Triple-tuned birdcage and single-tuned dipole array for quadri-nuclear head MRI at 7 T

PURPOSE

The purpose of this work was to design and build a coil for quadri-nuclear MRI of the human brain at 7 T.

METHODS

We built a transmit/receive triple-tuned (45.6 MHz for  2 $$ {}^2 $$ H, 78.6 MHz for  23 $$ {}^{23} $$ Na, and 120.3 MHz for  31 $$ {}^{31} $$ P) quadrature four-rod birdcage that was geometrically interleaved with a transmit/receive four-channel dipole array (297.2 MHz for  1 $$ {}^1 $$ H). The birdcage rods contained passive, two-pole resonant circuits that emulated capacitors required for single-tuning at three frequencies. The birdcage assembly also included triple-tuned matching networks, baluns, and transmit/receive switches. We assessed the performance of the coil with quality factor (Q) and signal-to-noise ratio (SNR) measurements, and performed in vivo multinuclear MRI and MR spectroscopic imaging (MRSI).

RESULTS

Q measurements showed that the triple-tuned birdcage efficiency was within 33% of that of single-tuned baseline birdcages at all three frequencies. The quadri-tuned coil SNR was 78%, 59%, 44%, and 48% lower than that of single or dual-tuned reference coils for  1 $$ {}^1 $$ H,  2 $$ {}^2 $$ H,  23 $$ {}^{23} $$ Na, and  31 $$ {}^{31} $$ P, respectively. Quadri-nuclear MRI and MRSI was demonstrated in brain in vivo in about 30 min.

CONCLUSION

While the SNR of the quadruple tuned coil was significantly lower than dual- and single-tuned reference coils, it represents a step toward truly simultaneous quadri-nuclear measurements.

Measurements of All-Particle Energy Spectrum and Mean Logarithmic Mass of Cosmic Rays from 0.3 to 30 PeV with LHAASO-KM2A

We present the measurements of all-particle energy spectrum and mean logarithmic mass of cosmic rays in the energy range of 0.3-30 PeV using data collected from LHAASO-KM2A between September 2021 and December 2022, which is based on a nearly composition-independent energy reconstruction method, achieving unprecedented accuracy. Our analysis reveals the position of the knee at 3.67±0.05±0.15  PeV. Below the knee, the spectral index is found to be -2.7413±0.0004±0.0050, while above the knee, it is -3.128±0.005±0.027, with the sharpness of the transition measured with a statistical error of 2%. The mean logarithmic mass of cosmic rays is almost heavier than helium in the whole measured energy range. It decreases from 1.7 at 0.3 PeV to 1.3 at 3 PeV, representing a 24% decline following a power law with an index of -0.1200±0.0003±0.0341. This is equivalent to an increase in abundance of light components. Above the knee, the mean logarithmic mass exhibits a power law trend towards heavier components, which is reversal to the behavior observed in the all-particle energy spectrum. Additionally, the knee position and the change in power-law index are approximately the same. These findings suggest that the knee observed in the all-particle spectrum corresponds to the knee of the light component, rather than the medium-heavy components.

Measurement of Ultra-High-Energy Diffuse Gamma-Ray Emission of the Galactic Plane from 10 TeV to 1 PeV with LHAASO-KM2A

The diffuse Galactic γ-ray emission, mainly produced via interactions between cosmic rays and the interstellar medium and/or radiation field, is a very important probe of the distribution, propagation, and interaction of cosmic rays in the Milky Way. In this Letter, we report the measurements of diffuse γ rays from the Galactic plane between 10 TeV and 1 PeV energies, with the square kilometer array of the Large High Altitude Air Shower Observatory (LHAASO). Diffuse emissions from the inner (15°10  TeV). The energy spectrum in the inner Galaxy regions can be described by a power-law function with an index of -2.99±0.04, which is different from the curved spectrum as expected from hadronic interactions between locally measured cosmic rays and the line-of-sight integrated gas content. Furthermore, the measured flux is higher by a factor of ∼3 than the prediction. A similar spectrum with an index of -2.99±0.07 is found in the outer Galaxy region, and the absolute flux for 10≲E≲60  TeV is again higher than the prediction for hadronic cosmic ray interactions. The latitude distributions of the diffuse emission are consistent with the gas distribution, while the longitude distributions show clear deviation from the gas distribution. The LHAASO measurements imply that either additional emission sources exist or cosmic ray intensities have spatial variations.

Pre- and Post-Treatment Patient-Reported Financial Toxicity in Head and Neck Cancer: Identifying Influential Factors and Clinical Significance

PURPOSE/OBJECTIVE(S)

Head and neck cancer patients are at high-risk for financial stress due to the often complex, time-consuming, and expensive treatments that can impact physical function and quality of life. It is important to identify factors that affect financial toxicity early on in treatment and to help mitigate their effects. The goals of this study are to assess patient-reported financial toxicity prior to and after completion of radiation therapy (RT) and to uncover any interactions with socioeconomic factors, quality of life, treatment satisfaction, and treatment adherence.

MATERIALS/METHODS

A total of 80 patients who were evaluated for RT to the head and neck region between July 2021 and December 2022 and had completed surveys prior to the initiation of RT were included. Surveys included the FACIT-COST and FACIT-TS-G. Patient clinical information and demographics were collected. Linear regression was used to evaluate categorical variables and Pearson correlation was used to evaluate continuous variables and their associations with COST.

RESULTS

The median pre-RT COST was 29.5 (range 4-44) with lower scores indicating worse financial toxicity. The majority of patients were white (69%), non-Hispanic (75%), and English-speaking (75%). 65% had Medicare, 14% had Medicaid, and 21% had other insurance. 60 of 80 (75%) patients ultimately underwent RT at our institution. 34 (57%) missed at least one day of scheduled RT fractions and 11 (14%) patients had G-tubes placed. Lower COST was associated with decreased age, thyroid primary disease, advanced stage, metastatic disease, Medicaid insurance, Hispanic ethnicity, unemployment, and G-tube placement. Higher COST was associated with cutaneous primary disease and ability to speak English, while Medicare insurance trended toward significance. 18 of 80 patients (23%) completed follow-up surveys post-RT and 9 reported a decrease in COST. At baseline, the standard deviation of the COST was 10.6. Effect size was defined as the number of standard deviation change. Mean decrease in COST was 9.4 (effect size of 89%). Mean FACT-TS-G was lower, indicating decreased treatment satisfaction, for these patients as compared to those that had the same or increased COST compared to baseline, (17.4 vs. 22.7, p < 0.01). There were more missed RT days, 4 vs. 1, and G-tube placements, 2 vs. 0, in those with decreased COST as well.

CONCLUSION

Worse baseline financial toxicity was associated with younger age, advanced stage, metastatic disease, Medicaid insurance, unemployment, and G-tube placement. Those that reported worsened financial toxicity after RT reported worse treatment satisfaction and had more missed RT days and G-tube placements. These findings support work to better understand financial toxicity as it may predict those at higher risk of missing treatments, particularly crucial considering prolonged RT duration is linked to poorer outcomes. Future efforts will focus on automating early referrals to case managers and social work services for these patients.

Replicability of proton MR spectroscopic imaging findings in mild traumatic brain injury: Implications for clinical applications

PURPOSE

Proton magnetic resonance spectroscopy (1H MRS) offers biomarkers of metabolic damage after mild traumatic brain injury (mTBI), but a lack of replicability studies hampers clinical translation. In a conceptual replication study design, the results reported in four previous publications were used as the hypotheses (H1-H7), specifically: abnormalities in patients are diffuse (H1), confined to white matter (WM) (H2), comprise low N-acetyl-aspartate (NAA) levels and normal choline (Cho), creatine (Cr) and myo-inositol (mI) (H3), and correlate with clinical outcome (H4); additionally, a lack of findings in regional subcortical WM (H5) and deep gray matter (GM) structures (H6), except for higher mI in patients' putamen (H7).

METHODS

26 mTBI patients (20 female, age 36.5 ± 12.5 [mean ± standard deviation] years), within two months from injury and 21 age-, sex-, and education-matched healthy controls were scanned at 3 Tesla with 3D echo-planar spectroscopic imaging. To test H1-H3, global analysis using linear regression was used to obtain metabolite levels of GM and WM in each brain lobe. For H4, patients were stratified into non-recovered and recovered subgroups using the Glasgow Outcome Scale Extended. To test H5-H7, regional analysis using spectral averaging estimated metabolite levels in four GM and six WM structures segmented from T1-weighted MRI. The Mann-Whitney U test and weighted least squares analysis of covariance were used to examine mean group differences in metabolite levels between all patients and all controls (H1-H3, H5-H7), and between recovered and non-recovered patients and their respectively matched controls (H4). Replicability was defined as the support or failure to support the null hypotheses in accordance with the content of H1-H7, and was further evaluated using percent differences, coefficients of variation, and effect size (Cohen's d).

RESULTS

Patients' occipital lobe WM Cho and Cr levels were 6.0% and 4.6% higher than controls', respectively (Cho, d = 0.37, p = 0.04; Cr, d = 0.63, p = 0.03). The same findings, i.e., higher patients' occipital lobe WM Cho and Cr (both p = 0.01), but with larger percent differences (Cho, 8.6%; Cr, 6.3%) and effect sizes (Cho, d = 0.52; Cr, d = 0.88) were found in the comparison of non-recovered patients to their matched controls. For the lobar WM Cho and Cr comparisons without statistical significance (frontal, parietal, temporal), unidirectional effect sizes were observed (Cho, d = 0.07 - 0.37; Cr, d = 0.27 - 0.63). No differences were found in any metabolite in any lobe in the comparison between recovered patients and their matched controls. In the regional analyses, no differences in metabolite levels were found in any GM or WM region, but all WM regions (posterior, frontal, corona radiata, and the genu, body, and splenium of the corpus callosum) exhibited unidirectional effect sizes for Cho and Cr (Cho, d = 0.03 - 0.34; Cr, d = 0.16 - 0.51).

CONCLUSIONS

We replicated findings of diffuse WM injury, which correlated with clinical outcome (supporting H1-H2, H4). These findings, however, were among the glial markers Cho and Cr, not the neuronal marker NAA (not supporting H3). No differences were found in regional GM and WM metabolite levels (supporting H5-H6), nor in putaminal mI (not supporting H7). Unidirectional effect sizes of higher patients' Cho and Cr within all WM analyses suggest widespread injury, and are in line with the conclusion from the previous publications, i.e., that detection of WM injury may be more dependent upon sensitivity of the 1H MRS technique than on the selection of specific regions. The findings lend further support to the corollary that clinic-ready 1H MRS biomarkers for mTBI may best be achieved by using high signal-to-noise-ratio single-voxels placed anywhere within WM. The biochemical signature of the injury, however, may differ and therefore absolute levels, rather than ratios may be preferred. Future replication efforts should further test the generalizability of these findings.

Role of Structural, Metabolic, and Functional MRI in Monitoring Visual System Impairment and Recovery

The visual system, consisting of the eyes and the visual pathways of the brain, receives and interprets light from the environment so that we can perceive the world around us. A wide variety of disorders can affect human vision, ranging from ocular to neurologic to systemic in nature. While other noninvasive imaging techniques such as optical coherence tomography and ultrasound can image particular sections of the visual system, magnetic resonance imaging (MRI) offers high resolution without depth limitations. MRI also gives superior soft-tissue contrast throughout the entire pathway compared to computed tomography. By leveraging different imaging sequences, MRI is uniquely capable of unveiling the intricate processes of ocular anatomy, tissue physiology, and neurological function in the human visual system from the microscopic to macroscopic levels. In this review we discuss how structural, metabolic, and functional MRI can be used in the clinical assessment of normal and pathologic states in the anatomic structures of the visual system, including the eyes, optic nerves, optic chiasm, optic tracts, visual brain nuclei, optic radiations, and visual cortical areas. We detail a selection of recent clinical applications of MRI at each position along the visual pathways, including the evaluation of pathology, plasticity, and the potential for restoration, as well as its limitations and key areas of ongoing exploration. Our discussion of the current and future developments in MR ocular and neuroimaging highlights its potential impact on our ability to understand visual function in new detail and to improve our protection and treatment of anatomic structures that are integral to this fundamental sensory system. LEVEL OF EVIDENCE 3:   TECHNICAL EFFICACY STAGE 3:  .

Global decrease in brain sodium concentration after mild traumatic brain injury

The pathological cascade of tissue damage in mild traumatic brain injury is set forth by a perturbation in ionic homeostasis. However, whether this class of injury can be detected in vivo and serve as a surrogate marker of clinical outcome is unknown. We employ sodium MRI to test the hypotheses that regional and global total sodium concentrations: (i) are higher in patients than in controls and (ii) correlate with clinical presentation and neuropsychological function. Given the novelty of sodium imaging in traumatic brain injury, effect sizes from (i), and correlation types and strength from (ii), were compared to those obtained using standard diffusion imaging metrics. Twenty-seven patients (20 female, age 35.9 ± 12.2 years) within 2 months after injury and 19 controls were scanned with proton and sodium MRI at 3 Tesla. Total sodium concentration, fractional anisotropy and apparent diffusion coefficient were obtained with voxel averaging across 12 grey and white matter regions. Linear regression was used to obtain global grey and white matter total sodium concentrations. Patient outcome was assessed with global functioning, symptom profiles and neuropsychological function assessments. In the regional analysis, there were no statistically significant differences between patients and controls in apparent diffusion coefficient, while differences in sodium concentration and fractional anisotropy were found only in single regions. However, for each of the 12 regions, sodium concentration effect sizes were uni-directional, due to lower mean sodium concentration in patients compared to controls. Consequently, linear regression analysis found statistically significant lower global grey and white matter sodium concentrations in patients compared to controls. The strongest correlation with outcome was between global grey matter sodium concentration and the composite z-score from the neuropsychological testing. In conclusion, both sodium concentration and diffusion showed poor utility in differentiating patients from controls, and weak correlations with clinical presentation, when using a region-based approach. In contrast, sodium linear regression, capitalizing on partial volume correction and high sensitivity to global changes, revealed high effect sizes and associations with patient outcome. This suggests that well-recognized sodium imbalances in traumatic brain injury are (i) detectable non-invasively; (ii) non-focal; (iii) occur even when the antecedent injury is clinically mild. Finally, in contrast to our principle hypothesis, patients' sodium concentrations were lower than controls, indicating that the biological effect of traumatic brain injury on the sodium homeostasis may differ from that in other neurological disorders. Note: This figure has been annotated.

[Correlation between(Pro) renin receptor levels and gender and disease severity in patients with obstructive sleep apnea syndrome]

Objective:The aim of this study is to investigate the relationship between the level of (pro) renin(P)RR in obstructive sleep apnea syndrome (OSA) patients, and the gender and disease severity of the disease.b>Method:From March 2010 to March 2018, eighty OSA patients who were treated and diagnosed in our hospital were selected as subjects. Another 20 healthy subjects were selected as the control group.Plasma soluble (pro) renin receptor ［s(P)RR］ levels and clinical parameters were measured in healthy subjects and OSA patients with different sex and disease severity. Result:The plasma s(P)RR concentrations were significantly higher in OSA patients than that in control group. In all patients, plasma s(P)RR concentrations increased with increasing disease levels and showed the same trend between men and women. In addition,in all patients, plasma s(P)RR concentrations were significantly positively correlated with waist-to-hip ratio, HbA1c, AHI, and oxygen desaturation index. There was a significant negative correlation between saturation (MSpO₂) and minimum oxygen saturation (minSpO₂) (P<0.05).In female subjects,plasma s(P)RR concentrations were significantly positively correlated with waist-to-hip ratio and AHI,but significantly negatively correlated with eGFR (P<0.05).In male subjects,plasma s(P)RR concentration was significantly positively correlated with waist-to-hip ratio,HbA1c,renin level,AHI and oxygen desaturation index, but negatively correlated with eGFR, MSpO₂ and minSpO₂ (P<0.05). Plasma s(P)RR concentrations were significantly reduced after treatment with nasal continuous positive airway pressure ventilator. In addition, ESS,AHI,MSpO₂,minSpO₂,and oxygen desaturation index were all significantly improved (P<0.05).Conclusion: Plasma s(P)RR levels in OSA patients are significantly positively correlated with the severity of the disease and can directly reflect the severity of the disease. In addition, the patient with higher waist-to-hip ratio and HbA1c, and lower eGFR can effect plasma s(P)RR levels, and may lead to OSA aggravation.

Helical tomotherapy with simultaneous integrated boost dose painting for the treatment of synchronous primary cancers involving the head and neck

OBJECTIVE

To demonstrate the feasibility of helical tomotherapy (HT)-based intensity-modulated radiotherapy (IMRT) for the treatment of synchronous primary cancers arising from the head and neck.

METHODS

14 consecutive patients with histologically proven squamous cell carcinoma of the head and neck were determined to have a second primary cancer in the upper aerodigestive tract on further evaluation and were treated with HT using simultaneous integrated boost IMRT. Megavoltage CT scans were acquired daily as part of an image-guided registration protocol. Concurrent platinum-based systemic therapy was given to nine patients (64%).

RESULTS

HT resulted in durable local control in 21 of the 28 primary disease sites irradiated, including a complete clinical and radiographic response initially observed at 17 of the 20 sites with gross tumour. The mean displacements to account for interfraction motion were 2.44 ± 1.25, 2.92 ± 1.09 and 2.31 ± 1.70 mm for the medial-lateral (ML), superior-inferior (SI) and anteroposterior (AP) directions, respectively. Table shifts of >3 mm occurred in 19%, 20% and 22% of the ML, SI and AP directions, respectively. The 2-year estimates of overall survival, local-regional control and progression-free survival were 58%, 73% and 60%, respectively.

CONCLUSION

The effectiveness of HT for the treatment of synchronous primary cancers of the head and neck was demonstrated.

ADVANCES IN KNOWLEDGE

HT is a feasible option for synchronous primary cancers of the head and neck and can result in long-term disease control with acceptable toxicity in appropriately selected patients.

Evaluation of hippocampus dose for patients undergoing intensity-modulated radiotherapy for nasopharyngeal carcinoma

OBJECTIVE

To evaluate the dose received by the hippocampus among patients undergoing intensity-modulated radiotherapy (IMRT) for nasopharyngeal cancer.

METHODS

10 patients with biopsy-proven, locally advanced nasopharyngeal cancer constituted the study population. The total prescribed dose to the planning target volume (PTV) was 70 Gy (D95%) delivered in 2.12-Gy daily fractions using IMRT. Using established anatomical guidelines, MRI co-registration and the assistance of a board-certified neuroradiologist, the right and left hippocampi were delineated on axial imaging from the CT scan obtained at simulation for each patient beginning at the most anterior portion of the lateral ventricle. IMRT treatment plans were generated without dose-volume constraints to the hippocampus. A range of dose-volume statistics was calculated.

RESULTS

The mean hippocampus volume was 6.01 ± 2.61 cm(3). The mean V20 was 72.2%; V40 was 22.0%; V50 was 10.2%; and V60 was 5.5%. The average mean, minimum and maximum hippocampus doses were 30.27 Gy (range, 19.08-47.99 Gy); 17.54 Gy (range, 11.66-33.17 Gy); and 54.95 Gy (range, 35.59-75.57 Gy), respectively. The hippocampus received a maximum dose exceeding 70 Gy in 30% of cases.

CONCLUSION

Our dosimetric analysis suggests that, for patients undergoing IMRT for nasopharyngeal cancer, the hippocampus routinely receives significantly high doses.

ADVANCES IN KNOWLEDGE

The hippocampus receives a fair amount of incidental radiation during treatment for nasopharyngeal cancer. Given the importance of this structure with respect to memory and neurocognitive function, consideration should be given to identifying the hippocampus as a critical organ at risk in the IMRT optimization process.

Clinical-dosimetric relationship between lacrimal gland dose and ocular toxicity after intensity-modulated radiotherapy for sinonasal tumours

OBJECTIVE

To characterise the relationship between lacrimal gland dose and ocular toxicity among patients treated by intensity-modulated radiotherapy (IMRT) for sinonasal tumours.

METHODS

40 patients with cancers involving the nasal cavity and paranasal sinuses were treated with IMRT to a median dose of 66.0 Gy. Toxicity was scored using the Radiation Therapy Oncology Group morbidity criteria based on conjunctivitis, corneal ulceration and keratitis. The paired lacrimal glands were contoured as organs at risk, and the mean dose, maximum dose, V10, V20 and V30 were determined. Statistical analysis was performed using logistic regression and the Akaike information criterion (AIC).

RESULTS

The maximum and mean dose to the ipsilateral lacrimal gland were 19.2 Gy (range, 1.4-75.4 Gy) and 14.5 Gy (range, 11.1-67.8 Gy), respectively. The mean V10, V20 and V30 values were 50%, 25% and 17%, respectively. The incidence of acute and late Grade 3+ toxicities was 23% and 19%, respectively. Based on logistic regression and AIC, the maximum dose to the ipsilateral lacrimal gland was identified as a more significant predictor of acute toxicity (AIC, 53.89) and late toxicity (AIC, 32.94) than the mean dose (AIC, 56.13 and 33.83, respectively). The V20 was identified as the most significant predictor of late toxicity (AIC, 26.81).

CONCLUSION

A dose-response relationship between maximum dose to the lacrimal gland and ocular toxicity was established. Our data suggesting a threshold relationship may be useful in establishing dosimetric guidelines for IMRT planning that may decrease the risk of acute and late lacrimal toxicities in the future.

ADVANCES IN KNOWLEDGE

A threshold relationship between radiation dose to the lacrimal gland and ocular toxicity was demonstrated, which may aid in treatment planning and reducing the morbidity of radiotherapy for sinonasal tumours.

Intensity-modulated radiotherapy for nasopharyngeal carcinoma: improvement of the therapeutic ratio with helical tomotherapy vs segmental multileaf collimator-based techniques

OBJECTIVES

The aim of the study was to compare differences in dosimetric, clinical and quality-of-life end points among patients treated with helical tomotherapy (HT) and segmental multileaf collimator (SMLC)-based intensity-modulated radiotherapy (IMRT) for nasopharyngeal carcinoma.

METHODS

From June 2005 to August 2009, 30 consecutive patients were treated with IMRT for nasopharyngeal carcinoma to a dose of 70 Gy. 14 patients (47%) were treated using HT and 16 (53%) were treated using SMLC-based IMRT. 28 patients (93%) received concurrent chemotherapy. The patients were evenly balanced between the two radiotherapy groups with respect to clinical and pathological characteristics. Median follow-up was 30 months (range, 6-62 months).

RESULTS

The 2-year estimates of overall survival, local-regional control and progression-free survival were 81%, 87% and 82%, respectively. There were no significant differences in any of these end points with respect to IMRT technique (p>0.05 for all). Dosimetric analysis revealed that patients treated by HT had significantly improved salivary sparing with respect to mean dose (27.3 vs 34.1 Gy, p=0.03) and volume receiving greater than or equal to 30 Gy (31.7% vs 47.3%, p=0.01) to the contralateral (spared) parotid gland. The incidence of Grade 3+ late xerostomia was 13 and 7% among patients treated with SMLC-based IMRT and HT, respectively (p=0.62). The corresponding proportion of patients who subjectively reported "too little" or "no" saliva at final follow-up was 38% and 7%, respectively (p=0.04).

CONCLUSION

The superior dosimetric outcome observed with HT appeared to translate into moderately improved clinical outcomes with respect to salivary sparing. Prospective trials are needed to validate this gain in the therapeutic ratio.

Changes in position and volume of lung cancer target volumes during stereotactic body radiotherapy (SBRT): is image guidance necessary?

The purpose of this study was to analyze inter- and intra-fractional changes in tumor volume with respect to both spatial and volumetric parameters among patients treated by SBRT for lung cancer. Twelve patients (13 tumors) were treated by SBRT with abdominal compression in 3-5 fractions over a 2 week period to a median dose of 60 Gy (range, 48 to 60 Gy). Kilovoltage cone-beam CT (CBCT) was obtained prior to the delivery of each fraction as well as intra-fractionally yielding a total of 55 CBCT scans. All CBCT scans were registered with the planning CT for target alignment and shifts were recorded and analyzed. Retrospectively, gross tumor volume (GTV) was contoured on all CBCT images and compared to initial planning volumes; positional differences were evaluated utilizing directional and vector analysis. Shifts greater than 5 mm were applied inter-fractionally in 6.8% (lateral), 29.5% (longitudinal), and 6.8% (vertical) of all delivered treatments. Using a 10 mm threshold, the corresponding percentages were 2.3%, 13.6%, and 2.3%, respectively. Across all fractions, the calculated inter-fractional shift vectors ranged from 0 to 31.2 mm, with 40.9%, 15.9%, and 11.4% of all fractions having shift vectors≥5 mm, ≥10 mm, and ≥20 mm, respectively. Intra-fractional shifts were also evaluated and found negligible in a small portion of patients evaluated. The mean overall reduction in GTV was 21.1% during SBRT. Significant changes in both position and volume occur during SBRT for lung cancer. Shifts (particularly in the superior-inferior axis) may exceed applied margins and compromise target coverage. Due to the extreme hypofractionation associated with SBRT, inter-fractional image guidance is necessary.

Comparison of IMRT techniques in the radiotherapeutic management of head and neck cancer: is tomotherapy "better" than step-and-shoot IMRT?

Currently, the most common method of delivering intensity-modulated radiotherapy (IMRT) is through step-and-shoot, segmental multi-leaf collimator (SMLC)-based techniques. Although rotational delivery methods such as helical tomotherapy (HT) have been proposed as offering advantages in the treatment of head and neck cancer, a lack of clinical data exists on its potential utility. This study compared dosimetric, clinical, and quality-of-life endpoints among 149 patients treated by HT and SMLC-IMRT for head and neck cancer. Dosimetric analysis revealed that the use of HT resulted in significant improvements with respect to mean dose (23.5 versus 27.9 Gy, p = 0.03) and V30 (30.1 versus 43.9 Gy, p = 0.01) to the contralateral (spared) parotid gland. However, the incidence of grade 3+ xerostomia in the late setting was 10% and 8% among patients treated by HT and SMLC-IMRT, respectively (p = 0.46). There were no significant differences in any of the quality of life endpoints among patients treated by HT and SMLC-IMRT (p > 0.05, for all). Acknowledging the biases inherent in this retrospective analysis, we found that the dosimetric advantages observed with HT compared to SMLC-IMRT failed to translate into significant improvements in clinical outcome. Prospective studies are needed to further evaluate how HT may affect the therapeutic ratio.

Intensity-modulated radiotherapy increases dose to the brachial plexus compared with conventional radiotherapy for head and neck cancer

OBJECTIVE

The preferential use of intensity-modulated radiotherapy (IMRT) over conventional radiotherapy (CRT) in the treatment of head and neck cancer has raised concerns regarding dose to non-target tissue. The purpose of this study was to compare dose-volume characteristics with the brachial plexus between treatment plans generated by IMRT and CRT using several common treatment scenarios.

METHOD

The brachial plexus was delineated on radiation treatment planning CT scans from 10 patients undergoing IMRT for locally advanced head and neck cancer using a Radiation Therapy Oncology Group-endorsed atlas. No brachial plexus constraint was used. For each patient, a conventional three-field shrinking-field plan was generated and the dose-volume histogram (DVH) for the brachial plexus was compared with that of the IMRT plan.

RESULTS

The mean irradiated volumes of the brachial plexus using the IMRT vs the CRT plan, respectively, were as follows: V50 (18±5 ml) vs (11±6 ml), p = 0.01; V60 (6±4 ml) vs (3±3 ml), p = 0.02; V66 (3±1 ml) vs (1±1 ml), p = 0.04, V70 (0±1 ml) vs (0±1 ml), p = 0.68. The maximum point dose to the brachial plexus was 68.9 Gy (range 62.3-78.7 Gy) and 66.1 Gy (range 60.2-75.6 Gy) for the IMRT and CRT plans, respectively (p = 0.01).

CONCLUSION

Dose to the brachial plexus is significantly increased among patients undergoing IMRT compared with CRT for head and neck cancer. Preliminary studies on brachial plexus-sparing IMRT are in progress.

Overstaging of cartilage invasion by multidetector CT scan for laryngeal cancer and its potential effect on the use of organ preservation with chemoradiation

OBJECTIVE

The two currently acceptable treatment options for locally advanced laryngeal cancer are total laryngectomy and organ preservation using chemoradiation. To facilitate therapeutic decision making, the accurate pre-treatment evaluation of cartilage invasion is of paramount importance. The purpose of this study was to evaluate the positive predictive value (PPV) and negative predictive value (NPV) of detecting neoplastic cartilage invasion in laryngeal cancer patients using fast-speed multidetector CT (MDCT).

METHODS

61 consecutive patients with clinically staged T3 or T4 squamous cell carcinoma of the larynx or hypopharynx who underwent total laryngectomy were analysed. All patients had MDCT of the neck within 2 weeks prior to surgery. Central radiographic and pathological review was performed in an attempt to correlate findings. MDCT invasion of cartilage was graded based on objective criteria.

RESULTS

MDCT scan was found to have a PPV of 78% and an NPV of 100% for detection of invasion through cartilage, with sensitivity being 100% and specificity 96%. For detection of any cartilage invasion (minor, major or through cartilage invasion), PPV and NPV were 63% and 92%, respectively. The sensitivity was 85% and specificity was 75%. For the detection of tumour invasion through cartilage or major cartilage invasion, MDCT scan had a PPV of 53% and an NPV of 95%. 47% (9/19) patients were down-staged from T4 to T3 after central pathology review.

CONCLUSION

The low PPV for cartilage destruction using MDCT suggests that a significant proportion of patients who were treated by total laryngectomy could have been appropriately offered organ preservation if more accurately staged at initial diagnosis.

Variations in consenting practice for laparoscopic cholecystectomy

INTRODUCTION

To compare the variations in consenting practice amongst trainees and consultant surgeons for laparoscopic cholecystectomy with specific reference to the documentation of significant risks of surgery.

PATIENTS AND METHODS

A proforma was devised which included significant and/or commonly recognised complications of laparoscopic cholecystectomy. This was then cross-referenced with the consent forms for the 80 patients included in the study and the documented risks explained in each case were noted.

RESULTS

The results showed that there is considerable variation between the three grades of clinicians involved in obtaining a patient's consent for laparoscopic cholecystectomy. There was a clear difference in emphasis of the significant complications depending on the seniority of the consenter. Over 80% of the consents in this study were still being obtained by junior staff.

CONCLUSIONS

More often than not, patients are not provided with consistent information to make an informed choice. We suggest that a preprinted consent form will provide a more uniform approach to consenting practice for laparoscopic cholecystectomy.

Aggregation between Xanthan and Nonyphenyloxypropyl β-Hydroxyltrimethylammonium Bromide in Aqueous Solution: MesoDyn Simulation and Binding Isotherm Measurement

The aggregation behavior of nonyphenyloxypropyl beta-hydroxyltrimethylammonium bromide (C9phNBr) and xanthan (XC) in aqueous solution was investigated by MesoDyn density functional simulation and binding isotherm measurement. The process of aggregate formation and the aggregate morphology are reported. The formation of aggregates includes three stages and the morphology of XC-C9phNBr aggregates is rodlike or ellipsoidal. The effects of temperature and XC concentration on the aggregation are analyzed. Results indicate that the formation of aggregates is an exothermic process, and their formation becomes more difficult and the formation rate decreases with increasing temperature. The formation of aggregates is also related to XC concentration, and it becomes much more difficult when the concentration of XC is higher than 20 vol %. The simulation results agree with binding isotherms of C9phNBr to XC obtained via the potentiometric titration method, which shows a typical cooperative binding between C9phNBr and XC.

Current and future applications of immunological attenuation via pegylation of cells and tissue

Prevention of immunological rejection of transplanted tissues is of crucial importance in transplantation medicine. Current procedures primarily use pharmacological agents such as cyclosporin, which, while effective, must be typically administered for the life of the individual. Furthermore, the drug-induced global immunosuppression of the patient predisposes the individual to infection and enhances their risk of developing certain forms of cancer. Hence, additional methods are needed to both enhance tissue engraftment and diminish the adverse effects of current immunosuppressive therapy. Studies from blood transfusion (i.e. a specialised form of cellular transplantation) suggest that covalent modification of cells and tissues with methoxypoly(ethylene glycol) [mPEG] can significantly diminish rejection episodes and may further enhance the induction of tolerance to donor tissues. The mechanisms underlying mPEG-mediated immunocamouflage are the loss of antigen recognition, impaired cell-cell interaction, and an inability of endogenous antibodies (e.g. immunoglobulin G) to effectively recognise and bind foreign epitopes. As a consequence of the global camouflage imparted by mPEG, the weak co-stimulation of alloreactive T cells may subsequently induce apoptosis, thus leading to tolerance. Initial studies on the transplantation of pegylated isogeneic rat pancreatic islets demonstrates that mPEG-derivatisation does not impair in vivo cellular signalling and function. Thus, in contrast to the pharmacological inhibition of the recipient's immune response, the mPEG-mediated immunocamouflage directly addresses the inherent antigenicity and immunogenicity of the donor tissue itself while leaving the recipient a fully competent immune system.

Correlates of cigarette smoking among Korean American adults in Alameda County, California

OBJECTIVE

To estimate the prevalence of cigarette smoking and to determine the sociodemographic correlates of smoking among Korean American adults in Alameda County, California, 1994-1995.

METHOD

Korean surname-based telephone survey; contingency table and multinomial logistic regression analyses.

FINDINGS

Almost 39% of Korean American men and 6% of Korean American women were current smokers. Among Korean American men those who attended religious activities less than monthly had nearly three times the odds of being current smokers, and those who did not speak English well had 2 1/2 times the odds of being current smokers as compared to never smokers. Those 18 to 24 years of age had more than 8 1/2 times the odds, and those who attended religious activities less than monthly had more than 3 1/2 times the odds of being current smokers as compared to former smokers. Among Korean American women those who were not married had more than 3 times the odds of being current smokers, and those who attended religious activities less than monthly had 22 times the odds of being current smokers as compared to never smokers. Those who attended religious activities less than monthly had almost 8 times the odds of being current smokers as compared to former smokers.

CONCLUSIONS

This study increases our understanding about the prevalence and correlates of cigarette smoking among Korean Americans and can contribute to the development of effective smoking cessation and prevention strategies in this understudied population.

Breast-conserving therapy in the setting of collagen vascular disease

BACKGROUND

It is unclear whether the presence of collagen vascular disease should be considered a contraindication to irradiation. This study was undertaken to determine whether women with pre-existing collagen vascular disease have an increased incidence of complications after breast-conserving therapy.

METHODS AND MATERIALS

A cohort of 36 patients with documented collagen vascular disease was conservatively treated for early-stage breast cancer between 1975 and 1998. All of these patients were treated with conventional radiation therapy to a total medium dose of 64 Gy. Seventeen had rheumatoid arthritis; four, scleroderma; four, Raynaud's phenomenon; five, lupus erythematosus; two, Sjögren's disease; and four, polymyositis. Each of these patients was matched to two control patients without a history of collagen vascular disease on the basis of age, radiation therapytechnique, chemotherapy or hormone therapy use, tumor histology, and date of treatment. Acute and late complications were assessed using a six-point scale from the toxicity criteria of the Radiation Therapy Oncology Group and the European Organization for Research and Treatment of Cancer. The scoring system for both acute and late reactions ranged from 0 (no change over baseline) to 5 (radiation led to death). For the purpose of statistical analysis, patients were classified as having a significant complication if they had a score of 3 or greater.

RESULTS

With a median clinical follow-up time of 12.5 years (range, 3.0-22.5 years), no significant difference was detected between the collagen vascular disease and control groups with respect to acute complications (14% vs 8%). With respect to late complications, a significant difference was observed (17% vs 3%) between the two groups. However, when patients in the collagen vascular disease group were analyzed by specific disease, this significance disappeared in all but the scleroderma group.

CONCLUSIONS

Patients with scleroderma have a statistically significant increased incidence of radiation therapy complications after breast-conserving surgery and radiation therapy. The presence of other collagen vascular diseases should not be considered a contraindication for this treatment modality.

[Experimental study on the hemostatic properties of collagen sponge]

OBJECTIVE

To validate the hemostatic properties of collagen sponge made in China.

METHODS

The experimental model of superficial cut of liver was established in 20 Sprague-Dawley adult rats, which were divided into two groups randomly. Collagen sponge or gelatin sponge was used to cover the cut respectively. Hemostatic result was observed. Afterwards, standard liver trauma model by resection left front liver lobe was made, wound was treated with collagen sponge or gelatin sponge respectively. Hemostatic result was observed. Concurrent hemostatic time and bleeding amount were noted. At 7, 14 and 20 days after operation, intra-abdominal adhension, infection and healing state of liver were observed by exploratory laparotomy. The histological changes of regenerate liver tissue were observed by microscopy.

RESULTS

Collagen sponge adhered to wound well. Concurrent hemostatic time and bleeding amount in collagen sponge group were superior to those of gelatin sponge (P < 0.05). The histological examination showed that collagen sponge was absorbed and degraded rapidly, regenerative hepatocytes could be induced.

CONCLUSION

Collagen sponge has fine hemostatic properties and can induce regeneration of hepatocytes effectively. It is worth popularizing for its convenience in clinical application and its properties of rapid degradation and absorption.

Interim assessment of a community intervention to improve breast and cervical cancer screening among Korean American women

Breast and cervical cancer screening practices are suboptimal among Korean American women. A community intervention program was launched in 1996 to improve breast and cervical cancer screening among Korean American women in Alameda County, California. After 18 months, interim program assessment revealed that mammograms improved, but Pap smears, breast self-examinations, and clinical breast examinations did not change significantly. However, results were similar for the control county probably because the program was not implemented fully. Several strategies for improving program implementation are discussed including recommendations for researchers planning community intervention projects.

[Study on adriamycin-porous tricalcium phosphate ceramic drug delivery system and its drug release test in vivo]

OBJECTIVE

To manufacture adriamycin-porous tricalcium phosphate (A-PTCP) ceramic drug delivery system (DDS) as a possible method for bone defect treatment after bone tumor operation.

METHODS

A-PTCP DDS was made from putting adriamycin into PTCP. Thirty rabbits were divided randomly into group A(24 rabbits) and group B(6 rabbits). A-PTCP was implanted in the greater trochanter of the right femur in group A. Adriamycin were injected into veins in group B. Muscle around A-PTCP and plasma were taken out at different period. Adriamycin concentrations in muscle and plasma were measured by high performance liquid chromatography (HPLC).

RESULTS

A-PTCP could gradually release adriamycin over 10 weeks. Adriamycin concentrations in the muscle were higher than that in plasma.

CONCLUSION

A-PTCP may be a new method for repairing bone defects after bone tumor operation.

Random breakage and reunion chromosome aberration formation model; an interaction-distance version based on chromatin geometry

PURPOSE

Using published FISH data for chromosome aberration production in human fibroblasts by hard X-rays to test a breakage-and-reunion model.

METHODS

The model assumed pairwise misrejoining, random apart from proximity effects, of DNA double-strand break (DSB) free ends. CAS (chromosome aberration simulator) Monte Carlo computer software implementing the model was modified to use a distance algorithm for misrejoining instead of using DSB interaction sites. The modification (called CAS2) allowed a somewhat more realistic approach to large-scale chromatin geometry, chromosome territories and proximity effects. It required adding a third adjustable parameter, the chromosome territory intersection factor, quantifying the amount of intertwining among different chromosomes.

RESULTS

CAS2 gave somewhat better results than CAS. A reasonable fit with a few discrepancies was obtained for the frequencies at three different radiation doses of many different aberration types and of aberrations involving various specific chromosomes in a large data set using one-paint FISH scoring. The optimal average chromosome territory intersection factor was approximately 1.1, indicating that, for an arbitrarily chosen location in the nucleus, on average slightly more than two chromosomes have very nearby loci. Without changing the three parameter values, a fit was also obtained for a corresponding, smaller, two-paint data set.

CONCLUSIONS

A random breakage-and-reunion model incorporating proximity effects by using a distance algorithm gave acceptable approximations for many details of hard X-ray aberration patterns. However, enough discrepancies were found that the possibility of an additional or alternate formation mechanism remains.

Porcine stem cell engraftment and seeding of murine thymus with class II+ cells in mice expressing porcine cytokines: toward tolerance induction across discordant xenogeneic barriers

BACKGROUND

Mixed hematopoietic chimerism is a reliable means of tolerance induction, but its utility has not been demonstrated in discordant xenogeneic combinations because of the difficulty in achieving lasting hematopoietic engraftment. Miniature swine are likely to be suitable organ donors for humans. To evaluate the ability of mixed chimerism to induce swine-specific tolerance in widely disparate xenogeneic recipients, this study aimed to achieve long-lasting chimerism in a pig to mouse combination.

METHODS

Immunodeficient transgenic mice were developed by crossing transgenic founders carrying porcine interleukin-3, granulocyte macrophage-colony stimulating factor, and stem cell factor genes with severe combined immunodeficient mice or non-obese diabetic/severe combined immunodeficient mice. Swine bone marrow transplantation was performed in these mice, and porcine chimerism was followed for 20 weeks.

RESULTS

Whereas swine cells became undetectable in all non-Tg littermates by 7 weeks, high levels of porcine hematopoietic chimerism, including the presence of porcine class II+ cells in the host thymus were maintained in Tg mice for >20 weeks. Colony-forming assays revealed the presence of large numbers of swine hematopoietic progenitor cells in the marrow of these mice at 20 weeks after bone marrow transplantation.

CONCLUSIONS

These transgenic mice demonstrate for the first time that spontaneous migration of marrow donor antigen-presenting cells to an intact recipient thymus can occur and that porcine stem cells can persist in this highly disparate species combination. These data therefore support the feasibility of the eventual goal of tolerance induction by mixed chimerism in discordant xenogeneic combinations.

[The effect of cefazolin loaded bone matrix gelatin on repairing large segmental bone defects and preventing infection after operation]

OBJECTIVE

To explore the possibility of repair long segmental bone defects and preventing infection with cefazolin loaded bone matrix gelatin (C-BMG).

METHODS

C-BMG was made from putting cefazolin into BMG by vacuum adsorption and freeze-drying techniques. The sustaining period of effective drug concentration in vitro and in vivo was detected by inhabition bacteria, and the drug concentration in local tissues (bone and muscle) and plasma after implantation of C-BMG was examined by high performance liquid chromatography(HPLC).

RESULTS

The effective inhibition time to staphylococcus aureus of C-BMG was 22 days in vitro, while 14 days in vivo. The drug concentration in local tissues(bone and muscle) were higher than that of plasma, and the drug concentration in local tissues was higher in early stage, later it kept stable low drug release. It suggested that C-BMG had excellent ability to repair segmental long bone defects.

CONCLUSION

C-BMG can gradually release cefazolin with effective drug concentration and has excellent ability to repair segmental long bone defects. It may be a novel method to repair segmental long bone defects and prevent infection after the operation.

Underprediction of visibly complex chromosome aberrations by a recombinational-repair ('one-hit') model

PURPOSE

Published low-LET FISH data were used to test two models of chromosome aberration production based on breakage-and-reunion or recombinational repair.

MATERIALS AND METHODS

Randomness of DNA double strand break induction and misrejoining is analyzed comprehensively and adopted as a working hypothesis. Proximity effects are approximated by using interaction sites. Model results are calculated using CAS (chromosome aberration simulator) Monte Carlo computer software with two adjustable parameters. CAS can emulate the specifics of any experimental painting protocol, allowing very detailed tests of the models.

RESULTS

To reasonable approximation, breakage-and-reunion model predictions are consistent with low-LET FISH results, including two large, elaborate, one-paint data sets. An explicitly specified version of the recombinational-repair model severely underpredicts the frequency of the visibly complex aberration patterns most commonly observed with one-paint FISH, and is inconsistent with some observed multi-paint patterns. When high-dose effects (distortion and saturation) are taken into account quantitatively, a dose-response relation for apparently simple interchanges slightly favours the breakage-and-reunion model over the recombinational-repair model, despite being approximately linear over the dose range 2-6 Gy.

CONCLUSIONS

The random breakage-and-reunion model gives comprehensive baseline predictions that are sufficiently accurate for the organization of experimental results. The data speak against complex aberrations being formed by the random recombinational repair pathway discussed here.

Development and analysis of transgenic mice expressing porcine hematopoietic cytokines: a model for achieving durable porcine hematopoietic chimerism across an extensive xenogeneic barrier

The capacity of mixed hematopoietic chimerism to induce tolerance has not been demonstrated in discordant xenogeneic species combinations because of the difficulty in achieving lasting hematopoietic engraftment. In an effort to create a model of long-lasting disparate xenogeneic hematopoietic chimerism, we have developed transgenic (Tg) mice carrying porcine cytokines. Three lines of Tg mice were generated: one carrying porcine IL-3 and GM-CSF genes only (termed IL/GM) and the remaining two lines carrying in addition, the soluble SCF gene (termed IL/GM/sS) or membrane-bound SCF gene (termed IL/GM/mS). Sera from mice with IL/GM and IL/GM/sS transgenes markedly stimulated the proliferation of swine marrow cells in vitro. However, proliferation of swine marrow cells was not induced in cultures containing IL/GM/mS sera. Consistent with these observations, ELISA assays revealed detectable levels of porcine cytokines in the sera of IL/ GM and IL/GM/sS, but not in sera of IL/GM/mS Tg mice. Marrow stromal cells prepared from all three kinds of Tg mice, but not those from non-Tg littermates, were capable of supporting the growth of porcine hematopoietic cells in vitro. Immunodeficient Tg mice were generated by crossing Tg founders with C.B-17 SCID mice for five generations. All Tg immunodeficient mice showed improved porcine hematopoietic engraftment compared with non-Tg controls. These Tg mice provide a useful model system for studying porcine hematopoietic stem cells, and for evaluating the feasibility of donor-specific tolerance induction by mixed chimerism across highly disparate xenogeneic barriers.

Role of antibody-independent complement activation in rejection of porcine bone marrow cells in mice

BACKGROUND

Although complement activation has been shown to be important in the rejection of solid organs in some xenogeneic species combinations, its role in the rejection of xenogeneic marrow engraftment is unknown.

METHODS

The effect of complement depletion with cobra venom factor on porcine bone marrow cell (BMC) engraftment was examined in 3 Gy-irradiated C.B-17 severe combined immunodeficiency mice receiving 10(8) pig BMC.

RESULTS

At 26 days after transplantation, the percentages of swine class I+, myeloid, and CD2+ cells in marrow, spleen, and peripheral blood, and the numbers of porcine myeloid progenitor cells in marrow, were increased in cobra venom factor-treated recipients compared with simultaneous control recipients. Consistent with the in vivo results, preheating serum (56 degrees C for 30 min) reduced the inhibitory effect of severe combined immunodeficiency mouse serum on the proliferation of pig BMC in vitro.

CONCLUSION

Murine complement is capable of resisting xenogeneic hematopoietic engraftment through an antibody-independent mechanism.

Clustering of radiation-produced breaks along chromosomes: modelling the effects on chromosome aberrations

PURPOSE

For high-LET radiations, and perhaps even for hard X-rays, DNA double-strand breaks (dsb) are clustered nonrandomly along chromosomes; disproportionately, many inter-dsb segments are less than a few Mbp (10(6) base pairs). The implications of such dsb clustering for chromosome aberrations are analysed.

METHODS

Chromosome segments between different dsb within one dsb cluster are assumed too small to detect in the aberration assay. Enumeration or Monte-Carlo computer simulations are used to compute the relative frequencies of many observable aberration patterns: apparently simple or visibly complex. The theoretical predictions are compared with X-ray data for human fibroblasts, involving painted chromosomes 1, 2, 4, 5, 7 or 13.

RESULTS AND CONCLUSIONS

Surprisingly, cryptic dsb multiplicity does not affect the frequency ratios predicted for aberration patterns by a random breakage-and-rejoining model. The model is generally consistent with current data on many different types of aberrations, whether or not dsb usually occur in cryptic clusters. For a Revell-type exchange model, however, the predictions do depend on clustering configurations; they gradually approach the predictions of the breakage-and-rejoining model as average cluster multiplicity increases. The model is consistent with the data, for example with the ratio of visibly complex to apparently simple aberrations, only if there is considerable dsb clustering even at low-LET, with approximately 1.5 or more reactive dsb per cluster on average.

Measurement of vertebral rotation: a comparison of two methods based on CT scans

This study compared Ho's and Aaro's method to measure vertebral axial rotation in order to find the more accurate one. Two hundred fifty-nine CT scans were taken from 11 cadaver vertebrae. The scans were performed with vertebrae in neutral position and angulated up to 20 degrees in the sagittal and frontal plane to simulate kyphosis/lordosis and side bending. Axial rotation was measured according to both methods. The mean difference between true and measured values was 3.7 +/- 6.7 (95% confidence limit) (Ho's method) and 2.3 +/- 3.7 (Aaro's method), respectively. Correlation with true axial rotation was r2 = 0.66 (Ho's method) and r2 = 0.77 (Aaro's method). We recommend using Aaro's method as the more accurate measure of axial rotation in scoliotic vertebrae.

Routine myocardial revascularization with the radial artery: a multicenter experience

BACKGROUND

Current literature documents use of the radial artery (RA) for myocardial revascularization only as an alternative conduit in cases where the saphenous veins have been previously harvested or are unsuitable for use. Large-scale routine clinical use of the RA as the conduit of choice has not been reported.

METHODS

This prospective study evaluated the harvest of the RA from 933 patients and the subsequent use of the conduit as a preferred coronary artery bypass graft second only to the left internal thoracic artery in 930 of these patients.

RESULTS

Unilateral RA harvest was performed in 786 patients and 147 patients had bilateral RA harvest. A total of 1080 RAs were harvested; 214 (19.8%) originated from the dominant forearm. There was a mean of 3.30+/-0.93 grafts per patient of which 2.43+/-0.83 were arterial grafts. The mean number of RA grafts was 1.43+/-0.53. Operative mortality was 2.3% with none due to the RA graft(s). There was no ischemia nor motor dysfunction in the operated hands. Thirty-two (3.4%) patients experienced transient thenar dysesthesia that resolved in 1 day to 6 weeks.

CONCLUSIONS

Our results demonstrate that routine total or near total arterial myocardial revascularization may be achieved safely and effectively with the use of one or both RAs in conjunction with the internal thoracic artery.

Rates and independent correlates of Pap smear testing among Korean-American women

OBJECTIVES

This study reports population estimates of Pap smear testing among Korean-American women and evaluates correlates of testing.

METHODS

Korean Americans in 2 California counties were surveyed by telephone. Frequencies were age-adjusted to the 1990 census to produce population estimates of testing. Logistic regression models were used to evaluate independent correlates of testing

RESULTS

Only 50% of the Korean-American women surveyed had a Pap test in the previous 2 years. The strongest independent correlate was having had a regular check-up in the previous 2 years (odds ratio 7.2, 95% confidence interval 4.2, 12.1).

CONCLUSIONS

Rates of Pap testing among Korean-American women are well below national objectives. Collaboration and community-sensitive research are essential to collect data and design programs to improve the health of ethnic minority communities.

Misrejoining of double-strand breaks after X irradiation: relating moderate to very high doses by a Markov model

Misrejoining of double-strand breaks (DSBs) detected with pulsed-field gel electrophoresis (PFGE) after X irradiation of human cells at very high doses (80-160 Gy) is related to dose-response relationships for chromosome aberrations at moderate doses (1-5 Gy) by the Sax-Markov binary eurejoining/misrejoining (SMBE) model. The SMBE model applies Sax's breakage-and-reunion hypothesis to a subset of DSBs active in binary misrejoining and in binary eurejoining (accidental restitution). The model is numerically consistent with both data on chromosome aberrations and the data obtained by PFGE if proximity effects (restrictions on the range of interactions of DSB free ends) are present. Proximity effects are modeled by partitioning the cell's nucleus into approximately 400 interaction sites, with two active DSB free ends capable of rejoining only if they were produced within the same site. Neglecting one-track action, the SMBE model predicts a quadratic-linear dose-response relationship for DSB misrejoining after exposure to low-LET radiation; i.e., there is a quadratic response at moderate doses which becomes linear as the dose becomes large, rather than vice versa. The linear region results because at very high doses almost all of the active DSB free ends misrejoin rather than eurejoin.

Mammography and clinical breast examination among Korean American women in two California counties

BACKGROUND

Mammography and clinical breast examination (CBE) are underutilized, especially by women from some racial/ethnic minorities. Few published studies of screening practices or correlates for these subgroups exist.

METHODS

A population-based telephone survey of 1,090 Korean Americans living in two California counties was conducted. To produce population estimates of mammography and CBE testing, we adjusted frequencies to account for different selection probabilities. Multivariable logistic regression was performed to determine independent correlates of testing.

RESULTS

Only 34% [95% confidence intervals (CI) 30%, 39%] of Korean American women age 50 and older were estimated to have had a mammogram in the past 2 years. Only 32% (95% CI 28%, 37%) had had a CBE in the past 2 years. The strongest independent correlate of testing was having a regular medical checkup [odds ratio (OR) for mammogram = 9.21, 95% CI 3.98, 21.35; OR for CBE = 11.58, 95% CI 4.71, 28.46].

CONCLUSIONS

These estimates are lower than the Healthy People 2000 objectives as well as published estimates for other populations in the United States. Planning and implementing tailored programs to improve screening are best done using a community-sensitive approach, which, because racial/ethnic subgroups are growing, will assume increasing public health importance.

"Health is strength": a research collaboration involving Korean Americans in Alameda County

INTRODUCTION

This is a preliminary report from a research collaboration between Asian Health Services (community health center); Koreans in Alameda County, California; and the University of California at Berkeley School of Public Health. This five-year Centers for Disease Control and Prevention project supports a collaborative community intervention to improve breast and cervical cancer screening behavior among Korean women.

METHODS

A Korean Community Advisory Board and Korean-American staff were recruited, and community sensitive research (CSR) and participatory action research (PAR) principles were applied: (1) building community infrastructure for sustainable action, (2) cultural appropriateness, (3) assuring responsiveness to community needs, and (4) a prevention focus that would assist health care providers. We conducted a population-based telephone survey on 676 Korean adults (272 men and 404 women).

RESULTS

The collaborative process yielded (1) a high response rate (79%), (2) baseline health information on Korean Americans, (3) broadening of the original research topic, (4) survey responses that will guide intervention design, (5) culturally competent strategies, and (6) expanded Korean-American Community capacity for local action.

CONCLUSIONS

Research collaboration between universities, community-based organizations, and ethnic communities can yield high-quality research. CSR and PAR approaches help break through cultural barriers in otherwise "hard to reach" API sub-populations. Determinants of success include sharing common goals; trust, honesty, and integrity; shared decision making; mutual respect of each partner's expertise; cultural sensitivity and cultural competence; flexibility, good communication, and mutual learning; and continuity of partners. Actively engaging members of the study population in the research process builds community capacity, thus laying the foundation for future projects that improve health status.

Computer simulation of data on chromosome aberrations produced by X rays or alpha particles and detected by fluorescence in situ hybridization

With fluorescence in situ hybridization (FISH), many different categories of chromosome aberrations can be recognized-dicentrics, translocations, rings and various complex aberrations such as insertions or three-way interchanges. Relative frequencies for the various aberration categories indicate mechanisms of radiation-induced damage and reflect radiation quality. Data obtained with FISH support a proximity version of the classic random breakage-and-reunion model for the formation of aberrations. A Monte Carlo computer implementation of the model, called the CAS (chromosome aberration simulator), is generalized here to high linear energy transfer (LET) and compared to published data for human cells irradiated with X rays or 238Pu alpha particles. For each kind of radiation, the CAS has two adjustable parameters: the number of interaction sites per cell nucleus and the number of reactive double-strand breaks (DSBs) per gray. Aberration frequencies for various painted chromosomes, of varying lengths, and for 11 different categories of simple or complex aberrations were simulated and compared to the data. The optimal number of interaction sites was found to be approximately 13 for X irradiation and approximately 25 for alpha-particle irradiation. The relative biological effectiveness (RBE) of alpha particles for the induction of reactive DSBs (which are a minority of all DSBs) was found to be approximately 4. The two-parameter CAS model adequately matches data for many different categories of aberrations. It can use data obtained with FISH for any one painting pattern to predict results for any other kind of painting pattern or whole-genome staining, and to estimate a suggested overall numerical damage indicator for chromosome aberration studies, the total misrejoining number.

Intra-arm and interarm chromosome intrachanges: tools for probing the geometry and dynamics of chromatin

Many chromosome-type, exchange-type chromosomal aberrations produced by radiation are intrachanges, i.e. involve only one chromosome. It is assumed such intrachanges are formed by illegitimate reunion of two double-strand breaks (DSBs) on the chromosome. The yield of intra-arm intrachanges (acentric rings or paracentric inversions) relative to that of interarm intrachanges (centric rings or pericentric inversions) is larger than would occur if production and illegitimate reunion of DSBs were spatially random. The excess of intra-arm intrachanges is presumably due to proximity effects for illegitimate reunions, i.e. enhancement of the intrachange probability when two DSBs are formed close to one another. Radiation track structure may also play a role. Using a polymer description for "large-scale" chromatin geometry (>2 Mb), and using two alternate (rapid or slow motion) models for the way that DSBs move after they are produced, theoretical estimates are given for size distributions of intrachanges at low or high linear energy transfer (LET). The ratio of intra-arm to interarm intrachanges is derived from the size distribution and compared with data from the literature on centric rings, inversions, interstitial deletions and excess acentric fragments. Proximity effects enhance yields of intra-arm relative to interarm intrachanges at least severalfold and perhaps as much as 10-fold compared to expectations based on spatial randomness. We argue that further measurements of intra-arm and interarm intrachanges would be informative about large-scale chromatin structure and chromosome motion. Because inversions are more frequent than estimates of randomness would indicate, and are transmissible to daughter cells, their size distribution could also help characterize past exposure to high-LET radiation.

Diversification of T cell responses to carboxy-terminal determinants within the 65-kD heat-shock protein is involved in regulation of autoimmune arthritis

The T cell response to the 65-kD mycobacterial heat-shock protein (Bhsp65) has been implicated in the pathogenesis of autoimmune arthritis. Adjuvant arthritis (AA) induced in the Lewis rat (RT-1(l)) by injection of Mycobacterium tuberculosis serves as an experimental model for human rheumatoid arthritis (RA). However, the immunological basis of regulation of acute AA, or of susceptibility/resistance to AA is not known. We have defined the specificity of the proliferative T cell responses to Bhsp65 during the course of AA in the Lewis rat. During the early phase of the disease (6-9 d after onset of AA), Lewis rats raised T cell responses to many determinants within Bhsp65, spread throughout the molecule. Importantly, in the late phase of the disease (8-10 wk after onset of AA), there was evidence for diversification of the T cell responses toward Bhsp65 carboxy-terminal determinants (BCTD) (namely, 417-431, 441-455, 465-479, 513-527, and 521-535). Moreover, arthritic rats in the late phase of AA also raised vigorous T cell responses to those carboxy-terminal determinants within self(rat) hsp65 (Rhsp65) that correspond in position to the above BCTD. These results suggest that the observed diversification is possibly triggered in vivo by induction of self(Rhsp65)-reactive T cells. Interestingly, another strain of rat, the Wistar Kyoto (WKY/NHsd) rat (RT-1(l)), with the same major histocompatibility complex class II molecules as the Lewis rat, was found to be resistant to AA. In WKY rats, vigorous responses to the BCTD, to which the Lewis rat responded only in the late phase of AA, were observed very early, 10 d after injection of M. tuberculosis, Strikingly, pretreatment with the peptides comprising the set of BCTD, but not its amino-terminal determinants, provided significant protection to naive Lewis rats from subsequent induction of AA. Thus, T cell responses to the BCTD are involved in regulating inflammatory arthritis in the Lewis rat and in conferring resistance to AA in the WKY rat. These results have important implications in understanding the pathogenesis of RA and in devising new immunotherapeutic strategies for this disease.

A rapid method for measuring pericentric inversions using fluorescence in situ hybridization (FISH)

We used three common fluorescent probes to measure pericentric inversion frequencies in 2.9 Gy 60Co gamma-irradiated human lymphocytes. For a given chromosome, the first probe is specific to one telomeric region, the second probe is specific to one subcentromeric region and the third probe is specific to the centromere. A pericentric inversion is made observable by the change in position (switching) of the fluorescent signals relative to the chromosome centromere. Our data showed equality between pericentric inversions and centric rings. The calculated whole-genome F-ratio of apparently simple translocations to pericentric inversions was 5.6.

Review: proximity effects in the production of chromosome aberrations by ionizing radiation

After ionizing radiation has induced double-strand DNA breaks (dsb), misrejoining produces chromosome aberrations. Aberration yields are influenced by "proximity' effects, i.e., by the dependence of misrejoining probabilities on initial dsb separations. We survey proximity effects, emphasizing implications for chromosome aberration-formation mechanisms, for chromatin geometry, and for dose-response relations. Evidence for proximity effects comes from observed biases for centric rings and against three-way interchanges, relative to dicentrics or translocations. Other evidence comes from the way aberration yields depend on radiation dose and quality, tightly bunched ionizations being relatively effective. We concludes (1) that misrejoining probabilities decrease as the distance between dsb at the time of their formation increases, and almost all misrejoining occurs among dsb initially separated by < 1/3 of a cell nucleus diameter; (2) that chromosomes occupy (irregular) territories during the G0/G1 phase of the cell cycle, having dimensions also roughly 1/3 of a cell nucleus diameter, (3) that proximity effects have the potential to probe how much different chromosomes intertwine on move relative to each other: and (4) that incorporation of proximity effects into the classic random breakage-and-reunion model allows quantitative interrelation of yields for many different aberration types and of data obtained with various FISH painting methods or whole-genome scoring.

Automatic target detection and recognition in multiband imagery: a unified ML detection and estimation approach

Multispectral or hyperspectral sensors can facilitate automatic target detection and recognition in clutter since natural clutter from vegetation is characterized by a grey body, and man-made objects, compared with blackbody radiators, emit radiation more strongly at some wavelengths. Various types of data fusion of the spectral-spatial features contained in multiband imagery developed for detecting and recognizing low-contrast targets in clutter appear to have a common framework. A generalized hypothesis test on the observed data is formulated by partitioning the received bands into two groups. In one group, targets exhibit substantial coloring in their signatures but behave either like grey bodies or emit negligible radiant energy in the other group. This general observation about the data generalizes the data models used previously. A unified framework for these problems, which utilizes a maximum likelihood ratio approach to detection, is presented. Within this framework, a performance evaluation and a comparison of the various types of multiband detectors are conducted by finding the gain of the SNR needed for detection as well as the gain required for separability between the target classes used for recognition. Certain multiband detectors become special cases in this framework. The incremental gains in SNR and separability obtained by using what are called target-feature bands plus clutter-reference bands are studied. Certain essential parameters are defined that effect the gains in SNR and target separability.

Proximity effects for chromosome aberrations measured by FISH

A Monte Carlo simulation computer program for radiation-produced chromosome aberrations, based on the breakage-and-reunion model, was extended to include proximity effects due to localization of chromosomes and limited range for break-break interactions. Two adjustable parameters were used. One corresponds to total dose: the other determines proximity effects by specifying the number of 'interaction regions' in a cell nucleus. The use of additional adjustable parameters was avoided by assuming randomness of break induction and aberration production. FISH chromosome painting data were obtained from 1.9 Gy 60Co gamma-rays-irradiated human lymphocytes. The data were compared with the computer simulation results, taking individual chromosome lengths into account. With about 13 interaction regions, agreement between the experiment and the simulation was good, even when detailed categories of damage were scored. An estimated average dsb-dsb interaction distance, based on 13 interaction regions, is about 1.3 micron. Monte Carlo methods give useful quantitative estimates of relative aberration yields, with a minimum of adjustable parameters and the theoretical assumptions, and indicated proximity effects. Computer simulation of FISH experiments can be adapted to any number of colours, any scoring criteria and any method of grouping aberrations into categories. Simulation allows systematic extrapolation of aberration data on painted chromosomes to whole-genome aberration frequencies.

Theoretical predictions on the equality of radiation-produced dicentrics and translocations detected by chromosome painting

Existing models of chromosome aberrations produced by ionizing-radiation predict equal numbers of dicentrics and translocations if the dose is so low that complex aberrations can be ignored. We show that, for a specific subset of aberrations detected by FISH, dicentric/translocation equality is predicted even at higher doses. Assuming one-colour whole-chromosome painting (with unpainted chromosomes counterstained and centromeres recognizable) the relevant restriction is that the final metaphase pattern be, in the terminology of Simpson and Savage, 'apparently simple'. This means that the painted pattern is required to have the colour/centromere appearance corresponding to a single complete reciprocal exchange but its actual formation, as reflected for example in lengths, is allowed to be more complicated. The restriction to apparent simplicity is significantly less limiting than ignoring all complex aberrations. Our analysis of predicted dicentric/translocation equality in this case uses examples, a combinatorial counting method, Monte Carlo computer programs, and a duality proof. However, we argue that for 'visibly complex' dicentrics or translocations, no similar equality is expected in general. Corresponding experimental results are briefly surveyed. Checking dicentric/translocation equality experimentally can provide a significant test of current chromosome aberration models.

Chromosome aberrations produced by ionizing radiation: Monte Carlo simulations and chromosome painting data

Monte Carlo simulations are used to analyze the reshuffling of chromosome segments which occurs when DNA is damaged by ionizing radiation. Programs are based on either Sax's classic breakage-and-reunion model or Revell's exchange model for chromosome aberrations. The simulations quantify the predictions of the two models in complete detail, using only one adjustable parameter which corresponds to total radiation dose. While testing subroutines, new analytic results on the chromosome/arm/break method of classifying aberrations were obtained. The model predictions were tested by using three-color fluorescence in situ hybridization (FISH) 'chromosome painting' on human lymphocyte cells irradiated with gamma-rays. Some of the per-cell aberration frequencies were observed to be intermediate between the predictions of the two models. This result indicates proximity 'effects', due to localization of chromosome interactions in space and time. Predictions based on chromosome arm lengths were found to be in good agreement with experiment. Monte Carlo simulations are a powerful, flexible way to compare models of chromosome aberration production with experiments quantitatively, using a minimum of theoretical presumptions.