Proof-of-concept of DosiTest: A virtual multicentric clinical trial for assessing uncertainties in molecular radiotherapy dosimetry

Clinical dosimetry in molecular radiotherapy (MRT) is a multi-step procedure, prone to uncertainties at every stage of the dosimetric workflow. These are difficult to assess, especially as some are complex or even impossible to measure experimentally. The DosiTest project was initiated to assess the variability associated with clinical dosimetry, by setting up a 'virtual' multicentric clinical dosimetry trial based on Monte Carlo (MC) modelling. A reference patient model with a realistic geometry and activity input for a specific tracer is considered. Reference absorbed dose rate distribution maps are generated at various time-points from MC modelling, combining precise information on density and activity distributions (voxel wise). Then, centre-specific calibration and patient SPECT/CT datasets are modelled, on which the clinical centres can perform clinical (i.e. image-based) dosimetry. The results of this dosimetric analysis can be benchmarked against the reference dosimetry to assess the variability induced by implementing different clinical dosimetry approaches. The feasibility of DosiTest is presented here for a clinical situation of therapeutic administration of ¹⁷⁷Lu-DOTATATE (Lutathera®) peptide receptor radionuclide therapy (PRRT). From a real patient dataset composed of 5 SPECT/CT images and associated calibrations, we generated the reference absorbed dose rate images with GATE. Then, simulated SPECT/CT image generation based on GATE was performed, both for a calibration phantom and virtual patient images. Based on this simulated dataset, image-based dosimetry could be performed, and compared with reference dosimetry. The good agreement, between real and simulated images, and between reference and image-based dosimetry established the proof of concept of DosiTest.

Symmetric bilateral transposition flap: a very versatile option in facial dermatological surgery

AIM

Repair following excision of large tumours of the face can be problematic; primary closure may not be achievable and grafting or secondary intention healing carry the risk of necrosis and lengthy healing times. Flaps are usually associated with earlier healing and better cosmetic results, as the skin used for closure is similar to the tissue requiring repair. However, large wound sizes and difficulty in finding a suitable donor area means flaps can be complicated to perform. The aim of this paper was to identify a comparatively quick and simple alternative to standard repair techniques for the closure of large wound defects in critical anatomical areas, when the only realistic alternative would be grafting, offering both good cosmetic results and minimal risk of complications.

RESULTS

We have developed a flap, modified from the classic, single lobe transposition flap. Two similar lobes placed symmetrically and perpendicularly to two opposite sides of the surgical wound are incised with fulcra centred on two opposite corners. The flaps are then rotated by approximately 80-90º into position side by side, sutured to the borders of the surgical wound and finally together with a longitudinal suture. The principle behind this flap is the split of the covering surface into 2 small units, rather than using a large single lobe, which, for large wounds, would make closure of the single donor area by first intention impossible. The split of the donor area in 2 smaller subunits makes it easier to close the two donor areas and allows a larger amount of tissue to be harvested.

CONCLUSION

We have developed a twinned symmetric transposition flap to close large wounds on the face when the only realistic alternative would have been the use of grafting. It offers minimal distortion, and is both quick and simple to perform. The use of tissue similar to the original defect ensures good cosmetic results. Healing times were usually very rapid and complications limited to a very few cases of end flap necrosis. This technique is not applicable where donor areas fall in anatomic spots where harvesting of the lobes is impossible, e.g. when the wound is too close to the hair line and transposition of the lobes would cause the transfer of hairy skin to an area where the presence of hair is not desirable.

Metformin for the treatment of hidradenitis suppurativa: a little help along the way

BACKGROUND

Despite recent insights into its aetiology, hidradenitis suppurativa (HS) remains an intractable and debilitating condition for its sufferers, affecting an estimated 2% of the population. It is characterized by chronic, relapsing abscesses, with accompanying fistula formation within the apocrine glandbearing skin, such as the axillae, ano-genital areas and breasts. Standard treatments remain ineffectual and the disease often runs a chronic relapsing course associated with significant psychosocial trauma for its sufferers.

OBJECTIVE

To evaluate the clinical efficacy of Metformin in treating cases of HS which have not responded to standard therapies.

METHODS

Twenty-five patients were treated with Metformin over a period of 24 weeks. Clinical severity of the disease was assessed at time 0, then after 12 weeks and finally after 24 weeks. Results were evaluated using Sartorius and DLQI scores.

RESULTS

Eighteen patients clinically improved with a significant average reduction in their Sartorius score of 12.7 and number of monthly work days lost reduced from 1.5 to 0.4. Dermatology life quality index (DLQI) also showed a significant improvement in 16 cases, with a drop in DLQI score of 7.6.

CONCLUSION

Metformin helps control HS with minimal side effects and good patient compliance and can represent a further agent in the spectrum of treatments available in the treatment of this disease.

The severe burns patient with tracheostomy: implications for management of dysphagia, dysphonia and laryngotracheal pathology

INTRODUCTION

Insertion of a tracheostomy for a severe burn patient is not uncommon. The method of decannulation, effects of the tracheostomy on voice and swallowing and subsequent complications have not been described in the literature specifically for this population. The aim of this study was to investigate the risk of dysphagia, dysphonia and laryngotracheal pathology in severe burn patients with tracheostomy and following decannulation.

METHOD

A retrospective chart review was conducted for severe burn patients admitted from January 2000 to December 2007 that received tracheostomy as part of their treatment.

RESULTS

Two hundred and thirty patients were admitted during the study period, 26 of whom underwent tracheostomy. Significant positive correlations were identified between tracheostomy duration and %TBSA burn, days to commence oral intake and days to commence pre-morbid oral diet. Several dysphagic features were identified within the oral and pharyngeal phases of swallowing and dysphonia was frequently demonstrated on perceptual voice assessment with the tracheostomy in situ and following decannulation. Laryngotracheal pathology was diagnosed in 12 of the 26 patients (46.2%) whilst the tracheostomy was in place; 2 with laryngeal granulation tissue, 2 with tracheal granulation tissue, 2 with supraglottic oedema and erythema and 6 with reduced vocal mobility.

CONCLUSION

Severe burn patients that have prolonged tracheostomy are likely to have a larger size burn, take longer to commence oral intake and achieve pre-morbid oral diet. These patients are also at risk for dysphagia, dysphonia and laryngotracheal pathology.

Lung function made easy: assessing lung size

Spirometry is available in most GP surgeries and provides an invaluable tool for assessing respiratory function in chronic obstructive pulmonary disease (COPD) and asthma. Spirometry alone may not provide the clinician with an accurate assessment of lung disease as it misses two important measurements of lung volume. By measuring Residual Volume (RV) and Total Lung Capacity (TLC) it is possible to determine true restrictive or hyperinflated disease processes. Helium dilution, body plethysmography and nitrogen washout are three different methods which may be used to measure lung volume. These tests are normally only provided in the acute setting. Comparing values of RV and TLC to predicted values makes it possible to grade the severity of disease far more accurately than spirometry. Four case studies of asthma, obesity, COPD and pulmonary fibrosis clearly demonstrate anomalies that may arise when interpreting lung disease from spirometry compared to the interpretation made with additional lung volume data.

o-Nitrotoluene-induced large intestinal tumors in B6C3F1 mice model human colon cancer in their molecular pathogenesis

In the previous 500 2-year chemical bioassays within the National Toxicology Program, large intestinal tumors (cecal carcinomas) related to chemical exposure have not been observed in B6C3F1 mice. The recently completed o-nitrotoluene study provided the first cecal tumor response and an opportunity to evaluate the morphology and molecular profile of oncogenes and tumor suppressor genes that are relevant to humans. Morphologically, the carcinomas were gland-forming tumors lined by tall columnar epithelial cells that were positive for cytokeratin 20 and negative for cytokeratin 7. Using immunohistochemistry beta-catenin (encoded by Catnb) protein accumulation was detected in 80% (8/10) of the cecal carcinomas, while increased cyclin D1 and p53 protein expression was detected in 73% (8/11), respectively. There was no difference in adenomatous polyposis protein expression between normal colon and cecal carcinomas. All tumors examined exhibited mutations in exon 2 (corresponds to exon 3 in humans) in the Catnb gene. Mutations in p53 were identified in nine of 11 carcinomas, and all were in exon 7. Analysis of the K-ras gene revealed mutations in 82% (9/11) of carcinomas; all had specific G --> T transversions (Gly --> Val) at codons 10 or 12. The alterations in cancer genes and proteins found in the mouse large intestinal tumors included mutations that activate signal transduction pathways (K-ras and Catnb) and changes that disrupt the cell-cycle and bypass G(1) arrest (p53, cyclin D1). These alterations, which are hallmarks of human colon cancer, probably contributed to the pathogenesis of the large intestinal carcinomas in mice following o-nitrotoluene exposure.

Chemical-specific alterations in ras, p53, and beta-catenin genes in hemangiosarcomas from B6C3F1 mice exposed to o-nitrotoluene or riddelliine for 2 years

The most prominent neoplastic lesions in mice in the 2-year studies of o-nitrotoluene and riddelliine were hemangiosarcomas. Fifteen o-nitrotoluene-induced hemangiosarcomas of the skeletal muscle, subcutaneous tissue, and mesentery; 12 riddelliine-induced hemangiosarcomas of the liver; and 15 spontaneous subcutaneous hemangiosarcomas were examined for genetic alterations in ras, p53, and beta-catenin genes. Mutations in at least one of these genes were identified in 13 of 15 (87%) of the o-nitrotoluene-induced hemangiosarcomas with missense mutations in p53 exons 5-8 detected in 11 of 15 (73%) of these neoplasms. Seven of 15 (47%) hemangiosarcomas from mice exposed to o-nitrotoluene had deletions at exon 2 splice sites or smaller deletions in the beta-catenin gene. K-ras mutation was detected in only 1 of the 15 (7%) o-nitrotoluene-induced hemangiosarcomas. In contrast to the o-nitrotoluene study, 7/12 (58%) riddelliine-induced hemangiosarcomas had K-ras codon 12 GTT mutations and, when screened by immunohistochemistry, 9/12 (75%) had strong staining for the p53 protein in malignant endothelial cells, the cells of origin of hemangiosarcomas. Riddelliine-induced hemangiosarcomas were negative for the beta-catenin protein. Spontaneous hemangiosarcomas from control mice lacked both p53 and beta-catenin protein expression and ras mutations. Our data indicated that p53 and beta-catenin mutations in the o-nitrotoluene-induced hemangiosarcomas and K-ras mutations and p53 protein expression in riddelliine-induced hemangiosarcomas most likely occurred as a result of the genotoxic effects of these chemicals. It also suggests that these mutations play a role in the pathogenesis of the respective hemangiosarcomas in B6C3F1(1) mice.

The shuttle walk exercise test in idiopathic pulmonary fibrosis

The shuttle walk test (SWT) is a validated, incremental walking test for chronic obstructive pulmonary disease, but not for idiopathic pulmonary fibrosis (IPF). The measurement of maximal oxygen consumption (VO2 max) is considered to be the gold standard measurement of functional capacity. This study examines the relationship between IPF patients' performance on the SWT and VO2 max. Twenty patients were recruited for the study, which consisted of two separate experiments. Firstly, the relationship between SWT performance on a conventional corridor SWT, with that on a programmable treadmill SWT designed to reproduce the corridor SWT was examined (n=10). In the second experiment, the relationship between performance on the treadmill equivalent SWT and VO2 max measurements was studied (n=10). There was a significant correlation between distance walked on the corridor SWT, and that walked on the treadmill equivalent SWT without VO2 max measurements (367 m vs. 410 m) (r=0.91, P=0.0003). There was a significant correlation between distance walked on the treadmill equivalent SWT (277 m), and the directly determined VO2 max (14.87 ml/kg/min) (r=0.74, P=0.01). During both experiments, a significant correlation was also observed between baseline PaO2 and SWT performance, and between DLCO and SWT performance. The shuttle walk test is a simple objective measure of functional capacity in IPF patients, which should facilitate the evaluation of new therapeutic compounds for IPF.

CB1 and CB2 cannabinoid receptors are implicated in inflammatory pain

The cannabinoid agonist, HU210 has been evaluated in vivo in nociceptive and inflammatory pain models in the rat. The ED50 for the anti-nociceptive (increasing mechanical withdrawal threshold) effect was 0.1 mg/kg-1 i.p., and for anti-hypersensitivity and anti-inflammatory activity was 5 g/kg-1 i.p. (in the carrageenan model). The selective CB1 antagonist, AM281 (0.5 microg/kg-1 i.p.) reversed effects of HU210 (10 and 30 microg/kg-1 i.p.) in both nociceptive and inflammatory models of hypersensitivity. The selective CB2 antagonist, SR144528 (1 mg/kg-1 i.p.) antagonised effects of HU210 (30 microg/kg-1 i.p.) in the carrageenan induced inflammatory hypersensitivity. The CB2 agonist, 1-(2,3-Dichlorobenzoyl)-5-methoxy-2-methyl-(2-(morpholin-4-yl)ethyl)-1H-indole (GW405833) inhibited the hypersensitivity and was anti-inflammatory in vivo. These effects were blocked by SR144528. These findings suggest that CB1 receptors are involved in nociceptive pain and that both CB1 and CB2 receptors are involved in inflammatory hypersensitivity. Future studies will investigate effects on identified inflammatory cells within the inflamed tissue to further elucidate the role of cannabinoid receptors.

Evidence of adequacy of the performance of the Pulvinal by measuring through-device peak inspiratory flow rate in severe airways obstruction in adults and children

Pulvinal is a novel DPI designed to deliver inhaled drugs to the airways. Previous in vitro and in vivo data has suggested that the peak inspiratory flow rate (PIFR), measured through Pulvinal, does not depend on the severity of expiratory airflow obstruction and that the lowest PIFR values seem sufficient to deliver an effective bronchodilator dose. To study this further, we have investigated through-Pulvinal PIFR in categories of patients who are likly to generate low inspiratory flow rates. Three different patients' groups were selected (severe asthmatics, n = 52, including elderly) patients with severe chronic obstructive pulmonary disease (COPD, n = 21) and children with asthma (n = 16). This study aimed to measure the through-device PIFR and also to assess whether this correlated with measures of expiratory flow rate. Inspiratory flow measurements were made with a Pulvinal inhaler inserted into the adapted mouthpiece of a pneumotochograph. No significant correlations were seen between through-device PIFR and expiratory volumes or flow rates when expressed as percent predicted normal (forced expiratory volume in 1 sec [FEV1] and peak expiratory flow rate [PEFR]) in any of the three studied populations. A significant correlation was present for FEV1 (when expressed in liters) and through-device PIFR in the adult asthmatic and COPD study groups. In spite of the disease severity in adult populations and the age of children, the lowest generated PIFR values were within the range producing adequate performance of Pulvinal DPI (>20 L/min). We conclude that inspiratory flow rates generated through the Pulvinal inhaler can be adequate in asthma and COPD, including patients at the extremes of severity and age, who may theoretically have a limitation in their inspiratory flow.

Loss of E-cadherin expression in gastric intestinal metaplasia and later stage p53 altered expression in gastric carcinogenesis

Gastric cancers are commonly subdivided into intestinal and diffuse subtypes on a morphologic basis, supported by corollary evidence of differences at the pathogenetic and molecular levels. Chronic atrophic gastritis with intestinal metaplasia is a common precursor lesion for the intestinal type of carcinoma. To identify early molecular changes, in this study we have examined 13 surgical specimens both for the expression of E-cadherin, p53 and beta-catenin by immunohistochemistry and for methylation of the CDH1 promoter (E-cadherin) by bisulfite genomic sequencing of laser capture microdissected samples. Each specimen examined contained areas of normal (nonmetaplastic) gastric mucosa, as well as areas of intestinal metaplasia and/or carcinoma. Reduced or absent E-cadherin and partial to complete methylation of one to multiple CpG sites examined in the CDH1 promoter were observed in all of the metaplasia samples. Thus, the methylation status of the CDH1 promoter and expression of E-cadherin together provide strong evidence that loss of E-cadherin is an early event in intestinal type gastric carcinogenesis. In contrast, expression of p53, assumed to be mutant p53, was generally not detected (except for isolated cells) until the carcinoma stage in tissues from these patients. These results suggest that mutation of p53 is a late event in intestinal type gastric cancer. The level of beta-catenin expression did not appear to change between normal, metaplastic and carcinoma cells of intestinal type, and no nuclear staining was visible in any of the tissues. These results suggest that the Wnt signaling pathway is not upregulated in this type of cancer.

Increased mast cells in the irritable bowel syndrome

Mast cells (MC) release potent mediators which alter enteric nerve and smooth muscle function and may play a role in the pathogenesis of the irritable bowel syndrome (IBS). The aim of this study was to determine if MC were increased in the colon of IBS patients compared to controls. Biopsy specimens were obtained from the caecum, ascending colon, descending colon and rectum of 28 patients: 14 IBS (Rome criteria); seven normal; and seven inflammatory controls. Tissue was stained immunohistochemically using a monoclonal mouse antibody for human mast cell tryptase (AA1). Tissue area occupied by tryptase-positive MC (volume density of mast cells) was quantified by image analysis. The number of plasma cells, lymphocytes, eosinophils, neutrophils and macrophages were each graded semiquantitatively (0-4) in haematoxylin and eosin stained sections. Mast cell volume density was significantly (P < 0.05) higher in IBS (0.91 +/- 0.18; CI 0.79; 1.0) than normal controls (0.55 +/- 0.14; CI 0.40; 0.69) in the caecum but not at other sites. Apart from MC, there was no evidence of increased cellular infiltrate in the IBS group. MC were significantly increased in the caecum of IBS patients compared to controls. The multiple effects of the intestinal mast cell alone, or as a participant of a persistent inflammatory response, may be fundamental to the pathogenesis of IBS.

Review article: the therapeutic potential of 5-HT3 receptor antagonists in the treatment of irritable bowel syndrome

There is evidence from studies, in both animals and humans, that 5-HT3 receptor blockade has potential value in the treatment of irritable bowel syndrome, particularly in those patients with diarrhoea-predominant bowel habits. New findings suggest that 5-HT3 receptors exist on gut afferent neurones and that their activation by locally released 5-HT leads to visceral nociceptive stimulation, in addition to increased neuronally-mediated motor and secretory activity. If this concept is validated, it will provide a rationale for the use of 5-HT3 receptor antagonists in patients with increased gut motility, reduced fluid absorption and low nociceptive thresholds leading to abdominal pain. Alosetron is a highly selective, potent 5-HT3 receptor antagonist which is well absorbed with a long pharmacodynamic half-life. Its ability to provide long-lasting blockade of 5-HT3 receptors throughout the body make it an ideal candidate within its class to evaluate the clinical hypothesis that sustained and ubiquitous 5-HT3 receptor blockade is of value in the treatment of IBS.

A quantitative autoradiographic comparison of binding to glutamate receptor sub-types in hippocampus and forebrain regions of a food-storing and a non-food-storing bird

In two species of birds, food-storing marsh tits, P. palustris, and non-storing blue tits, P. caeruleus, quantitative receptor autoradiography was used to localize NMDA (N-methyl-D-aspartate)-sensitive [3H]glutamate, [3H]MK801, and [3H]AMPA binding sites, in six regions of the forebrain: hippocampus and parahippocampus, hyperstriatum accessorium (vision) and ventrale (sensory integration), neostriatum (auditory), and lobus parolfactorius (basal ganglia). In both species high levels of labelling to both NMDA and AMPA receptors were observed throughout the forebrain. However, a marked difference in receptor labelling was apparent between the two species, with levels of binding to NMDA ion channel sites being significantly lower (20%) in both the hippocampus and parahippocampus, in food storers compared to non-food storers. The levels of binding to other forebrain regions were remarkably similar in the two species. No differences were seen in the binding to AMPA receptors in forebrain regions of either species.

Breath-holding time in normal subjects, snorers, and sleep apnea patients

BACKGROUND

The onset of irregular inspiratory muscle activity has been observed toward the breakpoint of the breath-holding maneuver. We wondered if this was similar to the increased respiratory effort with paradoxical breathing seen during the resolution of an apnea in obstructive sleep apnea syndrome (OSAS).

STUDY OBJECTIVE

To compare the breakpoint of breath holding in normal subjects, OSAS patients, and snorers.

METHODS

Thirty normal subjects, 30 patients with OSAS, and 16 snorers performed serial breath-holding maneuvers at functional residual capacity (FRC) under standardized pretest conditions using the rebreathing method of Read.

RESULTS

Intergroup comparisons were carried out by analysis of variance with post hoc Tukey's Highest Significant Difference tests. Basal end-tidal carbon dioxide (EtCO2) was significantly higher in OSAS than in normal subjects and snorers. Basal breath-holding time (BHT) was shorter in OSAS as compared with that in normal subjects and snorers (p < 0.05). The maximal EtCO2 level attained was higher in OSAS as compared with normal subjects (p < 0.05) and snorers (p = 0.052). The maximal BHT in OSAS was shorter than in normal subjects (p < 0.05) but not in snorers. The slope of BHT/EtCO2 differed significantly in OSAS compared with normal subjects and snorers (p < 0.05). No significant correlation was found between slope BHT/EtCO2 and age or body mass index using multiple regression analysis. The FRC of OSAS patients and snorers were similar (p = 0.792).

CONCLUSION

We conclude that BHT and slope of BHT/EtCO2 are different in OSAS subjects as opposed to those in normal subjects and snorers.

Nasal resistance in obstructive sleep apnea

BACKGROUND

Acute increases in nasal resistance are known to induce upper airway occlusion in predisposed subjects. With the limited efficacy of nasal surgery alone in the treatment of obstructive sleep apnea (OSA), the relevance of chronically increased nasal resistance in the pathophysiologic features of OSA remains undetermined.

METHODS

Seventy-one patients with OSA (apnea+hypopnea index > 15 [AHI]) and 70 antisocial snorers (ASS [AHI < 15]) referred for routine assessment of sleep-disordered breathing had concomitant measurement of combined (CNR) and highest unilateral (HUNR) nasal resistance by anterior rhinomanometry.

RESULTS

Nine individuals (five of 71 in the OSA group and 4 of 70 in the ASS group, 0.5 < p < 0.75) had an abnormally elevated CNR. The HUNR was increased in 21 individuals (11 of 70 in the ASS group and 10 of 71 in the OSA group, 0.25 < p < 0.5). There was no significant difference between CNR in OSA (1.5[0.5]) (mean [SE]) and ASS (1.6 [0.2]) groups. No correlation was found between CNR and the AHI in OSA or in ASS. The Mean HUNR in the OSA group was 5.5 (0.9) (mean [SE]) and in ASS was 5.3(0.6), which were not significantly different (p = 0.89). The HUNR also did not correlate with the AHI in either OSA or ASS.

CONCLUSION

Chronic changes in nasal resistance are not a significant risk factor for the development or severity of OSA.

Neurophysiological and behavioral development in birds: song learning as a model system

The avian song system is a particularly good model for studying the behavioral and physiological aspects of animal development. One seemingly trivial but very important reason for this is that the sound spectrograph enables sounds to be described, measured and analyzed objectively and in detail. Secondly, birdsong is one of the few behaviors which is performed by a separate chain of brain regions and is therefore relatively easy to investigate neurophysiologically. Work on song also provides a clear illustration of the subtle way in which birds are influenced by their internal and external environments during development.