Accuracy and Precision of Three Acceleromyographs, Three Electromyographs, and a Mechanomyograph Measuring the Train-of-four Ratio in the Absence of Neuromuscular Blocking Drugs

BACKGROUND

The accuracy and precision of currently available, widely used acceleromyograph and electromyograph neuromuscular blockade monitors have not been well studied. In addition, the normalization of the train-of-four ratio from acceleromyography (train-of-four ratio [T4/T1] divided by the baseline train-of-four ratio) has not been validated in comparison to mechanomyography.

METHODS

Enrolled patients had surgery under general anesthesia with a supraglottic airway and without any neuromuscular blocking drugs. Three acceleromyograph monitors, three electromyograph monitors, and a mechanomyograph built in the authors' laboratory were tested. Most patients had an electromyograph and the mechanomyograph on one arm and a third monitor on the contralateral arm. Train-of-four ratios were collected every 12 to 20 s for the duration of the anesthetic. At least 1,000 train-of-four ratios were recorded for each device. Gauge repeatability and reproducibility analysis was performed.

RESULTS

Twenty-eight patients were enrolled. In total, 9,498 train-of-four ratio measurements were collected. Since no neuromuscular blocking drugs were used, the expected train-of-four ratio was 1.0. All of the acceleromyograph monitors produced overshoot in the train-of-four ratio (estimated means, 1.10 to 1.13) and substantial variability (gauge SDs, 0.07 to 0.18). Normalization of the train-of-four ratio measured by acceleromyography improved the estimated mean for each device (0.97 to 1.0), but the variability was not improved (gauge SDs, 0.06 to 0.17). The electromyograph and the mechanomyograph monitors produced minimal overshoot (estimated means, 0.99 to 1.01) and substantially less variation (gauge SDs, 0.01 to 0.02). For electromyography and mechanomyography, 0.3% of all train-of-four ratios were outside of the range 0.9 to 1.1. For acceleromyography, 27 to 51% of normalized train-of-four ratios were outside the range of 0.9 to 1.1.

CONCLUSIONS

Three currently available acceleromyograph monitors produced overshoot and substantial variability that could be clinically significant. Normalization corrected the overshoot in the average results but did not reduce the wide variability. Three electromyograph monitors measured the train-of-four ratio with minimal overshoot and variability, similar to a mechanomyograph.

EDITOR’S PERSPECTIVE

Comparative performance of stimpod electromyography with mechanomyography for quantitative neuromuscular blockade monitoring

PURPOSE

The purpose of this study was to compare the Stimpod electromyograph neuromuscular blockade monitor to mechanomyography, which is widely considered to be the reference standard.

METHODS

The Stimpod electromyograph was used with its designated electrode array on the same hand as the mechanomyograph. Pairs of train-of-four measurements were recorded every 0.5-2 min. When the train-of-four count was zero on the electromyograph monitor, pairs of post tetanic count measurements were recorded every 2.5 min, instead of train-of-four measurements. Measurements were recorded from immediately after induction of anesthesia until just before emergence. Stimulation current was set to 60 mA with a duration of 200 microsec. The mechanomyography recording system recorded each twitch waveform for analysis. High resolution electromyograph waveforms were also recorded using a datalogger accessory provided by the manufacturer, facilitating inspection of individual waveforms. The administration of neuromuscular blocking drugs was left up to the discretion of the anesthesia care team.

RESULTS

Twenty-three patients contributed 1,088 data pairs suitable for analysis. Bland-Altman analysis of 415 pairs of train-of-four ratios showed a bias of 0.028 and limits of agreement of -0.18 and 0.24. Two hundred seventy-three train-of-four count data pairs were compared by Cohen's quadratically weighted kappa which was calculated to be 0.44, indicating moderate agreement. Three hundred thirty-eight post tetanic count data pairs were compared by Cohen's quadradically weighted kappa which was calculated to be 0.80, indicating substantial agreement.

CONCLUSION

The electromyograph produced results that were comparable to the mechanomyograph.

A Decrease in Effective Renal Perfusion Pressure Is Associated With Increased Acute Kidney Injury in Patients Undergoing Cardiac Surgery

PURPOSE

This study aimed to evaluate the relationship between intra-abdominal pressure (IAP), renal perfusion indices, and postoperative acute kidney injury (AKI) in cardiac patients.

METHODS

In a prospective cohort study conducted at a single academic institution, we collected data from adult patients undergoing open-heart operations with cardiopulmonary bypass (CPB) at our institution from February 2022 to April 2022 using the Accuryn SmartFoley system® (Potrero Medical, Hayward, CA). Patients on mechanical support devices, pregnant patients, and patients on hemodialysis were excluded. Demographics, hemodynamics, and mean airway pressure (mAir) were measured at the beginning of the cardiac operations and during the first four hours of ICU. Renal perfusion indices were then calculated (mean perfusion pressure (MPP) = mean arterial pressure (MAP) - central venous pressure (CVP); abdominal perfusion pressure (APP) = MAP - IAP; and effective renal perfusion pressure (eRPP) = MAP - (CVP + mAir + IAP)). Length of stay (LOS) was measured from the day of surgery to ICU discharge (ICU LOS) and hospital discharge (hospital LOS).

RESULTS

During the first four hours of ICU stay, the non-AKI group had lower IAP and higher renal perfusion indices (MPP, APP, and eRPP). Logistic regression showed high perfusion pressures correlated with lower postoperative AKI (all OR <1, p<0.05). The postoperative AKI group also had significantly longer ICU LOS (7.33 vs. 4.57 days) and hospital LOS (17.0 vs. 10.2 days).

CONCLUSION

Renal perfusion indices are a promising tool to predict postoperative AKI in cardiac surgery patients.

Clinical Outcome Comparison of Patients Requiring Extracorporeal Membrane Oxygenation With or Without COVID-19 Infection

In severe COVID-19-related respiratory failure, extracorporeal membrane oxygenation (ECMO) is a useful modality that is used to provide effective oxygenation and ventilation to the patient. This descriptive study aimed to investigate and compare the outcomes between COVID-19-infected patients and patients who were not infected and required ECMO support. A retrospective study was undertaken on a cohort of 82 adult patients ([Formula: see text]18-year-old) who required venoarterial (VA-ECMO) and venovenous (VV-ECMO) ECMO between January 2019 and December 2022 in a single academic center. Patients who were cannulated for COVID-19-related respiratory failure (C-group) were compared to patients who were cannulated for non-COVID etiologies (non-group). Patients were excluded if data were missing regarding cannulation, decannulation, presenting diagnosis, and survival status. Categorical data were reported as counts and percentages, and continuous data were reported as means with 95% confidence intervals. Out of the 82 included ECMO patients, 33 (40.2%) were cannulated for COVID-related reasons, and 49 (59.8%) were cannulated for reasons other than COVID-19 infection. Compared to the non-group, the C-group had a higher in-hospital (75.8% vs. 55.1%) and overall mortality rate (78.8% vs. 61.2%). The C-group also had an average hospital length of stay (LOS) of 46.6 ± 13.2 days and an average intensive care unit (ICU) LOS of 44.1 ± 13.3 days. The non-group had an average hospital LOS of 24.8 ± 6.6 days and an average ICU LOS of 20.8 ± 5.9 days. Subgroup analysis of patients only treated with VV-ECMO yielded a greater in-hospital mortality rate for the C-group compared to the non-group (75.0% vs. 42.1%). COVID-19-infected patients may experience different morbidity and mortality rates as well as clinical presentations compared to non-COVID-infected patients when requiring ECMO support.

Comparison of a Modern Digital Mechanomyograph to a Mechanomyograph Utilizing an Archival Grass Force Transducer

BACKGROUND

Mechanomyography is the traditional gold standard research technique for quantitative assessment of neuromuscular blockade. Mechanomyography directly measures the isometric force generated by the thumb in response to ulnar nerve stimulation. Researchers must construct their own mechanomyographs since commercial instruments are no longer available. We constructed a mechanomyograph and compared its performance against an archival mechanomyography system from the 1970s that utilized an FT-10 Grass force transducer, hypothesizing that train-of-four ratios recorded on each device would be equivalent.

METHODS

A mechanomyograph was constructed using 3D printed components and modern electronics. An archival mechanomyography system was assembled from original components, including an FT-10 Grass force transducer. Signal digitization for computerized data collection was utilized instead of the original paper strip chart recorder. Both devices were calibrated with standard weights to demonstrate linear voltage response curves. The mechanomyographs were affixed to opposite arms of patients undergoing surgery, and the train-of-four ratio was measured during the onset and recovery from rocuronium neuromuscular blockade.

RESULTS

Calibration measurements exhibited a positive linear association between voltage output and calibration weights with a linear correlation coefficient of 1.00 for both mechanomyography devices. The new mechanomyograph had better precision and measurement sensitivity than the archival system, 5.3mV vs. 15.5mV and 1.6mV vs. 5.7mV, respectively (p<0.001 for both). Seven hundred sixty-seven pairs of train-of-four ratio measurements obtained from 8 patients had positive linear association (R2 = 0.94; p<0.001). Bland Altman analysis resulted in bias of 3.8% and limits of agreement of -13% and 21%.

CONCLUSIONS

The new mechanomyograph resulted in similar train-of-four ratio measurements compared to an archival mechanomyography system utilizing an FT-10 Grass force transducer. These results demonstrated continuity of gold standard measurement of neuromuscular blockade spanning nearly 50 years, despite significant changes in the instrumentation technology.

A potent allele marker related to low bull conception rate in Japanese Black bulls

Over the years, there has been considerable variation in the bull conception rate (BCR) of Japanese Black cattle; moreover, several Japanese Black bulls with a low BCR of ≤10% have been identified. However, the alleles responsible for the low BCR are not determined yet. Therefore, in this study, we aimed to identify single-nucleotide polymorphisms (SNPs) for predicting low BCR. To this end, the genome of Japanese Black bulls was comprehensively examined by a genome-wide association study with whole-exome sequencing (WES), and the effect of the identified marker regions on BCR was determined. The WES analysis of six sub-fertile bulls with a BCR of ≤10% and 73 normal bulls with a BCR of ≥40% identified a homozygous genotype for low BCR in Bos taurus autosome 5 in the region between 116.2 and 117.9 Mb. The g.116408653G > A SNP in this region had the most significant effect on the BCR (P-value = 1.0 × 10^-23), and the GG (55.4 ± 11.2%) and AG (54.4 ± 9.4%) genotypes in the SNP had a higher phenotype than the AA (9.5 ± 6.1%) genotype for the BCR. The mixed model analysis revealed that g.116408653G > A was related to approximately 43% of the total genetic variance. In conclusion, the AA genotype of g.116408653G > A is a useful index for identifying sub-fertile Japanese Black bulls. Some positive and negative effects of SNP on the BCR were presumed to identify the causative mutations, which can help evaluate bull fertility.

A Dose-Finding Study of Sugammadex for Reversal of Rocuronium in Cardiac Surgery Patients and Postoperative Monitoring for Recurrent Paralysis

BACKGROUND

The dose of sugammadex recommended by the manufacturer for reversal of rocuronium is 2 mg/kg when the train-of-four count is 2 or more and 4 mg/kg when it is less than 2 but there is a post-tetanic count of at least 1. The purpose of this dose-finding study was to titrate sugammadex to produce a train-of-four ratio ≥0.9 at the conclusion of cardiac surgery, and to continue monitoring neuromuscular blockade in the ICU to identify recurrent paralysis. The hypothesis was that many patients would require less than the recommended dose of sugammadex, but that some would require more, and that recurrent paralysis would not occur.

METHODS

Neuromuscular blockade was monitored using electromyography during cardiac surgery. Administration of rocuronium was at the discretion of the anesthesia care team. During sternal closure, sugammadex was titrated in 50 mg increments every 5 minutes until a train-of-four ratio ≥0.9 was obtained. Neuromuscular blockade was monitored with electromyography in the ICU until sedation was discontinued prior to extubation or for a maximum of 7 hours.

RESULTS

Ninety-seven patients were evaluated. The dose of sugammadex required to achieve a train-of-four ratio of ≥0.9 varied from 0.43 to 5.6 mg/kg. There was a statistically significant relationship between the depth of neuromuscular blockade and the sugammadex dose required for reversal, but there was a large variation in dose required at any depth of neuromuscular blockade. Eighty-four of 97 patients (87%) required less than the recommended dose, and 13 (13%) required more. Two patients required additional sugammadex administration for recurrent paralysis.

CONCLUSIONS

When sugammadex was titrated to effect, the dose was usually less than the recommended dose, but it was more in some patients. Therefore, quantitative twitch monitoring is essential for ascertaining that adequate reversal has taken place following sugammadex administration. Recurrent paralysis was observed in 2 patients.

The Association Between Hypophosphatemia and Lactic Acidosis After Cardiac Surgery With Cardiopulmonary Bypass: A Retrospective Cohort Study

OBJECTIVES

The clinical significance of hypophosphatemia in cardiac surgery has not been investigated extensively. The aim of this study was to evaluate the association of postoperative hypophosphatemia and lactic acidosis in cardiac surgery patients at the time of intensive care unit (ICU) admission.

DESIGN

A retrospective cohort study.

SETTING

At a single academic center.

PARTICIPANTS

Patients who underwent nontransplant cardiac surgery with cardiopulmonary bypass between August 2009 and December 2020.

INTERVENTIONS

None.

MEASUREMENTS AND MAIN RESULTS

Serum phosphate and lactate levels were measured upon ICU admission in patients undergoing nontransplant cardiac surgery with cardiopulmonary bypass. There were 681 patients in the low-phosphate (<2.5 mg/dL) group and 2,579 patients in the normal phosphate group (2.5-4.5 mg/dL). A higher proportion of patients in the low phosphate group (26%; 179 of 681; 95% CI: 23-30) had severe lactic acidosis compared to patients in the normal phosphate group (16%; 417 of 2,579; 95% CI: 15-18). In an unadjusted logistic regression model, patients in the low phosphate group had 1.9-times the odds of having severe lactic acidosis (serum lactate ≥4.0 mmol/L) when compared to patients in the normal phosphate group (95% CI: 1.5-2.3), and still 1.4-times the odds (95% CI: 1.1-1.7) after adjusting for several possible confounders.

CONCLUSIONS

Hypophosphatemia is associated with lactic acidosis in the immediate postoperative period in cardiac surgery patients. Future studies will need to investigate it as a potential treatment target for lactic acidosis.

P-346 First comparison of the egg freezing and storage cost between medical adaptation and social adaptation of Japan fertility hospitals and clinics based on institution's websites

Study question

In Japan, how much of freezing cost and the yearly storage cost of medical and social egg freezing for fertility preservation is clearly disclosed on the institution's website?

Summary answer

Of the 621 infertility treatment institutions, 146 listed egg freezing on their websites, 46 specified the freezing cost, and 71 specified the yearly storage cost.

What is known already

In Japan, from April 2022, standard assisted reproductive technology will be covered by insurance, but medical and social egg freezing will continue to be privately funded. Therefore, it is unclear how many facilities in Japan perform egg freezing. Furthermore, while the cost of freezing and yearly storage varies significantly from facility to facility, there has been no data comparing egg freezing among facilities in Japan or other countries. Therefore, we extracted data about freezing and storage cost from each institution's website and compared them for the first time.

Study design, size, duration

This study is a web-based survey in which a single board-certified specialist by Japan Society for Reproductive Medicine exhaustively browsed the websites of all 621 fertility treatment institutions in Japan in October 2021 and analyzed the implementation of egg freezing, freezing costs, and yearly storage costs of egg are clearly stated on the websites. The costs of drugs used for egg retrieval and ovarian stimulation were excluded.

Participants/materials, setting, methods

Of the 621 institutions, 88 institutions that clearly stated on their websites that they offer egg freezing for medical reasons were divided into a medical group, and 58 institutions that clearly stated that they offer egg freezing for only social reasons were divided into social group for statistical analysis. We compared the freezing and the yearly storage cost, respectively, whether it varies depending on the number of eggs or whether it is a fixed cost.

Main results and the role of chance

Of the 621 institutions, 146 (23.5%), 88 in the medical group and 58 in the social group, specified that they offer egg freezing. The percentages of clarification for freezing cost and yearly storage cost on the website were 27.3% and 30.7% in the medical group, 72.4%, and 75.9% in the social group, so the social group was higher in both cases (p &lt; 0.01). The percentage of fixed costs for egg freezing was significantly lower in the social group (6/42, 14.3%) than in the medical group (9/24, 37.5%) (p &lt; 0.05). The percentage of fixed costs for yearly storage cost was samely significantly lower in the social group (30/44, 68.2%) than in the medical group (25/27, 92.6%) (p &lt; 0.05). The mean freezing cost/yearly storage cost was as follows for 1, 5, and 10 eggs. The medical group was (JPY45,527/JPY22,327, JPY65,179/JPY22,530, JPY90,311/JPY22,770), and the social group was (JPY56,822/JPY40,178, JPY88,429/JPY56,502, JPY136,550/JPY79,090), so the social group had the significantly highest amount of costs in each case. Note that JPY 10,000 is about EUR77.7. The most expensive clinic to store ten eggs was JPY500,000 (EUR3,883) per year, and the least university hospital was JPY 4,600 (EUR35.7) per year.

Limitations, reasons for caution

This survey was conducted by carefully browsing the facility's website, but since we did not confirm the information through questionnaires or e-mail, there is the possibility that the information may have been updated. Another limitation is that less than half of the medical groups list cost details on their websites.

Wider implications of the findings

This is the first report to analyze the cost of egg freezing in Japan using the institution's website. The rate of cost disclosure on the website is still low. Moreover, the costs of social freezing are significantly higher than medical reasons, but this may change with the insurance of ART.

Trial registration number

not applicable

Development of an aviation-style computerized checklist displayed on a tablet computer for improving handoff communication in the post-anesthesia care unit

Critical patient care information is often omitted or misunderstood during handoffs, which can lead to inefficiencies, delays, and sometimes patient harm. We implemented an aviation-style post-anesthesia care unit (PACU) handoff checklist displayed on a tablet computer to improve PACU handoff communication. We developed an aviation-style computerized checklist system for use in procedural rooms and adapted it for tablet computers to facilitate the performance of PACU handoffs. We then compared the proportion of PACU handoff items communicated before and after the implementation of the PACU handoff checklist on a tablet computer. A trained observer recorded the proportion of PACU handoff information items communicated, any resistance during the performance of the checklist, the type of provider participating in the handoff, and the time required to perform the handoff. We also obtained these patient outcomes: PACU length of stay, respiratory events, post-operative nausea and vomiting, and pain. A total of 209 PACU handoffs were observed before and 210 after the implementation of the tablet-based PACU handoff checklist. The average proportion of PACU handoff items communicated increased from 49.3% (95% CI 47.7-51.0%) before checklist implementation to 72.0% (95% CI 69.2-74.9%) after checklist implementation (p < 0.001). A tablet-based aviation-style handoff checklist resulted in an increase in PACU handoff items communicated, but did not have an effect on patient outcomes.

Aviation-Style Computerized Surgical Safety Checklist Displayed on a Large Screen and Operated by the Anesthesia Provider Improves Checklist Performance

BACKGROUND

Many hospitals have implemented surgical safety checklists based on the World Health Organization surgical safety checklist, which was associated with improved outcomes. However, the execution of the checklists is frequently incomplete. We reasoned that aviation-style computerized checklist displayed onto large, centrally located screen and operated by the anesthesia provider would improve the performance of surgical safety checklist.

METHODS

We performed a prospective before and after observational study to evaluate the effect of a computerized surgical safety checklist system on checklist performance. We created checklist software and translated our 4-part surgical safety checklist from wall poster into an aviation-style computerized format displayed onto a large, centrally located screen and operated by the anesthesia provider. Direct observers recorded performance of the first part of the surgical safety checklist that was initiated before anesthetic induction, including completion of each checklist item, provider participation and distraction level, resistance to use of the checklist, and the time required for checklist completion before and after checklist system implementation. We compared trends of the proportions of cases with 100% surgical safety checklist completion over time between pre- and postintervention periods and assessed for a jump at the start of intervention using segmented logistic regression model while controlling for potential confounding variables.

RESULTS

A total of 671 cases were observed before and 547 cases were observed after implementation of the computerized surgical safety checklist system. The proportion of cases in which all of the items of the surgical safety checklist were completed significantly increased from 2.1% to 86.3% after the computerized checklist system implementation (P < .001). Before computerized checklist system implementation, 488 of 671 (72.7%) cases had <75% of checklist items completed, whereas after a computerized checklist system implementation, only 3 of 547 (0.5%) cases had <75% of checklist items completed.

CONCLUSIONS

The implementation of a computerized surgical safety checklist system resulted in an improvement in checklist performance.

A comparison of a prototype electromyograph vs. a mechanomyograph and an acceleromyograph for assessment of neuromuscular blockade

The extent of neuromuscular blockade during anaesthesia is frequently measured using a train‐of‐four stimulus. Various monitors have been used to quantify the train‐of‐four, including mechanomyography, acceleromyography and electromyography. Mechanomyography is often considered to be the laboratory gold standard of measurement, but is not commercially available and has rarely been used in clinical practice. Acceleromyography is currently the most commonly used monitor in the clinical setting, whereas electromyography is not widely available. We compared a prototype electromyograph with a newly constructed mechanomyograph and a commercially available acceleromyograph monitor in 43 anesthetised patients. The mean difference (bias; 95% limits of agreement) in train‐of‐four ratios was 4.7 (−25.2 to 34.6) for mechanomyography vs. electromyography; 14.9 (−13.0 to 42.8) for acceleromyography vs. electromyography; and 9.8 (−31.8 to 51.3) for acceleromyography vs. mechanomyography. The mean difference (95% limits of agreement) in train‐of‐four ratios between opposite arms when using electromyography was −0.7 (−20.7 to 19.3). There were significantly more acceleromyography train‐of‐four values > 1.0 (23%) compared with electromyography or mechanomography (2–4%; p < 0.0001). Electromyography most closely resembled mechanomyographic assessment of neuromuscular blockade, whereas acceleromyography frequently produced train‐of‐four ratio values > 1.0, complicating the interpretation of acceleromyography results in the clinical setting.

The effects of an aviation-style computerised pre-induction anaesthesia checklist on pre-anaesthetic set-up and non-routine events

This prospective, observational study compared the proportion of cases with missing critical pre-induction items before and after the implementation of an aviation-style computerised pre-induction anaesthesia checklist. Trained observers recorded the availability of critical pre-induction items and evaluated the characteristics of the pre-induction anaesthesia checklist performance including provider participation and distraction level, resistance to the use of the checklist and the time required for completion. Surgical cases that met the criteria for inclusion in the National Surgical Quality Improvement Program at a single academic hospital were selected for observation. A total of 853 cases were observed before and 717 after implementation of the checklist. The proportion of cases with failure to perform all pre-induction steps decreased from 10.0% to 6.4% (p = 0.012). There was also a significant decrease in the proportion of cases with non-routine events from 1.2% cases before to none after checklist implementation (p = 0.003). In 17 cases, the checklist alerted the anaesthesia provider to correct a mistake in pre-induction preparation.

Frequency and risk factors of thoracic metastases and optimisation of the use of cross-sectional chest imaging in follow-up patients with cervical cancer

AIM

To optimise cross-sectional chest imaging usage by identifying frequency and risk factors associated with thoracic metastases in cervical cancer patients after initial definitive treatment.

MATERIALS AND METHODS

This study, conducted during 2004-2015, examined 361 consecutive patients with histopathologically proven cervical carcinoma with at least 1 year of follow-up. Electronic medical records and all available imaging modes were used to record and assess patient and tumour characteristics and timing of thoracic metastases. Associations with these characteristics and thoracic metastases were assessed using univariate and multivariable Cox proportional hazards modelling.

RESULTS

Of the 361 patients, 31 developed thoracic metastases. Multivariate regression results showed that adeno/adenosquamous carcinomas (hazard ratio [HR], 2.46; 95% confidence interval [CI], 1.06 to 5.72), other histology (HR, 5.61; 95% CI, 1.81 to 17.42), high International Federation of Gynaecology and Obstetrics (FIGO) stage (HR, 2.84; 95% CI, 1.09 to 7.37), and presence of initial intra-abdominal lymph node metastases (HR, 2.46; 95% CI, 1.02 to 5.90) were associated significantly and independently with thoracic metastases. The second analysis among the subgroup of surgical treatment identified intermediate-high risk classification of recurrence (HR, 5.12; 95% CI, 1.14 to 22.94), high FIGO stage (HR, 2.73; 95% CI, 1.05 to 7.13), and other histology (HR, 11.51; 95% CI, 3.66 to 36.19) as independent predictors of thoracic metastases. Two of the 361 and 2/313 patients with thoracic metastases who did not correspond to the conditions above were in the respective evaluation groups.

CONCLUSION

Assessment of negative prognostic factors for thoracic metastases might contribute to reduced need for chest cross-sectional chest computed tomography examinations.

Abstract P6-01-02: Machine learning-based structural analysis and oxygen saturation measurement of tumor-associated vessels in breast cancer using a photoacoustic tomography system

Introduction

Breast cancer induces angiogenesis, one of the primary factors responsible for tumor progression. Therefore, the ability to visualize angiogenesis at a higher resolution is crucial. Photoacoustic tomography is a noninvasive method of visualizing angiogenesis involving light absorption and ultrasonic wave emission. If the irradiation light wavelength is adjusted for hemoglobin, vascular imaging is possible. Furthermore, using two wavelengths for oxidized and reduced hemoglobin, “S-factor,” can be calculated, which nearly corresponds to oxygen saturation. Therefore, photoacoustic imaging allows the assessment of breast lesions from vascular structural and functional viewpoints.

Objectives

This study aimed to demonstrate the possible utility of photoacoustic tomography for clinical application focusing on the morphologic features and oxygen saturation status of breast tumor-related vessels.

Methods

For the morphological analysis, we applied a machine learning-based method for automatic vessel extraction, and for the functional analysis we evaluated hemoglobin oxygen saturation calculating signals obtained at two wavelengths. In our system, a 3D ultrasound image was simultaneously acquired as a volume image of a tumor, which helped analyze the positional relationship between the vessels and the tumor.

Results

On morphological analysis, the fine structure of tumor-related vessels was rendered in high resolution. In our system, the blood vessels branched toward the tumor 2-3 more times more frequently than observed on contrast-enhanced MRI, illustrating a finer level of blood vessels near the tumor on our system than on MRI. Next, we analyzed the six morphologic features of vessels (radius, volume, curvature, contraction, maximum angle and vessel branch number) that are associated with the pathologic condition in neuroscience. We determined that the feature distribution of vessels located close to the tumor differed from that located away from the tumor. For example, vessels near the tumor had higher curvature, which means they are more tortuous than healthy vessels. The difference in the distribution of all six features was statistically significant on the Kolmogorov-Smirnov test.

On functional analysis, S-factor measurement of the healthy human breast demonstrated clearly demarcated arteries and veins. The S-factor of any artery was nearly 100%, while that of the veins inside the breast cancer tended to be a little higher (approximately 5%) compared to that in the healthy part. This tendency of veins was not recognized in benign tumors. This could show arteriovenous shunt in cancer microenvironment. We found low saturation signals emerging in the tumor tissue following bevacizumab-containing chemotherapy, indicating the possibility that our system reveals microenvironment changes.

Discussion

If our system can identify the structure or oxygen saturation characteristics unique to tumor-associated vasculature, it could contribute to the improved accuracy of breast cancer diagnosis and allow the observation of tumor vessel normalization because of the drug treatment. An earlier grasp of the therapeutic effect could lead to the provision of individualized medicine.

Citation Format: Matsumoto Y, Gu L, Bise R, Asao Y, Sekiguchi H, Yoshikawa A, Ishii T, Takada M, Kataoka M, Sakurai T, Yagi T, Sato I, Togashi K, Shiina T, Toi M. Machine learning-based structural analysis and oxygen saturation measurement of tumor-associated vessels in breast cancer using a photoacoustic tomography system [abstract]. In: Proceedings of the 2018 San Antonio Breast Cancer Symposium; 2018 Dec 4-8; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2019;79(4 Suppl):Abstract nr P6-01-02.

Comparison of Different Parathyroid Hormone Radioimmunoassays in Uremic Patients with Secondary Hyperparathyroidism

Parathyroid hormone (PTH) levels of patients with chronic renal failure (CRF) were measured by three different radioimmunoassays (RIA); RIA for mid-region PTH by antibody CH9 (i-PTH) (1), RIA for intact fragments of PTH (intact PTH) and RIA for C-terminal fragments of PTH (PTH-C). PTH levels were higher in CRF patients undergoing hemodialysis therapy (hemodialysis patients) by all three methods. However, PTH levels measured only by i-PTH assay and intact PTH assay were significantly higher in patients with CRF who were not on dialysis (non-dialyzed CRF patients). PTH levels were above normal when creatinine clearance was below 45 ml/min in the intact PTH assay and 66 ml/min in the i-PTH assay. I-PTH levels were well correlated with the severity of osteitis fibrosa evaluated by the degree of periosteal resorption in the digits of hemodialysis patients. Since special handling of the sample is required for the intact PTH assay, i-PTH assay is the most suitable method for diagnosing secondary hyperparathyroidism in patients with CRF.