Developing a novel quasi-3D movable water phantom for radiation therapy workable in the magnetic resonance environment

Background

The use of magnetic resonance linear accelerators (MR-LINACs) for clinical treatment has opened up new possibilities and challenges in the field of radiation oncology. However, annual quality assurance (QA) is relatively understudied due to practical considerations. Thus, to overcome the difficulty of measuring the dose with a small water phantom for TRS-398 or TG-51 in all external beam radiation treatment unit environments, such as MR compatibility, we designed a remote phantom with a three-axis changeable capacity for QA.

Methods

The designed water phantom was tested under an MR environment. The water phantom system comprised of three parts: a phantom box, a dose measurement tool, and a PMD401 drive system. The UNIDOSE universal dosimeter was used to collect beam data. The manufacturer's developer tools were utilized to position the measurement. To ensure magnetic field homogeneity, a distortion phantom was prepared using sixty fish oil capsules aligned radially to distinguish the oil and free air. The phantom was scanned in both the MR simulator and computed tomography (CT), and the acquired images were analyzed to determine the position shift.

Results

The dimensions of the device are 30 cm in the X-axis, 20 cm in the Y-axis, and 17 cm in the Z-axis. Total cost of materials was no more than $10,000 US dollars. Our results indicate that the device can function normally in a regular 1.5 T MR environment without interference from the magnetic field. The water phantom's traveling speed was found to be approximately 5 mm/s with a position difference confined within 6 cm intervals during normal use. The distortion test results showed that the prepared MR environment has uniform magnetic field homogeneity.

Conclusions

In this study, we constructed a prototype water phantom device that can function in an MR simulator without interference between the magnetic field and electronic components. Compared to other commercially available MR-LINAC water phantoms, our device offers a more cost-effective solution for routine monthly QA. It can shorten the duration of QA tests and relieve the burden on medical physicists.

[The value of immunohistochemical expression of Ki-67 and CD34 in differentiating ductal carcinoma in situ from ductal carcinoma in situ-like invasive breast cancer]

Objective: To investigate the expression of Ki-67 and CD34 in the differential diagnosis of ductal carcinoma in situ (DCIS) and DCIS-like invasive breast cancer (DLIBC). Methods: A total of 100 cases of DCIS and 150 cases of DLIBC diagnosed pathologically in Yantai Yuhuangding Hospital from January 2019 to March 2022 were collected. The expression of p63, CK5/6, Ki-67 and CD34 in both groups were detected by immunohistochemical (IHC) staining and evaluated. Results: The 100 cases of DCIS included 11 cases of low-grade DCIS, 28 cases of intermediate-grade DCIS and 61 cases of high-grade DCIS. IHC staining of p63 and CK5/6 showed the myoepithelial cells around cancerous duct were complete or partial absence. Ki-67 expression showed two patterns: high expression in the basal layers and scattered expression within the tumor. Most cases showed mainly high basal expression (77/100, 77%), and the proportion of this pattern was significantly different between low grade and high grade DCIS (P<0.05). All cases showed complete CD34 expression surrounding the cancerous duct with different proportion (vascular necklace) suggested small vessels proliferation. The 150 cases of DLIBC included 142 cases of invasive ductal carcinoma (IDC) (three cases of basal-like breast cancer was included), two cases of secretory carcinoma, three cases of solid papillary carcinoma, two cases of adenoid cystic carcinoma and one case of acinar cell carcinoma. Among 142 cases of IDC, 13 cases were grade Ⅰ, 77 were grade Ⅱ and 52 were grade Ⅲ. IHC staining of p63 showed complete absence of myoepithelium. CK5/6 was negative in most cases and only positively expressed within the tumor in 3 cases of basal-like breast cancer. Ki-67 indicated a scattered expression pattern within the tumor. In most cases, CD34 immunostaining showed scattered positive blood vessels within the tumor while only two cases showed incomplete expression of CD34 around the tumor (2/150, 1.3%). The different expression patterns of Ki-67 and CD34 in DCIS and DLIBC was statistically significant (P<0.05). Conclusions: The different expression patterns of Ki-67 and CD34 are helpful to distinguish DLIBC from DCIS. The appearance of "vascular necklace" with CD34 and the high expression of Ki-67 around the cancerous duct highly support the diagnosis of DCIS, and the scattered expression pattern of CD34 supports DLIBC.

Low cost multifunctional 3D printed image quality and dose verification phantom for an image-guided radiotherapy system

Purpose

Image-guided radiation therapy (IGRT) is used to precisely deliver radiation to a tumour to reduce the possible damage to the surrounding normal tissues. Clinics use various quality assurance (QA) equipment to ensure that the performance of the IGRT system meets the international standards set for the system. The objective of this study was to develop a low-cost and multipurpose module for evaluating image quality and dose.

Methods

A multipurpose phantom was designed to meet the clinical requirements of high accuracy, easy setup, and calibration. The outer shell of the phantom was fabricated using acrylic. Three dimensional (3D) printing technology was used to fabricate inner slabs with the characteristics of high spatial resolution, low-contrast detectability, a 3D grid, and liquid-filled uniformity. All materials were compatible with magnetic resonance (MR). Computed tomography (CT) simulator and linear accelerator (LINAC) modules were developed and validated.

Results

The uniformity slab filled with water is ideal for the assessment of Hounsfield units, whereas that filled with wax is suitable for consistency checks. The high-spatial-resolution slab enables measurements with a resolution up to 5 lp/cm. The low-contrast detectability slab contains rods of 5 different sizes that can be clearly visualised. These components meet the American College of Radiology (ACR) standards for QA of CT simulators and LINACs.

Conclusions

The multifunctional phantom module meets the ACR recommended QA guidelines and is suitable for both LINACs and CT-sim. Further measurements in an MR simulator and an MR linear accelerator (MR-LINAC) will be arranged in the future.

Design of a motion simulation system to assist respiratory gating for radiation therapy

Stereotactic ablative radiotherapy (SABR) aims to deliver high doses of radiation to kill cancer cells and shrink tumors in less than or equal to 6 fractions. However, organ motion during treatment is a challenging issue for this kind of technique. We develop a control system via Bluetooth technology to simulate and correct body motion during SABR.

METHODS

Radiation doses were analyzed, and the radiation damage protection capability was checked by external beam therapy 3 (EBT3) films irradiated by a linear accelerator. A wireless signal test was also performed. A validation was performed with 8 previously treated patient respiratory pattern records and 8 healthy volunteers.

RESULTS

The homemade simulation system consisted of 2 linear actuators, one movable stage with a maximal moving distance of 6.5 cm × 12.5 cm × 5 cm to simulate the respiratory pattern of 8 patients precisely with a median error of 0.36 mm and a maximal motion difference of 1.17 mm, and 3.17 and chipset transited signals to display them as a waveform. From the test with 8 volunteers, the chip could detect deep respiratory movement up to 3 cm. The effect of the chip on a radiation dose of 400 monitor units (MUs) by 6 MV photons and 200 MUs by 10 MV photons showed high penetration rates of 98.8% and 98.6%, respectively.

CONCLUSIONS

We invented a tubeless and wireless respiratory gating detection chip. The chip has minimal interference with the treatment angles, good noise immunity and the capability to easily penetrate a variety of materials. The simulation system consisting of linear actuators also successfully simulates the respiratory pattern of real patients.

Impact of breath-hold level on positional error aligned by stent/Lipiodol in Hepatobiliary radiotherapy with breath-hold respiratory control

Background

Respiratory motion management with breath hold for patients with hepatobiliary cancers remain a challenge in the precise positioning for radiotherapy. We compared different image-guided alignment markers for estimating positional errors, and investigated the factors associated with positional errors under breath-hold control.

Methods

Spirometric motion management system (SDX) for breath holds was used in 44 patients with hepatobiliary tumor. Among them, 28 patients had a stent or embolized materials (lipiodol) as alignment markers. Cone-beam computed tomography (CBCT) and kV-orthogonal images were compared for accuracy between different alignment references. Breath-hold level (BHL) was practiced, and BHL variation (ΔBHL) was defined as the standard deviation in differences between actual BHLs and baseline BHL. Mean BHL, ΔBHL, and body-related factors were analyzed for the association with positional errors.

Results

Using the reference CBCT, the correlations of positional errors were significantly higher in those with stent/lipiodol than when the vertebral bone was used for alignment in three dimensions. Patients with mean BHL > 1.4 L were significantly taller (167.6 cm vs. 161.6 cm, p = 0.03) and heavier (67.1 kg vs. 57.4 kg, p = 0.02), and had different positional error in the craniocaudal direction (− 0.26 cm [caudally] vs. + 0.09 cm [cranially], p = 0.01) than those with mean BHL < 1.4 L. Positional errors were similar for patients with ΔBHL< 0.03 L and > 0.03 L.

Conclusion

Under rigorous breath-hold respiratory control, BHL correlated with body weight and height. With more accurate alignment reference by stent/lipiodol, actual BHL but not breath-hold variation was associated with craniocaudal positional errors.

Loss of heterozygosity on the short arm of chromosome 17 in human astrocytomas

Using restriction fragment length polymorphism (RFLP) analysis, we demonstrated in 4 of 20 patients with astrocytomas loss of heterozygosity on the short arm of chromosome 17 (17p), in the telomeric segment distal to DNA marker pEW301 (locus D17S58). The loss of heterozygosity may uncover a mutation in a tumour suppressor gene and thus lead to or permit tumour formation. The p53 tumour suppressor gene, which is localized at 17p13, is a likely candidate for the tumour suppressor gene involved. Of the 4 patients with loss of heterozygosity on 17p, one patient had a grade I astrocytoma, another patient had a grade II astrocytoma and 2 patients had glioblastoma multiforme. Since the loss of heterozygosity on 17p was detected in low-grade as well as in high-grade astrocytomas, it is possible that p53 suppressor gene loss may be an early genetic event in the multistep process of astrocytoma formation.

Lumbosacral spine and marrow cavity modeling of acute hematologic toxicity in patients treated with intensity modulated radiation therapy for squamous cell carcinoma of the anal canal

PURPOSE

To identify various dosimetric parameters of bone marrow cavity that correlate with acute hematologic toxicity (HT) in patients with anal squamous cell carcinoma treated with definitive chemoradiation therapy (CRT).

METHODS AND MATERIALS

We analyzed 32 patients receiving CRT. The whole pelvic bone marrow (PBM) and the lumbosacral spine (LSS) subregion were contoured for each patient. Marrow cavities were contoured using the Hounsfield units (HUs) of 100, 150, 200, and 250 as maximum density threshold levels. The volume of each region receiving at least 5, 10, 15, 20, 30, and 40 Gy was calculated. The endpoint was grade ≥3 HT (HT3+). Normal-tissue complication probability (NTCP) was evaluated with the Lyman-Kutcher-Burman (LKB) model. Maximal likelihood estimate was used to compare the parameter set. Logistic regression was used to test associations between HT and both dosimetric and clinical parameters.

RESULTS

Ten patients (31%) experienced HT3+. While dose to both LSS and PBM significantly predicted for HT3+, LSS was superior to PBM by logistic regression and LKB modeling. Constrained optimization of the LKB model for HT3+ yielded the parameters m = 0.21, n = 1, and TD50 = 32 Gy for LSS. The NTCP fits were better with the whole bone than with marrow cavity using any HU threshold. Mean LSS doses of 21 Gy and 23.5 Gy result in a 5% and 10% risk of HT3+, respectively. Mean dose and low-dose radiation parameters (V5, V10, V15, V20) of whole bone or bone cavities of LSS were correlated most significantly with HT3+.

CONCLUSIONS

For predicting the risk of HT3+, whole-bone contours were superior to marrow cavity and LSS was superior to PBM by LKB modeling. The results confirm PBM and LSS as parallel organs when predicting hematologic toxicity. Recommended dose constraints to the LSS are V10 ≤80%. An LSS mean dose of 23.5 Gy is associated with a 10% risk of HT.

Early detection of Lewis lung carcinoma tumor control by irradiation using diffusion-weighted and dynamic contrast-enhanced MRI

PURPOSE

To investigate the correlation between diffusion-weighted (DW) and dynamic contrast-enhanced (DCE) magnetic resonance imaging (MRI) derived parameters and radioresponsiveness of Lewis lung carcinoma (LLC) tumor.

MATERIALS AND METHODS

LLC tumor growth in C57BL/6 mouse limb was used for the experiment. The tumors were irradiated with 10 Gy×5, or 30 Gy×2 vs. sham irradiation. Fourteen tumors were subjected to DW-MRI and DCE-MRI pre-radiotherapy and weekly imaging after radiotherapy. The temporal changes in apparent diffusion coefficient (ADC) and DCE-MRI derived parameters (K(trans), k(ep), v(e), and v(p)) were correlated with tumor size, and were histologically compared with CD31 staining of resected tumors.

RESULTS

The 10 Gy×5 dose inhibited tumor growth for a week, while 30 Gy×2 controlled tumor growth for a 3-week observation period. One week after radiotherapy (week 2), irradiated tumors showed significantly higher values of ADC than untreated ones (10 Gy×5, p = 0.004; 30 Gy×2, p = 0.01). Significantly higher values of v(e) were shown earlier by 30 Gy×2 vs. sham (p = 0.01) and 10 Gy×5 vs. sham irradiation (p = 0.05). Sustained higher v(e) from 10 Gy×5 compared to sham irradiated tumors was evident at week 3 (p = 0.016) and week 4 (p = 0.046). A 13.8% early increase in ADC for 30 Gy×2 tumor group (p = 0.002) and a 16.5% increase for 10 Gy×5 group were noted (p = 0.01) vs. sham irradiation (which showed a 2.2% decrease). No differences were found for K(trans), k(ep), or v(p). Both radiotherapy groups demonstrated significant reduction in microvessel counts.

CONCLUSION

Early increase in ADC and v(e) correlated with tumor control by irradiation.

Practically acquired and modified cone-beam computed tomography images for accurate dose calculation in head and neck cancer

BACKGROUND

On-line cone-beam computed tomography (CBCT) may be used to reconstruct the dose for geometric changes of patients and tumors during radiotherapy course. This study is to establish a practical method to modify the CBCT for accurate dose calculation in head and neck cancer.

PATIENTS AND METHODS

Fan-beam CT (FBCT) and Elekta's CBCT were used to acquire images. The CT numbers for different materials on CBCT were mathematically modified to match them with FBCT. Three phantoms were scanned by FBCT and CBCT for image uniformity, spatial resolution, and CT numbers, and to compare the dose distribution from orthogonal beams. A Rando phantom was scanned and planned with intensity-modulated radiation therapy (IMRT). Finally, two nasopharyngeal cancer patients treated with IMRT had their CBCT image sets calculated for dose comparison.

RESULTS

With 360° acquisition of CBCT and high-resolution reconstruction, the uniformity of CT number distribution was improved and the otherwise large variations for background and high-density materials were reduced significantly. The dose difference between FBCT and CBCT was < 2% in phantoms. In the Rando phantom and the patients, the dose-volume histograms were similar. The corresponding isodose curves covering ≥ 90% of prescribed dose on FBCT and CBCT were close to each other (within 2 mm). Most dosimetric differences were from the setup errors related to the interval changes in body shape and tumor response.

CONCLUSION

The specific CBCT acquisition, reconstruction, and CT number modification can generate accurate dose calculation for the potential use in adaptive radiotherapy.

Set-up errors due to endorectal balloon positioning in intensity modulated radiation therapy for prostate cancer

PURPOSE

To investigate the set-up errors and deformation associated with daily placement of endorectal balloons in prostate radiotherapy.

MATERIALS AND METHODS

Endorectal balloons were placed daily in 20 prostate cancer patients undergoing radiotherapy. Electronic portal images (EPIs) were collected weekly from anterior-posterior (AP) and lateral views. The EPIs were compared with digitally reconstructed radiographs from computed tomography scans obtained during pretreatment period to estimate displacements. The interfraction deformation of balloon was estimated with variations in diameter in three orthogonal directions throughout the treatment course.

RESULTS

A total of 154 EPIs were evaluated. The mean displacements of balloon relative to bony landmark were 1.8mm in superior-inferior (SI), 1.3mm in AP, and 0.1mm in left-right (LR) directions. The systematic errors in SI, AP, and LR directions were 3.3mm, 4.9 mm, and 4.0mm, respectively. The random (interfraction) displacements, relative to either bony landmarks or treatment isocenter, were larger in SI direction (4.5mm and 4.5mm), than in AP (3.9 mm and 4.4mm) and LR directions (3.0mm and 3.0mm). The random errors of treatment isocenter to bony landmark were 2.3mm, 3.2mm, and 2.6mm in SI, AP, and LR directions, respectively. Over the treatment course, balloon deformations of 2.8mm, 2.5mm, and 2.6mm occurred in SI, AP, and LR directions, respectively. The coefficient of variance of deformation was 7.9%, 4.9%, and 4.9% in these directions.

CONCLUSIONS

Larger interfractional displacement and the most prominent interfractional deformation of endorectal balloon were both in SI direction.

Effect of ocular artifact removal in brain computer interface accuracy

We report the effect of removing ocular artifacts on the performance of a word-processing application based on the event related potential P300. Various methods of removing artifacts have been reported. The efficiency of these algorithms are usually done by subjective visual comparisons. Noting that there is a direct correlation of artifact rectifying algorithms to the accuracy in a brain computer interface system's accuracy, we present this work as a means to compare different algorithms.

Torticollis as a sign of cervico-thoracic epidural haematoma in an infant with severe haemophilia A

We describe the case of a spinal epidural haematoma in an infant with severe haemophilia A. Initial signs and symptoms were non-specific resulting in delay of the diagnosis and more definitive therapy. The patient eventually developed torticollis, acute flaccid paralysis of the upper extremities, and respiratory distress, prompting radiological examination of the spinal cord. The patient was treated with recombinant FactorVIII and laminectomy. Neurological recovery was complete 3 months following the event. We hypothesize that infants with haemophilia may be at higher risk for this rare complication because of their increasing mobility, frequent falls while cruising furniture, and lack of prophylactic factor replacement. Non-specific signs such as irritability without a focus should alert the clinician to this diagnostic possibility. Torticollis should prompt rapid radiological evaluation of the cervical spine with magnetic resonance imaging to avoid delay in diagnosis.

Clotting factor concentrates given to prevent bleeding and bleeding-related complications in people with hemophilia A or B

BACKGROUND

People with severe hemophilia A or B, X-linked bleeding disorders due to decreased blood levels of coagulants, suffer recurrent bleeding into joints and soft tissues. Before clotting factor concentrates were available, most people with severe hemophilia developed crippling musculoskeletal deformities. Clotting factor concentrate prophylaxis aims to preserve joint function by converting severe hemophilia (factor VIII or IX less than 1%) into a clinically milder form of the disease. Prophylaxis has long been used in Sweden, but not universally adopted because of medical, psychosocial, and cost controversies. Use of clotting factor concentrates is the single largest predictor of cost in treating hemophilia.

OBJECTIVES

To determine the effectiveness of clotting factor concentrate prophylaxis in the management of people with hemophilia A or B.

SEARCH STRATEGY

We searched the Cystic Fibrosis and Genetic Disorders Group's Trials Register comprising references from comprehensive electronic database searches and handsearches of journals and abstract books. Reference lists of relevant articles were reviewed. Most recent search: November 2005.

SELECTION CRITERIA

Randomized controlled trials (RCTs) evaluating people with severe hemophilia A or B, receiving prophylactic clotting factor concentrates.

DATA COLLECTION AND ANALYSIS

Two authors independently reviewed studies for eligibility, assessed methodological quality and extracted data.

MAIN RESULTS

Twenty-nine studies were identified; four studies (including 37 participants) were eligible for inclusion. Three studies evaluated hemophilia A; one showed a decrease in frequency of joint bleeds with prophylaxis compared to placebo (non-physiological dose), with a rate difference (RD) -10.80 (95% confidence interval (CI) -16.33 to -5.27) bleeds per year. The remaining two studies evaluating hemophilia A compared two prophylaxis regimens, one study showed no difference in joint bleed frequency, RD -5.04 (95%CI -17.02 to 6.94) bleeds per year and another failed to demonstrate an advantage of factor VIII dosing based on individual pharmacokinetic data over the standard prophylaxis regimen with RD -0.14 (95% CI -1.34 to 1.05) bleeds per year. The fourth study evaluated hemophilia B and showed fewer joint bleeds with weekly (15 IU/kg) versus bi-weekly (7.5 IU/kg) prophylaxis, RD -3.30 (95% CI -5.50 to - 1.10) bleeds per year.

AUTHORS' CONCLUSIONS

There is insufficient evidence from randomised controlled trials to determine whether prophylactic clotting factor concentrates decrease bleeding and bleeding-related complications in hemophilia A or B, compared to placebo, on-demand treatment, or prophylaxis based on pharmacokinetic data from individuals. Well-designed RCTs are needed to assess the effectiveness of prophylactic clotting factor concentrates. Two clinical trials are ongoing.

Inclusion of biological factors in parallel-architecture normal-tissue complication probability model for radiation-induced liver disease

PURPOSE

To include biologic factors in parallel-architecture normal-tissue complication probability (NTCP) model for radiation-induced liver disease (RILD) after three-dimensional conformal radiotherapy (3D-CRT) for gastric or hepatic cancer.

METHODS AND MATERIALS

A total of 151 patients (89 with hepatocellular carcinoma and 62 with gastric cancer) who received 3D-CRT to the liver were included (isocenter dose range 33.0 to 66.0 Gy; mean 48.0 Gy). RILD was defined as grade 3 or higher liver toxicity according to Common Toxicity Criteria Version 2.0 of the National Cancer Institute within 4 months after 3D-CRT. Possible correlations of patient-related or dosimetric factors with RILD were tested. Maximum-likelihood analysis estimated NTCP model parameters for group and subgroups. Goodness-of-fit analysis estimated deviance of NTCP model parameters between subgroups.

RESULTS

RILD developed in 25 patients. Hepatitis B virus carrier status (p < 0.001) was the only significant independent factor. The 4 parallel NTCP model parameters, mean functional reserve (V(50)), width of functional reserve distribution (sigma), dose damage to 50% of liver subunits (D(50)), and slope parameter for subunit dose-response (k), were respectively, 0.54, 0.14, 50 Gy, 0.18 (group); 0.53, 0.07, 50 Gy, 4.6 x 10(-7) (carriers); 0.59, 0.12, 25 Gy, 59.8 (noncarriers). In carrier-state subgroups, goodness-of-fit deviance with 1 subgroup's parameter set would have been worse in the other group. Across subgroups, patients with RILD all had liver fraction damage (f) greater than 0.4 compared with wider distribution for the whole group.

CONCLUSIONS

RILD is described with a parallel-architecture NTCP model for HBV carriers and noncarriers with a threshold effect greater than 0.4. The main difference is in slope parameter for subunit dose-response.

Clotting factor concentrates given to prevent bleeding and bleeding-related complications in people with hemophilia A or B

BACKGROUND

People with severe hemophilia A or B, X-linked bleeding disorders due to decreased blood levels of coagulants, suffer recurrent bleeding into joints and soft tissues. Before clotting factor concentrates were available, most people with severe hemophilia developed crippling musculoskeletal deformities. Clotting factor concentrate prophylaxis aims to preserve joint function by converting severe hemophilia (factor VIII or IX less than 1%) into a clinically milder form of the disease. Prophylaxis has long been used in Sweden, but not universally adopted because of medical, psychosocial, and cost controversies. Use of clotting factor concentrates is the single largest predictor of cost in treating hemophilia.

OBJECTIVES

To determine the effectiveness of clotting factor concentrate prophylaxis in the management of people with hemophilia A or B.

SEARCH STRATEGY

We searched the Cystic Fibrosis and Genetic Disorders Group's Trials Register comprising references from comprehensive electronic database searches and handsearches of journals and abstract books. Reference lists of relevant articles were reviewed. Most recent search: January 2002.

SELECTION CRITERIA

Randomized controlled trials (RCTs) evaluating people with severe hemophilia A or B, receiving prophylactic clotting factor concentrates.

DATA COLLECTION AND ANALYSIS

Two reviewers independently reviewed studies for eligibility, assessed methodological quality and extracted data.

MAIN RESULTS

Twenty-nine studies were identified, of which four (including 37 participants) were eligible for inclusion. Three studies evaluated hemophilia A; one showed a decrease in frequency of joint bleeds with prophylaxis compared to placebo (non-physiological dose), with a rate difference (RD) -10.80 (95% confidence interval (CI) -16.33 to -5.27) bleeds per year. The remaining two studies evaluating hemophilia A compared two prophylaxis regimens, one study showed no difference in joint bleed frequency, RD -5.04 (95%CI -17.02 to 6.94) bleeds per year and another failed to demonstrate an advantage of factor VIII dosing based on individual pharmacokinetic data over the standard prophylaxis regimen with RD -0.14 (95% CI -1.34 to 1.05) bleeds per year. The fourth study evaluated hemophilia B and showed fewer joint bleeds with weekly (15 IU/kg) versus bi-weekly (7.5 IU/kg) prophylaxis, RD -3.30 (95% CI -5.50 to - 1.10) bleeds per year.

AUTHORS' CONCLUSIONS

There is insufficient evidence to determine whether prophylactic clotting factor concentrates decrease bleeding and bleeding-related complications in hemophilia A or B, compared to placebo, on-demand treatment, or prophylaxis based on pharmacokinetic data from individuals. Well-designed RCTs are needed to assess the effectiveness of prophylactic clotting factor concentrates. Two clinical trials are ongoing.

Biologic susceptibility of hepatocellular carcinoma patients treated with radiotherapy to radiation-induced liver disease

PURPOSE

To identify the factors associated with radiation-induced liver disease (RILD) and to describe the difference in normal tissue complication probability (NTCP) between subgroups of hepatocellular carcinoma patients undergoing three-dimensional conformal radiotherapy (3D-CRT).

METHODS AND MATERIALS

A total of 89 hepatocellular carcinoma patients who completed 3D-CRT for local hepatic tumors were included. The average isocenter dose was 49.9 +/- 6.2 Gy. Logistic regression analysis was used for the association between statistically significant factors and RILD (defined as Grade 3 or 4 hepatic toxicity of elevated transaminases or alkaline phosphatase within 4 months of completing 3D-CRT) in multivariate analysis. Maximal likelihood analysis was conducted to obtain the best estimates of the NTCP model parameters.

RESULTS

Of the 89 patients, 17 developed RILD. In univariate analysis, hepatitis B virus (HBV)-positive status and the mean radiation dose to the liver were the two factors significantly associated with the development of RILD. Of the 65 patients who were HBV carriers, 16 had RILD compared with 1 of 24 non-carrier patients (p = 0.03). The mean radiation dose to liver was significantly greater in patients with RILD (22.9 vs. 19.0 Gy, p = 0.05). On multivariate analysis, HBV carrier status (odds ratio, 9.26; p = 0.04) and Child-Pugh B cirrhosis of the liver (odds ratio, 3.65; p = 0.04) remained statistically significant. The best estimates of the NTCP parameters were n = 0.35, m = 0.39, and TD(50)(1) = 49.4 Gy. The n, m, TD(50)(1) specifically estimated from the HBV carriers was 0.26, 0.40, and 50.0 Gy, respectively, compared with 0.86, 0.31, and 46.1 Gy, respectively, for non-carrier patients.

CONCLUSION

Hepatocellular carcinoma patients who were HBV carriers or had Child-Pugh B cirrhosis presented with a statistically significantly greater susceptibility to RILD after 3D-CRT.

Unique role of proximal rectal dose in late rectal complications for patients with cervical cancer undergoing high-dose-rate intracavitary brachytherapy

PURPOSE

To investigate the correlation of the radiation dose to the upper rectum, proximal to the International Commission of Radiation Units and Measurements (ICRU) rectal point, with late rectal complications in patients treated with external beam radiotherapy (EBRT) and high-dose-rate (HDR) intracavitary brachytherapy (ICRT) for carcinoma of the uterine cervix.

METHODS AND MATERIALS

Between June 1997 and February 2001, 75 patients with cervical carcinoma completed definitive or preoperative RT and were retrospectively reviewed. Of the 75 patients, 62 with complete dosimetric data and a minimal follow-up of at least 1 year were included in this analysis. Of the 62 patients, 36 (58%) also received concurrent chemotherapy, mainly with cisplatin during EBRT. EBRT consisted of a mean of 50.1 +/- 1.3 Gy of 18-MV photons to the pelvis. A parametrial boost was given to 55 patients. Central shielding was used after 40-45 Gy of pelvic RT. HDR ICRT followed EBRT, with a median dose of 5 Gy/fraction given twice weekly for a median of four fractions. The mean dose to point A from HDR ICRT was 23.9 +/- 3.0 Gy. In addition to the placement of a rectal tube with a lead wire during ICRT, 30-40 mL of contrast medium was instilled into the rectum to demonstrate the anterior rectal wall up to the rectosigmoid junction. Late rectal complications were recorded according to the Radiation Therapy Oncology Group grading system. The maximal rectal dose taken along the rectum from the anal verge to the rectosigmoid junction and the ICRU rectal dose were calculated. Statistical tests were used for the correlation of Grade 2 or greater rectal complications with patient-related variables and dosimetric factors. Correlations among the point A dose, ICRU rectal dose, and maximal proximal rectal dose were analyzed.

RESULTS

Fourteen patients (23%) developed Grade 2 or greater rectal complications. Patient-related factors, definitive or preoperative RT, and the use of concurrent chemotherapy were not associated with the occurrence of rectal complications. The maximal rectal dose during ICRT was at the proximal rectum rather than at the ICRU rectal point in 55 (89%) of 62 patients. Patients with Grade 2 or greater rectal complications had received a significantly greater total maximal proximal rectal dose from ICRT (25.6 Gy vs. 19.2 Gy, p = 0.019) and had a greater maximal proximal rectal dose/point A dose ratio (1.025 vs. 0.813, p = 0.024). In contrast, patients with and without rectal complications had a similar dose at point A (25.0 Gy vs.23.6 Gy, p = 0.107). The differences in the ICRU rectal dose (17.8 Gy vs.15.4 Gy, p = 0.065) and the ICRU rectal dose/point A dose ratio (0.71 vs. 0.66, p = 0.210) did not reach statistical significance. Patients with >62 Gy of a direct dose sum from EBRT and ICRT to the proximal rectum (12 of 29 vs. 2 of 33, p = 0.001) and >110 Gy of a total maximal proximal rectal biologic effective dose (13 of 40 vs. 1 of 22, p = 0.012) presented with a significantly increased frequency of Grade 2 or greater rectal complications. The correlations between the maximal proximal rectal dose and the ICRU rectal dose were less satisfactory (Pearson coefficient 0.375). Moreover, 11 of the 14 patients with rectal complications had colonoscopic findings of radiation colitis at the proximal rectum, the area with the maximal rectal dose.

CONCLUSION

Eighty-nine percent of our patients had a maximal rectal dose from ICRT at the proximal rectum instead of the ICRU rectal point. The difference between patients with and without late rectal complications was more prominent for the proximal rectal dose than for the ICRU rectal dose. It is important and useful to contrast the whole rectal wall up to the rectosigmoid junction and to calculate the dose at the proximal rectum for patients undergoing HDR ICRT.

Radiation-induced liver disease after three-dimensional conformal radiotherapy for patients with hepatocellular carcinoma: dosimetric analysis and implication

PURPOSE

To analyze the correlation of radiation-induced liver disease (RILD) with patient-related and treatment-related dose-volume factors and to describe the probability of RILD by a normal tissue complication probability (NTCP) model for patients with hepatocellular carcinoma (HCC) treated with three-dimensional conformal radiotherapy (3D-CRT).

METHODS AND MATERIALS

Between November 1993 and December 1999, 93 patients with intrahepatic malignancies were treated with 3D-CRT at our institution. Sixty-eight patients who were diagnosed with HCC and had complete 3D dose-volume data were included in this study. Of the 68 patients, 50 had chronic viral hepatitis before treatment, either type B or type C. According to the Child-Pugh classification for liver cirrhosis, 53 patients were in class A and 15 in class B. Fifty-two patients underwent transcatheter arterial chemoembolization with an interval of at least 1 month between transcatheter arterial chemoembolization and 3D-CRT to allow adequate recovery of hepatic function. The mean dose of radiation to the isocenter was 50.2 +/- 5.9 Gy, in daily fractions of 1.8-2Gy. No patient received whole liver irradiation. RILD was defined as Grade 3 or 4 hepatic toxicity according to the Common Toxicity Criteria of the National Cancer Institute. All patients were evaluated for RILD within 4 months of RT completion. Three-dimensional treatment planning with dose-volume histogram analysis of the normal liver was used to compare the dosimetric difference between patients with and without RILD. Maximal likelihood analysis was conducted to obtain the best estimates of parameters of the Lyman NTCP model. Confidence intervals of the fitted parameters were estimated by the profile likelihood method.

RESULTS

Twelve of the 68 patients developed RILD after 3D-CRT. None of the patient-related variables were significantly associated with RILD. No difference was found in tumor volume (780 cm(3) vs. 737 cm(3), p = 0.86), normal liver volume (1210 cm(3) vs. 1153 cm(3), p = 0.64), percentage of normal liver volume with radiation dose >30 Gy (V(30 Gy); 42% vs. 33%, p = 0.05), and percentage of normal liver volume with >50% of the isocenter dose (V(50%); 45% vs. 36%, p = 0.06) between patients with and without RILD. The mean hepatic dose was significantly higher in patients with RILD (2504 cGy vs. 1965 cGy, p = 0.02). The probability of RILD in patients could be expressed as follows: probability = 1/[1 + exp(-(0.12 x mean dose - 4.29))], with coefficients significantly different from 0. The best estimates of the parameters in the Lyman NTCP model were the volume effect parameter of 0.40, curve steepness parameter of 0.26, and 50% tolerance dose for uniform irradiation of whole liver [TD(50)(1)] of 43 Gy. Patients with RILD had a significantly higher NTCP than did those with no RILD (26.2% vs. 15.8%; p = 0.006), using the best-estimated parameters.

CONCLUSION

Dose-volume histogram analysis can be effectively used to quantify the tolerance of the liver to RT. Patients with RILD had received a significantly higher mean dose to the liver and a significantly higher NTCP. The fitted volume effect parameter of the Lyman NTCP model was close to that from the literature, but much lower in our patients with HCC and prevalent chronic viral hepatitis than that reported in other series with patients with normal liver function. Additional efforts should be made to test other models to describe the radiation tolerance of the liver for Asian patients with HCC and preexisting compromised hepatic reserve.

Removal of arsenic from groundwater using point-of-use reverse osmosis and distilling devices

Ground water in both the northeastern and southwestern coast areas of Taiwan may contain high concentrations of arsenic. Since no central water supply system is available in some of those areas, point-of-use (POU) water purification devices are considered as an option for providing safe drinking water. In this study, removal of arsenic, using two types of POU purification devices, reverse osmosis (RO) systems and distillers, was investigated. Three commercially available RO systems and two distillers were selected to test their removal efficiency of arsenic from synthetic and real ground water. Experimental results of the three RO systems using synthetic ground water showed that only one system had good removal efficiency for arsenic. In subsequent experiments using real ground water with 0.7 mg l(-1) arsenic, only one RO system was able to meet the drinking water standard after producing about 1,000 l of treated water. For the distilling systems, 99% of the arsenic was removed from both synthetic and real groundwater. The arsenic concentrations in the finished water of both distillers were all below the standard for drinking water. Although systems with higher arsenic removal efficiency seemed to have better removal of total dissolved solids (TDS), no correlation could be found after analysis.

Characteristics of patients at a Taipei summer rock concert festival

BACKGROUND

Rock concerts are popular mass gatherings in Taiwan. Millions of fans participate in rock concerts in Taiwan each year. However, there were no reports on the characteristics of the patients seen in rock concerts in Taiwan.

METHODS

Medical care for a summer rock concert festival held in an outdoor stadium in Taipei was coordinated by emergency physicians of a medical center. About 50,000 attendees participated in the two-night concert. Three stations were set up to provide advanced medical care. A standardized form was used to collect information about patients.

RESULTS

A total of 28 cases visited the medical stations, fourteen cases each day. They were aged from 13 to 40 years, with an average of 20.8 +/- 6.4. Twenty-one cases were female and seven were male. Twenty-two (79%) were spectators, five (18%) were on-duty staff, and one was a by-stander. Based on an estimation of totally 50,000 participants in the stadium for this two-night festival, the medical use rate was roughly 5.6 PPTT (patients per ten thousand attendees). The most common major problem was fainting which accounted for 13 cases (46%). Of these 13 cases, three cases (23%) lost consciousness and 12 cases (92%) were female. Sixteen cases (57%) were classified as requiring ALS (advanced life support) and 12 cases (43%) as requiring BLS (basic life support). Most cases improved and were discharged after onsite treatment. Only one case was transferred by ambulance due to persistent chest pain. However, she recovered several hours later.

CONCLUSIONS

By this preliminary data, first reported in Taiwan, we found that the most common problem was fainting. More than half of the cases seen at the concert required advanced life support. A well-designed emergency medical service (EMS) system is mandatory to provide services for these events.

Lipid-associated sialoprotein in the cerebrospinal fluid: association with brain malignancies

BACKGROUND

Changes in the glycosylation process by tumor cells result in larger amounts of sialoproteins on their surface compared with normal cells. Sialoproteins then are released into the surrounding environment primarily by shedding or cell lysis. In the current study, the authors attempted to evaluate whether lipid-associated sialoprotein (LSP) in the cerebrospinal fluid (CSF) can distinguish patients with primary and metastatic brain tumors from those without brain tumors as well as determine response to treatment.

METHODS

CSF samples were obtained from a tissue bank. The concentration of LSP was determined after chloroform:methanol extraction followed by protein precipitation. One-way analysis of variance and Scheffe pairwise comparisons were used for statistical analysis.

RESULTS

The CSF of neurologically normal controls, patients with a normal leukocyte count (< or = 5/microl), and patients with various neurologic disorders or systemic tumors without central nervous system (CNS) malignancies contained similar levels of LSP. The CSF from patients with a normal leukocyte count and newly diagnosed primary or metastatic brain tumors contained on average 3.7-fold higher levels of LSP compared with CSF from patients without CNS tumors (P = 0.0001). The CSF from patients with brain tumors with progressive disease not responding to treatment contained high levels of LSP comparable to the levels found in newly diagnosed patients. The CSF from treatment-responsive patients contained decreased levels of LSP similar to that found in control patients.

CONCLUSIONS

The LSP in CSF may be a useful marker with which to determine the presence of intracranial malignancies and assess response to treatment.

Adsorption of arsenite and arsenate within activated alumina grains: equilibrium and kinetics

Equilibrium and kinetic adsorption of tri-valent (arsenite) and penta-valent (arsenate) arsenic to activated alumina is elucidated. The properties of activated alumina, including porosity, specific surface area, and skeleton density were first measured. A batch reactor with temperature control was employed to determine both adsorption capacity and adsorption kinetics for arsenite and arsenate to activated-alumina grains. The Freundlich and Langmuir isotherm equations were then used to describe the partitioning behavior for the system at different pH. A pore diffusion model, coupled with the observed Freundlich or Langmuir isotherm equations, was used to interpret an observed experimental adsorption kinetic curve for arsenite at one specific condition. The model was found to fit with the experimental data fairly well, and pore diffusion coefficients can be extracted. The model, incorporated with the interpreted pore diffusion coefficient, was then employed to predict the experimental data for arsenite and arsenate at various conditions, including different initial arsenic concentrations, grain sizes of activated alumina, and system pHs. The model predictions were found to describe the experimental data fairly well, even though the tested conditions substantially differed from one another. The agreement among the models and experimental data indicated that the adsorption and diffusion of arsenate and arsenite can be simulated by the proposed model.

Gap junctions: the "kiss of death" and the "kiss of life"

Cells expressing herpes simplex-thymidine kinase (HSV-tk) can be killed "in vitro" within 5 days of treatment with 20 microM ganciclovir (GCV) and transmit this toxicity to adjacent cells lacking HSV-tk; this phenomenon was termed "bystander effect" or "kiss of death". On testing a large number of cell lines in vitro, a wide range of sensitivity to GCV-mediated bystander killing has been reported. Although intercellular transfer of GCV metabolites through gap junction channels seems to be a likely mechanism for the "kiss of death", some studies suggest that other pathways may contribute to induced apoptosis of neighboring cells. To further investigate the mechanism underlying cell death mediated by HSV-tk and to evaluate the efficacy of gap junction channels formed by different connexins in this process, we have stably transfected a virtually uncoupled mouse neuroblastoma cell line (N2A cells) with different connexin-types expressed by neural cells (Cx32, Cx37, Cx40, Cx43) and co-cultured these cells with N2A cells stably transfected with Cx37 and HSV-tk. Here, we confirm our previous studies and those of others that the extent of cell death and sensitivity to GCV depend on the degree of connexin expression in transfectants. Further, we show that the bystander effect also depends on which connexin is expressed; reported disparities regarding the extent of GCV-mediated cellular apoptosis are likely due both to the degree of functional coupling and the type of connexin expressed. These results support the notion that gap junction hemichannels formed of certain connexins are more likely than others to pair functionally with Cx37, and suggest co-transfection strategies that might prove effective in sensitizing tumor cell populations to GCV. In addition, potential applications are discussed for use of the "good Samaritan effect", a mechanism by which bystander cells have been suggested to prevent cytotoxicity.

Inhibition of IMP-1 metallo-beta-lactamase and sensitization of IMP-1-producing bacteria by thioester derivatives

IMP-1 metallo-beta-lactamase is a transferable carbapenem-hydrolyzing enzyme found in some clinical isolates of Pseudomonas aeruginosa, Serratia marcescens and Klebsiella pneumoniae. Bacteria that express IMP-1 show significantly reduced sensitivity to carbapenems and other beta-lactam antibiotics. A series of thioester derivatives has been shown to competitively inhibit purified IMP-1. As substrates for IMP-1, the thioesters yielded thiol hydrolysis products which themselves were reversible competitive inhibitors. The thioesters also increased sensitivity to the carbapenem L-742,728 in an IMP-1-producing laboratory stain of Escherichia coli, but will need further modification to improve their activity in less permeable organisms such as Pseudomonas and Serratia. Nonetheless, the thioester IMP-1 inhibitors offer an encouraging start to overcoming metallo-beta-lactamase-mediated resistance in bacteria.

Clonal analysis of a case of multiple meningiomas using multiple molecular genetic approaches: pathology case report

OBJECTIVE

Multiple meningiomas are uncommon brain tumors occurring concurrently in several intracranial locations in the same patient. In the present study, we determined the clonality, methylation status of deoxyribonucleic acid, and relationship of genetic alterations in eight meningiomas from one female patient.

METHODS

Six molecular genetic techniques, including two methylation-based clonality assays and one transcription-based clonality assay, methylation analysis of CpG islands by methylation-specific polymerase chain reaction, loss of heterozygosity, microsatellite instability, and mutational analysis of the NF2 gene on chromosome 22, were used in comparative investigations on clonality and genetic alterations.

RESULTS

The presence of clonal tumor cells was demonstrated by 1) loss of the same copy of chromosome 22 in all eight tumors; 2) transcription of the human AR gene from the same allele in six of eight tumors; 3) a common unmethylated allele at the AR locus in all eight tumors; and 4) the identical single-basepair insertion mutation in exon 9 of the NF2 gene in six of eight tumors. In addition, loss of a copy of the X chromosome in one tumor nodule and microsatellite instability in another nodule were observed.

CONCLUSION

Taken together, this case of multiple meningiomas was most likely monoclonal in origin. Loss of chromosome 22 was an early event during the development of multiple meningiomas and was followed by mutations at the NF2 locus. Later events, including loss of the X chromosome, variation of AR gene expression, or microsatellite instability, may also have played a role in the development of multiple meningiomas in this patient.

Noninvasive evaluation of blunt abdominal trauma: prospective study using diagnostic algorithms to minimize nontherapeutic laparotomy

A prospective study was performed to investigate the feasibility and benefit of evaluating blunt abdominal trauma (BAT) without diagnostic peritoneal lavage (DPL) or other invasive methods. Diagnostic algorithms were designed by using ultrasonography (US) as a screening method. For unstable patients, a free fluid >/= 2 mm thickness on US images over any one of the intraperitoneal spaces (bilateral subphrenic, Morrison, and Douglas pouch) was used as an indicator for laparotomy. For stable patients, any intraabdominal free fluid detected by US was used as an indicator for further investigations. Computed tomography served as a principal complementary method. To further clarify the clinical results, the rate of nontherapeutic laparotomy (NTL) was compared with that from a previous 5-year review done before this study. During studying period of 1 year, 170 patients were consecutively enrolled. There was no delayed diagnosis, and 66 patients were found to have BAT; 17 patients were initial unstable, among whom 15 had free fluid shown by US and 13 patients had confirmed BAT. Eight of the unstable patients with free fluid on US were saved from NTL, of whom six had retroperitoneal hematoma. There was no NTL in unstable patients. Twenty-two patients underwent laparotomy. Two laparotomies done for a suspicion of bowel injury turned out to be NTL. The rate of NTL in the present study was significant lower than that in a previous review (9.1% vs. 32.2%, p = 0.025). Hence following well designed algorithms, noninvasive evaluation of BAT can proceed with safety, and NTL is minimized.

Connexins are expressed in primary brain tumors and enhance the bystander effect in gene therapy

OBJECTIVE

Experimental brain tumor gene therapy with the herpes simplex virus thymidine kinase (HSV-tk) gene has demonstrated that not only HSV-tk transduced but surrounding non-HSV-tk transduced cells are killed when given ganciclovir. This so-called bystander effect has recently been shown to be dependent on connexin-mediated intercellular communication. To assess potential susceptibility to the bystander effect, we examined levels of connexin-26 and connexin-43 expression in a series of primary brain tumors. Connexin-26 expression has not previously been studied in primary brain tumors and connexin-43 expression has not been studied in nonastrocytic primary brain tumors. We also attempted to enhance the bystander effect in vitro by overexpressing connexin in tumor cells with high basal levels of connexin expression.

METHODS

Western blot analysis and immunohistochemistry were used to determine levels of connexin-26 and connexin-43 expression in a series of primary brain tumors. Wild-type 9L gliosarcoma cells were transfected in vitro with the connexin-43 gene and the HSV-tk gene or the HSV-tk gene alone. The bystander effect of each transfectant was then assessed and compared.

RESULTS

Most of the primary brain tumors tested, including low-grade astrocytomas, anaplastic astrocytomas, glioblastomas, oligodendrogliomas, gangliogliomas, meningiomas, and medulloblastomas, showed connexin-26 and connexin-43 expression. Bystander experiments revealed a significant enhancement of the bystander effect in the gliosarcoma cells transfected with connexin-43 and HSV-tk, as compared with gliosarcoma cells transfected with HSV-tk alone.

CONCLUSION

Most primary brain tumors express connexin-26 and connexin-43. This suggests that most primary brain tumors may be susceptible to the bystander effect of HSV-tk gene therapy. The bystander effect can be enhanced in vitro by overexpression of connexin-43 in a cell line with a high basal level of connexin-43 expression.

A non-invasive immobilization system and related quality assurance for dynamic intensity modulated radiation therapy of intracranial and head and neck disease

PURPOSE

To develop and implement a non-invasive immobilization system guided by a dedicated quality assurance (QA) program for dynamic intensity-modulated radiotherapy (IMRT) of intracranial and head and neck disease, with IMRT delivered using the NOMOS Corporation's Peacock System and MIMiC collimator.

METHODS AND MATERIALS

Thermoplastic face masks are combined with cradle-shaped polyurethane foaming agents and a dedicated quality assurance program to create a customized headholder system (CHS). Plastic shrinkage was studied to understand its effect on immobilization. Fiducial points for computerized tomography (CT) are obtained by placing multiple dabs of barium paste on mask surfaces at intersections of laser projections used for patient positioning. Fiducial lines are drawn on the cradle along laser projections aligned with nasal surfaces. Lateral CT topograms are annotated with a crosshair indicating the origin of the treatment planning and delivery coordinate system, and with lines delineating the projections of superior-inferior field borders of the linear accelerator's secondary collimators, or with those of the fully open MIMiC. Port films exposed with and without the MIMIC are compared to annotated topograms to measure positional variance (PV) in superior-inferior (SI), right-left (RL), and anterior posterior (AP) directions. MIMiC vane patterns superposed on port films are applied to verify planned patterns. A 12-patient study of PV was performed by analyzing positions of 10 anatomic points on repeat CT topograms, plotting histograms of PV, and determining average PV.

RESULTS AND DISCUSSION

A 1.5+/-0.3 mm SD shrinkage per 70 cm of thermoplastic was observed over 24 h. Average PV of 1.0+/-0.8, 1.2+/-1.1, and 1.3+/-0.8 mm were measured in SI, AP, and RL directions, respectively. Lateral port films exposed with and without the MIMiC showed PV of 0.2+/-1.3 and 0.8+/-2.2 mm in AP and SI directions. Vane patterns superimposed on port films consistently verified the planned patterns.

CONCLUSION

The CHS provided adequately reproducible immobilization for dynamic IMRT, and may be applicable to decrease PV for other cranial and head and neck external beam radiation therapy.

Unanticipated inhibition of the metallo-beta-lactamase from Bacteroides fragilis by 4-morpholineethanesulfonic acid (MES): a crystallographic study at 1.85-A resolution

As part of a structure-aided effort to design clinically useful inhibitors of metallo-beta-lactamases, the X-ray crystal structure of a complex between the metallo-beta-lactamase from Bacteroides fragilis and 4-morpholinoethanesulfonic acid (MES) has been determined and a model for the structure has been refined to a crystallographic R-factor of 0.151 for data between 10.0- and 1.85-A resolution. Although the binding of MES was an adventitious result of the use of MES as a buffer in the crystallization mixture, MES was subsequently shown to be a competitive inhibitor of the enzyme, with a Ki of 23 +/- 5 mM. MES binds in the same fashion to both of the molecules in the crystallographic asymmetric unit; both direct and solvent-mediated hydrogen bonds to the protein and to the binuclear zinc cluster are observed, involving the oxygens of the sulfonic acid group and the nitrogen of the morpholino ring. In addition, there are hydrophobic interactions between the morpholino ring and residues in the flexible beta-strand of the enzyme between residues 26 and 36. Comparison of this structure with the previously reported unliganded structures of the same enzyme [Concha, N. O., Rasmussen, B. A., Bush, K., and Herzberg, O. (1996) Structure 4, 823-836; Carfi, A., Duée, E., Paul-Soto, R., Galleni, M., Frère, J. -M., and Dideberg, O. (1998) Acta Crystallogr. D54, 47-57] reveals that although the overall conservation of structure in the three different crystal lattices is very high, binding of MES is correlated with a significant change in the conformation of this beta-strand. The flexibility of this beta-strand will be an important consideration in the design of inhibitors of the metallo-beta-lactamases.

Antibiotic sensitization using biphenyl tetrazoles as potent inhibitors of Bacteroides fragilis metallo-beta-lactamase

BACKGROUND

High level resistance to carbapenem antibiotics in gram negative bacteria such as Bacteroides fragilis is caused, in part, by expression of a wide-spectrum metallo-beta-lactamase that hydrolyzes the drug to an inactive form. Co-administration of metallo-beta-lactamase inhibitors to resistant bacteria is expected to restore the antibacterial activity of carbapenems.

RESULTS

Biphenyl tetrazoles (BPTs) are a structural class of potent competitive inhibitors of metallo-beta-lactamase identified through screening and predicted using molecular modeling of the enzyme structure. The X-ray crystal structure of the enzyme bound to the BPT L-159,061 shows that the tetrazole moiety of the inhibitor interacts directly with one of the two zinc atoms in the active site, replacing a metal-bound water molecule. Inhibition of metallo-beta-lactamase by BPTs in vitro correlates well with antibiotic sensitization of resistant B. fragilis.

CONCLUSIONS

BPT inhibitors can sensitize a resistant B. fragilis clinical isolate expressing metallo-beta-lactamase to the antibiotics imipenem or penicillin G but not to rifampicin.

Dosimetric verification of the dynamic intensity-modulated radiation therapy of 92 patients

PURPOSE

To verify that optimized dose distributions provided by an intensity-modulated radiation therapy (IMRT) system are delivered accurately to human patients.

METHODS AND MATERIALS

Anthropomorphic phantoms are used to measure IMRT doses. Four types of verification are developed for: I) system commissioning with beams optimized to irradiate simulated targets in phantoms, II) plans with patient-optimized beams directed to phantoms simulating the patient, III) patient-phantom hybrid plans with patient-optimized beams calculated in phantom without further optimization, and IV) in vivo measurements. Phantoms containing dosimeters are irradiated with patient-optimized beams. Films are scanned and data were analyzed with software. Percent difference between verified and planned maximum target doses is defined as "dose discrepancy" (deltavp). The frequency distribution of type II deltavp from 204 verification films of 92 IMRT patients is fit to a Gaussian. Measurements made in vivo yield discrepancies specified as deltaivp, also fit to a Gaussian.

RESULTS AND DISCUSSION

Verification methods revealed three systematic errors in plans that were corrected prior to treatment. Values of [deltavp] for verification type I are <2%. Type II verification discrepancies are characterized by a Gaussian fit with a peak 0.2% from the centroid, and 158 [deltavp] <5%. The 46 values of [deltavp] >5% arise from differences between phantom and patient geometry, and from simulation, calculation, and other errors. Values of [deltavp] for verification III are less than half of the values of [deltavp] for verification II. A Gaussian fit of deltaivp from verification IV shows more discrepancy than the fit of deltavp, attributed to dose gradients in detectors, and exacerbated by immobilization uncertainty.

CONCLUSIONS

Dosimetric verification is a critical step in the quality assurance (QA) of IMRT. Hybrid Verification III is suggested as a preliminary quality standard for IMRT.

Screening for loss of heterozygosity and microsatellite instability in oligodendrogliomas

To assess the frequency of loss of heterozygosity (LOH) and microsatellite instability (MI) in oligodendrogliomas, we performed an extensive screening of 16 oligodendrogliomas and nine anaplastic oligodendrogliomas by using 132 microsatellite markers on chromosomes 1 through 12 and 15 through 21. In total, 3,135 loci were examined in 25 tumor samples. Only 33/1,965 (1.7%) of oligodendroglioma (low-grade) and 11/1,070 (1.0%) of anaplastic oligodendroglioma (high-grade) loci exhibited MI. High-frequency LOH regions were identified on chromosome arms 1p (31-73% for oligodendrogliomas and 60-100% for anaplastic oligodendrogliomas) and 19q (23-69% for oligodendrogliomas and 100% for anaplastic oligodendrogliomas). In addition, regions on chromosomes 4, 6, and 11 were found to be lost in 30-80% of both oligodendrogliomas and anaplastic oligodendrogliomas. Increased LOH frequency of chromosome 17 (38-40%) was found only in high-grade oligodendrogliomas. The differences in LOH frequencies between low-grade and high-grade oligodendrogliomas in all loci combined and at three loci (DIS447, DIS226, and DIS252) on chromosome arm 1p were determined to be statistically significant [chi 2(1) = 20.2, P < 0.0001, and Fisher's exact test respective P values: 0.01, 0.03, and 0.02]. Our results provide evidence that microsatellite instability does not play an important role in the development of oligodendrogliomas. Furthermore, high LOH frequency on chromosomes 6 and 11 in addition to that identified previously on chromosomes 1, 19, and 4 suggests that multiple candidate tumor suppressor genes on these chromosomes may underlie the processes of initiation and/or progression in oligodendroglioma tumorigenesis.

Soluble penicillin-binding protein 2a: beta-lactam binding and inhibition by non-beta-lactams using a 96-well format

High level methicillin resistance in Staphylococcus aureus is dependent upon the acquisition of the mecA gene encoding penicillin-binding protein 2a (PBP2a). PBP2a is a member of a family of peptidoglycan biosynthetic enzymes involved in assembly of the cell wall in bacteria and is poorly inactivated by beta-lactam antibiotics. We describe a 96-well-filter binding assay using recombinant, soluble PBP2a which allows for kinetic measurement of penicillin binding. The deacylation rate constant for the PBP2a-penicillin G covalent complex was found to be 5.7 +/- 1.0 x 10(-5) s-1 at 30 degrees C (half-life of approximately 200 min). For the PBP2a acylation reaction, the value of K(m) (penicillin G) = 0.5 +/- 0.1 mM and kcat = 1 x 10(-3) s-1, which yields a second-order rate constant (kcat/K(m)) for inactivation of 2.0 M-1 s-1. Using this assay, several non-beta-lactam inhibitors including Cibacron blue have been found which exhibit IC50 values between 10 and 30 microM. The binding affinities of several carbapenems and beta-lactams correlated well between the filter binding assay described in this report and an electrophoretic assay for PBP2a using membranes prepared form methicillin-resistant S. aureus.

A technique for accurate planning of stereotactic brain implants prior to head ring fixation

PURPOSE

A two-step procedure is described for accurate planning of stereotactic brain implants prior to head-ring fixation.

METHODS AND MATERIALS

Approximately 2 weeks prior to implant a CT scan without the head ring is performed for treatment-planning purposes. An entry point and a reference point, both marked with barium and later tattooed, facilitate planning and permit correlation of the images with a later CT scan. A plan is generated using a conventional treatment-planning system to determine the number and activity of I-125 seeds required and the position of each catheter. I-125 seed anisotropy is taken into account by means of a modification to the treatment planning program. On the day of the implant a second CT scan is performed with the head ring affixed to the skull and with the same points marked as in the previous scan. The planned catheter coordinates are then mapped into the coordinate system of the second CT scan by means of a manual translational correction and a computer-calculated rotational correction derived from the reference point coordinates in the two scans.

RESULTS

The rotational correction algorithm was verified experimentally in a Rando phantom before it was used clinically. For analysis of the results with individual patients a third CT scan is performed 1 day following the implant and is used for calculating the final dosimetry.

CONCLUSION

The technique that is described has two important advantages: 1) the number and activity of seeds required can be accurately determined in advance; and 2) sufficient time is allowed to derive the best possible plan.

Response of intracranial melanoma metastases to stereotactic radiosurgery

We analyzed our recent stereotactic radiosurgery (SRS) experience to determine the radiographic response of intracranial metastatic melanomas to SRS. Twelve patients with 21 intracranial melanoma metastases treated with SRS were evaluated. Fifteen (72%) metastases were hemispheric, 3 (14%) were cerebellar, and 3 (14%) were in the basal ganglion or thalamus. All lesions were 2.5 cm or less in maximum diameter. Eleven patients also had whole brain external beam radiotherapy. Mean SRS dosage was 1,800 cGy to the 85% isodose surface and median dose was 1,800 cGy to the 80% isodose surface (range 1,100-3, 100 cGy at the 80-95% isodose surface). Overall, 12 (57%) lesions showed decrease or stabilization of tumor volume (i.e., local control), while 9 (43%) showed enlargement. Division of metastases into small (< or = 1.0 cm diameter) and large (> 1.0 cm diameter) tumors showed that the small tumors were more likely to regress than the large tumors (chi-square test; P < 0.03). Only 1 of 9 (11%) large lesions regressed as opposed to 7 of 12 (58%) small lesions regressed with SRS. We conclude that SRS is suited for small melanoma brain metastases, but lesions between 1.0 and 2.5 cm in diameter, while still generally considered appropriate for SRS, may not be as responsive to SRS at currently employed dosages.

Evidence for clonal origin of neoplastic neuronal and glial cells in gangliogliomas

Gangliogliomas are rare tumors of the central nervous system that account for approximately 1% of all brain tumors. Histologically, gangliogliomas are composed of intimately admixed glial and neuronal components, the pathological origins of which remain to be characterized. Clonal analysis through examination of the pattern of the X chromosome inactivation allows one to distinguish monoclonal differentiation of a genetically abnormal progenitor cell from parallel, but independent, clonal expansion of two different cell types during tumorigenesis in biphasic neoplasms, such as gangliogliomas. In the present study, we investigated the clonality of eight gangliogliomas from female patients using both methylation- and transcription-based clonality assays at the androgen receptor locus (HUMARA) on the X chromosome. Among tumors from seven patients who were heterozygous at the HUMARA locus, five were identified as monoclonal with the methylation-based clonality assay, and the results were confirmed by the transcription-based method, whereas two were shown to be polyclonal by the methylation-based clonality assay but monoclonal by transcription-based clonality analysis. We conclude that the predominant cell types in most gangliogliomas are monoclonal in origin and derive from a common precursor cell that subsequently differentiates to form neoplastic glial and neuronal elements.

The bystander effect exerted by tumor cells expressing the herpes simplex virus thymidine kinase (HSVtk) gene is dependent on connexin expression and cell communication via gap junctions

To elucidate the role gap junctions play in the bystander effect, we examined the cytotoxic effect of herpes simplex virus thymidine kinase (HSVtk) modified tumor cells on gap junction communication-deficient tumor cells and their connexin transfectants. Communication competent Walker 256 tumor cells engineered to express the HSVtk gene (Walker-tk+) when cocultured with N2A mouse neuroblastoma and PC12 rat pheochromocytoma cells with absent endogenous junctional conductance showed no bystander cytotoxicity. Transfection of N2A cells with the rat connexin37 gene (5Q) and PC12 cells with the human connexin43 gene rendered them susceptible to bystander cell death. Additionally, communication-deficient N2A cells transfected with the HSVtk gene failed to exert a bystander effect, whereas N2A transfectants coexpressing the connexin37 and HSVtk genes (5Qtk+ cells) exerted bystander cytotoxicity on gap junction communication-competent 5Q but not on communication-deficient N2A cells in vitro. In vivo experiments also showed tumor growth inhibition of communication-competent 5Q but not communication-incompetent N2A cells by 5Qtk+ cells. In conclusion, these results indicate that in several cellular environments the bystander effect is dependent on connexin expression and gap junctional communication between HSVtk-positive and HSVtk-negative cells.

[Clinical study of effect of yinji capsule on left ventricular systolic function of angina pectoris patients with blood stasis syndrome]

OBJECTIVE

To explore the Yinji Capsule (YJC) in improving the left ventricular systolic function of angina pectoris patients with Blood Stasis Syndrome.

METHODS

The systolic function of left ventricle (LV) in cardiac cycle of 28 angina pectoris patients with Blood Stasis Syndrome was examined with three-dimensional echocardiograph (3-DE) before and after treatment with YJC.

RESULTS

The total symptomatic effective rate was 85.7%. The changes of LV systolic function were those: left ventricle ejection fraction (LVEF) increased from 45.0 +/- 4.9% to 48.2 +/- 3.5% (P < 0.05); EF on early stage and late stage increased from 22.6 +/- 2.1%, 8.3 +/- 1.2% to 28.1 +/- 3.0% and 10.3 +/- 0.9% respectively (P < 0.01, P < 0.05), myocardial region with segment systole (SS) < 5% decreased significantly (P < 0.01).

CONCLUSION

YJC could improve LV systolic function on early stage and late stage in cardiac cycles, and mainly improve the systolic function of the region with low SS of LV.