The 24-Hour Cardiac Autonomic Activity in Patients With Allergic Rhinitis.

BACKGROUND: Definitive knowledge of the 24-hour cardiac autonomic activity in patients with allergic rhinitis (AR) is lacking. Thus, we aimed to evaluate heart rate variability (HRV), which is used to measure cardiac autonomic activity by 24-hour Holter monitoring in patients with AR. METHODS: We enrolled 32 patients who visited our clinic and were diagnosed with AR. The control group was selected four-fold (n = 128) by matching (age, sex, hypertension, and diabetes) in the AR group from a Holter registry in the cardiology department. The HRV results, which were measured using 24-hour Holter monitoring, were compared between the AR and control groups. RESULTS: All time-domain parameters of HRV revealed no differences between the groups. However, among the frequency domain parameters of HRV, the low-frequency to high-frequency ratio and low-frequency power in normalized units were significantly lower in the AR group. Conversely, high-frequency power in normalized units was significantly higher in the AR group. In the multiple regression analysis, AR was independently associated with sympathetic withdrawal (adjusted odds ratio = 3.393, P = 0.020) after adjusting for age, sex, hypertension, diabetes mellitus, and hyperlipidemia. CONCLUSIONS: The present findings suggest differences in cardiac autonomic activity which are related with sympathetic withdrawal in patients with AR compared with that in the normal population over 24 hours.

Effect of sinus opacification on the severity of obstructive sleep apnea.

PURPOSE: The association between rhinosinusitis and obstructive sleep apnea (OSA) remains unclear. Here, we aimed to elucidate the association between sinus opacification and OSA severity. METHODS: Patients with snoring problems who visited our clinic from April 2018 to December 2020 were retrospectively enrolled. Among these patients, we included those who underwent a physical examination, overnight polysomnography, and osteomeatal-unit computed tomography. We evaluated the association between apnea-hypopnea index (AHI) and Lund-Mackay score (LMS). LMS ≥ 5 was considered indicative of sinus opacification. RESULTS: Among the 122 patients included in the study, LMS exhibited an increasing trend based on OSA severity. The LMS in the moderate OSA group was significantly higher than that in the no OSA group (P = 0.002), and the LMS in the severe OSA group was significantly higher than that in the no OSA (P < 0.001) and mild OSA (P = 0.006) groups. A correlation analysis revealed that AHI was significantly associated with body mass index (BMI) (r = 0.367, P < 0.001) and LMS (r = 0.255, P = 0.005). A multivariate analysis revealed that sinus opacification was associated with moderate and severe OSA [Adjusted odds ratio = 11.986 (P = 0.005) and 3.756 (P = 0.044), respectively] after adjusting for age, sex, BMI, smoking, hypertension, atopy, tonsil size, and palatal position. The effect of sinus opacification on OSA severity was comparable to that of overweight. CONCLUSION: Sinus opacification may increase OSA severity since moderate and severe OSA is independently associated with it.

Heterogeneity of Adult Rhinitis for Multimorbidity and Age at Onset among Non-Sensitized Rhinitis and Mono-/Poly-Sensitized Rhinitis: A Retrospective Cross-Sectional Study.

BACKGROUND: Recent studies have proposed that clinical and immunological differences exist between mono- and poly-sensitized subjects with allergic diseases, and poly-sensitization was related to multimorbidity of allergic diseases among children and adolescents. OBJECTIVE: We compared the clinical characteristics and multimorbidity of allergic diseases between adult rhinitis patients mono- and poly-sensitized to common aeroallergens using a retrospective cross-sectional study for tertiary care subjects. METHODS: The medical records of 1,615 patients who were clinically diagnosed with rhinitis by an otolaryngologist and evaluated with skin prick tests were reviewed. The severity of the rhinitis symptoms, comorbidities (asthma, conjunctivitis, and eczema), family history of allergic diseases, and the results of skin prick tests were evaluated. RESULTS: There were 392 patients with mono-sensitized rhinitis (mono-sR), 325 with poly-sensitized rhinitis (poly-sR), and 898 with non-sensitized rhinitis (non-sR). Comorbid conjunctivitis and eczema were most common in poly-sR, followed by mono-sR, and least common in non-sR patients. The age at onset of rhinitis was clearly different between adult patients with non-sR and mono-/poly-sR, but not between patients with mono-sR and poly-sR. However, the age at onset of rhinitis was much younger in non-sR and mono-sR patients with conjunctivitis or eczema than those without such comorbidities. CONCLUSION: Thefrequency of comorbid conjunctivitis and eczema in adult rhinitis patients differed by a quantitative trait of immunoglobulin E sensitization. Depending on the multimorbidity of allergic diseases, onset age of rhinitis seems to be different in adult rhinitis patients.

Caffeic acid phenethyl ester promotes anti-inflammatory effects by inhibiting MAPK and NF-κB signaling in activated HMC-1 human mast cells.

CONTEXT: Caffeic acid phenethyl ester (CAPE), an active component of honeybee propolis, is known to have antioxidant, anti-inflammatory, and other beneficial medicinal properties. However, the molecular mechanisms underlying its anti-allergic effects in mast cells are unknown. OBJECTIVE: The purpose of the present study was to examine whether CAPE modulates the immunoglobulin E (IgE)-mediated local allergic reaction in animals, as well as to elucidate the effects of CAPE on mast cells in vitro. MATERIALS AND METHODS: To investigate the bioactive potential of CAPE (10 or 20 µM), HMC-1 cells were stimulated with phorbol 12-myristate 13-acetate plus calcium ionophore A23187 (PMACI) for 24 h in the presence or absence of CAPE. To study the pharmacological effects of CAPE, enzyme-linked immunosorbent assays (ELISAs), RT-PCR, Western blot analysis, electrophoretic mobility shift assays (EMSAs), and fluorescence assays were used. RESULTS: CAPE (10 mg/kg) inhibited local IgE-mediated allergic reactions (0.164 versus 0.065 O.D.) in a mouse model. Additionally, CAPE (20 µM) attenuated PMACI-stimulated histamine release (3146.42 versus 2564.83 pg/ml) and the production of inflammatory cytokines, such as interleukin (IL)-1ß (4.775 versus 0.713 pg/ml, IC50 = 6.67 µM), IL-6 (4771.5 versus 449.1 pg/ml, IC50 = 5.25 µM), and IL-8 (5991.7 versus 2213.1 pg/ml, IC50 = 9.95 µM) in HMC-1 cells. In activated HMC-1 cells, pretreatment with CAPE decreased the phosphorylation of c-Jun N-terminal kinase. In addition, CAPE inhibited PMACI-induced nuclear factor (NF)-κB activation by suppressing IκBα phosphorylation and its degradation. DISCUSSION AND CONCLUSION: Our results indicated that CAPE can modulate mast cell-mediated allergic disease.

Prevalence and factors associated with neck and jaw muscle modulation of tinnitus.

Forceful contractions of neck and jaw muscles have consistently been shown to modulate tinnitus and can be used to screen patients who are responsive to somatic stimulation and, therefore, optimal candidates for somatosensory-based treatment. To identify the factors associated with somatic modulation of tinnitus, 163 patients underwent 19 neck and jaw maneuvers after an extensive physiological and audiological profile was compiled. Overall, tinnitus was modulated in 57.1% of ears tested. Unilateral tinnitus showed greater prevalence of modulation. Neck maneuvers generally decreased tinnitus loudness, whereas jaw maneuvers increased loudness. Female gender and buzzing tinnitus were associated with a high prevalence of modulation and a decrease in tinnitus loudness. Loud tinnitus and low-pitched tonal tinnitus were associated with exacerbation of the condition as a result of somatic testing. Use of these characteristics to select optimal candidates for somatosensory-based tinnitus therapies may be essential for the development of an effective approach for tinnitus treatment.

Regulation of ca(2+) signaling in pulmonary hypertension.

Understanding the cellular and molecular mechanisms involved in the development and progression of pulmonary hypertension (PH) remains imperative if we are to successfully improve the quality of life and life span of patients with the disease. A whole plethora of mechanisms are associated with the development and progression of PH. Such complexity makes it difficult to isolate one particular pathway to target clinically. Changes in intracellular free calcium concentration, the most common intracellular second messenger, can have significant impact in defining the pathogenic mechanisms leading to its development and persistence. Signaling pathways leading to the elevation of [Ca(2+)](cyt) contribute to pulmonary vasoconstriction, excessive proliferation of smooth muscle cells and ultimately pulmonary vascular remodeling. This current review serves to summarize the some of the most recent advances in the regulation of calcium during pulmonary hypertension.

Clonazepam quiets tinnitus: a randomised crossover study with Ginkgo biloba.

OBJECTIVE: To assess the effect of Ginkgo biloba and clonazepam, a γ-aminobutyric acid (GABA)-receptor agonist, upon tinnitus. METHODS: This was an open-label, randomised, crossover study. 27 men and 11 women (aged 16-80 (mean 58)) with tinnitus for more than 2 months were enrolled. Participants were randomised to either clonazepam or G biloba for the first 3 weeks. For the next 2 weeks of washout no medication was taken. For the final 3 weeks, subjects were given the other drug. The initial dose of clonazepam and G biloba was one tablet daily (clonazepam 0.5 mg; G biloba 40 mg). Subjects were instructed to increase the dose by one tablet every 3 days to a maximum of four tablets daily until they perceived a satisfactory decrease in tinnitus loudness or intolerable side effects. Tinnitus was assessed with pitch and loudness matching, tinnitus handicap inventory, and visual analogue scales of loudness, duration and annoyance. RESULTS: Comparing before and after each drug, clonazepam significantly improved tinnitus loudness (74% of subjects), duration (63%), annoyance (79%), and tinnitus handicap inventory score (61%), whereas the G biloba showed no significant differences on any of these measures. CONCLUSION: Clonazepam is effective in treating tinnitus; G biloba is ineffective.

The validity of the assignment book-based structured interview in predicting academic performance in medical schools: a retrospective cohort study.

PURPOSE: Structured interviews have become essential in the medical schools admission selection because structured interviews predict academic achievement after admission. The purpose of this study was to determine validity and fairness of the new structural interview technique, assignment book-based structured interview (ABSI), in predicting future academic achievement of the medical students. METHODS: The validity of this new interview technique and academic achievement was evaluated based on the data of all the applicants and successful applicants who applied for on-time admission between the year 2011 and 2014. RESULTS: The ABSI technique showed a significant correlation and predictive validity for academic achievement in the medical school. The retention group received significantly lower T-scores of ABSI compared with the superior student group. CONCLUSION: The results indicate that ABSI is a feasible, reliable, fair and valid admission selection tool. The ABSI may be meaningful and fair method for predicting academic achievements, and it could be incorporated as one of the contents in the multiple mini-interview.

The differences between daytime and nighttime heart rate variability may usefully predict the apnea-hypopnea index in patients with obstructive sleep apnea.

STUDY OBJECTIVES: The association between daytime/nighttime heart rate variability (HRV) and the apnea-hypopnea index (AHI) remains unclear. We sought a relationship between AHI and the daytime-to-nighttime HRV ratio as measured by 24-hour Holter monitoring in patients with obstructive sleep apnea. METHODS: We prospectively enrolled 66 patients who visited our sleep clinic complaining of habitual snoring or sleep apnea. All underwent 24-hour Holter monitoring (to measure HRV) combined with full-night polysomnography. Sixty-two met our enrollment criteria. We evaluated the associations between HRV frequency domains and the polysomnography indices. We also considered medical histories and anthropometric data. RESULTS: The nighttime very-low-frequency (VLF), low-frequency (LF), and high-frequency HRVs were significantly higher than the daytime values. On correlation analysis, the day/night VLF (r = .550, P < .001), LF (r = .556, P < .001), and high-frequency (r = .303, P = .017) HRVs were significantly related to the AHI. Of the day/night HRV ratios, the VLF (P for trend = .003) and LF (P for trend = .013) ratios decreased significantly by obstructive sleep apnea severity. Multivariable analysis showed that the day/night VLF (ß = 16.387, P < .001) and day/night LF (ß = 25.248, P < .001) were independently (and significantly) associated with the AHI. CONCLUSIONS: Twenty-four-hour Holter monitoring may usefully predict AHI. The day/night VLF and day/night LF ratios tended to decrease by obstructive sleep apnea severity and were independently associated with the AHI. CITATION: Nam E-C, Chun KJ, Won JY, Kim J-W, Lee WH. The differences between daytime and nighttime heart rate variability may usefully predict the apnea-hypopnea index in patients with obstructive sleep apnea. J Clin Sleep Med. 2022;18(6):1557-1563.

Investigation of Electronic Signal Processing Chains for a Prototype TOF-PET System With 100-ps Coincidence Time Resolution.

We have evaluated CTR performance of four different mixed-signal front-end electronic readout configurations with the goal to achieve 100 picoseconds (ps) coincidence time resolution (CTR). The proposed TOF-PET detector elements are based on two 3 × 3 × 10 mm3 "fast LGSO" crystal segments, side-coupled to linear arrays of 3 × 3 mm2 silicon photomultipliers (SiPMs), to form a total crystal length of 20 mm. We studied multiple configurations and components for the front-end readout: 1) high speed radio frequency (RF) amplifiers; 2) an ASIC-based discriminator; 3) combination of RF amplifier, balun transformer, and discriminator ASIC; and 4) combination of balun transformer, and discriminator ASIC. Using two 3 × 3 × 10 mm3 fast LGSO crystals side coupled to a linear array of three SiPMs, coincidence data were experimentally acquired for each readout configuration in combination with a low jitter field programmable gate array (FPGA)-based time to digital converter (TDC). After evaluating timing performance of the three readout schemes, the best CTR value of 99.4 ± 1.9 ps FWHM was achieved for configuration (3), which is more than 20 ps better than the results achieved using configurations (1) and (2).

Age Differences in Pet Sensitization by Pet Ownership.

OBJECTIVES: The association between pet sensitization and pet ownership remains unclear. Therefore, we aimed to elucidate the association between pet sensitization and pet ownership by age. METHODS: We retrospectively reviewed 2,883 patients who visited our allergy clinic for nasal symptoms from January 2003 to December 2014, of whom 1,957 patients with data on skin-prick tests and questionnaire responses were included and divided into adults (age >19 years) and children (age ≤19 years). The association between pet sensitization and pet ownership was evaluated in both groups. RESULTS: Among children, dog and cat sensitization showed no associations with dog and cat ownership, respectively. However, among adults, dog sensitization was significantly associated with dog ownership (odds ratio [OR], 3.283; P<0.001), and cat sensitization with cat ownership (OR, 13.732; P<0.001). After adjustment for age, sex, familial history of allergy, sinusitis, diabetes mellitus, other pet ownership, and non-pet sensitization, significant associations remained between dog sensitization and dog ownership (adjusted OR [aOR], 3.881; P<0.001), and between cat sensitization and cat ownership (aOR, 10.804; P<0.001) among adults. Dog ownership did not show any association with allergic rhinitis, asthma, or atopic dermatitis, whereas atopic dermatitis had a significant association with cat ownership in adults (aOR, 4.840; P<0.001). CONCLUSION: Pet ownership in adulthood increased the risk of pet sensitization. However, pet ownership was not associated with the prevalence of atopic disorders, regardless of age, except for atopic dermatitis and cat ownership in adults.

Scalable electronic readout design for a 100 ps coincidence time resolution TOF-PET system.

We have developed a scalable detector readout design for a 100 ps coincidence time resolution (CTR) time of flight (TOF) positron emission tomography (PET) detector technology. The basic scintillation detectors studied in this paper are based on 2 × 4 arrays of 3 × 3 × 10 mm3'fast-LGSO:Ce' scintillation crystals side-coupled to 6 × 4 arrays of 3 × 3 mm2silicon photomultipliers (SiPMs). We employed a novel mixed-signal front-end electronic configuration and a low timing jitter Field Programming Gate Array-based time to digital converter for data acquisition. Using a22Na point source, >10 000 coincidence events were experimentally acquired for several SiPM bias voltages, leading edge time-pickoff thresholds, and timing channels. CTR of 102.03 ± 1.9 ps full-width-at-half-maximum (FWHM) was achieved using single 3 × 3 × 10 mm3'fast-LGSO' crystal elements, wrapped in Teflon tape and side coupled to a linear array of 3 SiPMs. In addition, the measured average CTR was 113.4 ± 0.7 ps for the side-coupled 2 × 4 crystal array. The readout architecture presented in this work is designed to be scalable to large area module detectors with a goal to create the first TOF-PET system with 100 ps FWHM CTR.

Development and Initial Results of a Brain PET Insert for Simultaneous 7-Tesla PET/MRI Using an FPGA-Only Signal Digitization Method.

In study, we developed a positron emission tomography (PET) insert for simultaneous brain imaging within 7-Tesla (7T) magnetic resonance (MR) imaging scanners. The PET insert has 18 sectors, and each sector is assembled with two-layer depth-of-interaction (DOI)-capable high-resolution block detectors. The PET scanner features a 16.7-cm-long axial field-of-view (FOV) to provide entire human brain images without bed movement. The PET scanner early digitizes a large number of block detector signals at a front-end data acquisition (DAQ) board using a novel field-programmable gate array (FPGA)-only signal digitization method. All the digitized PET data from the front-end DAQ boards are transferred using gigabit transceivers via non-magnetic high-definition multimedia interface (HDMI) cables. A back-end DAQ system provides a common clock and synchronization signal for FPGAs over the HDMI cables. An active cooling system using copper heat pipes is applied for thermal regulation. All the 2.17-mm-pitch crystals with two-layer DOI information were clearly identified in the block detectors, exhibiting a system-level energy resolution of 12.6%. The PET scanner yielded clear hot-rod and Hoffman brain phantom images and demonstrated 3D PET imaging capability without bed movement. We also performed a pilot simultaneous PET/MR imaging study of a brain phantom. The PET scanner achieved a spatial resolution of 2.5 mm at the center FOV (NU 4) and a sensitivity of 18.9 kcps/MBq (NU 2) and 6.19% (NU 4) in accordance with the National Electrical Manufacturers Association (NEMA) standards.

Clinical Manifestations of Allergic Rhinitis by Age and Gender: A 12-Year Single-Center Study.

OBJECTIVES: Currently, epidemiological data on allergic rhinitis collected through the skin prick test are scarce. Moreover, the relationship of age and sex to allergic rhinitis is not comprehensively understood. This study aimed to characterize allergic rhinitis and the associated clinical manifestations by age and sex. METHODS: We retrospectively investigated data from 2883 patients who visited a single university hospital for rhinitis symptoms between January 2003 and December 2014. Of these 2883 patients, 1964 who underwent a skin prick test with 11 standardized allergen extracts and completed a nasal symptom questionnaire were enrolled. The clinical characteristics of allergen sensitization and nasal symptoms were analyzed by sex and age distribution. RESULTS: The prevalence of allergen sensitization progressively decreased with age after peaking at between 20 and 29 years. The sensitization rate was higher in males than in females (P = .046). The sensitization rate to house dust mites decreased with age, while sensitization to mugwort and ragweed increased. Six allergens (Dermatophagoides pteronyssinus, Dermatophagoides farinae, mugwort, trees, ragweed, and cats) were sufficient to identify >96% of patients with allergen sensitization. Nasal obstruction tended to decrease with age and was more prevalent in males (P = .002) than in females, while rhinorrhea (P = .007) and itching (P = .013) were more prevalent in females. Total nasal symptom scores did not differ by sex. CONCLUSIONS: The clinical characteristics of allergic rhinitis, including allergen-sensitization patterns and related symptoms, varied by age and sex. Six common allergens could be sufficient to generate a cost-effective tool to identify allergic rhinitis.

Comparator-less PET data acquisition system using single-ended memory interface input receivers of FPGA.

In this study, we propose a linear field-programmable gate array (FPGA)-based charge measurement method by combining a charge-to-time converter (QTC) with a single-ended memory interface (SeMI) input receiver. The QTC automatically converts the input charge into a dual-slope pulse, which has a width proportional to the input charge. Dual-slope pulses are directly digitized by the FPGA input/output (I/O) buffers configured with SeMI input receivers. A proof-of-concept comparator-less QTC/SeMI data acquisition (DAQ) system, consisting of 132 energy and 33 timing channels, was developed and applied to a prototype brain-dedicated positron emission tomography (PET) scanner. The PET scanner consisted of 14 sectors, each containing 2 × 1 block detectors, and each block detector yielded four energy signals and one timing signal. Because a single QTC/SeMI DAQ system can receive signals from up to eight sectors, two QTC/SeMI DAQ systems connected using high-speed gigabit transceivers were used to acquire data from the PET scanner. All crystals in the PET block detectors, consisting of dual-layer stacked lutetium oxyorthosilicate (LSO) scintillation crystal and silicon photomultiplier arrays, were clearly resolved in the flood maps with an excellent energy resolution. The PET images of hot-rod, cylindrical, and two-dimensional Hoffman brain phantoms were also acquired using the prototype PET scanner and two QTC/SeMI DAQ systems.

Blood eosinophils may predict radiographic sinus opacification in patients with chronic rhinitis.

BACKGROUND: The association between chronic rhinosinusitis (CRS) and chronic rhinitis remains unclear. The aim of this study was to estimate the predictive factors for sinus opacification in chronic rhinitis patients without obvious CRS. METHODS: We retrospectively studied a total of 332 adult patients with chronic rhinitis who visited our clinic from January 2015 to December 2017. All of the patients underwent endoscopic examination, allergy test, and osteomeatal-unit computed tomography. The subjects were assigned to the normal sinus (NS) group (Lund-Mackay score [LMS] <5) and sinus opacification (SO) group (LMS ≥5). RESULTS: A total of 288 patients were eligible for this study. Of them, 183 (63.5%) were classified in the NS group and 105 (36.5%) in the SO group. Total immunoglobulin E (IgE) level and peripheral blood eosinophil count were significantly higher in the SO than NS group (p = 0.031 and p < 0.0001, respectively). Using Pearson correlation coefficients, we determined that eosinophil count had a positive correlation with the LMS (r = 0.282). In logistic analysis, the interquartile range increase (0.19 × 109 /L) of the eosinophil count was significantly associated with SO (odds ratio [OR] 1.76; 95% confidence interval [CI], 1.30 to 2.39). After adjusting for age, gender, smoking, drinking, and underlying disease, the interquartile range increase of the eosinophil count increased the odds of SO to 1.69-fold; this increase was statistically significant (p = 0.007; 95% CI, 1.17 to 2.43). CONCLUSION: Peripheral blood eosinophil count is an independent predictor of CRS in patients with chronic rhinitis.

Highly Integrated FPGA-Only Signal Digitization Method Using Single-Ended Memory Interface Input Receivers for Time-of-Flight PET Detectors.

We propose a new highly integrated field-programm-able gate array (FPGA) only signal digitization method for individual signal digitization of time-of-flight positron emission tomography (TOF PET). We configured I/O port of the FPGA with a single-ended memory interface (SeMI) input receiver. The SeMI is a single-ended voltage-referenced interface that has a common reference voltage per I/O Bank, such that each SeMI input receiver can serve as a voltage comparator. The FPGA-only digitizer that uses the single-ended input receivers does not require a separate digitizing integrated chip, and can obtain twice as many signals as that using LVDS input receivers. We implemented a highly integrated digitizer consisting of 82 energy and 82 timing channels using a 28-nm FPGA. The energy and arrival time were measured using a 625-ps binary counter, and a 10-ps time-to-digital converter (TDC), respectively. We first measured the intrinsic characteristics of the proposed FPGA-only digitizer. The SeMI input receiver functioned as the voltage comparator without undesirable offset voltage. The standard deviation value of the time difference measured using two SeMI input receivers with respective TDCs was less than 14.6 ps RMS. In addition, we fed signals from the TOF PET detectors to the SeMI input receivers directly and collected data. The TOF PET detector consisted of a 3 × 3 × 20 mm3 LYSO crystal coupled with a silicon photomultiplier. The energy resolutions were 7.7% and 7.1% for two TOF PET detectors. The coincidence resolving time was 204 ps full width at half maximum. The SeMI digitizer with a high-performance signal digitizer, processor, and high-speed transceivers provides a compact all-in-one data acquisition system.

Performance of a new accelerating-electrode-equipped fast-time-response PMT coupled with fast LGSO.

In this study, we measured the performance of a newly developed Hamamatsu Photonics R13478 photomultiplier tube (PMT) and compared the results with those of an existing R9800 PMT. In R13478, an accelerating electrode is placed between the focusing electrode and first dynode for time resolution improvement through reduced transit time jitter. We investigated the time resolution dependence on the supply voltage and time pickoff method for R13478 and R9800 PMTs, each coupled with a 2.9 × 2.9 × 20 mm3 fast LGSO:Ce (0.025 mol%) crystal. In addition, we measured the PMT time resolutions coupled with the crystals in edge and laid positions to determine the effects of the reduced position dependence of transit time in R13478. R13478 exhibited a better time performance than R9800 in various ways. The rise time of R13478 for our experimental setup was 1.54 ns, 100 ps shorter than that of R9800 because of the reduced transit time. Further, R13478 achieved a 169 ps single time resolution at the recommended supply voltage, while this value was 187 ps for R9800. The time resolution of R13478 was also significantly better for a low time pickoff threshold level and a high supplied voltage, which are conditions vulnerable to transit time jitter and noise, respectively. A considerable difference in time resolution was observed for the laid position (R13478: 144 ps; R9800: 167 ps), indicating that the accelerating electrode reduced spatial transit time difference. Overall, we showed the effects of the differentiated characteristics of R13478 PMT compared with R9800 and confirmed its excellent time performance. We suggest use of this device as a photodetector effective for fast timing applications such as time-of-flight positron emission tomography.

Proof-of-concept prototype time-of-flight PET system based on high-quantum-efficiency multianode PMTs.

PURPOSE: Time-of-flight (TOF) information in positron emission tomography (PET) scanners enhances the diagnostic power of PET scans owing to the increased signal-to-noise ratio of reconstructed images. There are numerous additional benefits of TOF reconstruction, including the simultaneous estimation of activity and attenuation distributions from emission data only. Exploring further TOF gains by using TOF PET scanners is important because it can broaden the applications of PET scans and expand our understanding of TOF techniques. Herein, we present a prototype TOF PET scanner with fine-time performance that can experimentally demonstrate the benefits of TOF information. METHODS: A single-ring PET system with a coincidence resolving time of 360 ps and a spatial resolution of 3.1/2.2 mm (filtered backprojection/ordered-subset expectation maximization) was developed. The scanner was based on advanced high-quantum-efficiency (high-QE) multianode photomultiplier tubes (PMTs). The impact of its fine-time performance was demonstrated by evaluating body phantom images reconstructed with and without TOF information. Moreover, the feasibility of the scanner as an experimental validator of TOF gains was verified by investigating the improvement of images under various conditions, such as the use of joint estimation algorithms of activity and attenuation, erroneous data correction factors (e.g., without normalization correction), and incompletely sampled data. RESULTS: The prototype scanner showed excellent performance, producing improved phantom images, when TOF information was employed in the reconstruction process. In addition, investigation of the TOF benefits using the phantom data in different conditions verified the usefulness of the developed system for demonstrating the practical effects of TOF reconstruction. CONCLUSIONS: We developed a prototype TOF PET scanner with good performance and a fine-timing resolution based on advanced high-QE multianode PMTs and demonstrated its feasibility as an experimental validator of TOF gains, suggesting its usefulness for investigating new applications of PET scans and clarifying TOF techniques in detail.

Delay grid multiplexing: simple time-based multiplexing and readout method for silicon photomultipliers.

In this paper, we propose a fully time-based multiplexing and readout method that uses the principle of the global positioning system. Time-based multiplexing allows simplifying the multiplexing circuits where the only innate traces that connect the signal pins of the silicon photomultiplier (SiPM) channels to the readout channels are used as the multiplexing circuit. Every SiPM channel is connected to the delay grid that consists of the traces on a printed circuit board, and the inherent transit times from each SiPM channel to the readout channels encode the position information uniquely. Thus, the position of each SiPM can be identified using the time difference of arrival (TDOA) measurements. The proposed multiplexing can also allow simplification of the readout circuit using the time-to-digital converter (TDC) implemented in a field-programmable gate array (FPGA), where the time-over-threshold (ToT) is used to extract the energy information after multiplexing. In order to verify the proposed multiplexing method, we built a positron emission tomography (PET) detector that consisted of an array of 4 × 4 LGSO crystals, each with a dimension of 3 × 3 × 20 mm3, and one- to-one coupled SiPM channels. We first employed the waveform sampler as an initial study, and then replaced the waveform sampler with an FPGA-TDC to further simplify the readout circuits. The 16 crystals were clearly resolved using only the time information obtained from the four readout channels. The coincidence resolving times (CRTs) were 382 and 406 ps FWHM when using the waveform sampler and the FPGA-TDC, respectively. The proposed simple multiplexing and readout methods can be useful for time-of-flight (TOF) PET scanners.