the heart and aortic root and access route in a preoperative evaluation before transcatheter aortic valve implantation (TAVI). Thirty-five patients who underwent preoperative CT before TAVI using SPBI (contrast media: 24.5 mgI /kg/s, injected for 12 s for heart scan and then injected for 8 s for access route) were examined. Electrocardiogram (ECG) gated scans of the heart were performed by volume scan, after a period of time, non-gated helical scans of the aorto-iliac were performed (SPBI method). For comparison, 40 patients who had a single bolus injection (26.5 mg I/kg/s, injected for period of the scan time plus 3 s) and a VHP scan (SI method) before the SPBI method was performed were included in the study. The image qualities of the coronary arteries, aortic root, and access route (aorta-iliac), as well as radiation and iodine doses, were assessed. In visual assessment, image quality of coronary artery was significantly better with the SPBI method (grade; excellent: 57.1% in SPBI vs. 24.3% in SI, p = 0.03). There was no significant difference in image quality of the aortic root by visual assessment. The signal-to-noise (SNR) and contrast-to-noise ratio (CNR) of coronary and aortic root were not significantly different between the two methods. The access route showed significantly higher SNR (45.7 ± 11.5 vs. 34.3 ± 9.8, p < 0.001) and CNR (36.0 ± 9.7 vs. 28.0 ± 8.8, p < 0.001) for the SPBI method. The SPBI method compared to SI method reduced iodine dose by 10% and radiation dose by 45%. Preoperative CT imaging before TAVI using SPBI with volume scan is useful and can reduce iodine and radiation doses.

Development of an x-ray-opaque-marker system for quantitative phantom positioning in patient-specific quality assurance.

PURPOSE: We developed an x-ray-opaque-marker (XOM) system with inserted fiducial markers for patient-specific quality assurance (QA) in CyberKnife (Accuray) and a general-purpose linear accelerator (linac). The XOM system can be easily inserted or removed from the existing patient-specific QA phantom. Our study aimed to assess the utility of the XOM system by evaluating the recognition accuracy of the phantom position error and estimating the dose perturbation around a marker. METHODS: The recognition accuracy of the phantom position error was evaluated by comparing the known error values of the phantom position with the values measured by matching the images with target locating system (TLS; Accuray) and on-board imager (OBI; Varian). The dose perturbation was evaluated for 6 and 10 MV single-photon beams through experimental measurements and Monte Carlo simulations. RESULTS: The root mean squares (RMSs) of the residual position errors for the recognition accuracy evaluation in translations were 0.07 mm with TLS and 0.30 mm with OBI, and those in rotations were 0.13° with TLS and 0.15° with OBI. The dose perturbation was observed within 1.5 mm for 6 MV and 2.0 mm for 10 MV from the marker. CONCLUSIONS: Sufficient recognition accuracy of the phantom position error was achieved using our system. It is unnecessary to consider the dose perturbation in actual patient-specific QA. We concluded that the XOM system can be utilized to ensure quantitative and accurate phantom positioning in patient-specific QA with CyberKnife and a general-purpose linac.