CT number calibration audit in photon radiation therapy

BACKGROUND

Inadequate computed tomography (CT) number calibration curves affect dose calculation accuracy. Although CT number calibration curves registered in treatment planning systems (TPSs) should be consistent with human tissues, it is unclear whether adequate CT number calibration is performed because CT number calibration curves have not been assessed for various types of CT number calibration phantoms and TPSs.

PURPOSE

The purpose of this study was to investigate CT number calibration curves for mass density (ρ) and relative electron density (ρe ).

METHODS

A CT number calibration audit phantom was sent to 24 Japanese photon therapy institutes from the evaluating institute and scanned using their individual clinical CT scan protocols. The CT images of the audit phantom and institute-specific CT number calibration curves were submitted to the evaluating institute for analyzing the calibration curves registered in the TPSs at the participating institutes. The institute-specific CT number calibration curves were created using commercial phantom (Gammex, Gammex Inc., Middleton, WI, USA) or CIRS phantom (Computerized Imaging Reference Systems, Inc., Norfolk, VA, USA)). At the evaluating institute, theoretical CT number calibration curves were created using a stoichiometric CT number calibration method based on the CT image, and the institute-specific CT number calibration curves were compared with the theoretical calibration curve. Differences in ρ and ρe over the multiple points on the curve (Δρm and Δρe,m , respectively) were calculated for each CT number, categorized for each phantom vendor and TPS, and evaluated for three tissue types: lung, soft tissues, and bones. In particular, the CT-ρ calibration curves for Tomotherapy TPSs (ACCURAY, Sunnyvale, CA, USA) were categorized separately from the Gammex CT-ρ calibration curves because the available tissue-equivalent materials (TEMs) were limited by the manufacturer recommendations. In addition, the differences in ρ and ρe for the specific TEMs (ΔρTEM and Δρe,TEM , respectively) were calculated by subtracting the ρ or ρe of the TEMs from the theoretical CT-ρ or CT-ρe calibration curve.

RESULTS

The mean ± standard deviation (SD) of Δρm and Δρe,m for the Gammex phantom were -1.1 ± 1.2 g/cm3 and -0.2 ± 1.1, -0.3 ± 0.9 g/cm3 and 0.8 ± 1.3, and -0.9 ± 1.3 g/cm3 and 1.0 ± 1.5 for lung, soft tissues, and bones, respectively. The mean ± SD of Δρm and Δρe,m for the CIRS phantom were 0.3 ± 0.8 g/cm3 and 0.9 ± 0.9, 0.6 ± 0.6 g/cm3 and 1.4 ± 0.8, and 0.2 ± 0.5 g/cm3 and 1.6 ± 0.5 for lung, soft tissues, and bones, respectively. The mean ± SD of Δρm for Tomotherapy TPSs was 2.1 ± 1.4 g/cm3 for soft tissues, which is larger than those for other TPSs. The mean ± SD of Δρe,TEM for the Gammex brain phantom (BRN-SR2) was -1.8 ± 0.4, implying that the tissue equivalency of the BRN-SR2 plug was slightly inferior to that of other plugs.

CONCLUSIONS

Latent deviations between human tissues and TEMs were found by comparing the CT number calibration curves of the various institutes.

[Analysis of Preventive Cases Using Resilience Engineering in Radiotherapy Department]

PURPOSE

Resilience engineering is the ability of a system to adjust its own functions and maintain the required behavior in the face of changes and disturbances, and resilience potential is a necessary requirement. We aimed to clarify the relationship between resilience potential and error prevention cases.

METHOD

Based on the error cases reported in our department, we aggregated the relationship with resilience potential for each radiation treatment process.

RESULT

As a result of tabulating the relationship, we were able to recognize and prevent errors by taking preventive measures from past cases. On the other hand, in cases that slipped through the check mechanism, errors were discovered because of a sense of discomfort in unusual situations, and some error cases could be prevented by increasing the resilience potential.

CONCLUSION

This study found that preparation, observation, coping, and utilization of past experiences are related to resilience potential in preventive cases.

Unbiased evaluation of predicted gamma passing rate by an event-mixing technique

BACKGROUND

Predicting models of the gamma passing rate (GPR) have been studied to substitute the measurement-based gamma analysis. Since these studies used data from different radiotherapy systems comprising TPS, linear accelerator, and detector array, it has been difficult to compare the performances of the predicting models among institutions with different radiotherapy systems.

PURPOSE

We aimed to develop unbiased scoring methods to evaluate the performance of the models predicting the GPR, by introducing both best and worst limits for the performance of the GPR prediction.

METHODS

Two hundred head-and-neck VMAT plans were used to develop a framework. The GPRs were measured using the ArcCHECK device. The predicted GPR [p] was generated using a deep learning-based model [pDL ]. The predicting model was evaluated using four metrics: standard deviation (SD) [σ], Pearson's correlation coefficient (CC) [r], mean squared error (MSE) [s], and mean absolute error (MAE) [a]. The best limit [σ m ${\sigma _m}$ ,r m ${r_m}$ ,s m ${s_m}$ , anda m ${a_m}$ ] was estimated by measuring the SD of measured GPR [m] by shifting the device along the longitudinal direction to measure different sampling points. Mimicked best and worst p's [pbest and pworst ] were generated from pDL . The worst limit was defined such that m and p have no correlation [CC ∼ 0]. The worst limit [σMix , rMix , sMix , and aMix ] was generated using the event-mixing (EM) technique originally introduced in high-energy physics experiments. The range of σ, r, s, and a was defined to be[ σ m , σ Mix ] $[ {{\sigma _m},{\sigma _{{\mathrm{Mix}}}}} ]$ ,[ 0 , r m ] $[ {0,{r_m}} ]$ ,[ s m , s Mix ] $[ {{s_m},{s_{{\mathrm{Mix}}}}} ]$ , and[ a m , a Mix ] $[ {{a_m},{a_{{\mathrm{Mix}}}}} ]$ . The achievement score (AS) independently based on σ, r, s, and a were calculated for pDL , pbest and pworst . The probability that p fails the gamma analysis (alert frequency; AF) was estimated as a function ofσ d ${\sigma _d}$ values within the [σ m ${\sigma _m}$ , σMix ] range for the 3%/2 mm data with a 95% criterion.

RESULTS

SDs of the best limit were well reproduced byσ m = 0.531 100 - m ${\sigma _m} = \;0.531\sqrt {100 - m} $ . The EM technique successfully generated the( m , p ) $( {m,p} )$ pairs with no correlation. The AS using four metrics showed good agreement. This agreement indicates successful definitions of both best and worst limits, consistent definitions of the AS, and successful generations of mixed events. The AF for the DL-based model with the 3%/2 mm tolerance was 31.5% and 63.0% with CL's 99% and 99.9%, respectively.

CONCLUSION

We developed the AS to evaluate the predicting model of the GPR in an unbiased manner by excluding the effects of the precision of the radiotherapy system and the spreading of the GPR. The best and worst limits of the GPR prediction were successfully generated using the measured precision of the GPR and the EM technique, respectively. The AS andσ p ${\sigma _p}$ are expected to enable objective evaluation of the predicting model and setting exact achievement goal of precision for the predicted GPR.

Classification of Patients with Painful Tumors to Predict the Response to Palliative Radiotherapy

PURPOSE/OBJECTIVE(S)

Palliative radiotherapy is an effective and commonly used treatment for pain relief in metastatic cancer patients. This study aimed to classify the patients to predict their response to palliative radiotherapy.

MATERIALS/METHODS

This study used the data from our single-center, prospective observational study (UMIN000044984), which included all patients undergoing palliative radiotherapy for the painful tumor, except for postoperative setting or brain metastases. The eligibility criteria were as follows: (1) numerical rating scale (NRS) was two or more before treatment, and (2) underwent palliative radiotherapy between August 2021 and September 2022. Questionnaires for pain site, NRS, and presence/dose of opioids were obtained before, on the last day of treatment, two weeks later, one month later, three months later, and every three months after that. Patients with severe performance status (PS) were contacted by telephone. Pain response was defined to reduce NRS 2 or more at the treated site without an analgesic increase. The primary outcome was the response rate within three months of the treatment. We used multivariable logistic regression to find the independent prognostic factors for the response based on the following covariates: age, sex, PS, body mass index, NRS, history of radiotherapy, treated site, radiographic features (lytic/sclerotic/mixed), metastatic complication, presence/dose of opioids, bone-modifying agents, radiation dose, type of primary tumor, radiosensitivity, number of metastases, and days from diagnosis to treatment. A classification model was created using significant factors, and response rates were calculated for each class. Statistical significance was defined as P<0.05.

RESULTS

Among 488 targets of 300 patients registered, 366 targets of 261 patients met the criteria. The median age was 65 years, 44% were female, and PS (0/1/2/3/4) was 6/63/18/9/4%. The major type of tumor was gastrointestinal (32%), lung (19%), and breast (12%). Bone metastases were 75% at treated sites. Opioids were used by 72%, BMA was 27%, and chemotherapy was 50%. Re-irradiation rate was 22%. With a median follow-up of 5.8 months, 113 patients were alive, 129 had died, and 20 were lost follow-up. The average NRS was reduced from 6.1 to 3.1 from pretreatment to 3 months later per evaluable 232 targets, resulting in a pain relief rate of 60%. Opioids use (P<0.001) and re-irradiation (P<0.001) were significant factors of poor response in multivariate analysis. In our classification model, 89 targets were classified as class 1 (no opioids & no irradiation history), 211 were class 2 (other than class 1 and 3), and 66 were class 3 (opioids & re-irradiation), were 75/61/36% (P<0.001) of response rate. The 6-month cumulative pain progression rate was 12/22/32% (P<0.001), respectively.

CONCLUSION

Palliative radiotherapy is highly effective for patients with painful tumors especially for those without previous irradiation history or use of opioids.

Effectiveness of Spacers in Brachytherapy With 198Au Grains for Patients With Buccal Mucosa Cancer

BACKGROUND/AIM

The aim of this study was to investigate the use of spacers and their efficacy in brachytherapy with ¹⁹⁸Au grains for buccal mucosa cancer.

PATIENTS AND METHODS

Sixteen patients with squamous cell carcinoma of the buccal mucosa who were treated with ¹⁹⁸Au grain brachytherapy were included. The distance between ¹⁹⁸Au grains, distance between ¹⁹⁸Au grains and the maxilla or mandible, and the maximum dose/cc to the jawbone (D1cc) with and without a spacer was investigated in three out of 16 patients.

RESULTS

The median distance between ¹⁹⁸Au grains without and with a spacer was 7.4 and 10.7 mm, respectively; this was significantly different. The median distance between ¹⁹⁸Au grains and the maxilla without and with a spacer was 10.3 and 18.5 mm, respectively; again this was significantly different. The median distance between ¹⁹⁸Au grains and the mandible without and with a spacer was 8.6 and 17.3 mm, respectively; the difference was significant. The D1cc to the maxilla without and with a spacer were 14.9, 68.7, and 51.8 Gy and 7.5, 21.2, and 40.7 Gy in cases 1, 2, and 3, respectively. The D1cc to the mandible without and with a spacer were 27.5, 68.7, and 85.8 Gy and 11.3, 53.6, and 64.9 Gy in cases 1, 2, and 3, respectively. No osteoradionecrosis of the jaw bones was observed in any case.

CONCLUSION

The spacer enabled maintenance of the distance between ¹⁹⁸Au grains, and between ¹⁹⁸Au grains and the jawbone. In buccal mucosa cancer, using a spacer in brachytherapy with ¹⁹⁸Au grains appears to reduce jawbone complications.

Evaluation of Inappropriate Positioning of Dosimeters in Medical Workers Based on Dose Equivalent Hp(10)

This report presents a new method to characterize the inappropriate positioning of dosimeters based on the dose equivalent Hp(10). The Hp(10) values of medical workers were measured monthly for 12 mo using two personal dosimeters. Using the ratio between the values of Hp(10) recorded from dosimeters worn over and under protective aprons [Hp(10) over and Hp(10) under , respectively], 670 pairs of dosimeter readings were categorized into a proper use group [Hp(10) over /Hp(10) under ≥ 5] and a misuse group [Hp(10) over /Hp(10) under < 5]. Following personal interviews, the readings in the misuse group were classified into the following six subgroups: "reversed," "sometimes reversed," "both under," "both over," "without apron," and "not specified." Ultimately, the scatter plot of "Hp(10) over - Hp(10) under " vs. Hp(10) over was identified as the most promising tool for clarifying the misuse patterns of dosimeters, as individual readings were mapped to the locations of the corresponding subgroups in the obtained graphs. Our results are expected to facilitate efficient and accurate usage of dosimeters by medical workers.

Robust optimization of VMAT for prostate cancer accounting for geometric uncertainty

The aim of this study was to propose optimal robust planning by comparing the robustness with setup error with the robustness of a conventional planning target volume (PTV)‐based plan and to compare the robust plan to the PTV‐based plan for the target and organ at risk (OAR). Data from 13 patients with intermediate‐to‐high‐risk localized prostate cancer who did not have T3b disease were analyzed. The dose distribution under multiple setup error scenarios was assessed using a conventional PTV‐based plan. The clinical target volume (CTV) and OAR dose in moving coordinates were used for the dose constraint with the robust plan. The hybrid robust plan added the dose constraint of the PTV‐rectum to the static coordinate system. When the isocenter was shifted by 10 mm in the superior–inferior direction and 8 mm in the right‐left and anterior directions, the doses to the CTV, bladder, and rectum of the PTV‐based plan, robust plan, and hybrid robust plan were compared. For the CTV D_99% in the PTV‐based plan and hybrid robust plan, over 95% of the prescribed dose was secured in all directions, except in the inferior direction. There was no significant difference between the PTV‐based plan and the hybrid robust plan for rectum V_70Gy, V_60Gy, and V_40Gy. This study proposed an optimization method for patients with prostate cancer. When the setup error occurred within the PTV margin, the dose robustness of the CTV for the hybrid robust plan was higher than that of the PTV‐based plan, while maintaining the equivalent OAR dose.

Reduction of margin to compensate the respiratory tumor motion by the analysis of dosimetric internal target volume in lung SBRT with nonuniform volume prescription method

PURPOSE

To develop a dosimetric internal target volume (ITV) margin (DIM) for respiratory motion in lung stereotactic body radiotherapy (SBRT) and to evaluate DIM with a nonuniform volume prescription (NVP) and the point prescription (PP).

METHODS

Volumetric modulated arc therapy (VMAT) treatment plans with PP and NVP were created on a heterogeneous programmable respiratory motion phantom, with a tumor (30-mm diameter) inside a cylindrical lung insert. The tumor was defined as the gross tumor volume (GTV), equal to the clinical target volume (CTV). Five-millimeter and 0-mm margins were used for the ITV and setup margins, respectively. The phantom was moved in cranio-caudal direction with a biquadratic sinusoidal waveform with a 4-s cycle and an amplitude of ±5-10 mm. The interplay effect was evaluated by measuring the dose profile with a film in the sagittal plane for different respiratory periods and different initial respiratory phases. DIM was based on the respiratory motion amplitude that satisfied 100% and 95% coverage of the prescribed dose by the minimum dose of the CTV. Moreover, the absolute dose was measured with and without respiratory motion for NVP by a pinpoint chamber.

RESULTS

The dose difference in the tumor region due to the interplay effect was within 1.0%. The gamma passing rate was over 95.1% for different respiratory periods and 98.6% for different initial respiratory phases. DIM with PP was almost equivalent to the margin of the respiratory motion. However, DIM with NVP was 2.0 and 1.8 times larger than the margin of the respiratory motion for the 100% and 95% coverage of the prescribed doses, respectively.

CONCLUSION

The interplay effects experienced between the MLC sequence and tumor motion were negligible for NVP. The DIM analysis revealed that the margin to compensate the respiratory tumor motion could be reduced by more than 44-50% for NVP in SBRT.

Efficacy and safety of abiraterone acetate plus prednisolone in patients with early metastatic castration-resistant prostate cancer who failed first-line androgen-deprivation therapy: a single-arm, phase 4 study

Aim

The aim was to evaluate the efficacy and safety of abiraterone acetate plus prednisolone in patients with chemotherapy-naïve early metastatic castration-resistant prostate cancer who failed first-line androgen deprivation therapy.

Methods

Patients with early metastatic castration-resistant prostate cancer with confirmed prostate-specific antigen progression within 1-year or prostate-specific antigen progression without having normal prostate-specific antigen level (<4.0 ng/mL) during first-line androgen deprivation therapy were enrolled and administered abiraterone acetate (1000 mg) plus prednisolone (10 mg). A minimum of 48 patients were required according to Simon’s minimax design. The primary endpoint was prostate-specific antigen response rate (≥50% prostate-specific antigen decline by 12 weeks), secondary endpoints included prostate-specific antigen progression-free survival and overall survival. Safety parameters were also assessed.

Results

For efficacy, 49/50 patients were evaluable. Median age was 73 (range: 55–86) years. The median duration of initial androgen deprivation therapy was 32.4 (range: 13.4–84.1) weeks and 48 patients experienced prostate-specific antigen progression within 1-year after initiation of androgen deprivation therapy. prostate-specific antigen response rate was 55.1% (95% confidence interval: 40.2%–69.3%), median prostate-specific antigen–progression-free survival was 24.1 weeks, and median overall survival was 102.9 weeks (95% confidence interval: 64.86 not estimable [NE]). Most common adverse event was nasopharyngitis (15/50 patients, 30.0%). The most common ≥grade 3 adverse event was alanine aminotransferase increased (6/50 patients, 12.0%).

Conclusions

Abiraterone acetate plus prednisolone demonstrated a high prostate-specific antigen response rate of 55.1%, suggesting tumor growth still depends on androgen synthesis in patients with early metastatic castration-resistant prostate cancer. However, prostate-specific antigen–progression-free survival was shorter than that reported in previous studies. Considering the benefit–risk profile, abiraterone acetate plus prednisolone would be a beneficial treatment option for patients with chemotherapy-naive metastatic prostate cancer who show early castration resistance.

An overview of the medical-physics-related verification system for radiotherapy multicenter clinical trials by the Medical Physics Working Group in the Japan Clinical Oncology Group-Radiation Therapy Study Group

The Japan Clinical Oncology Group-Radiation Therapy Study Group (JCOG-RTSG) has initiated several multicenter clinical trials for high-precision radiotherapy, which are presently ongoing. When conducting multi-center clinical trials, a large difference in physical quantities, such as the absolute doses to the target and the organ at risk, as well as the irradiation localization accuracy, affects the treatment outcome. Therefore, the differences in the various physical quantities used in different institutions must be within an acceptable range for conducting multicenter clinical trials, and this must be verified with medical physics consideration. In 2011, Japan's first Medical Physics Working Group (MPWG) in the JCOG-RTSG was established to perform this medical-physics-related verification for multicenter clinical trials. We have developed an auditing method to verify the accuracy of the absolute dose and the irradiation localization. Subsequently, we credentialed the participating institutions in the JCOG multicenter clinical trials that were using stereotactic body radiotherapy (SBRT) for lungs, intensity-modulated radiotherapy (IMRT) and volumetric-modulated arc therapy (VMAT) for several disease sites, and proton beam therapy (PT) for the liver. From the verification results, accuracies of the absolute dose and the irradiation localization among the participating institutions of the multicenter clinical trial were assured, and the JCOG clinical trials could be initiated.

Characterization of thromboembolic and bleeding risks in cancer patients with acute myocardial infarction under the use of guideline-recommended dual-antiplatelet therapy

Background

Atherosclerotic cardiovascular disease including acute myocardial infarction (AMI) has become one of major co-existing diseases in cancer patients due to their improved survival rate. Current guideline recommends dual-antiplatelet therapy (DAPT) in patients with AMI. Given that the presence of cancer elevates not only coagulability but bleeding risks, these substrate may further worsen cardiovascular outcomes and bleeding risks in cancer subjects with AMI receiving DAPT.

Methods

We retrospectively analyzed 712 AMI patients treated by primary PCI with drug-eluting stent and DAPT between 2007 and 2017. The diagnosis of cancer was determined through medical record review. Clinical characteristics, thromboembolic (=all-cause death+non-fatal MI+stroke) and bleeding events were compared in AMI subjects with vs. without cancer.

Results

Cancer was identified in 11.1% (=79/712) of study subjects. Of these, around 40% of them had gastrointestinal cancer (=35/79), followed by lung cancer (=5/79) and breast cancer (=8/79). Cancer patients were more likely to be older (77±7 v. 69±13 years, p&lt;0.001) with a history of Af (25 v. 10%, p&lt;0.001), CKD (eGFR&lt;60: 60 v. 42%, p=0.002), anemia (hemoglobin: 12.8±1.8 v. 13.9±1.8 g/dl, p&lt;0.001). Under anti-thrombotic (DAPT=86%, triple-antiplatelet therapy=14%) and optimal medical therapies (ACE-I=90%, beta-blocker=76%, statin=96%), more frequent occurrence of thromboembolic events was observed in patients with cancer (34.2 v. 12.6%, p=0.004, Picture). Furthermore, the presence of cancer was associated with more than four times greater risk of bleeding events compared to non-cancer subjects (18.9 v. 4.3%, p&lt;0.001, Picture). In particular, the frequency of both major (10.1 vs. 3.3%, p=0.003) and minor (8.9 vs. 0.9%, p&lt;0.001) bleeding events was significantly higher in patients with cancer. In multivariate analysis, cancer independently predicted bleeding events (Table).

Conclusions

Under the use of guideline recommended DAPT, the concomitance of cancer in AMI subjects was a predictor for thromboembolic as well as bleeding events. In particular, the relationship between cancer and bleeding was significant. These observations underscore the appropriate selection and duration of anti-thrombotic agents in AMI subjects with cancer.

Cardiac/Bleeding Events in AMI Subjects

Funding Acknowledgement

Type of funding source: None

Characterization of plaque features exhibiting physiological mismatch between fractional flow reserve and resting index: near-infrared spectroscopy imaging analysis

Background

In addition to fractional flow reserve (FFR), resting indexes (RI) have been shown as another physiological measure to evaluate myocardial ischemia. Despite the clinical usefulness of RI without the use of intravenous vasodilatory agent, discrepancy between FFR and RI infrequently occurs. Whether this physiological mismatch is derived by specific plaque feature remains unknown.

Purpose

To characterize coronary plaques associated with coronary physiological mismatch.

Methods

We analyzed 59 coronary arteries (LAD/RCA/LCX=49/4/6) with FFR≤0.80 in 57 stable CAD subjects receiving PCI. Following measurement of FFR and RI, culprit lesion was evaluated by near-infrared spectroscopy and intravascular ultrasound (NIRS/IVUS). The analyzed vessels were stratified according to FFR and RI values: FFR≤0.75+RI&gt;0.89 (n=6: physiological mismatch), FFR&gt;0.75+RI&gt;0.89 (n=6), FFR≤0.75+RI≤0.89 (n=33) and FFR&gt;0.75+RI≤0.89 (n=14).

Results

The median values of percent diameter stenosis, FFR and RI were 51%, 0.75 and 0.87, respectively. Physiological mismatch was observed in 10.1% (=6/59) of analyzed vessels. On IVUS imaging, maximum percent plaque area was greater than 70% in all groups (p=0.29). Furthermore, there were no significant differences in angiographic and IVUS-derived minimum lumen area across 4 groups (Table). However, culprit lesions exhibiting physiological mismatch contained a substantially larger amount of lipid plaque, reflected by a higher maximum 4-mm lipid-core burned index (maxLCBI4mm: p=0.04) on NIRS imaging (Table). Multivariate analysis demonstrated maxLCBI4mm as the only plaque feature associated with physiological mismatch (odds ratio=1.010, 95% CI: 1.001–1.019, p=0.02).

Conclusion

Plaque feature associated with coronary physiological mismatch was the extent of lipidic materials but not the quantity of coronary atheroma. Since the accumulation of lipidic plaque component is caused by endothelial dysfunction, this vascular substrate could impair baseline vasomotion, thereby causing a lower FFR despite preserved RI value. Evaluation of lipidic burden may be a potential option to avoid unnecessary deferral of revascularization in subjects with normal RI value.

maxLCBI4mm in each group

Funding Acknowledgement

Type of funding source: None

Halo Structure of the Neutron-Dripline Nucleus ^{19}B

The heaviest bound isotope of boron ^{19}B has been investigated using exclusive measurements of its Coulomb dissociation, into ^{17}B and two neutrons, in collisions with Pb at 220  MeV/nucleon. Enhanced electric dipole (E1) strength is observed just above the two-neutron decay threshold with an integrated E1 strength of B(E1)=1.64±0.06(stat)±0.12(sys)  e^{2} fm^{2} for relative energies below 6 MeV. This feature, known as a soft E1 excitation, provides the first firm evidence that ^{19}B has a prominent two-neutron halo. Three-body calculations that reproduce the energy spectrum indicate that the valence neutrons have a significant s-wave configuration and exhibit a dineutronlike correlation.

Development of a CT number calibration audit phantom in photon radiation therapy: A pilot study

PURPOSE

In photon radiation therapy, computed tomography (CT) numbers are converted into values for mass density (MD) or relative electron density to water (RED). CT-MD or CT-RED calibration tables are relevant for human body dose calculation in an inhomogeneous medium. CT-MD or CT-RED calibration tables are influenced by patient imaging (CT scanner manufacturer, scanning parameters, and patient size), the calibration process (tissue-equivalent phantom manufacturer, and selection of tissue-equivalent material), differences between tissue-equivalent materials and standard tissues, and the dose calculation algorithm applied; however, a CT number calibration audit has not been established. The purposes of this study were to develop a postal audit phantom, and to establish a CT number calibration audit process.

METHODS

A conventional stoichiometric calibration conducts a least square fit of the relationships between the MD, material weight, and measured CT number, using two parameters. In this study, a new stoichiometric CT number calibration scheme has been empirically established, using three parameters to harmonize the calculated CT number with the measured CT number for air and lung tissue. In addition, the suitable material set and the minimal number of materials required for stoichiometric CT number calibration were determined. The MDs and elemental weights from the International Commission on Radiological Protection Publication 110 were used as standard tissue data, to generate the CT-MD and CT-RED calibration tables. A small-sized, CT number calibration phantom was developed for a postal audit, and stoichiometric CT number calibration with the phantom was compared to the CT number calibration tables registered in the radiotherapy treatment planning systems (RTPSs) associated with five radiotherapy institutions.

RESULTS

When a least square fit was performed for the stoichiometric CT number calibration with the three parameters, the calculated CT number showed better agreement with the measured CT number. We established stoichiometric CT number calibration using only two materials because the accuracy of the process was determined not by the number of used materials but by the number of elements contained. The stoichiometric CT number calibration was comparable to the tissue-substitute calibration, with a dose difference less than 1%. An outline of the CT number calibration audit was demonstrated through a multi-institutional study.

CONCLUSIONS

We established a new stoichiometric CT number calibration method for validating the CT number calibration tables registered in RTPSs. We also developed a CT number calibration phantom for a postal audit, which was verified by the performances of multiple CT scanners located at several institutions. The new stoichiometric CT number calibration has the advantages of being performed using only two materials, and decreasing the difference between the calculated and measured CT numbers for air and lung tissue. In the future, a postal CT number calibration audit might be achievable using a smaller phantom.

In silico experiments of bone remodeling explore metabolic diseases and their drug treatment

Bone structure and function are maintained by well-regulated bone metabolism and remodeling. Although the underlying molecular and cellular mechanisms are now being understood, physiological and pathological states of bone are still difficult to predict due to the complexity of intercellular signaling. We have now developed a novel in silico experimental platform, V-Bone, to integratively explore bone remodeling by linking complex microscopic molecular/cellular interactions to macroscopic tissue/organ adaptations. Mechano-biochemical couplings modeled in V-Bone relate bone adaptation to mechanical loading and reproduce metabolic bone diseases such as osteoporosis and osteopetrosis. V-Bone also enables in silico perturbation on a specific signaling molecule to observe bone metabolic dynamics over time. We also demonstrate that this platform provides a powerful way to predict in silico therapeutic effects of drugs against metabolic bone diseases. We anticipate that these in silico experiments will substantially accelerate research into bone metabolism and remodeling.

P5635Predictive ability of lipdic burden for FFR-derived physiological measures: insights from near-infrared spectroscopy imaging analysis

Background

Fractional flow reserve (FFR) has enabled to physiologically assess the myocardial ischemia of coronary artery with intermediate stenosis. Mechanistically, not only the severity of coronary stenosis but also the extent of maximal vasodilatation within the entire coronary artery potentially affects this physiological measure. Since the accumulation of lipidic materials within vessel wall increases vascular stiffness via inducing endothelial dysfunction, the presence of lipidic atheroma burden may affect physiological measures.

Purpose

To investigate the association of FFR with lipidic coronary atheroma by near-infrared spectroscopy/intravascular ultrasound (NIRS/IVUS) imaging, which quantitatively visualize lipidic burden in vivo.

Methods

We analyzed 61 coronary arteries (LAD/RCA/LCX=52/5/4) with FFR≤0.80 in 59 stable coronary artery disease subjects receiving PCI. Following FFR measurement, NIRS/IVUS imaging was conducted to evaluate the extent of atheroma burden (maximum percent plaque area=max%PA) and lipidic materials (lipid core burden index within the entire vessel=LCBIvessel). The analyzed vessels were stratified according to FFR: definite FFR group (FFR≤0.74, n=34) and gray-zone FFR group (0.75≤FFR≤0.80, n=27).

Results

NIRS/IVUS imaging analysis (analyzed longitudinal length=77±7mm) was more likely to exhibit a significantly higher LCBIvessel and a larger max%PA in the definite FFR group (Table). Of note, FFR was significantly correlated to LCBIvessel (ρ=-0.299, p=0.02), but not max%PA (ρ=-0.255, p=0.07). Multivariate analysis demonstrated that an independent determinant of FFR≤0.74 was LCBIvessel [odds ratio (OR)=1.016, 95% confidential interval (CI)=1.002–1.031, p=0.02], but not max%PA [OR=1.084, 95% CI=0.994–1.182, p=0.07]. Area under the receiver-operating characteristic curve analysis elucidated that the addition of LCBIvessel to angiography- and IVUS-derived measures resulted in a significant improvement for detecting FFR≤0.74 (picture).

Definite FFR Group (FFR≤0.74, n=34) Gray-zone FFR Group (0.75≤FFR≤0.80, n=27) p value Fractional flow reserve (FFR) 0.68±0.05 0.78±0.02 <0.01 Percent diameter stenosis (%) 56.2±13.1 51.9±7.8 0.16 Maximum percent plaque area (max%PA, %) 84.3±6.9 79.9±7.2 0.01 Lipid core burden index within the entire vessel (LCBIvessel) 102.0±60.2 65.6±51.6 0.01

ROC analysis for detecting FFR≦0.74

Conclusion

The propagation of lipidic burden associates with the physiological measures. The present findings indicate the possibility that vessel characteristics or instability may have influence for causing ischemia on the coronary artery.

P1561An elevated risk of heart failure and stroke events in octogenarian Japanese patients with acute myocardial infarction who received percutaneous coronary intervention

Background

The proportion of the octogenarian population is expanding especially in Eastern society. Due to the clustering of risk factors, acute myocardial infarction (AMI) represents a major cardiovascular complication in octogenarian subjects. This suggests the need to further optimize their therapeutic management to prevent future cardiac events after AMI. However, analysis of clinical characteristics and cardiovascular outcomes in octogenarian subjects with AMI who received the current established medical therapies is limited.

Purpose

To investigate clinical features and prognosis in octogenarian AMI subjects treated with percutaneous coronary intervention (PCI).

Methods

We analyzed 1547 AMI subjects underwent PCI between 2007 and 2017. Baseline characteristics and the occurrence of composite major adverse cardiovascular events (cardiac death, non-fatal MI, revascularization, heart failure and stroke) were compared in octogenarian and non-octogenarian subjects.

Results

22.0% (340/1547) of study subjects was octogenarian. They were more likely to have chronic kidney disease (CKD) and a lower level of LDL-C on admission (Table). Moreover, a higher prevalence of severer Killip class and LVEF <30% were observed in octogenarians (Table). However, they were not optimally treated with the established medical therapies at discharge (Table). During the observational period (median=3.1 years), the composite of cardiovascular events more frequently occurred in octogenarian subjects. Of note, they exhibited a 2.15-fold and 3.01-fold increased risk for heart failure and stroke events, respectively (Figure).

Table 1 Non-Octogenarian (n=1207) Octogenarian (n=340) P-value CKD* (%) 33.8 63.2 <0.0001 LVEF <30% (%) 5.7 10.3 0.02 Killip class 1.33±0.03 1.55±0.05 <0.0001 LDL-C (mmol/L) 3.20±0.03 2.80±0.05 <0.0001 Statin (%) 86.3 78.2 0.0006 Beta-blocker (%) 74.0 65.8 0.005 ACE-I/ARB (%) 87.3 76.6 <0.0001 DAPT (%) 86.0 88.6 0.42 *CKD is defined as estimated glomerular filtration rate (eGFR) <60 ml/min/1.73 m2.

Figure 1

Conclusions

Octogenarian subjects with AMI were high-risk group associated with heart failure and stroke events. Their distinct clinical backgrounds may affect the adoption of optimal medical therapies, potentially resulting in worse cardiovascular outcomes. Further intensified management should be applied to octogenarian subjects with AMI.

Photon and electron backscatter dose and energy spectrum analysis around Lipiodol using flattened and unflattened beams

Purpose

The aim of the current study was to evaluate the backscatter dose and energy spectrum from the Lipiodol with flattening filter (FF) and flattening filter‐free (FFF) beams. Moreover, the backscatter range, that was defined as the backscatter distance (BD) are revealed.

Methods

6 MVX FF and FFF beams were delivered by TrueBeam. Two dose calculation methods with Monte Carlo calculation were used with a virtual phantom in which the Lipiodol (3 × 3 × 3 cm³) was located at a depth of 5.0 cm in a water‐equivalent phantom (20 × 20 × 20 cm³). The first dose calculation was an analysis of the dose and energy spectrum with the complete scattering of photons and electrons, and the other was a specified dose analysis only with scattering from a specified region. The specified dose analysis was divided into a scattering of primary photons and a scattering of electrons.

Results

The lower‐energy photons contributed to the backscatter, while the high‐energy photons contributed the difference of the backscatter dose between the FF and FFF beams. Although the difference in the dose from the scattered electrons between the FF and FFF beams was within 1%, the difference of the dose from the scattered photons between the FF and FFF beams was 5.4% at a depth of 4.98 cm.

Conclusions

The backscatter range from the Lipiodol was within 3 mm and depended on the Compton scatter from the primary photons. The backscatter dose from the Lipiodol can be useful in clinical applications in cases where the backscatter region is located within a tumor.

Tolerance levels of mass density for CT number calibration in photon radiation therapy

Computed tomography (CT) data are required to calculate the dose distribution in a patient's body. Generally, there are two CT number calibration methods for commercial radiotherapy treatment planning system (RTPS), namely CT number-relative electron density calibration (CT-RED calibration) and CT number-mass density calibration (CT-MD calibration). In a previous study, the tolerance levels of CT-RED calibration were established for each tissue type. The tolerance levels were established when the relative dose error to local dose reached 2%. However, the tolerance levels of CT-MD calibration are not established yet. We established the tolerance levels of CT-MD calibration based on the tolerance levels of CT-RED calibration. In order to convert mass density (MD) to relative electron density (RED), the conversion factors were determined with adult reference computational phantom data available in the International Commission on Radiological Protection publication 110 (ICRP-110). In order to validate the practicability of the conversion factor, the relative dose error and the dose linearity were validated with multiple RTPSes and dose calculation algorithms for two groups, namely, CT-RED calibration and CT-MD calibration. The tolerance levels of CT-MD calibration were determined from the tolerance levels of CT-RED calibration with conversion factors. The converted RED from MD was compared with actual RED calculated from ICRP-110. The conversion error was within ±0.01 for most standard organs. It was assumed that the conversion error was sufficiently small. The relative dose error difference for two groups was less than 0.3% for each tissue type. Therefore, the tolerance levels for CT-MD calibration were determined from the tolerance levels of CT-RED calibration with the conversion factors. The MD tolerance levels for lung, adipose/muscle, and cartilage/spongy-bone corresponded to ±0.044, ±0.022, and ±0.045 g/cm3 , respectively. The tolerance levels were useful in terms of approving the CT-MD calibration table for clinical use.

Imaging of Temporal Bone

Multidetector computed tomography has been the benchmark for visualizing bony changes of the ear, but has recently been challenged by cone-beam computed tomography. In both methods, all inner ear bony structures can be visualized satisfactorily with 2D or 3D imaging. Both methods produce ionizing radiation and induce adverse health effects, especially among children. In 3T magnetic resonance imaging, the soft tissue can be imaged accurately. Use of gadolinium chelate (GdC) as a contrast agent allows the partition of fluid spaces to be visualized, such as the bulging of basilar and Reissner's membranes. Both intravenous and intratympanic administration of GdC has been used. The development of positive endolymph imaging method, which visualizes endolymph as a bright signal, and the use of image subtraction seems to allow more easily interpretable images. This long-awaited possibility of diagnosing endolymphatic hydrops in living human subjects has enabled the definition of Hydropic Ear Disease, encompassing typical Meniere's disease as well as its monosymptomatic variants and secondary conditions of endolymphatic hydrops. The next challenge in imaging of the temporal bone is to perform imaging at the cellular and molecular levels. This chapter provides an overview of current temporal bone imaging methods and a review of emerging concepts in temporal bone imaging technology.

First Observation of ^{20}B and ^{21}B

The most neutron-rich boron isotopes ^{20}B and ^{21}B have been observed for the first time following proton removal from ^{22}N and ^{22}C at energies around 230  MeV/nucleon. Both nuclei were found to exist as resonances which were detected through their decay into ^{19}B and one or two neutrons. Two-proton removal from ^{22}N populated a prominent resonancelike structure in ^{20}B at around 2.5 MeV above the one-neutron decay threshold, which is interpreted as arising from the closely spaced 1^{-},2^{-} ground-state doublet predicted by the shell model. In the case of proton removal from ^{22}C, the ^{19}B plus one- and two-neutron channels were consistent with the population of a resonance in ^{21}B 2.47±0.19  MeV above the two-neutron decay threshold, which is found to exhibit direct two-neutron decay. The ground-state mass excesses determined for ^{20,21}B are found to be in agreement with mass surface extrapolations derived within the latest atomic-mass evaluations.

Contribution of pharmacists with expertise in infectious diseases to appropriate individualized vancomycin dosing

BACKGROUND/AIM

Dose adjustment of vancomycin (VCM) is important in improving clinical outcomes and avoiding adverse effects such as nephrotoxicity. Although pharmacist-managed VCM therapy has been reported to optimize treatment, there are no studies focused on pharmacist expertise to date. In this study, we compared the contribution of pharmacists trained for infectious diseases and general pharmacists to dose adjustment of VCM.

PATIENTS AND METHODS

We retrospectively investigated VCM trough concentration after dose adjustment by both trained (n = 67) and general (without special training for infectious diseases; n = 85) pharmacists. We also compared the incidence of nephrotoxicity during VCM treatment in both groups.

RESULTS

The rate of achieving therapeutic VCM trough concentration (10-20 μg/mL) was higher in the trained group than in the control group (80.6 vs. 54.1%, p < 0.001). No significant differences in incidence of nephrotoxicity were observed between the two groups (p = 0.744). Trained pharmacists could contribute more successfully to the achievement of therapeutic VCM concentration ranges without increasing the risk of nephrotoxicity.

Evaluation of optimization workflow using design of experiment (DoE) for various field configurations in volumetric-modulated arc therapy

PURPOSE

In volumetric-modulated arc therapy (VMAT), field configurations such as couch or arc angles are defined manually or using a template. A field configuration is reselected through trial-and-error in the case of undesirable resultant planning. To efficiently plan for desirable quality, configurations should be assessed before dose calculation. Design of experiments (DoE) is an optimization technique that efficiently reveals the influence of inputs on outputs. We developed an original tool using DoE to determine the field configuration selection and evaluated the efficacy of this workflow for clinical practice.

METHODS

Computed-tomography scans of 17 patients and target structures were acquired retrospectively from a brain tumor treated using a dual-arc VMAT plan. The configurations of the couch, arc, collimator angles, field sizes, and beam energy were determined using DoE. The resultant dose distributions obtained using the DoE-selected configuration were compared with the clinical plan.

RESULTS

The averaged differences between the DoE and clinical plan for 17 patients of doses to 50% of the planning target volume (PTV-D50%), Brain-D60%, Brain-D30%, Brain stem-D1%, Left eye-D1%, Right eye-D1%, Optic nerve-D1%, and Chiasm-D1% were 0.2 ± 0.5%, -1.0 ± 4.6%, 1.7 ± 3.5%, -2.5 ± 6.7%, -0.2 ± 4.9%, -1.2 ± 3.6%, -2.8 ± 7.3%, and -2.1 ± 5.7%, respectively.

CONCLUSIONS

Our optimization workflow obtained using DoE for various field configurations provided the same or slightly superior plan quality compared with that created by experts. This process is feasible for clinical practice and will efficiently improve treatment quality while removing the influence of the planner's experience.

Effect of secondary electron generation on dose enhancement in Lipiodol with and without a flattening filter

PURPOSE

Lipiodol, which was used in transcatheter arterial chemoembolization before liver stereotactic body radiation therapy (SBRT), remains in SBRT. Previous we reported the dose enhancement in Lipiodol using 10 MV (10×) FFF beam. In this study, we compared the dose enhancement in Lipiodol and evaluated the probability of electron generation (PEG) for the dose enhancement using flattening filter (FF) and flattening filter free (FFF) beams.

METHODS

FF and FFF for 6 MV (6×) and 10× beams were delivered by TrueBeam. The dose enhancement factor (DEF), energy spectrum, and PEG was calculated using Monte Carlo (MC) code BEAMnrc and heavy ion transport code system (PHITS).

RESULTS

DEFs for FF and FFF 6× beams were 7.0% and 17.0% at the center of Lipiodol (depth, 6.5 cm). DEFs for FF and FFF 10× beams were 8.2% and 10.5% at the center of Lipiodol. Spectral analysis revealed that the FFF beams contained more low-energy (0-0.3 MeV) electrons than the FF beams, and the FF beams contained more high-energy (>0.3 MeV) electrons than the FFF beams in Lipiodol. The difference between FFF and FF beam DEFs was larger for 6× than for 10×. This occurred because the 10× beams contained more high-energy electrons. The PEGs for photoelectric absorption and Compton scattering for the FFF beams were higher than those for the FF beams. The PEG for the photoelectric absorption was higher than that for Compton scattering.

CONCLUSIONS

FFF beam contained more low-energy photons and it contributed to the dose enhancement. Energy spectra and PEGs are useful for analyzing the mechanisms of dose enhancement.

Interfractional diaphragm changes during breath-holding in stereotactic body radiotherapy for liver cancer

Aim and background

IGRT based on bone matching may produce a large target positioning error in terms of the reproducibility of expiration breath-holding on SBRT for liver cancer. We evaluated the intrafractional and interfractional errors using the diaphragm position at the end of expiration by utilising Abches and analysed the factor of the interfractional error.

Materials and methods

Intrafractional and interfractional errors were measured using a couple of frontal kV images, planning computed tomography (pCT) and daily cone-beam computed tomography (CBCT). Moreover, max-min diaphragm position within daily CBCT image sets with respect to pCT and the maximum value of diaphragm position difference between CBCT and pCT were calculated.

Results

The mean ± SD (standard deviation) of the intra-fraction diaphragm position variation in the frontal kV images was 1.0 ± 0.7 mm in the C-C direction. The inter-fractional diaphragm changes were 0.4 ± 4.6 mm in the C-C direction, 1.4 ± 2.2 mm in the A-P direction, and -0.6 ± 1.8 mm in the L-R direction. There were no significant differences between the maximum value of the max-min diaphragm position within daily CBCT image sets with respect to pCT and the maximum value of diaphragm position difference between CBCT and pCT.

Conclusions

Residual intrafractional variability of diaphragm position is minimal, but large interfractional diaphragm changes were observed. There was a small effect in the patient condition difference between pCT and CBCT. The impact of the difference in daily breath-holds on the interfractional diaphragm position was large or the difference in daily breath-holding heavily influenced the interfractional diaphragm change.

Simulation study of volumetric modulated arc therapy for thoracic esophageal cancer using automated-radiotherapy planning software

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Background: To prevent cardiac toxicity after chemoradiotherapy for esophageal cancer (EC), decrease of high irradiation dose to the heart without expanding the volume of lung irradiated low dose is needed, but this is not easy under the conventional techniques. Purpose of this study is to investigate the utility of volumetric modulated arc therapy using automated-radiotherapy planning software (auto-VMAT) to solve this issue. Methods: In this simulation study, data of 12 patients with stage I-III ECs previously treated by 3D-conformal radiotherapy (3DCRT) was used. We performed auto-VMAT planning using commercially available ‘Pinnacle3 Auto-Planning’ software. Targets for gross tumor (PTV1) and elective nodal region (PTV2), and organs at risk (OARs: lung, heart, left ventricle, epicardium, left pleura, liver and spinal cord) were delineated. Multi-portal beams were used for 3DCRT and dose description was 40 Gy in 20 fractions for PTV1+2 and 20 Gy in 10 fractions-boost for PTV1. We used the simultaneous integrated boost method for auto-VMAT with a dose description of 60 Gy for PTV1 and 48 Gy for PTV2 in 30 fractions. We performed planning in consideration with decrease of volumes irradiated middle to high dose in left ventricle and achievement of volume irradiated 5 Gy (V5) in lung < 50% as high-priority dose constraints. Results: Prescribed dose coverage of PTVs was equivalent between 3DCRT and auto-VMAT, while auto-VMAT showed better dose-conformity. Auto-VMAT showed a significant decrease of mean dose and V20-V60 in heart, left ventricle and epicardium and significant decrease of V50-V60 in lung and left pleura. V5 in lung was equivalent between 3DCRT and auto-VMAT (46.6±9.6% vs 45.6±4.7%; p = 0.72). Auto-VMAT achieved the V5 in lung < 50% in 10 among 12 patients and the max V5 in lung was 52.5%. Conclusions: Auto-VMAT for ECs achieved better dose conformity of targets, decrease of middle-high dose in heart, left ventricle and epicardium, and equivalent low dose volumes in lung. Auto-VMAT planning brings high quality dose distribution, uniformity of quality of planning, laborsaving and timesaving in treatment planning.

The utility of FDG-PET for detecting multiple primary cancers in hypopharyngeal cancer patients

Aim: To examine the utility of 2'-[18F]-fluoro-2'-deoxy-D-glucose positron emission tomography (FDG-PET) for detecting multiple primary cancers (MPC) in patients with hypopharyngeal cancer (HPC). Patients, methods: Seventy patients with HPC underwent FDGPET to determine the staging. Routine clinical examinations were carried out, including computed tomography (CT), magnetic resonance imaging (MRI), ultrasound (US), and oesophagealgastroduodenoscopy (EGDS). The detection rate of synchronous and metachronous cancer was calculated based on FDG-PET alone or FDG-PET combined with clinical routine examination. Sensitivity, specificity, positive predictive values (PPV), negative predictive values (NPV), and accuracy were used to diagnose oesophageal cancer using FDG-PET. Results: Of the 70 patients, 12 (17.1%) had 15 synchronous tumours, and 2 of the 58 remaining patients (3.4%) had metachronous tumours. Oesophageal cancer was discovered most frequently: superficial type (n = 6), advanced type (n = 4). On a per-patient basis, 11 of 12 patients (91.6%) were diagnosed with synchronous tumours, and on a per-lesion basis, 12 of 15 lesions (80.0%) were detected by FDG-PET. The sensitivity, specificity, accuracy, PPV, and NPV of FDG-PET regarding oesophageal cancer were 70%, 100%, 95.7%, 100%, and 95.2% respectively. Three of the six superficial types were positive on FDG-PET. Both of the metachronous tumour lesions were detected by FDG-PET. Conclusion: FDG-PET is useful for estimating the MPC in HPC patients. Since 3 of 10 synchronous oesophageal cancer were missed with PET alone, a combination with EGDS should be considered to exclude synchronous oesophageal cancer.

Energy spectrum and dose enhancement due to the depth of the Lipiodol position using flattened and unflattened beams

Aim

Lipiodol was used for stereotactic body radiotherapy combining trans arterial chemoembolization. Lipiodol used for tumour seeking in trans arterial chemoembolization remains in stereotactic body radiation therapy. In our previous study, we reported the dose enhancement effect in Lipiodol with 10× flattening-filter-free (FFF). The objective of our study was to evaluate the dose enhancement and energy spectrum of photons and electrons due to the Lipiodol depth with flattened (FF) and FFF beams.

Methods

FF and FFF for 6 MV beams from TrueBeam were used in this study. The Lipiodol (3 × 3 × 3 cm³) was located at depths of 1, 3, 5, 10, 20, and 30 cm in water. The dose enhancement factor (DEF) and the energy fluence were obtained by Monte Carlo calculations of the particle and heavy ion transport code system (PHITS).

Results

The DEFs at the centre of Lipiodol with the FF beam were 6.8, 7.3, 7.6, 7.2, 6.1, and 5.7% and those with the FFF beam were 20.6, 22.0, 21.9, 20.0, 12.3, and 12.1% at depths of 1, 3, 5, 10, 20, and 30 cm, respectively, where Lipiodol was located in water. Moreover, spectrum results showed that more low-energy photons and electrons were present at shallow depth where Lipiodol was located in water. The variation in the low-energy spectrum due to the depth of the Lipiodol position was more explicit with the FFF beam than that with the FF beam.

Conclusions

The current study revealed variations in the DEF and energy spectrum due to the depth of the Lipiodol position with the FF and FFF beams. Although the FF beam could reduce the effect of energy dependence due to the depth of the Lipiodol position, the dose enhancement was overall small. To cause a large dose enhancement, the FFF beam with the distance of the patient surface to Lipiodol within 10 cm should be used.

SS-MIX: A Ministry Project to Promote Standardized Healthcare Information Exchange

Objectives: To promote healthcare information exchange between providers and to allow hospital information systems (HIS) export information in standardized format (HL7 and DICOM) in an environment of widespread legacy systems, which only can export data in proprietary format.

Methods: Through the Shizuoka prefecture EMR project in 2004–2005, followed by the ministry’s SS-MIX project, many software products have been provided, which consist of 1) a standardized storage to receive HL7 v2.5 mes sages of patient demographics, prescription orders, laboratory results, and diagnostic disease in ICD-10, 2) a referral letter creation system, 3) a formatted document creation system, 4) a progress note/nursing record system, and 5) an archive/viewer to incorporate incoming healthcare data CD and allow users to view on HIS terminal. Meanwhile, other useful applications have been produced, such as adverse event reporting and clinical information retrieval. To achieve the above-mentioned objectives, these software products were created and propagated, because users can use these software products, provided that their HIS can export the above information to the standardized storage in HL7 v2.5 format.

Results: In 20 hospitals of Japan, the standardized storage has been installed and some applications have been used. As major HIS vendors are shipping HIS with HL7 export function since 2007, HIS of 594 hospitals in Japan became capable of exporting data in HL7 v2.5 format (as of March 2010).

Conclusions: In high CPOE installation rate (85% in 400+ bed hospitals), though most of them only capable of exporting data in proprietary format, prefecture and ministry projects were effective to promote healthcare information exchange between providers. The standardized storage became an infrastructure for many useful applications, and many hospitals started using them. Ministry designation of proposed healthcare standards was effective so as to allow vendors to conform their products, and users to install them.

Tolerance levels of CT number to electron density table for photon beam in radiotherapy treatment planning system

The accuracy of computed tomography number to electron density (CT-ED) calibration is a key component for dose calculations in an inhomogeneous medium. In a previous work, it was shown that the tolerance levels of CT-ED calibration became stricter with an increase in tissue thickness and decrease in the effective energy of a photon beam. For the last decade, a low effective energy photon beam (e.g., flattening-filter-free (FFF)) has been used in clinical sites. However, its tolerance level has not been established yet. We established a relative electron density (ED) tolerance level for each tissue type with an FFF beam. The tolerance levels were calculated using the tissue maximum ratio (TMR) and each corresponding maximum tissue thickness. To determine the relative ED tolerance level, TMR data from a Varian accelerator and the adult reference computational phantom data in the International Commission on Radiological Protection publication 110 (ICRP-110 phantom) were used in this study. The 52 tissue components of the ICRP-110 phantom were classified by mass density as five tissues groups including lung, adipose/muscle, cartilage/spongy-bone, cortical bone, and tooth tissue. In addition, the relative ED tolerance level of each tissue group was calculated when the relative dose error to local dose reached 2%. The relative ED tolerances of a 6 MVFFF beam for lung, adipose/muscle, and cartilage/spongy-bone were ±0.044, ±0.022, and ±0.044, respectively. The thicknesses of the cortical bone and tooth groups were too small to define the tolerance levels. Because the tolerance levels of CT-ED calibration are stricter with a decrease in the effective energy of the photon beam, the tolerance levels are determined by the lowest effective energy in useable beams for radiotherapy treatment planning systems.

Accuracy of the raw-data-based effective atomic numbers and monochromatic CT numbers for contrast medium with a dual-energy CT technique

OBJECTIVE

To evaluate the accuracy of raw-data-based effective atomic number (Z_eff) values and monochromatic CT numbers for contrast material of varying iodine concentrations, obtained using dual-energy CT.

METHODS

We used a tissue characterization phantom and varying concentrations of iodinated contrast medium. A comparison between the theoretical values of Z_eff and that provided by the manufacturer was performed. The measured and theoretical monochromatic CT numbers at 40-130 keV were compared.

RESULTS

The average difference between the Z_eff values of lung (inhale) inserts in the tissue characterization phantom was 81.3% and the average Z_eff difference was within 8.4%. The average difference between the Z_eff values of the varying concentrations of iodinated contrast medium was within 11.2%. For the varying concentrations of iodinated contrast medium, the differences between the measured and theoretical monochromatic CT values increased with decreasing monochromatic energy. The Z_eff and monochromatic CT numbers in the tissue characterization phantom were reasonably accurate.

CONCLUSION

The accuracy of the raw-data-based Z_eff values was higher than that of image-based Z_eff values in the tissue-equivalent phantom. The accuracy of Z_eff values in the contrast medium was in good agreement within the maximum SD found in the iodine concentration range of clinical dynamic CT imaging. Moreover, the optimum monochromatic energy for human tissue and iodinated contrast medium was found to be 70 keV. Advances in knowledge: The accuracy of the Z_eff values and monochromatic CT numbers of the contrast medium created by raw-data-based, dual-energy CT could be sufficient in clinical conditions.

The comparison of nasal surgery and CPAP on daytime sleepiness in patients with OSAS

OBJECTIVE

Residual sleepiness after continuous positive airway pressure (CPAP) is a critical problem in some patients with obstructive sleep apnea syndrome (OSAS). However, nasal surgery is likely to reduce daytime sleepiness and feelings of unrefreshed sleep. The aim of this study is to clarify the effects of nasal surgery and CPAP on daytime sleepiness.

METHODOLOGY

This is a retrospective and matched-case control study. The participants were consecutive 40 patients with OSAS who underwent nasal surgery (Surgery group) and 40 matched patients who were treated with CPAP (CPAP group).

RESULTS

In the Surgery group, although the nasal surgery did not decrease either apnea or hypopnea, it improved oxygenation, the quality of sleep. In the CPAP Group, the CPAP treatment reduced apnea and hypopnea, and improved oxygenation, quality of sleep. The degree of relief from daytime sleepiness was different between the two groups. The improvement of Epworth Sleepiness Scale was more significant in the Surgery Group than those in the CPAP Group (Surgery from 11.0 to 5.1, CPAP from 10.0 to 6.2).

DISCUSSION

These findings suggest that the results of the nasal surgery is more satisfactory for some patients with OSAS than CPAP on daytime sleepiness.

Clinical outcomes of concurrent chemoradiotherapy with volumetric modulated arc therapy in patients with locally advanced nasopharyngeal carcinoma

PURPOSE

The purpose of this study was to analyze the clinical results of concurrent chemoradiotherapy (CCRT) with volumetric modulated arc therapy (VMAT) for nasopharyngeal carcinoma (NPC) patients.

MATERIALS AND METHODS

Patients with stage II-IVB NPC who received CCRT with VMAT between 2010 and 2014 were included in this study. The planned dose was 70 Gy in 35 fractions.

RESULTS

Twenty patients aged between 28 and 85 years (median 60 years) were assessed. With a median follow-up time of 47 months, the 3-year overall survival and progression-free survival rates were 85 and 65%, respectively. The 3-year local, regional and distant control rates were 78, 88 and 79%, respectively. At 0, 3, 6 and 12 months from CCRT, 19, 6, 3, and 1 patients had grade 2 dry mouth, respectively. No cases of grade 3 or worse dry mouth were observed. The severity of dry mouth was downgraded from grade 2 to grade 0 or 1 significantly earlier in younger patients (<70 years, p = 0.02) or patients in whom the mean dose to one parotid gland was lower (<26 Gy, p = 0.04).

CONCLUSIONS

Our clinical results regarding CCRT with VMAT for NPC patients showed favorable survival rates while maintaining organ function.