Racial differences in predictive value of the 21-gene recurrence score assay: a population-based study using the SEER database.

PURPOSE: The 21-gene recurrence score (RS) assay is currently used for predicting chemotherapeutic benefits for hormone receptor-positive (HR +) early-stage breast cancer patients without consideration regarding racial differences in that predictive value. This study aimed at demonstrating racial differences in the predictive values of the 21-gene RS assay. METHODS: The study cohort was selected from the Surveillance, Epidemiology, and End Results (SEER) database. Breast cancer-specific mortality (BCSM) was compared between patients who received chemotherapy (the "CTx group") and those who did not (the "no CTx group") to estimate the predictive value of the assay. This comparison was repeated for each racial group. RESULTS: Among 88,498 T1 - 2N0 HR + breast cancer patients who had results of 21-gene RS, 13,123 patients had RS > 25, which included 10,697 Whites, 1282 Blacks, and 1,144 Asian Americans/Pacific Islanders (AAPIs). Chemotherapy was administered to 8364 patients (63.4%). The adjusted hazard ratio for BCSM in the CTx group (vs. no CTx group) was 0.734 (95% confidence interval [CI] 0.588-0.917) in Whites, 0.748 (95% CI 0.428-1.307) in Blacks, and 1.343 (95% CI 0.558-3.233) in AAPIs. No subgroup within patients with RS > 25 among non-White women showed a significant predictive value of the 21-gene RS assay, except for Black women with grade 3 tumors. CONCLUSION: The predictive value of the 21-gene RS assay for assessing chemotherapy benefit was validated in White women based on the SEER database, although the predictive value was not warranted in non-White women.

Pneumonia-targeted lopinavir/ritonavir-based treatment for patients with COVID-19: an early-period retrospective single center observational study.

BACKGROUND: Robust evidenced treatment strategy for Coronavirus disease 2019 (COVID-19) has not been established yet. Early, targeted, comprehensive management approach can be essential. METHODS: A lopinavir/ritonavir (LPV/r)-based antiviral treatment was administered to the patients with computed tomography (CT)-documented pneumonia. Medical records of patients with COVID-19, previously discharged or hospitalized for ≥ 21 days at the Seoul Medical Center from January 29 to April 15, 2020 were reviewed to analyze clinical and virological outcomes. Patients were divided into two groups (PCR-Negative conversion group vs. Non-negative conversion group and requiring oxygen group vs. Non-requiring oxygen group). RESULTS: In total, 136 patients with a mean age of 41.8 ± 18.2 years were included with median 3-day delay of hospitalization after illness. Thirteen (9.56%) were initially asymptomatic, and 5 (3.67%) were persistently asymptomatic. Eighty-five (62.5%) had CT-documented pneumonia, 94% of whom received LPV/r treatments. A total of 53 patients (38.97%) had negative polymerase chain reaction (PCR) results within 28 days. Eight (9.4%) out of 85 pneumonic patients received oxygen supplementation. Patients with initial lower respiratory symptoms showed significant delay in PCR negative conversion (> 28 days) (odds ratio [OR] 0.166; 95% confidence interval [CI] 0.067-0.477; P < 0.001). However, antiviral treatment for pneumonic patients was significantly related with early conversion within 28 days (OR 3.049; 95% CI 1.128-8.243; P = 0.028). Increasing age increased the likelihood of oxygen supplementation requirement in the pneumonic patient group (OR 1.108; 95% CI 1.021-1.202; P = 0.014). CONCLUSIONS: Early, pneumonia targeted LPV/r-based antiviral therapy resulted in a significantly higher probability of negative conversion of PCR within 28 days compared to symptomatic treatment.

Feasibility Study of a Time-of-Flight Brain Positron Emission Tomography Employing Individual Channel Readout Electronics.

The purpose of this study was to investigate the feasibility of a time-of-flight (TOF) brain positron emission tomography (PET) providing high-quality images. It consisted of 30 detector blocks arranged in a ring with a diameter of 257 mm and an axial field of view of 52.2 mm. Each detector block was composed of two detector modules and two application-specific integrated circuit (ASIC) chips. The detector module was composed of an 8 × 8 array of 3 × 3 mm2 multi-pixel photon counters and an 8 × 8 array of 3.11 × 3.11 × 15 mm3 lutetium yttrium oxyorthosilicate scintillators. The 64-channel individual readout ASIC was used to acquire the position, energy, and time information of a detected gamma ray. A coincidence timing resolution of 187 ps full width at half maximum (FWHM) was achieved using a pair of channels of two detector modules. The energy resolution and spatial resolution were 6.6 ± 0.6% FWHM (without energy nonlinearity correction) and 2.5 mm FWHM, respectively. The results of this study demonstrate that the developed TOF brain PET could provide excellent performance, allowing for a reduction in radiation dose or scanning time for brain imaging due to improved sensitivity and signal-to-noise ratio.

Influence of Metabolic Syndrome on Risk of Breast Cancer: A Study Analyzing Nationwide Data from Korean National Health Insurance Service.

BACKGROUND: To investigate the influence of metabolic syndrome and its components on the risk of breast cancer. METHODS: Retrospective nationwide cohort study analyzing data of 13,377,349 women older than 19 years from Korean National Health Insurance Service was performed. Cox proportional hazards model was used to calculate HR and 95% confidence interval (CI) of breast cancer risk. RESULTS: The presence of metabolic syndrome decreased the risk of all breast cancer types in all subjects (HR, 0.954; 95% CI, 0.939-0.970). In women with age ≤50 years, metabolic syndrome decreased the risk of all breast cancer types, with similar findings for all subject groups (HR, 0.915; 95% CI, 0.892-0.939). In women with age >50 years, metabolic syndrome increased the risk of all breast cancer types (HR, 1.146; 95% CI, 1.123-1.170), especially in age groups of more than 55 years. In women with age >50 years, HRs increased as the number of metabolic syndrome components increased, while HRs decreased as the number of metabolic syndrome components increased in women with age ≤50 years. CONCLUSIONS: The presence of metabolic syndrome increased the risk of breast cancers in postmenopausal women, but decreased the risk in premenopausal women. Every metabolic syndrome component played similar roles on the risk of breast cancer as metabolic syndrome, and their effects became stronger when the number of components increased. IMPACT: Metabolic syndrome is associated with the risk of breast cancer having different effect according to age groups.

The 21-Gene Recurrence Score Assay and Prediction of Chemotherapy Benefit: A Propensity Score-Matched Analysis of the SEER Database.

BACKGROUND: To evaluate the performance of the 21-gene recurrence score (RS) assay in predicting chemotherapy benefit in the Surveillance, Epidemiology, and End Results population, we aimed to assess breast cancer-specific mortality (BCSM) by chemotherapy use within each of the RS categories. METHODS: Data on breast cancer (BC) cases diagnosed between 2004 and 2015 with available RS results were released. Our analysis included patients with hormone receptor-positive, node-negative early-stage BC (n = 89,402), and three RS groups were defined; RS < 11, low; RS 11-25, intermediate; RS > 25, high. A propensity score matched-analysis was performed to assess and compare BCSM. RESULTS: Chemotherapy was significantly associated with a reduced risk of BC death among patients in the high RS group (hazard ratio = 0.782; 95% CI, 0.618-0.990; p = 0.041). However, in the low and intermediate RS groups, there were no significant differences in BCSM between patients who received chemotherapy and those who did not. Among those with RS 11-25, chemotherapy benefit varied with tumor size (p = 0.001). CONCLUSIONS: Our findings provide real-world evidence that the 21-gene RS assay is predictive of chemotherapy benefit among patients in clinical practice. More refined risk estimates would be needed for patients with an intermediate RS.

Validating the ACOSOG Z0011 Trial Result: A Population-Based Study Using the SEER Database.

The Z0011 trial demonstrated that axillary lymph node dissection (ALND) could be omitted in spite of 1-2 metastatic sentinel lymph nodes. This study aimed to validate the results on a population-based database. The Surveillance, Epidemiology, and End Results (SEER) database was searched for patients comparable to the Z0011 participants. The type of axillary surgery was estimated using the total number of examined axillary lymph nodes (ALNs). Breast cancer-specific mortality (BCSM) was compared between patients with ≥10 ALNs (the sentinel lymph node dissection (SLND) and ALND group, or "SLND + ALND group") and patients with one or two ALNs (the "SLND group"). During 2010-2015, the SEER database included 7077 and 6620 patients categorized in the SLND group and the SLND + ALND group, respectively. Death was observed for 515 patients (7.3%) in the SLND group and 589 patients (8.9%) in the SLND + ALND group based on a median follow-up of 41 months. After propensity-score matching, the adjusted hazard ratio for BCSM in the SLND group (vs. the SLND + ALND group) was 1.038 (95% confidence interval: 0.798-1.350). Regardless of the SLND criteria, the outcomes were not significantly different between the two groups. This retrospective cohort study of Z0011-comparable patients revealed that ALND could be omitted based on the Z0011 strategy, even among patients with ≤2 dissected ALNs.

Long-term prognostic effect of hormone receptor subtype on breast cancer.

PURPOSE: To determine the long-term prognostic role of hormone receptor subtype in breast cancer using surveillance, epidemiology, and end results (SEER) database. METHODS: Data of 810,587 female operable invasive breast cancer patients from SEER database with a mean follow-up period of 94.2 months (range, 0-311 months) were analyzed. Hormone receptor subtype was classified into four groups based on estrogen receptor (ER) and progesterone receptor (PR) statuses: ER(+)/PR(+), ER(+)/PR(-), ER(-)/PR(+), and ER(-)/PR(-). RESULTS: Numbers of subjects with ER(+)/PR(+), ER(+)/PR(-), ER(-)/PR(+), ER(-)/PR(-), and unknown were 496,279 (61.2%), 86,858 (10.7%), 11,545 (1.4%), 135,441 (16.7%), and 80,464 (9.9%), respectively. The ER(+)/PR(+) subtype showed the best breast-cancer-specific survival, followed by ER(+)/PR(-), ER(-)/PR(+), and ER(-)/PR(-) subtypes in the respective order (all p < 0.001). Survival difference among hormone receptor subtypes was maintained in subgroup analysis according to anatomic stage, race, age group, and year of diagnosis. Hormone receptor subtype was a significant independent prognostic factor in multivariable analyses (p < 0.001). Hazard ratios of ER(+)/PR(-), ER(-)/PR(+), and ER(-)/PR(-) for breast-cancer-specific mortality risk were 1.419 (95% confidence interval [CI] 1.383-1.456), 1.630 (95% CI 1.537-1.729), and 1.811 (95% CI 1.773-1.848), respectively, with ER(+)/PR(+) as reference. CONCLUSION: Hormone receptor subtype is a significant independent prognostic factor in female operable invasive breast cancer patients with long-term effect. The ER(+)/PR(+) subtype shows the most favorable prognosis, followed by ER(+)/PR(-), ER(-)/PR(+), and ER(-)/PR(-) subtypes in the respective order. Prognostic impacts of hormone receptor subtypes are also maintained in subgroup analysis according to anatomic stage, race, age, and year of diagnosis.

Prognostic influence of Korean public medical insurance system on breast cancer patients.

PURPOSE: To investigate the prognostic influence of Korean public medical insurance system on breast cancer patients. METHODS: Data of 1,068 patients with primary invasive breast cancer were analyzed. Korean public medical insurance status was classified into 2 groups: National Health Insurance and Medical Aid. Kaplan-Meier estimator and Cox proportional hazards model were used for survival analysis. RESULTS: The Medical Aid group showed worse prognoses compared to the National Health Insurance group both in overall survival (P = 0.001) and recurrence-free survival (P = 0.006). The Medical Aid group showed higher proportion of patients with tumor size > 2 cm (P = 0.022), more advanced stage (P = 0.039), age > 50 years (P = 0.003), and low education level (P = 0.003). The Medical Aid group showed higher proportion of patients who received mastectomy (P < 0.001) and those who received no radiation therapy (P = 0.013). The Medical Aid group showed a higher rate of distant recurrence (P = 0.014) and worse prognosis for the triple negative subtype (P = 0.006). Medical insurance status was a significant independent prognostic factor in both univariate analysis and multivariate analysis. CONCLUSION: The Medical Aid group had worse prognosis compared to the National Health Insurance group. Medical insurance status was a strong independent prognostic factor in breast cancer. Unfavorable clinicopathologic features could explain the worse prognosis for the Medical Aid group. Careful consideration should be given to medical insurance status as one of important prognostic factors for breast cancer patients.

Retrospectively validating the results of the ACOSOG Z0011 trial in a large Asian Z0011-eligible cohort.

PURPOSE: The Z0011 trial demonstrated that axillary dissection (ALND) could be omitted during breast-conserving therapy for cT1-2N0 breast cancers with 1-2 metastatic SLNs. However, that result has not been validated in a larger cohort and the significance of the small number of SLNs remains unclear. This study aimed to validate the Z0011 results within an Asian Z0011-eligible cohort and determine whether the number of sentinel lymph nodes (SLNs) influenced the Z0011-based outcomes. METHODS: Data from Asian patients who fulfilled the Z0011 criteria were collected from five hospitals. Disease recurrence (DR) was compared between patients who underwent ALND or SLN dissection (SLND) alone. Propensity-score matching was performed to reduce the effects of potential selection biases. RESULTS: During 2010-2016, 1750 Asian patients had 1-2 SLN metastases and fulfilled the Z0011 criteria. These patients included 707 cases treated using SLND alone (40%) and 967 patients with ≤ 2 SLNs (55%). Ninety-five patients (5.4%) experienced DR at a median interval of 50 months, although the rates of DR were similar in the ALND and SLND groups. The adjusted hazard ratios for DR after ALND omission were 0.95 (95% CI 0.55-1.64) among the entire cohort and 0.83 (95% CI 0.34-2.03) among patients with ≤ 2 SLNs. CONCLUSIONS: In this Asian Z0011-eligible cohort, ALND omission did not increase risk of DR, even among patients with ≤ 2 SLNs. Therefore, the Z0011 strategy might be safely applied in Asia, and a small number of SLNs did not significantly influence this strategy.

Performance evaluation of a small animal PET scanner a high level of multiplexing and charge-signal transmission.

Small animal positron emission tomography (PET) is a noninvasive imaging modality that enables in vivo imaging and quantification of the biological processes of small experimental animals. We have developed a small animal PET that utilizes a high-resolution multiplexed readout and charge signal transmission (CST) method. The small animal PET was composed of six detector blocks consisting of SiPMs and LYSO arrays. Six detector blocks were mounted on a PET gantry having an inner diameter of 76 mm, outer diameter of 112 mm, and axial length of 40.8 mm. The charge signals of SiPM output were transmitted to the input of multiplexed readout using 4 m flexible flat cables. The multiplexed readout was composed of six main boards, each of which included 36 detector boards, to reduce the number of readout channels by a factor of 36, with a multiplexing ratio of 144:4. The performance of the small animal PET was evaluated using NEMA NU 4-2008 standards, and its imaging capability was demonstrated by in vivo mouse imaging studies. The average energy and time resolutions were 13.2% ± 0.3% and 3.8 ns, respectively. The spatial resolution at the center of the transaxial FOV was 1.1 mm, and the peak sensitivity at the center of the axial FOV was 1.5%. The peak noise equivalent count (NEC) rate and scatter fraction were 21.1 kcps at 18.2 MBq and 21%, respectively. The acquired images demonstrated high quality tracer uptake patterns of small experimental animals. The results of performance evaluation and animal imaging indicate that the small animal PET developed in this study can provide high-quality small animal imaging with cost-effectiveness and compactness.

Prognostic Role of KRAS mRNA Expression in Breast Cancer.

PURPOSE: We investigated the prognostic role of KRAS mRNA expression in breast cancer using The Cancer Genome Atlas (TCGA) and Molecular Taxonomy of Breast Cancer International Consortium (METABRIC) databases. METHODS: Clinical and biological data of 1,093 breast cancers from TCGA database and 1,904 breast cancers from METABRIC database were analyzed. Overall survival (OS) and breast cancer-specific survival (BCSS) were determined. RESULTS: The group with high KRAS mRNA expression showed worse survival than the group with low KRAS mRNA expression regarding both OS (p = 0.012 in TCGA, p < 0.001 in METABRIC) and BCSS (p = 0.001 in METABRIC). According to multivariate analysis, the level of KRAS mRNA expression was an independent prognostic factor in both TCGA (hazard ratio [HR], 1.570; 95% confidence interval [CI], 1.026-2.403; p = 0.038) and METABRIC (HR, 1.254; 95% CI, 1.087-1.446; p = 0.002) databases. The prognostic impact of mRNA expression was effective only for luminal A subtype (p < 0.001 in METABRIC). Positive correlation was observed between mRNA expression and copy number alteration (CNA) (r = 0.577, p < 0.001 in TCGA; ρ = 0.343, p < 0.001 in METABRIC). Methylation showed negative correlations with both mRNA expression and CNA (r = -0.272, p < 0.001 in TCGA). The expression of mRNA had little association with the mutation status in breast cancers, having a mutation frequency of approximately 0.6%. CONCLUSION: KRAS mRNA expression was significantly associated with breast cancer prognosis. It was found to be an independent prognostic factor for breast cancer. Prognostic role of KRAS mRNA expression was effective only in luminal A subtype. Further studies are needed to validate the prognostic role of KRAS mRNA expression in breast cancer, thus paving a way for clinical application of KRAS in practice.

Impact of Breast Cancer Subtypes on Prognosis of Women with Operable Invasive Breast Cancer: A Population-based Study Using SEER Database.

PURPOSE: To determine the prognostic roles of breast cancer subtypes in females with operable invasive breast cancer.Experimental Design: Data of 321,958 patients from Surveillance, Epidemiology, and End Results (SEER) database were analyzed. Breast cancer subtypes were classified into four categories according to the status of hormone receptor (HRc) and HER2: HRc(+)/HER2(-), HRc(+)/HER2(+), HRc(-)/HER2(+), and HRc(-)/HER2(-). RESULTS: Proportions of HRc(+)/HER2(-), HRc(+)/HER2(+), HRc(-)/HER2(+), HRc(-)/HER2(-), and unknown subtype were 70.3%, 9.4%, 3.9%, 10.4%, and 6.0%, respectively. HRc(+)/HER2(-) showed the highest 5-year breast cancer-specific survival (BCSS) rate (95.5%), followed by HRc(+)/HER2(+) (94.1%), HRc(-)/HER2(+) (89.3%), and HRc(-)/HER2(-) (83.1%). HRc(+)/HER2(-) and HRc(+)/HER2(+) showed higher 5-year overall survival (OS) rates (88.4% and 88.2%, respectively) than HRc(-)/HER2(+) and HRc(-)/HER2(-) (83.9% and 76.5%, respectively). HRc(-)/HER2(-) showed the worst BCSS irrespective of race, age, or stage. Although proportions of HRc(-)/HER2(-) in the subgroup with negative event regarding BCSS and OS were 10.4% and 10.2%, respectively, they were 34.2% and 22.7%, respectively, in the subgroup with positive event. Subtype was a significant factor in both univariable and multivariable analyses regarding both BCSS and OS (all P < 0.001). CONCLUSIONS: Breast cancer subtype was a significant independent prognostic factor regarding both BCSS and OS in multivariable analyses. HRc(+) subtypes showed better prognosis compared with HRc(-) subtypes regarding both BCSS and OS. HRc(-)/HER2(+) showed better prognosis than HRc(-)/HER2(-) but worse prognosis than HRc(+) subtypes regarding both BCSS and OS. The triple-negative subtype showed the worst BCSS compared with the other subtypes irrespective of race, age, or stage.

Clinical implication of subcategorizing T2 category into T2a and T2b in TNM staging of breast cancer.

Regarding TNM staging in breast cancer, T2 category is currently not divided into subcategories even though it covers a wider range of tumor sizes than T1 category. Using Korean Breast Cancer Registry database, data of 41 071 women diagnosed as non-metastatic T2 breast cancer between 2001 and 2014 were analyzed. Cutoff value for optimal tumor size was approximated by receiver operating characteristic (ROC) curve to subcategorize T2 tumors. Overall survival (OS) was compared between two subcategories. Median follow-up period was 65 months. Of 41 071 patients, 4504 (11.0%) died. Based on ROC curve analysis, 3.0 cm was selected as the cutoff value. Five-year OS rate was 91% in patients with breast tumors ≤3.0 cm (T2a) and 86% in patients with breast tumors >3.0 cm (T2b) (log-rank P < 0.001). T2b subcategory showed worse OS than T2a subcategory regardless of node status (log-rank P < 0.001 for all node categories). Within every subgroup defined by primary OS analysis covariates, T2b subcategory consistently showed worse outcome compared to T2a subcategory. By multivariate analysis, T2b subcategory was a significant independent prognostic factor of OS (hazard ratio: 1.26, 95% CI = 1.18-1.34). T2 category of breast cancer could be subcategorized into T2a and T2b with a cutoff value of 3 cm. These subcategories definitely showed different OSs even after adjusted for known prognostic factors. Subcategorization of T2 category might be useful for predicting prognosis more accurately and tailoring adjuvant therapy.

Prognostic Influence of Preoperative Mammographic Breast Density in Operable Invasive Female Breast Cancer.

We aimed to investigate the potential of preoperative mammographic breast density (MBD) as a prognostic factor in breast cancer. Data of 969 patients with primary breast cancer were analyzed. We defined low MBD as fatty or fibroglandular breast, and high MBD as heterogeneously dense or extremely dense breast, respectively. The high MBD group demonstrated a superior overall survival rate compared to the low MBD group (p < 0.001). Favorable prognostic effects of high MBD were observed in subgroups aged >50 years (p < 0.001) and with positive hormone receptor (HRc) and negative human epidermal growth factor receptor 2 (HER2) (p < 0.001). The high MBD group had a higher proportion of patients aged ≤50 years (p < 0.001) and patients with body mass index (BMI) ≤25 kg/m2 (p < 0.001), and a higher proportion of patients who received chemotherapy (p < 0.001). MBD was a significant independent prognostic factor by multivariable analysis (hazard ratio, 0.382; 95% confidence interval, 0.206-0.708). The high MBD group was associated with superior overall survival rates. Preoperative MBD was a strong independent prognostic factor in operable primary invasive female breast cancer, especially in patients with age >50 years and the HRc(+)/HER2(-) subtype. Favorable clinicopathologic features, active treatments, and other factors could contribute to this causality.

Analog and digital signal processing method using multi-time-over-threshold and FPGA for PET.

PURPOSE: The goal of this study was to develop an analog and digital signal processing method using multi-time-over-threshold (MTOT) and field programmable gate arrays (FPGAs) to extract PET event information by using the internal clock of FPGA (~350 MHz), without ADC and TDC. METHODS: The PET detector modules were composed of a 4 × 4 matrix of 3 × 3 × 20 mm3 LYSO and 4 × 4 SiPM array. Output charge signals of PET detector modules were amplified and fed into four comparators to generate trigger signals. The energy of the detected gamma ray was calculated by integrating the digitized pulse and the arrival time was determined from the time stamp of the lowest trigger signal by FPGA. The data packet containing energy, time, and position information was stored in list mode on the host computer. RESULTS: The performance of analog and digital signal processing circuits using MTOT method and FPGA was evaluated by measuring energy and time resolution of the proposed method and the values were 19% and 900 ps, respectively. CONCLUSION: This study demonstrated that the proposed MTOT method consisting of only FPGA without ADC and TDC could provide a simple and cost-effective analog and digital signal processing system for PET.

An improved time over threshold method using bipolar signals.

The time over threshold (TOT) method has been recently proposed as a signal processing method used to calculate time and energy information by measuring the pulse arrival time and pulse duration over a preset threshold. Although TOT has been reported as an effective method for front end readout in PET applications, it has several limitations, including its non-linearity, lower dynamic range, and a trade-off between energy resolution and coincidence resolving time (CRT). In this study, we propose a novel design we developed to improve performance with regard to these problems occurring in the conventional TOT by employing a bipolar signal and two comparators. Using a high frequency CR shaping filter, a detected signal was converted into a bipolar signal, and the positive pulse of the converted bipolar signal had a fast rising time, while the negative pulse had a linear slope. The bipolar TOT circuit was composed of a preamplifier, a CR shaping filter, and two comparators. The PET detector was composed of a single LYSO coupled with 4 × 4 SiPM arrays, a bipolar TOT circuit, and an FPGA based TDC. And this was constructed to evaluate the performance of the proposed bipolar TOT method. A 16-ch PET detector module consisting of a 4 × 4 array LYSO coupled to a 4 × 4 SiPM arrays, an Anger logic discretized positioning circuit, and a 4-ch bipolar TOT circuit was also constructed to evaluate the functionality of the bipolar TOT method for PET applications. The pulse height resolution and CRT were measured using both the bipolar TOT method and the conventional TOT method. While the bipolar TOT method provided a similar pulse height resolution (10.4% ± 0.1%), the integral non-linearity (1.4%) and CRT (168 ± 4 ps) measured using the bipolar TOT method were greatly improved compared to those (17.2% and 258 ± 15 ps, respectively) measured with the conventional TOT method. The positions of the crystals were clearly identified, as seen in the flood histogram acquired using the 4-ch bipolar TOT circuit. The measured average pulse height resolution and average CRT for the 16-ch detector module were 11.5% ± 0.2% and 516 ± 24 ps. The results obtained in this study indicate that the bipolar TOT method requiring a relatively small number of electronic components could effectively improve the CRT, linearity and dynamic range. Furthermore, they also demonstrated the extendibility allowing the development of a PET system that consists of a large number of detectors.

Development of PET/MRI with insertable PET for simultaneous PET and MR imaging of human brain.

PURPOSE: The purpose of this study was to develop a dual-modality positron emission tomography (PET)/magnetic resonance imaging (MRI) with insertable PET for simultaneous PET and MR imaging of the human brain. METHODS: The PET detector block was composed of a 4 × 4 matrix of detector modules, each consisting of a 4 × 4 array LYSO coupled to a 4 × 4 Geiger-mode avalanche photodiode (GAPD) array. The PET insert consisted of 18 detector blocks, circularly mounted on a custom-made plastic base to form a ring with an inner diameter of 390 mm and axial length of 60 mm. The PET gantry was shielded with gold-plated conductive fabric tapes with a thickness of 0.1 mm. The charge signals of PET detector transferred via 4 m long flat cables were fed into the position decoder circuit. The flat cables were shielded with a mesh-type aluminum sheet with a thickness of 0.24 mm. The position decoder circuit and field programmable gate array-embedded DAQ modules were enclosed in an aluminum box with a thickness of 10 mm and located at the rear of the MR bore inside the MRI room. A 3-T human MRI system with a Larmor frequency of 123.7 MHz and inner bore diameter of 60 cm was used as the PET/MRI hybrid system. A custom-made radio frequency (RF) coil with an inner diameter of 25 cm was fabricated. The PET was positioned between gradient and the RF coils. PET performance was measured outside and inside the MRI scanner using echo planar imaging, spin echo, turbo spin echo, and gradient echo sequences. MRI performance was also evaluated with and without the PET insert. The stability of the newly developed PET insert was evaluated and simultaneous PET and MR images of a brain phantom were acquired. RESULTS: No significant degradation of the PET performance caused by MR was observed when the PET was operated using various MR imaging sequences. The signal-to-noise ratio of MR images was slightly degraded due to the PET insert installed inside the MR bore while the homogeneity was maintained. The change of gain of the 256 GAPD/scintillator elements of a detector block was <3% for 60 min, and simultaneous PET and MR images of a brain phantom were successfully acquired. CONCLUSIONS: Experimental results indicate that a compact and lightweight PET insert for hybrid PET/MRI can be developed using GAPD arrays and charge signal transmission method proposed in this study without significant interference.

Evaluation of uncompensated unilateral vestibulopathy using the modified clinical test for sensory interaction and balance.

OBJECTIVE: To compare the results of the Modified Clinical Test for Sensory Interaction and Balance (mCTSIB) and the Sensory Organization Test (SOT) of computerized dynamic posturography (CDP) to better understand the role and limitations of the mCTSIB in the diagnosis and rehabilitation of patients with uncompensated unilateral vestibulopathy. STUDY DESIGN: Prospective blind study. SETTING: Tertiary referral center. INTERVENTIONS: Ninety-eight patients with uncompensated unilateral vestibulopathy were enrolled. After diagnosis was established through ocular motor studies, head roll and Dix-Hallpike tests, caloric testing, and pure tone audiometry, the mCTSIB and SOT were administered simultaneously. MAIN OUTCOME MEASURE: Composite or comprehensive scores and equilibrium scores. RESULTS: When composite or comprehensive scores were used to classify subjects as normal or abnormal, the mCTSIB and SOT showed significant agreement (p > 0.256). SOT condition 2 (eyes closed on a firm surface) showed a greater degree of correlation than did other conditions; the foam-surface or eyes-open conditions yielded poor correlation coefficients. CONCLUSION: The mCTSIB can be used instead of the SOT in screening to distinguish normality from abnormality in dizzy patients with unilateral vestibulopathy. However, the degree of dizziness assessed by SOT condition was poorly correlated with mCTSIB results, especially in conditions with the eyes open and those using a foam surface.

Development of brain PET using GAPD arrays.

PURPOSE: In recent times, there has been great interest in the use of Geiger-mode avalanche photodiodes (GAPDs) as scintillator readout in positron emission tomography (PET) detectors because of their advantages, such as high gain, compact size, low power consumption, and magnetic field insensitivity. The purpose of this study was to develop a novel PET system based on GAPD arrays for brain imaging. METHODS: The PET consisted of 72 detector modules arranged in a ring of 330 mm diameter. Each PET module was composed of a 4 × 4 matrix of 3 × 3 × 20 mm(3) cerium-doped lutetium yttrium orthosilicate (LYSO) crystals coupled with a 4 × 4 array three-side tileable GAPD. The signals from each PET module were fed into preamplifiers using a 3 m long flat cable and then sent to a position decoder circuit (PDC), which output a digital address and an analog pulse of the interacted channel among 64 preamplifier signals transmitted from four PET detector modules. The PDC outputs were fed into field programmable gate array (FPGA)-embedded data acquisition (DAQ) boards. The analog signal was then digitized, and arrival time and energy of the signal were calculated and stored. RESULTS: The energy and coincidence timing resolutions measured for 511 keV gamma rays were 18.4 ± 3.1% and 2.6 ns, respectively. The transaxial spatial resolution and sensitivity in the center of field of view (FOV) were 3.1 mm and 0.32% cps/Bq, respectively. The rods down to a diameter of 2.5 mm were resolved in a hot-rod phantom image, and activity distribution patterns between the white and gray matters in the Hoffman brain phantom were well imaged. CONCLUSIONS: Experimental results indicate that a PET system can be developed using GAPD arrays and the GAPD-based PET system can provide high-quality PET imaging.