Peer review in MRI: A quality improvement programme and pilot study

INTRODUCTION

The aim of this pilot study was to implement a peer review programme to evaluate MRI images and protocols, with the goal of improving quality and standardising protocols.

METHOD

A plan-do-check-act method of action research was adopted. A checklist was designed and two radiographers scored the images (Optimal, Diagnostic or Suboptimal). A sample of five Lumbar Spine examinations were selected and reviewed on two separate occasions, one month apart. A consultant radiologist also scored the selected examinations.

RESULTS

There was excellent intra-rater reliability for both observers. At first assessment, Cohen's weighted Kappa analysis indicated moderate inter-rater agreement (0.457) rising to substantial agreement (0.606) at second assessment. Variations in sequence parameter settings by the radiographers were noted. Feedback via educational sessions were implemented and enhancement of protocols were made.

CONCLUSIONS

Radiographers manipulate many parameters during MRI examinations, and image quality can be degraded if sequences are not optimised. This may lead to misinterpretation. Initial results suggest peer review can result in improved image quality, better protocols, and improved staff confidence. There are opportunity costs involved in releasing staff from clinical work and time and resources required for image appraisal training, however we suggest this model can be extended to other departments and modalities as a healthcare improvement initiative.

IMPLICATIONS FOR PRACTICE

Initial results suggest peer review processes performed by radiographers can result in improvement to protocols and image quality in MRI. With appropriate training, radiographers can implement and undertake appraisal of image quality in MRI as part of clinical governance. The purpose of feedback must be made clear, and good professional relationships should be forged to allow candid and supportive feedback with a focus on development and education.

Targeting synthetic lethality between the SRC kinase and the EPHB6 receptor may benefit cancer treatment

Application of tumor genome sequencing has identified numerous loss-of-function alterations in cancer cells. While these alterations are difficult to target using direct interventions, they may be attacked with the help of the synthetic lethality (SL) approach. In this approach, inhibition of one gene causes lethality only when another gene is also completely or partially inactivated. The EPHB6 receptor tyrosine kinase has been shown to have anti-malignant properties and to be downregulated in multiple cancers, which makes it a very attractive target for SL applications. In our work, we used a genome-wide SL screen combined with expression and interaction network analyses, and identified the SRC kinase as a SL partner of EPHB6 in triple-negative breast cancer (TNBC) cells. Our experiments also reveal that this SL interaction can be targeted by small molecule SRC inhibitors, SU6656 and KX2-391, and can be used to improve elimination of human TNBC tumors in a xenograft model. Our observations are of potential practical importance, since TNBC is an aggressive heterogeneous malignancy with a very high rate of patient mortality due to the lack of targeted therapies, and our work indicates that FDA-approved SRC inhibitors may potentially be used in a personalized manner for treating patients with EPHB6-deficient TNBC. Our findings are also of a general interest, as EPHB6 is downregulated in multiple malignancies and our data serve as a proof of principle that EPHB6 deficiency may be targeted by small molecule inhibitors in the SL approach.

Therapeutic relevance of the protein phosphatase 2A in cancer

Chromosomal Instability (CIN) is regarded as a unifying feature of heterogeneous tumor populations, driving intratumoral heterogeneity. Polo-Like Kinase 1 (PLK1), a serine-threonine kinase that is often overexpressed across multiple tumor types, is one of the key regulators of CIN and is considered as a potential therapeutic target. However, targeting PLK1 has remained a challenge due to the off-target effects caused by the inhibition of other members of the polo-like family. Here we use synthetic dosage lethality (SDL), where the overexpression of PLK1 is lethal only when another, normally non-lethal, mutation or deletion is present. Rather than directly inhibiting PLK1, we found that inhibition of PP2A causes selective lethality to PLK1-overexpressing breast, pancreatic, ovarian, glioblastoma, and prostate cancer cells. As PP2A is widely regarded as a tumor suppressor, we resorted to gene expression datasets from cancer patients to functionally dissect its therapeutic relevance. We identified two major classes of PP2A subunits that negatively correlated with each other. Interestingly, most mitotic regulators, including PLK1, exhibited SDL interactions with only one class of PP2A subunits (PPP2R1A, PPP2R2D, PPP2R3B, PPP2R5B and PPP2R5D). Validation studies and other functional cell-based assays showed that inhibition of PPP2R5D affects both levels of phospho-Rb as well as sister chromatid cohesion in PLK1-overexpressing cells. Finally, analysis of clinical data revealed that patients with high expression of mitotic regulators and low expression of Class I subunits of PP2A improved survival. Overall, these observations point to a context-dependent role of PP2A that warrants further exploration for therapeutic benefits.

Building high-resolution synthetic lethal networks: a 'Google map' of the cancer cell

The most commonly used therapies for cancer involve delivering high doses of radiation or toxic chemicals to the patient that also cause substantial damage to normal tissue. To overcome this, researchers have recently resorted to a basic biological concept called 'synthetic lethality' (SL) that takes advantage of interactions between gene pairs. The identification of SL interactions is of considerable therapeutic interest because if a particular gene is SL with a tumor-causing mutation, then the targeting that gene carries therapeutic advantages. Mapping these interactions in the context of human cancer cells could hold the key to effective, targeted cancer treatments. In this review, we cover the recent advances that aim to identify these SL interactions using unbiased genetic screens.

Mutations at F637 in the NMDA receptor NR2A subunit M3 domain influence agonist potency, ion channel gating and alcohol action

BACKGROUND AND PURPOSE

NMDA receptors are important molecular targets of ethanol action in the CNS. Previous studies have identified a site in membrane-associated domain 3 (M3) of the NR1 subunit and two sites in M4 of the NR2A subunit that influence alcohol action; the sites in NR2A M4 also regulate ion channel gating. The purpose of this study was to determine whether mutations at the site in the NR2A subunit corresponding to the NR1 M3 site influence alcohol action and ion channel gating.

EXPERIMENTAL APPROACH

We investigated the effects of mutations at phenylalanine (F) 637 of the NR2A subunit using whole-cell and single-channel patch-clamp electrophysiological recording in transiently-transfected HEK 293 cells.

KEY RESULTS

Mutations at F637 in the NR2A subunit altered peak and steady-state glutamate EC(50) values, maximal steady-state to peak current ratios (I(ss):I(p)), mean open time, and ethanol IC(50) values. Differences in glutamate potency among the mutants were not due to changes in desensitization. Ethanol IC(50) values were significantly correlated with glutamate EC(50) values, but not with maximal I(ss):I(p) or mean open time. Ethanol IC(50) values were linearly and inversely related to molecular volume of the substituent.

CONCLUSIONS AND IMPLICATIONS

These results demonstrate that NR2A(F637) influences NMDA receptor affinity, ion channel gating, and ethanol sensitivity. The changes in NMDA receptor affinity are likely to be the result of altered ion channel gating. In contrast to the cognate site in the NR1 subunit, the action of ethanol does not appear to involve occupation of a critical volume at NR2A(F637).

Glucocorticoids upregulate taurocholate transport by ileal brush-border membrane

The regulation of the enterohepatic circulation of bile acids has not been fully elucidated. Substrate availability has been shown to have a regulatory role on the ileal uptake of taurocholate (TC) by a positive feedback mechanism. Other mechanisms are likely to be involved in regulating ileal bile acid uptake. The present study was designed to test the hypothesis that the ileal bile acid transporter (iBAT) is glucocorticoid sensitive and that changes in expression are mediated by changes in iBAT synthesis. Adult Sprague-Dawley rats (300-400 g) received intraperitoneal injections with either corticosterone (5 mg/ 100 g body weight) or an equivalent vehicle (control) daily for 3 days. On day 4, ileal brush-border membrane vesicles (BBMV) and hepatic basolateral membrane vesicles (BLMV) were prepared, and TC transport was performed using the rapid filtration technique. Initial velocity was measured at selected time points, and kinetics were calculated over a range of TC concentrations. Ileal RNA was isolated, and Northern analysis of steady-state iBAT mRNA levels was determined. Western blot analysis was performed to quantitate the level of the 48-kDa iBAT protein. The initial velocity of Na(+)-dependent TC uptake at 30 s by ileal BBMV was higher in treated animals (264.3 +/- 64.6 pmol/mg protein) compared with control animals (148.3 +/- 41.1 pmol/mg protein; P = 0.07). The maximal velocity of uptake (Vmax) was significantly higher in treated vs. control animals (1,091 +/- 62.7 vs. 689.1 +/- 55.0 pmol.min-1.mg protein-1, respectively; P = 0.002), whereas there was no significant difference in the Michaelis constant (Km) between the control and treated animals (43.3 +/- 7.2 vs. 35.3 +/- 8.7 microM, respectively; P = not significant). Steady-state iBAT mRNA levels were increased twofold in the treated vs. control groups. Western blot analysis showed that the abundance of the 48-kDa iBAT protein was eightfold higher in the treated animals compared with control. Kinetic analysis of hepatic Na(+)-dependent TC uptake revealed nearly identical Vmax and Km between the study and control animals. Therefore, we conclude that TC transport by ileal BBMV is upregulated by administration of glucocorticoids. The increase in BBMV transport Vmax corresponds to an increase in both iBAT transcript and protein.

Downregulation of taurocholate transport by ileal BBM and liver BLM in biliary-diverted rats

The enterohepatic circulation of bile salts may be substrate dependent. We hypothesize that decreased intestinal delivery of bile salts results in downregulation of ileal and hepatocyte bile salt transport in the biliary-diverted rat. Maximal velocity (Vmax) of taurocholate transport by ileal brush-border membrane (BBM) vesicles was downregulated in the bile-diverted animals by 45.5% (559.9 +/- 57.8 pmol.mg protein-1.min-1 in bile-diverted rats vs. 1,026.6 +/- 170.9 pmol.mg protein-1.min-1 in shams). Similarly, taurocholate transport Vmax by hepatocyte basolateral membrane (BLM) was downregulated by 37.8% (2.62 +/- 0.18 pmol.mg protein-1.min-1 in bile-diverted rats vs. 6.93 +/- 0.41 pmol.mg protein-1.min-1 in shams). Cholesterol content (mumol/mg protein) of the membranes was increased in both BBM (0.478 +/- 0.055 vs. 0.272 +/- 0.029) and BLM (0.410 +/- 0.052 vs. 0.294 +/- 0.044) in diverted rats compared with shams. Fluorescence anisotropy was significantly higher in diverted animals compared with shams for both BBM (0.2333 +/- 0.001 vs. 0.2120 +/- 0.004) and BLM (0.1524 +/- 0.002 vs. 0.1426 +/- 0.005). We conclude that biliary diversion in the rat leads to downregulation of both ileal BBM and hepatocyte BLM taurocholate transport. Alterations in transporter expression caused by diversion may, in part, be mediated by changes in membrane lipid composition or fluidity.

A New Biopolymer for High-Temperature Profile Control: Part 1-Laboratory Testing

Summary

An extracellular polysaccharide produced by Alcaligenes bacteria has beencrosslinked to form firm gels that are stable for long periods at elevatedtemperatures. The biopolymer can be gelled with multivalent ions such as Cr +3;it can also be gelled at the 2,000-to-4,000-ppm level without Cr +3 inhigh-salinity [∼20% total dissolved solids (TDS)] brines. Gel samples have beenstable for 2 years at 74 and 93 degrees C. Gels could be formed over a wide pHrange, but best long-term stability was achieved in the pH range of 7 to 8. Aflow test of Alcaligenes biopolymer gel in Berea sandstone at 74 degrees Cshowed that the gel gave a brine permeability reduction factor of 320.permeability reduction factor of 320.

Introduction

Chromium-complexed xanthan biopolymers recently have been used to modifyinjection profiles for the improvement of waterfloods. The use of xanthanbiopolymers is somewhat limited by their decreasing stability with increasingtemperature. Ryles stated that the useful limit for xanthan biopolymer is 70degrees C. Wellington found that xanthan biopolymer will maintain its stabilityfor 1 year at 97 degrees C if suitable stabilizers are added. Seright and Henrici believe that under ideal conditions, a xanthan solution could maintainone-half its viscosity for 5 years if the temperature were not raised above the75 to 80 degrees C range. Finally, Lambert and Rinaudo's short-term studies ofxanthan stability at 90 degrees C found that chemical additives are needed toimprove stability. These earlier investigators focused on maintaining theviscosity of uncrosslinked xanthan solutions for mobility control. Crosslinkedbiopolymers may have different temperature sensitivities; however, we have notbeen able to form chromium crosslinked xanthan gels that maintain long-termstability above 66 degrees C. Crosslinked polyacrylamides do not seem to be aviable alternative to biopolymers at elevated temperatures because of theirsensitivity to salinity, particularly to divalent cations. Ryles stated thatpolyacrylamides undergo moderate hydrolysis at 70 degrees C, whilepolyacrylamides undergo moderate hydrolysis at 70 degrees C, while Moradi-Araghi and Doe contended that the "safe" limit forpolyacrylamides in brines containing 2,000 ppm or more hardness ions is 75degrees C. Complex Cr +3 crosslinked polyacrylamides have demonstratedlong-term stability with careful exclusion of oxygen at temperatures as high as124 degrees C, but it appears that these results were obtained in the absenceof divalent cations. The Natl. Petroleum Council reports that neitherbiopolymers nor polyacrylamides are good above 71 degrees C without theinclusion of chemical stabilizers and that the propagation of such stabilizersthrough a reservoir is problematic. Clearly, profile-control materials thatwill be stable and useful above 70 degrees C are needed. This paper describeswork with one such material, an extracellular polysaccharide produced by Alcaligenes bacteria. The polymer contains glucose, rhamnose, mannose, andglucuronic acid monomer units and has a molecular weight of about 8 million. The backbone of the polymer consists of glucose, glucuronic acid, and rhamnosemonomers. About every fourth monomer unit, a branch of either rhamnose(two-thirds of the time) or mannose (one-third of the time) is attached to aglucose unit. In contrast, xanthan gum contains glucose, mannose, andglucuronic acid monomer units with various amounts of acetic and pyruvate. Xanthan gum is branched more often than the Alcaligenes biopolymer (at everyother unit), and the branches are three sugar residues long rather than one. Fig. 1 shows the chemical structure of the Alcaligenes biopolymer, and Fig. 2shows the chemical structure of xanthan biopolymer.

Experimental

Materials.

The biopolymer used in our studies is available in powder form ofabout 93% activity. Great care has to be taken to hydrate the polymer properly. The material was made up with slow (∼5 minutes) addition of polymer to brineand lengthy (∼30 minutes) mixing in a blender. Initial tests showed that Alcaligenes biopolymer could be gelled at room temperature with Cr+3 in a 7%brine. Subsequent studies, however, focused on highly saline [∼20% totaldissolved solids (TDS)] waters. This salinity corresponded to that of theproduced water in a target Oklahoma field, the Southeast Bradley "A" Unit, which has a formation temperature of 74 degrees C. It was found that the Alcaligenes biopolymer would gel in this brine at elevated temperatures withoutadded crosslinkers.

Long-Term Static Stability Tests.

Long-term static stability tests wereinitiated with 100-mL samples in the 20% TDS brine. The effects of biopolymerconcentration, crosslinkers, and pH on gel quality and stability were tested. All but five of these tests were carried out at 74 degrees C. The remainingfive tests were performed at 93 degrees C. All but nine of the 57 samplescontained 400 ppm formaldehyde as a biocide. The samples were observedfrequently during the first 4 months. Following that initial period, individualsamples were observed occasionally, but comprehensive observations were takenon four widely spaced occasions. Observations of gel quality and amount ofsyneresis were qualitative, and some of the observations reflect the intrinsicproblems in visual observations of this type. For example, the recordedobservations in some cases indicate a decrease in syneresis from an earlierobservation. The validity of this trend is doubtful, and it more likelyreflects the uncertainty in a visual estimation of the degree of syneresis. Nevertheless, visual observations of this type can document gross trends over along period of time. Some later bottle tests were carried out to examine theeffect of single cations on Alcaligenes biopolymer gelation.

Core Tests.

The core tests were carried out in a linear flow apparatus, consisting of a Hassler-type core holder connected to a positive-displacementpump. Cores were held in a rubber sleeve to positive-displacement pump. Coreswere held in a rubber sleeve to which a confining pressure was applied toprevent fluid bypass. A pressure transmitter measured the pressure drop acrosssections of pressure transmitter measured the pressure drop across sections ofthe core through pressure taps spaced evenly along the core length. Fig. 3 is aschematic of the core apparatus. The porous medium used was Berea sandstonewith a nominal air permeability of 500 md.

Comparison between continuous and discrete sources in the Paris system of implants

Since the Paris system of interstitial brachytherapy is based on iridium wires, the consequences resulting from the substitution of discrete point sources in afterloading ribbons have been analyzed. The results are presented in this article for single ribbons, single plane implants of thicknesses 0.5 and 1.0 cm, and biplanar implants of both equal and unequal areas of sizes most frequently used clinically in the thickness range 1.5-3.0 cm. These results indicate changes in the quality of implants using wires and point sources up to the maximum spacing of 1.5 cm. The quality of the implants is judged on the basis of a parameter, the uniformity index, which takes into account both the size of the treatment volume for a given target volume and the homogeneity within the treatment volume as determined from the integral dose. Other implant parameters such as total activity, treatment volume, total volume receiving greater than twice the stated dose rate, average dose rate, and variation of basal dose rate, etc., are also provided to indicate quality of the implants. The results with the customary seed spacing of 1 cm are compatible with those using wires and are found to have improved quality in many cases.

Characteristics of clometacin-induced hepatitis with special reference to the presence of anti-actin cable antibodies

The clinical, biochemical, histopathological and immunological features of 30 cases of clometacin-induced hepatitis are described. The age range of the patients was 32-84 years with a notable female predominance of 29:1. The hepatitis was highly cytolytic with high values of transaminases but with little or no cholestasis. Gammaglobulins were higher than 18 g/l in 73% of the cases. 25 liver biopsies were performed and showed acute hepatitis with a predominant centrilobular necrosis in 17; chronic aggressive hepatitis was noted in 8 cases but 1 showed concomitant cirrhotic changes. Anti-tissue antibodies were looked for in all cases. Anti-smooth muscle antibodies of anti-actin cable type (titre 1/80 to 1/2, 560) were detected in 19 cases, anti-nucleus antibodies in 16 cases which were associated to the former in 14 cases. The above findings show that clometacin produces a hepatitis syndrome quite akin to autoimmune chronic active hepatitis (lupoid hepatitis) and to the hepatopathy induced by oxyphenisatin.

Uniform analysis of dose distribution in interstitial brachytherapy dosimetry systems

In brachytherapy, articles are published with dose and homogeneity specifications using different systems which are hard to compare. For the same "stated dose", the dose delivered, volume treated and activity chosen are not the same in different systems, due to the fact that the source placement rules are different. In this article, the authors have circumvented this problem by the use of an approach not applied hitherto, viz. by determining the value of the Uniformity index (UI) of an implant using different systems. This value takes into account the integral dose within the treatment volume and is compared with an idealized implant, where the dose is uniform and the target and treatment volumes are the same. This method of evaluation has been applied for single plane, multiple plane and cylindrical volume implants using the Manchester, Quimby and Paris systems. Although the results obtained are different, the degree of closeness of these values are striking, with some minor exceptions. Thus, it is possible to combine all the brachytherapy parameters, such as: dose, homogeneity, treatment volume within a single value to determine the quality of an implant.

AAPM Task Group 21 protocol: dosimetric evaluation

The AAPM Task Group 21 protocol is the latest amongst the protocols introduced in recent years covering the dosimetry of high-energy x-ray and electron beams used in radiotherapy. We have found that the C lambda value for 15-MV x rays requires 1.6% upward adjustment, whereas the CE values for electrons in the range 7-18 MeV require downward adjustment of 1%-3% compared to our previous values. The adjustment values given in this paper pertain to the specific measuring systems and high-energy beams considered here and would not necessarily be applicable to other systems. The dose to medium, calculated for different modalities, was verified by thermoluminescent dosimetry and the results were found to be consistent. These values of C lambda and CE have also been compared with those derived using other protocols, particularly the Nordic Association of Clinical Physics 80 and 81, and the discrepancies discussed.

Characteristics of Mevatron 77 15-MV photon beam

The characteristics of 15-MV photon beam of Mevatron 77 have been examined with respect to clinical parameters. Some of the characteristics of this 15-MV photon beam are different from those of similar machines used in radiotherapy. The tissue-maximum ratio values have been determined experimentally for SAD 100 cm and percentage depth dose values have been determined from tissue-maximum ratio data. It is found that the experimentally determined PDD values for SSD 80, 100, and 120 cm are within +/- 1% of the calculated data. The scatter-maximum ratio data have been calculated from the experimentally determined zero area attenuation coefficient and tissue-maximum ratio data and are presented as function of depth and radii of circular fields. The relative dose factors have been determined both for square and rectangular fields. The relative dose factor for rectangular fields depends on the two pairs of jaws differently and the maximum difference is about 1.5%. The flatness and symmetry are within the specifications set by the manufacturer.

Dosimetric reliability of thermoluminescent phosphors (TLD-too)

The dosimetric reliability of TLD-100 has been studied in view of the fact that these TLDs are extensively used for patient dosimetry in the case of irregular fields and where patient's contour creates special problems. TLDs have also been used in intercavitary dosimetry (e.g. esophagus and rectum) and in some cases of dosimetric comparison of radiation output. However, it appears that these TLDs are unsuitable for most practical dosimetry due to poor reproducibility and system error. It is found that the same TLD-chip gives widely divergent readings for the same exposure even when correction for the system error is made. The composite uncertainty under the best experimental conditions is about +/-3.5%.