On dosimetric characteristics of detectors for relative dosimetry in small fields: a multicenter experimental study

Objective. In this multicentric collaborative study, we aimed to verify whether the selected radiation detectors satisfy the requirements of TRS-483 Code of Practice for relative small field dosimetry in megavoltage photon beams used in radiotherapy, by investigating four dosimetric characteristics. Furthermore, we intended to analyze and complement the recommendations given in TRS-483.Approach. Short-term stability, dose linearity, dose-rate dependence, and leakage were determined for 17 models of detectors considered suitable for small field dosimetry. Altogether, 47 detectors were used in this study across ten institutions. Photon beams with 6 and 10 MV, with and without flattening filters, generated by Elekta Versa HDTMor Varian TrueBeamTMlinear accelerators, were used.Main results. The tolerance level of 0.1% for stability was fulfilled by 70% of the data points. For the determination of dose linearity, two methods were considered. Results from the use of a stricter method show that the guideline of 0.1% for dose linearity is not attainable for most of the detectors used in the study. Following the second approach (squared Pearson's correlation coefficientr2), it was found that 100% of the data fulfill the criteriar2> 0.999 (0.1% guideline for tolerance). Less than 50% of all data points satisfied the published tolerance of 0.1% for dose-rate dependence. Almost all data points (98.2%) satisfied the 0.1% criterion for leakage.Significance. For short-term stability (repeatability), it was found that the 0.1% guideline could not be met. Therefore, a less rigorous criterion of 0.25% is proposed. For dose linearity, our recommendation is to adopt a simple and clear methodology and to define an achievable tolerance based on the experimental data. For dose-rate dependence, a realistic criterion of 1% is proposed instead of the present 0.1%. Agreement was found with published guidelines for background signal (leakage).

Online Adaptive MRI-Guided Stereotactic Body Radiotherapy for Pancreatic and Other Intra-Abdominal Cancers

A 1.5T MRI combined with a linear accelerator (Unity®, Elekta; Stockholm, Sweden) is a device that shows promise in MRI-guided stereotactic body radiation treatment (SBRT). Previous studies utilized the manufacturer's pre-set MRI sequences (i.e., T2 Weighted (T2W)), which limited the visualization of pancreatic and intra-abdominal tumors and organs at risk (OAR). Here, a T1 Weighted (T1W) sequence was utilized to improve the visualization of tumors and OAR for online adapted-to-position (ATP) and adapted-to-shape (ATS) during MRI-guided SBRT. Twenty-six patients, 19 with pancreatic and 7 with intra-abdominal cancers, underwent CT and MRI simulations for SBRT planning before being treated with multi-fractionated MRI-guided SBRT. The boundary of tumors and OAR was more clearly seen on T1W image sets, resulting in fast and accurate contouring during online ATP/ATS planning. Plan quality in 26 patients was dependent on OAR proximity to the target tumor and achieved 96 ± 5% and 92 ± 9% in gross tumor volume D90% and planning target volume D90%. We utilized T1W imaging (about 120 s) to shorten imaging time by 67% compared to T2W imaging (about 360 s) and improve tumor visualization, minimizing target/OAR delineation uncertainty and the treatment margin for sparing OAR. The average time-consumption of MRI-guided SBRT for the first 21 patients was 55 ± 15 min for ATP and 79 ± 20 min for ATS.

A Comparison of Treatment Plan Adaptation Methods on PTV Margin Coverage in MR-Linac Prostate SBRT

PURPOSE/OBJECTIVE(S)

MRI-Linac guided radiotherapy is a novel treatment modality allowing for daily online adaptation of contours and treatment planning. MRI-Linac prostate SBRT (MRL-SBRT) has recently been shown to provide a tangible benefit in decreasing both acute and late toxicity, due to the ability to evaluate soft tissue contrast, directly monitor organ motion, and anatomical changes during the entire treatment course. Multiple MRI-Linac platforms are available, which provide different advantages with regards to imaging and motion management. We undertook this study to assess coverage of the clinical target volume with use of a standard PTV margin in patients receiving either adapt-to-position (ATP) only treatment or a combination of adapt-to-position and adapt-to-shape (ATP+ATS) on the Elekta Unity MR-Linac.

MATERIALS/METHODS

Data was collected retrospectively in patients who underwent prostate SBRT using a 1.5 T MR-Linac (Unity, Elekta AB, Stockholm, Sweden). Prior to each fraction, determination of ATP or ATS planning was at the discretion of the treating physician. Prostate and organs at risk (OAR's) were contoured on the reference MRI and daily MR image sets acquired prior to each fraction. The prostate PTV consisted of a 5mm margin, except 3mm posteriorly. Contours were merged to account for target and OAR volumes during all fractions. Target volumes from the reference plan were then compared to the clinical target volume (CTV) on pre-treatment MR-Linac imaging as well as intersection with OAR's.

RESULTS

Nineteen men, median age 72 years (range 67-75), with prostate cancer underwent treatment from May 2021 to January 2023 with MRL-SBRT. The average time for ATP vs ATP+ATS was 45 minutes (range 35-60) and 60 minutes (range 50-80), respectively. The mean CTV treated was 43.4cc (range 31-60) for ATP and 51.8cc (range 36-67) for ATP+ATS. Prior to plan adaptation, target volumes in 92.6% of fractions were not covered completely by the PTV. In the ATP cohort, 89% of fractions had a portion of the CTV uncovered with an average of 2.9cc. In the ATP+ATS cohort, 96.4% had a portion of the CTV uncovered, with an average of 6.9cc. There was no difference in the amount of PTV intersection for ATP or ATP+ATS plans with the rectum (1.1cc vs. 1.5cc) and bladder (9.2cc vs. 12.6cc), respectively. All patients completed the planned course of treatment.

CONCLUSION

Adaptive radiation therapy for prostate cancer utilizing an MR-Linac based approach with the Elekta Unity was feasible for patients requiring either ATP only or ATP+ATS plans. As expected, ATS plans required longer treatment time, allowing for improved coverage of the target when deemed clinically necessary. Despite a larger overall volume treated in ATS plans, there was no difference in overlap with OARs between ATP and ATS plans. Adaption for each daily fraction and intrafraction motion monitoring improved CT coverage with our pre-specified PTV margin.

Assessment of Daily Target Motion to Optimize ITV Margins in Online Adaptive Plan for Liver and Pancreatic SBRT on MR-LINAC

PURPOSE/OBJECTIVE(S)

Accurate measurement of daily target motion on online plan adaptation is essential for re-optimizing the internal target volume (ITV) margins. In this study, by analyzing 2D cine MR images acquired in a 1.5T MR-Linac, we assessed daily target motion and its inter-fractional variations, which is then used to customize ITV margins for MR-based online adaptive plan of liver and pancreatic stereotactic body radiotherapy (SBRT).

MATERIALS/METHODS

Twenty-threepatients, enrolled in this study, underwent MR-guided online adaptive SBRT on 1.5 T MR-Linac: liver (n = 12 without compression belt (CB), n = 2 with CB) and pancreas (n = 9 with CB). Target motion in a 2D coronal and sagittal MR images (> 200 cine images to cover multiple breathing cycles), as well as a set of 4D-CT images during the simulation, was analyzed to determine patient specific ITV margins for a reference plan. On every fraction of online adaptive SBRT, the 2D MR images were exported to commercially available software along with a planning MR images: a T1-wighted MR image set for pancreas and or a navigated T2-wighted MR image set for liver. Daily target motion was then measured by overlaying the orthogonal cine image set on the T1- or T2-wighted image set. The ITV margin was adjusted when required prior to online plan optimization RESULTS: Thisstudy successfully assessed the daily target motion and inter-fractional variations in 23 liver or pancreatic cancer patients. We found a discrepancy of daily target motion of orthogonal 2D cine MR images from that of 4D-CT, required to adjust the ITV margin for online plan adaptation. In liver SBRT without CB, 15 out of 45 fractions from 12 patients (33.3 %) went through adjusted ITV margin. The tumor motion was large up to a 2.2 cm along the inferior direction in a patient without CB and thus the patient was treated on a conventional Linac with the active breathing control (ABC) unit for breath-hold. On the other hand, no adjustments were necessary for 2 liver patients with CB. In 9 patients with pancreatic cancers, we found the inter-fractional ITV variations in 3 out of 45 fractions (6.7 %) adjusted the ITV margin. The daily target motion in the pancreatic patients with CB was more stable and relatively smaller than that of the liver patients.

CONCLUSION

Theorthogonal 2D cine MR images are evidently essential for assessing daily target motion to evaluate the inter-fractional variation and achieve daily ITV-customized liver and pancreatic SBRT in the 1.5 T MR-Linac. The customized ITV approach will improve the treatment outcome of the MR-guided online adaptive therapy.

Application of TG-100 risk analysis methods to the acceptance testing and commissioning process of a Halcyon linear accelerator

PURPOSE

A new type of linear accelerator (linac) was recently introduced into the market by a major manufacturer. Our institution is one of the early users of this preassembled and preconfigured dual-layer multileaf collimator (MLC), ring-gantry linac - Halcyon™ (1st version). We performed a set of full acceptance testing and commissioning (ATC) measurements for three Halcyon machines and compared the measured data with the standard beam model provided by the manufacturer. The ATC measurements were performed following the guidelines given in different AAPM protocols as well as guidelines provided by the manufacturer. The purpose of the present work was to perform a risk assessment of the ATC process for this new type of linac and investigate whether the results obtained from this analysis could potentially be used as a guideline for improving the design features of this type of linac.

METHODS

AAPM's TG100 risk assessment methodology was applied to the ATC process. The acceptance testing process relied heavily on the use of a manufacturer-supplied phantom and the automated analysis of electronic portal imaging device (EPID) images. For the commissioning process, a conventional measurement setup and process (e.g., use of water tank for scanning) was largely used. ATC was performed using guidelines recommended in various AAPM protocols (e.g., TG-106, TG-51) as well as guidelines provided by the manufacturer. Six medical physicists were involved in this study. Process maps, process steps, and failure modes (FMs) were generated for the ATC procedures. Failure modes and effects analysis (FMEA) were performed following the guidelines given in AAPM TG-100 protocol. The top 5 and top 10 highest-ranked FMs were identified for the acceptance and commissioning procedures, respectively. Quality control measures were suggested to mitigate these FMs.

RESULTS

A total of 38 steps and 88 FMs were identified for the entire ATC process. Fourteen steps and 34 FMs arose from acceptance testing. The top 5 FMs that were identified could potentially be mitigated by the manufacturer. For commissioning, a total of 24 steps and 54 potential FMs were identified. The use of separate measurement tools that are not machine-integrated has been identified as a cause for the higher number of steps and FMs generated from the conventional ATC approach. More than half of the quality control measures recommended for both acceptance and commissioning could potentially be incorporated by the manufacturer in the design of the Halcyon machine.

CONCLUSION

This paper presents the results of FMEA and quality control measures to mitigate the FMs for the ATC process for Halcyon machine. Unique FMs that result from the differences in the ATC guidelines provided by the vendor and current conventional protocols, and the challenges of performing the ATC due to the new linac features and ring-gantry design were highlighted for the first time. The FMs identified in the present work along with the suggested quality control measures, could potentially be used to improve the design features of future ring-gantry type of linacs that are likely to be preassembled, preconfigured, and heavily reliant on automation and image guidance.

A dosimetric evaluation of the IAEA-AAPM TRS483 code of practice for dosimetry of small static fields used in conventional linac beams and comparison with IAEA TRS-398, AAPM TG51, and TG51 Addendum protocols

PURPOSE

The International Atomic Energy Agency (IAEA) and the American Association of Physicists in Medicine (AAPM) have jointly published a new code of practice (CoP), TRS483, for the dosimetry of small static photon fields used in external beam radiotherapy. It gave recommendations on how to perform reference dosimetry in nonstandard machine-specific reference (msr) fields and measure field output factors in small fields. The purpose of this work was to perform a dosimetric evaluation of the recommendations given in this CoP.

METHODS

All measurements were done in a Varian TrueBeam™ STx linear accelerator. Five ionization chambers were used for beam quality measurements, four Farmer type ionization chambers for performing reference dosimetry and two diodes for performing field output factor measurements. Field output factor measurements were done for fourteen field sizes (ranging from 0.5 cm × 0.5 cm to 10 cm × 10 cm). Beam energies used were: 6 MV WFF, 6 MV FFF, 10 MV WFF, and 10 MV FFF. Where appropriate, results from this study were compared with those obtained from the recommendations given in the IAEA TRS398 CoP, AAPM TG51 and TG51 Addendum protocols.

RESULTS

Beam quality measurements show that for all beam energies and for equivalent square msr field sizes ranging from 4 cm × 4 cm to 10 cm × 10 cm, agreement between calculated and measured values of TPR20,10 (10) was within 0.6%. When %dd(10,10)X was used as beam quality specifier, the agreement was found to be within 0.8%. Absorbed dose to water per unit monitor unit at the depth of maximum dose zmax in a beam of quality Q, Dw,Qzmax/MU, was determined using both %dd(10,10)X and TPR20,10 (10) as beam quality specifiers. Measured ratios of Dw,Q (zmax )/MU, determined using the two approaches, ranged between 0.999 and 1.000 for all the beam energies investigated. Comparison with TRS398, TG51 and TG51 addendum protocols show that depending on beam energy, the mean values of the ratios TRS398/TRS483, TG51/TRS483, and TG51 Addendum/TRS483 of Dw,Q (zmax )/MU determined using both approaches show excellent agreement with TRS398 CoP (to within 0.05%); agreement with TG51 and TG51 addendum was to within 0.3% for all four beam energies investigated. Field output factors, determined using the two methods recommended in the TRS483 CoP, showed excellent agreement between the two methods. For the 1 cm collimator field size, the mean value of the field output factor obtained from an average of the two detectors investigated was found to be 2% lower than the mean value of the uncorrected ratio of readings.

CONCLUSION

For beams with and without flattening filters, the values of Dw,Q (zmax )/MU obtained following the new CoP are found to be consistent with those obtained using TRS398, TG51 and TG51 addendum protocols to within 0.3%. Field output factors for small beams can be improved when the correction factors for different detectors included in TRS483 are appropriately incorporated into their dosimetry.

Estimated long-term dietary exposure to lead, cadmium, and mercury in young Korean children

BACKGROUND

Controlling for day-to-day variation is a key issue in estimating long-term dietary exposure to heavy metals using 24-hour recall (24HR) data from a relatively small number of days.

OBJECTIVES

This study was conducted to estimate long-term dietary exposure to lead, cadmium and mercury among Korean children using the Iowa State University (ISU) method and to assess the contributions of different food groups to heavy metal intake.

METHODS

We analyzed 2 days of 24HR data from 457 children between 0 and 6 years of age in 2010. Using bootstrapped concentration data for 118 representative foods, 93.5% of total intake was included in the exposure estimates in this study. Using the 2-day exposure data, we estimated long-term exposure by controlling for within-individual variation using the ISU method.

RESULTS

The long-term dietary exposure estimates (mean±standard deviation) for lead, cadmium, and mercury were 0.47±0.14, 0.38±0.20, and 0.22±0.08 μg/kg bw/day, respectively. For lead and cadmium, the percentages of children whose exposure was greater than the reference value were 35 and 42%, respectively. Fruits were an important source of lead exposure, and cereal and fish and shellfish made the greatest contributions to the total cadmium and mercury exposure.

CONCLUSIONS

Our findings also suggest that the long-term exposure to lead and cadmium was somewhat greater than the reference values, whereas mercury exposure was well below than the reference value in this population. Further studies may be necessary to evaluate the food items contributing to heavy metal exposure, and continuous monitoring is needed to ensure the safety of food intake and dietary patterns among vulnerable groups in Korea.

A NOVEL INTRINSIC UNSCENTED KALMAN FILTER FOR TRACTOGRAPHY FROM HARDI*

The unscented Kalman filter (UKF) was recently introduced in literature for simultaneous multi-tensor estimation and tractography. This UKF however was not intrinsic to the space of diffusion tensors. Lack of this key property leads to inaccuracies in the multi-tensor estimation as well as in tractography. In this paper, we propose an novel intrinsic unscented Kalman filter (IUKF) in the space of symmetric positive definite matrices, which can be used for simultaneous recursive estimation of multi-tensors and tractography from diffusion weighted MR data. In addition to being more accurate, IUKF retains all the advantages of UKF for instance, multi-tensor estimation is only performed in the places where it is needed for tractography, which would be much more efficient than the two stage process involved in methods that do tracking post diffusion tensor estimation. The accuracy and effectiveness of the proposed method is demonstrated via real data experiments.

Electromechanical and structural alterations in the aging rabbit heart and aorta

Aging increases the risk for arrhythmias and sudden cardiac death (SCD). We aimed at elucidating aging-related electrical, functional, and structural changes in the heart and vasculature that account for this heightened arrhythmogenic risk. Young (5-9 mo) and old (3.5-6 yr) female New Zealand White (NZW) rabbits were subjected to in vivo hemodynamic, electrophysiological, and echocardiographic studies as well as ex vivo optical mapping, high-field magnetic resonance imaging (MRI), and histochemical experiments. Aging increased aortic stiffness (baseline pulse wave velocity: young, 3.54 ± 0.36 vs. old, 4.35 ± 0.28 m/s, P < 0.002) and diastolic (end diastolic pressure-volume relations: 3.28 ± 0.5 vs. 4.95 ± 1.5 mmHg/ml, P < 0.05) and systolic (end systolic pressure-volume relations: 20.56 ± 4.2 vs. 33.14 ± 8.4 mmHg/ml, P < 0.01) myocardial elastances in old rabbits. Electrophysiological and optical mapping studies revealed age-related slowing of ventricular and His-Purkinje conduction (His-to-ventricle interval: 23 ± 2.5 vs. 31.9 ± 2.9 ms, P < 0.0001), altered conduction anisotropy, and a greater inducibility of ventricular fibrillation (VF, 3/12 vs. 7/9, P < 0.05) in old rabbits. Histochemical studies confirmed an aging-related increased fibrosis in the ventricles. MRI showed a deterioration of the free-running Purkinje fiber network in ventricular and septal walls in old hearts as well as aging-related alterations of the myofibrillar orientation and myocardial sheet structure that may account for this slowed conduction velocity. Aging leads to parallel stiffening of the aorta and the heart, including an increase in systolic stiffness and contractility and diastolic stiffness. Increasingly, anisotropic conduction velocity due to fibrosis and altered myofibrillar orientation and myocardial sheet structure may contribute to the pathogenesis of VF in old hearts. The aging rabbit model represents a useful tool for elucidating age-related changes that predispose the aging heart to arrhythmias and SCD.

ATLAS CONSTRUCTION FROM HIGH ANGULAR RESOLUTION DIFFUSION IMAGING DATA REPRESENTED BY GAUSSIAN MIXTURE FIELDS

Groupwise image registration is an essential part of atlas construction which is a very import and challenging task in medical image analysis. In this paper, we present a novel atlas construction technique using a groupwise registration of high angular resolution diffusion (MR) imaging datasets each of which is represented by a Gaussian Mixture field. To solve the registration problem, an L(2) distance is used to measure the similarity between two Gaussian Mixtures, which leads to an energy function whose gradient can be computed in closed form. A projection method is developed to construct a "sharp" (not blurred) atlas from the result of this groupwise registration. Synthetic and real data experiments are presented to demonstrate the efficacy of the proposed method.

Iatrogenic cardiovocal syndrome caused by transcatheter coil closure of patent ductus arteriosus

Two infants developed hoarseness unexpectedly the day after transcatheter coil closure of a slender patent ductus arteriosus (PDA). The pathogenesis of this complication appears to be similar to that of the classic cardiovocal syndrome. During the intervention, the inappropriately implanted coil might have distorted the slender PDA, thereby causing angulation of the pliable PDA itself and precipitating impingement on the left recurrent laryngeal nerve. Fortunately, both infants recovered spontaneously from the hoarseness within several weeks. At present, the definite underlying neuropathology of this complication is unknown as we have not yet confirmed recovery of the left vocal cord movement by follow-up fibreoptic bronchoscopy.

CONCLUSION

Iatrogenic cardiovocal syndrome could occur in infants after transcatheter coil closure of a slender PDA, using the currently popular 0.038-inch coil. A coil with a smaller diameter might prevent the occurrence of this syndrome.

The structural and functional organization of the yeast mediator complex

The Mediator complex of Saccharomyces cerevisiae is required for diverse aspects of transcription by RNA polymerase II (pol II). Mediator is composed of two functionally distinct subcomplexes, Rgr1 and Srb4. To identify the structures and functions of each subcomplex, we expressed recombinant proteins for each subunit and assayed their interactions with each other and with basal transcription proteins. The Rgr1 subcomplex is composed of the Gal11 module, which binds activators, and the Med9/10 module. The Med9/10 module is required for both transcriptional activation and repression, and these activities appear to be carried out by two submodules. Proteins in the Med9 submodule interact physically and genetically with Srb10/11, suggesting that the Med9 submodule mediates the repression of pol II. Purified recombinant Srb4 subcomplex stimulated basal transcription of pol II but had little effect on activated transcription and phosphorylation of the C-terminal domain of the Rpb1 subunit of pol II. Both subcomplexes of Mediator interacted with a distinct set of basal transcription factors and pol II. The modular organization of Mediator and the associated functions suggest that the Mediator complex may recruit and/or stabilize the preinitiation complex through several points of contact with transcriptional regulators and basal transcription factors.

Effect of head rotation on lateral cephalometric radiographs

The purpose of this study was to identify the potential projection errors of lateral cephalometric radiographs due to head rotation in the vertical Z-axis. For this investigation, 17 human dry skull samples with permanent dentition were collected from the Department of Anatomy in the College of Medicine, Chosun University. They had no gross asymmetry and were well preserved. Each dry skull was rotated from 0 degrees to +/- 15 degrees at 1 degrees intervals. A vertical axis, the Z-axis, was used as a rotational axis to have 527 lateral cephalometric radiographs exposed. The findings were that: (1) angular measurements have fewer projection errors than linear measurements; (2) the greater the number of landmarks on the midsagittal plane that are included in angular measurements, the fewer the projection errors occurring; (3) horizontal linear measurements decrease gradually in length as the rotational angle toward the film increases, whereas a small increase and then decrease of the length occurs as the rotational angle toward the focal spot increases; (4) horizontal linear measurements have more projection errors than vertical linear measurements according to head rotation; and (5) projection errors of vertical linear measurements increase as the distance from the rotational axis increases. In summary, angular measurements of lateral cephalometric radiographs are more useful than linear measurements in minimizing the projection errors associated with head rotation on a vertical axis.

Inhibition of c-erbB-2 expression an activity in human ovarian carcinoma cells by hypericin

The c-erbB-2 oncogene encodes a tyrosine kinase that constitutes the internal and transmembrane part of the epidermal growth factor receptor (EGFR). ErbB-2 overexpression has been reported in 20% to 30% of human adenocarcinomas of the breast and ovary, and has been linked to an unfavorable prognosis in patients. Hypericin is a protein tyrosine kinase inhibitor that has been exploited in models for anti-tumor and anti-viral activity. In this study, we investigated the effects of hypericin on the activity of the c-erbB-2 oncoprotein and its downstream kinases. We also investigated the effect of hypericin on metastasis. We used ovarian SK-OV-3 cells as a model to determine whether hypericin-induced cell death was associated with inhibition of c-erbB-2 expression and activation. The IC50 of hypericin after 72 hrs exposure was 7.5 microM as determined by the MTT assay. Apoptosis, which was assessed by morphological changes and a flow cytometric assay, was observed at 24 h after continuous exposure to 5 microM hypericin. Inhibition of expression of the c-erbB-2 protein was detected, using a monoclonal anti-erbB-2 antibody after 12-48 hrs of exposure to hypericin. Hypericin was found to inhibit autophosphorylation of the erbB-2 protein and downstream kinases such as MEK and ERK1/2. We also found up-regulation of p21WAF1 expression and down-regulation of Bcl-2 in hypericin treated cells. An invasion assay showed that hypericin inhibited the movement of SK-OV-3 cells into the Matrigel. However, gelatin zymography showed that hypericin had no effect on the secretion of matrix metalloproteinases (MMPs) in SK-OV-3 cells. From these results, we conclude that hypericin inhibits the growth of SK-OV-3 ovarian cancer cells, inhibits the autophosphorylation of c-erbB-2, induces apoptosis, and may inhibit invasion.

In vivo requirement of activator-specific binding targets of mediator

There has been no unequivocal demonstration that the activator binding targets identified in vitro play a key role in transcriptional activation in vivo. To examine whether activator-Mediator interactions are required for gene transcription under physiological conditions, we performed functional analyses with Mediator components that interact specifically with natural yeast activators. Different activators interact with Mediator via distinct binding targets. Deletion of a distinct activator binding region of Mediator completely compromised gene activation in vivo by some, but not all, transcriptional activators. These demonstrate that the activator-specific targets in Mediator are essential for transcriptional activation in living cells, but their requirement was affected by the nature of the activator-DNA interaction and the existence of a postrecruitment activation process.

Clinical features and risk factors of pulmonary oedema after enterovirus-71-related hand, foot, and mouth disease

BACKGROUND

In Taiwan, from April to July, 1998, an epidemic of hand, foot, and mouth disease associated with enterovirus 71 (EV71) occurred with fatal complications. We did a clinical study of EV71-related diseases in Taiwan.

METHODS

We studied 154 children with virus-culture confirmed EV71 infection. Children were divided into three groups: 11 patients with pulmonary oedema; 38 patients with central nervous system (CNS) involvement and no pulmonary oedema; and 105 children without complications. We compared the clinical features, laboratory findings, risk factors, and outcome among these three groups.

FINDINGS

Nine children with pulmonary oedema had hand, foot, and mouth disease, one had herpangina, and one had febrile illness with eight children with limb weakness and one with limb hypesthesia. All children had had sudden onset of tachycardia, tachypnoea, and cyanosis 1-3 days after onset of the disease. Nine of 11 children died within 12 h of intubation; one child was braindead within 15 h and died 17 days after intubation; one child was in deep coma and died 3 months later. In children with CNS complication and no pulmonary oedema, one child died of pneumonia after 4 months of ventilator support and four children had sequelae. All 105 children without complications recovered. There was a significant association between CNS involvement and pulmonary oedema (odds ratio 12.4 [95% CI 2.6-60.1], p=0.001). Risk factors for pulmonary oedema after CNS involvement were hyperglycaemia, leucocytosis, and limb weakness. Hyperglycaemia was the most significant prognostic factor for pulmonary oedema (odds ratio 21.5 [3-159], p=0.003).

INTERPRETATION

EV71 can cause hand, foot, and mouth disease, CNS involvement with severe sequelae, and fatal pulmonary oedema. Hyperglycaemia is the most important prognostic factor.

Guillain-Barré syndrome: MR imaging findings of the spine in eight patients

PURPOSE

To evaluate magnetic resonance (MR) imaging findings of the spine in patients with Guillain-Barré syndrome.

MATERIALS AND METHODS

MR imaging findings in eight patients (three male, five female; age range, 2-47 years) with Guillain-Barré syndrome were retrospectively reviewed. Guillain-Barré syndrome was diagnosed mainly on the basis of symptoms and also on the basis of supportive ancillary data, such as the results cerebrospinal fluid analysis and electrophysiologic evaluation. In addition, follow-up MR imaging was performed in three patients, who had slight clinical improvement.

RESULTS

All patients had thickening of the intrathecal spinal nerve roots and cauda equina, with varying degrees of enhancement on gadolinium-enhanced axial T1-weighted images. Two enhancement patterns were noted. One was enhancement of both the anterior and posterior spinal nerve roots (n = 2); the other was enhancement of the anterior spinal nerve roots only (n = 6). Follow-up MR imaging in the three patients with slight improvement of symptoms revealed that the thickening and the degree of enhancement of the spinal nerve roots were diminished.

CONCLUSION

Although the enhancement of the intrathecal spinal nerve roots is not specific to Guillain-Barré syndrome and can be seen in neoplasia and other inflammatory processes, the enhancement of only the anterior spinal nerve roots is strongly suggestive of Guillain-Barré syndrome.

A virtual image cryptosystem based upon vector quantization

We propose a new image cryptosystem to protect image data. It encrypts the original image into another virtual image. Since both original and virtual images are significant, our new cryptosystem can confuse illegal users. Besides the camouflage, this new cryptosystem has three other benefits. First, our cryptosystem is secure even if the illegal users know that our virtual image is a camouflage. Second, this cryptosystem can compress image data. Finally, our method is more efficient than a method that encrypts the entire image directly.

Selective inhibition of the effects of phorbol ester on doxorubicin resistance and P-glycoprotein by the protein kinase C inhibitor 1-(5-isoquinolinesulfonyl)-2-methylpiperazine (H7) in multidrug-resistant MCF-7/Dox human breast carcinoma cells

The possible regulation of the multidrug-resistant (MDR) phenotype and P-glycoprotein by protein kinase C (PKC) was investigated in the doxorubicin (Dox)-resistant MCF-7 cell line (MCF-7/Dox). In a clonogenic assay, cells exposed to 100 nM phorbol 12-myristate 13-acetate (PMA) for 1 hr were about 3-fold more resistant to Dox than were cells exposed to Dox alone. The PKC inhibitor 1-(5-isoquinolinesulfonyl)-2-methylpiperazine (H7, 30 microM) completely blocked the PMA-induced effect, but did not reverse the MDR phenotype. Complete down-regulation of PKC from MCF-7/Dox cells by 24-hr preincubation with PMA did not alter the degree of Dox resistance. Intracellular accumulation of [14C]Dox decreased from a baseline of 28 pmol/10(6) cells to 15 pmol/10(6) cells in the presence of 100 nM PMA. The reduced Dox accumulation in the presence of PMA was not blocked by pretreatment of cells with H7. Following a 24-hr pretreatment with PMA, the cells accumulated almost equal amounts of [14C]Dox in the absence or presence of PMA. Cells from PMA-treated colonies showed significantly higher levels of expression of P-glycoprotein when compared with those from control colonies. H7 did not affect the basal level of P-glycoprotein in cells from control colonies or PMA-induced overexpression of P-glycoprotein in cells from PMA-treated colonies. Upon stimulation with PMA (100 nM), PKC alpha and beta translocated to the cell membrane and nucleus and PKC delta and epsilon to the perinuclear membrane and the nucleus, respectively. H7 (30 microM) completely inhibited PMA-induced translocations of PKC delta and epsilon, whereas it only partially blocked the translocations of PKC alpha and beta. These results suggest that PMA appears to alter Dox resistance and intracellular Dox accumulation in a PKC-dependent manner and to induce increased expression of P-glycoprotein in MCF-7/Dox cells. Differential effects of H7 on the PMA-induced changes suggest that different isoforms of PKC may be involved in cell growth and drug accumulation processes as well as P-glycoprotein expression.

Non-hyperventilation respiratory therapy of persistent pulmonary hypertension of the newborn

Persistent pulmonary hypertension of the newborn (PPHN) is one of the most challenging situations in the neonatal intensive care nursery and it is associated with a high mortality rate. Hyperventilation therapy has been recommended as the primary ventilator management during recent decades. The associations of pulmonary barotrauma, chronic lung disease and hearing impairment raised the questions of significant pulmonary and neurological complications with this therapeutic modality. From July 1990 to April 1993, 14 cases of neonatal persistent pulmonary hypertension were treated with nonhyperventilation respiratory therapy at the Chang Gung Memorial Hospital. The goals of this therapy were to attain a pH level between 7.40 and 7.50, a PaO2 level between 60 and 90 mmHg and a PaCO2 level between 30 and 50 mmHg. High peak inflating pressure (> 35 cmH2O) and high ventilator rates (> 60/min) were avoided. The average duration on a ventilator was 6.8 +/- 2.9 days. Four patients had pulmonary barotrauma (29%); three of which were pulmonary interstitial emphysema and one pneumothorax. Three patients died (21%). Only one patient had neurological sequelae. No one had developed chronic lung disease. The non-hyperventilation approach for PPHN may be considered as an alternative ventilator management before starting a more aggressive hyperventilation therapy.

Neonatal meningococcal meningitis: report of two cases

Two neonates with meningococcal meningitis and meningococcemia are reported. The two, aged 28 and 16 days, respectively, presented similar symptoms of fever, poor appetite and poor activity. Both blood and cerebrospinal fluid cultures of each patient grew Neisseria meningitidis. The isolated bacteria were sensitive to penicillin, and both patients recovered completely after penicillin treatment for 22 and 15 days, respectively. In the antibiotic era, only 22 cases of neonatal meningococcal meningitis have been reported in the English literature. Among these reports, at least 7 patients survived without sequelae; 6 of those were treated with different combinations of antibiotics, including penicillin, for variable durations of 7-14 days. Therefore, effective antibiotic therapy for 14 days should be adequate in the treatment of uncomplicated neonatal meningococcal meningitis and meningococcemia.

[Pulmonary nocardiosis with cerebral abscess successfully treated by medication alone--a case report]

Nocardiosis is an illness caused by members of the genus Nocardia. Although it is usually an opportunistic infection in immunocompromised hosts, it can also occur in patients without a definable predisposing condition. Three species are recognized as being responsible for what most frequently seen. The primary site of infection is overwhelmingly the lungs. Brain abscess is by far the most common site for nocardial metastasis from pulmonary lesion. Although surgical intervention must always be considered in the treatment of nocardial brain abscess, it can clearly be cured by medical therapy alone. We report this case and also review the literature.

[Acute pneumonitis caused by inhalation of mercury vapor--report of a case]

Two characteristics, volatility and biotransformation, make mercury somewhat unique as environmental toxicant, and make mercury poisoning as one of occupational diseases in the industry. Acute mercury vapor poisoning is a rare event. It often occurs during industrial accident or ignorant experiment. We report a case, a 28-year-old male waterworks technician, who developed dyspnea, cough, chest pain, metallic taste and ache in the whole body three hours after heating approximately 30 ml of liquid mercury during an experiment. Diarrhea with tarry stool occurred the next day. Chest roentgenogram revealed diffuse pulmonary infiltrates similar to pulmonary edema in both lungs, and was complicated by pneumomediastinum and subcutaneous emphysema later. The concentration of mercury in the plasma was over the toxic level. The urinary excretion of mercury greatly exceeded normal value. During hospitalization, the patient's liver and renal function tests were both normal. He was treated with penicillamine, 300 mg every six hours orally for 10 days in addition to a support treatment and oxygen therapy. He was discharged on the 15th hospital day with partial resolution of pulmonary infiltrates and was free of symptom.