Iso-uncertainty control in an experimental fluoroscopy system

PURPOSE

X-ray fluoroscopy remains an important imaging modality in a number of image-guided procedures due to its real-time nature and excellent spatial detail. However, the radiation dose delivered raises concerns about its use particularly in lengthy treatment procedures (>0.5 h). The authors have previously presented an algorithm that employs feedback of geometric uncertainty to control dose while maintaining a desired targeting uncertainty during fluoroscopic tracking of fiducials. The method was tested using simulations of motion against controlled noise fields. In this paper, the authors embody the previously reported method in a physical prototype and present changes to the controller required to function in a practical setting.

METHODS

The metric for feedback used in this study is based on the trace of the covariance of the state of the system, tr(C). The state is defined here as the 2D location of a fiducial on a plane parallel to the detector. A relationship between this metric and the tube current is first developed empirically. This relationship is extended to create a manifold that incorporates a latent variable representing the estimated background attenuation. The manifold is then used within the controller to dynamically adjust the tube current and maintain a specified targeting uncertainty. To evaluate the performance of the proposed method, an acrylic sphere (1.6 mm in diameter) was tracked at tube currents ranging from 0.5 to 0.9 mA (0.033 s) at a fixed energy of 80 kVp. The images were acquired on a Varian Paxscan 4030A (2048 × 1536 pixels, ∼ 100 cm source-to-axis distance, ∼ 160 cm source-to-detector distance). The sphere was tracked using a particle filter under two background conditions: (1) uniform sheets of acrylic and (2) an acrylic wedge. The measured tr(C) was used in conjunction with a learned manifold to modulate the tube current in order to maintain a specified uncertainty as the sphere traversed regions of varying thickness corresponding to the acrylic sheets in the background.

RESULTS

With feedback engaged, the tracking error was found to correlate well with the specified targeting uncertainty. Tracking of the fiducial was found to be robust to changes in the attenuation presented by the varying background conditions. For a desired uncertainty of 5.0 mm, comparison of the feedback framework with a comparable system employing fixed exposure demonstrated dose savings of 29%.

CONCLUSIONS

This work presents a relation between a state descriptor, tr(C), the x-ray tube current used, and an estimate of the background attenuation. This relation is leveraged to modulate the tube current in order to maintain a desired geometric uncertainty during fluoroscopy. The authors' work demonstrates the use of the method in a real x-ray fluoroscopy system with physical motion against varying backgrounds. The method offers potential savings in imaging dose to patients and staff while maintaining tracking uncertainty during fluoroscopy-guided treatment procedures.

Histo-pathological Features of Genital Tract Malignancies as Seen in a Tertiary Health Center in North-Western Nigeria: A 10-year Review

Background:

The pattern of gynecological malignancies varies among nations and even within health institution in the same country. Understanding the histo-pathological pattern of these malignancies will help in the management of the patient.

Aim:

The aim of the following study is to establish the frequency, histo-pathological features, and distribution of genital tract malignancies as seen in a tertiary health institution in North - western Nigeria.

Materials and Methods:

A retrospective analysis of data from ward admissions and discharge records, surgical biopsy materials from the theater and the histopathology laboratory results of slides. The study was carried out at the Usmanu Dan-Fodiyo University Teaching Hospital Sokoto, Nigeria. Data were entered into a study proforma and analysis was through SPSS version 15 (Chicago IL) for windows. The results were expressed in simple percentages, tables and charts.

Results:

During the study period (2000-2009), there were 404 cases of gynecological malignancies recorded in the hospital. Cervical cancer was the most common gynecological malignancy 274/404 (69%), followed by choriocarcinoma 52/404 (13.1%), ovarian cancer 46/404 (11.4%) while the least common was vaginal cancer 1/404 (0.3%). The mean age of the cancers was 54 years (28.3). The mean age of incidence of all ovarian cancers was 52.5 years (SD ± 16.2). Epithelial ovarian tumors had a mean age incidence of 67 (12) years, while that of ovarian germ cell tumors was 18.5 (8) years. The incidence of cervical cancer showed a rising trend. Moderately differentiated squamous cell carcinoma was the most common histological variant of cervical carcinoma 170/252 (67.5%). Among the ovarian tumors, epithelial cancers were the most common 38/46 (82.6%), and were followed by the germ cell tumors 5/46 (10.9%). Dysgerminoma was the predominant ovarian germ cell tumour 4/5 (80%). There were 50 deaths from these cancers in our hospital.

Conclusion:

Cervical cancer is the most common gynecological malignancy in our centerand it was followed by Choriocarcinoma. Efforts to reduce the cancer burden should focus on heath education of the masses, national organized screening especially for cervical cancer and establishing regional centers for monitoring and evaluation of these programs.

Measurement of a reaction-diffusion crossover in exciton-exciton recombination inside carbon nanotubes using femtosecond optical absorption

Exciton-exciton recombination in isolated semiconducting single-walled carbon nanotubes was studied using femtosecond transient absorption. Under sufficient excitation to saturate the optical absorption, we observed an abrupt transition between reaction- and diffusion-limited kinetics, arising from reactions between incoherent localized excitons with a finite probability of ~0.2 per encounter. This represents the first experimental observation of a crossover between classical and critical kinetics in a 1D coalescing random walk, which is a paradigm for the study of nonequilibrium systems.

Composition and Antimicrobial Activity of the Essential Oil from Leaves of Curcuma longa L. Kasur Variety

The essential oil from the leaves of Curcuma longa L. Kasur variety grown in Pakistan was extracted by hydro-distillation. Chemical constituents of the essential oil were identified by gas chromatography/mass spectrometry. The chromatographic analysis of oil showed 25 constituents, out of which nine chemical constituents were identified. The eucalyptol (10.27%) was the major component of the essential oil. α-pinene (1.50%), β-phellandrene (2.49%), β-pinene (3.57%), limonene (2.73%), 1,3,8-p-menthatriene (1.76%), ascaridole epoxide (1.452%), 2-methylisoborneol (2.92%), 5-isopropyl-6-methyl-hepta-3, dien-2-ol (2.07%) were also present in considerable quantity. The antimicrobial properties of leaves of Curcuma longa were tested by disc diffusion method against various human pathogens, including eight fungal and five bacterial strains. Essential oil showed maximum resistance against Fusarium miniformes MAY 3629 followed by Bacillus subtilis ATCC 6633 whereas; it exhibited least resistance against Fusarium oxysporium ATCC 48122. The results of the antimicrobial assay revealed that essential oil showed significant inhibitory activity against the tested organisms.

Azacitidine fails to eradicate leukemic stem/progenitor cell populations in patients with acute myeloid leukemia and myelodysplasia

Epigenetic therapies demonstrate significant clinical activity in acute myeloid leukemia (AML) and myelodysplasia (MDS) and constitute an important new class of therapeutic agents. However hematological responses are not durable and disease relapse appears inevitable. Experimentally, leukemic stem/progenitor cells (LSC) propagate disease in animal models of AML and it has been postulated that their relative chemo-resistance contributes to disease relapse. We serially measured LSC numbers in patients with high-risk AML and MDS treated with 5'-azacitidine and sodium valproate (VAL-AZA). Fifteen out of seventy-nine patients achieved a complete remission (CR) or complete remission with incomplete blood count recovery (CRi) with VAL-AZA therapy. There was no significant reduction in the size of the LSC-containing population in non-responders. While the LSC-containing population was substantially reduced in all patients achieving a CR/CRi it was never eradicated and expansion of this population antedated morphological relapse. Similar studies were performed in seven patients with newly diagnosed AML treated with induction chemotherapy. Eradication of the LSC-containing population was observed in three patients all of whom achieved a durable CR in contrast to patients with resistant disease where LSC persistence was observed. LSC quantitation provides a novel biomarker of disease response and relapse in patients with AML treated with epigenetic therapies. New drugs that target this cellular population in vivo are required.

Minimizing dose during fluoroscopic tracking through geometric performance feedback

PURPOSE

There is a growing concern regarding the dose delivered during x-ray fluoroscopy guided procedures, particularly in interventional cardiology and neuroradiology, and in real-time tumor tracking radiotherapy and radiosurgery. Many of these procedures involve long treatment times, and as such, there is cause for concern regarding the dose delivered and the associated radiation related risks. An insufficient dose, however, may convey less geometric information, which may lead to inaccuracy and imprecision in intervention placement. The purpose of this study is to investigate a method for achieving the required tracking uncertainty for a given interventional procedure using minimal dose.

METHODS

A simple model is used to demonstrate that a relationship exists between imaging dose and tracking uncertainty. A feedback framework is introduced that exploits this relationship to modulate the tube current (and hence the dose) in order to maintain the required uncertainty for a given interventional procedure. This framework is evaluated in the context of a fiducial tracking problem associated with image-guided radiotherapy in the lung. A particle filter algorithm is used to robustly track the fiducial as it traverses through regions of high and low quantum noise. Published motion models are incorporated in a tracking test suite to evaluate the dose-localization performance trade-offs.

RESULTS

It is shown that using this framework, the entrance surface exposure can be reduced by up to 28.6% when feedback is employed to operate at a geometric tracking uncertainty of 0.3 mm.

CONCLUSIONS

The analysis reveals a potentially powerful technique for dynamic optimization of fluoroscopic imaging parameters to control the applied dose by exploiting the trade-off between tracking uncertainty and x-ray exposure per frame.

Children with significant cervical lymphadenopathy: clinicopathological analysis and role of fine-needle aspiration in Indian setup

OBJECTIVE

To study the clinicopathological profile of children from India with cervical lymphadenopathy and the role of fine-needle aspiration cytology with special emphasis on tuberculosis as a cause.

METHODS

A total of 89 children in the age group of 10 months to 12 years, presenting to our hospital from April 2004 to March 2005, were included. All the patients underwent thorough clinical and investigational assessment vis-à-vis cervical lymphadenopathy. Outcome measurements included clinical status and ability of conventional tests to categorize different types of lymphadenopathy and their utility in diagnosing tubercular lymphadenitis. Interobserver variability was analyzed measuring kappa test and was found to be in agreement.

RESULTS

Reactive hyperplasia was the most common type of lymphadenitis, followed by granulomatous involvement. Unilateral posterior triangle lymph nodes were the most commonly affected in the tubercular cervical lymphadenopathy group. Fine-needle aspiration followed by Ziehl-Neelsen staining, histopathology and culture in combination were able to perform the diagnosis in 85.7% of cases affected with tubercular etiology.

CONCLUSIONS

Fine-needle aspiration is a valuable diagnostic tool in the management of children with the clinical presentation of enlarged cervical lymph nodes. The technique reduces the need for more invasive and costly procedures, especially in a Third World country. Culture and histopathology, however, should be considered in cases where repeated fine-needle aspiration cytology is non-diagnostic.

Platelet activation, upregulation of CD11b/ CD18 expression on leukocytes and increase in circulating leukocyte-platelet aggregates in Indian women chronically exposed to biomass smoke

The majority of households in rural India still rely on unprocessed solid biomass for domestic energy. The aim of this study was to investigate whether chronic exposure to biomass smoke causes activation of leukocytes and the formation of leukocyte-platelet aggregates. We conducted flow cytometric analysis of beta2 Mac-1 integrin (CD11b/CD18) expression on polymorphonuclear leukocytes (PMN) and monocytes, and P-selectin (CD62P) expression on the platelets of 165 women from eastern India, who cook solely with wood, dung and agricultural wastes, and 155 age- and socio-economic condition-matched control subjects, who used relatively cleaner fuel, liquefied petroleum gas (LPG). Leukocyte-platelet aggregates were defined as CD11b-positive PMN and monocytes co-expressing platelet-specific markers CD41 or CD62P. A significant increase in leukocyte-platelet aggregates was found in women who used biomass as cooking fuel. In addition, they showed increased surface expression of CD11b/CD18 in circulating PMN and monocytes and CD62P expression on platelets. The mean fluorescence intensity (MFI) of CD11b on the surface of circulating monocytes and PMN of biomass users increased by 50 and 68%, respectively. Similarly, a 62 and 48% increase in MFI was observed in CD18 expression on the surface of these cells in biomass users. The results show that chronic biomass smoke exposure activates circulating platelets, PMN and monocytes, and increases the number of leukocyte-platelet aggregates, which are considered a risk factor for thrombosis.

Tuberculosis among healthcare workers in a tertiary-care hospital in South India

It is possible that tuberculosis is transmitted from patients to healthcare workers (HCWs). However, there are few data on this from developing countries. The object of this study was to document the incidence of tuberculosis among HCWs in the Christian Medical College (CMC), Vellore, India during a 10-year period (January 1992-December 2001). Data were collected from records maintained in the staff and students health services of CMC. A total of 125 cases were diagnosed during the period of study. The overall incidence of sputum positive cases was similar to that observed in the general population, during most years. However, it appears that focal outbreaks occur with transmission between HCWs. The chance of developing extra-pulmonary tuberculosis was higher in HCWs compared with the general population.

Comparison of protein carbonyl and antioxidant levels in brain tissue from intracerebral haemorrhage and control cases

BACKGROUND

In an attempt to develop a clearer understanding of the pathological mechanisms underlying intracerebral haemorrhage (ICH), the objective of this investigation was to obtain evidence for free radical-induced oxidative damage in brain tissue following intracerebral haemorrhage.

METHODS

Brain cortex samples were obtained from the ischaemic penumbra (overlying the haematoma) from 10 patients with spontaneous ICH and from six control cases (normal tissue obtained during tumour removal or aneurysm repair). Following extraction via homogenization and subsequent derivatization with dinitrophenylhydrazine (DNPH), tissue samples were analysed for the presence of protein carbonyl moieties (a hallmark of tissue protein oxidation). This procedure involved SDS-polyacrylamide gel electrophoresis and Western immunoblotting using a commercially available primary monoclonal antibody to DNPH, with final visualization of oxidized protein bands via enhanced chemiluminescence.

RESULTS

Samples from ICH cases showed a number (10-15) of well-defined bands of medium to strong staining intensity (not present in nonderivatized samples), corresponding to proteins of molecular mass 25-200 kDa, indicating the presence of oxidatively damaged proteins in these samples. However, tissue samples from control cases also showed the presence of oxidized protein bands, with fractionation patterns for individual ICH or control samples being qualitatively and quantitatively similar. In addition, there was no significant difference in the levels of the following antioxidants (as additional indirect markers of free radical activity) in ICH or control brain tissue: glutathione, glutathione peroxidase, glutathione reductase, catalase, superoxide dismutase, and total antioxidant status.

CONCLUSIONS

It is concluded from the above data that (i) evidence for free radical involvement in ICH based on protein carbonyl analysis should be interpreted with caution, since normal brain tissue contains a surprisingly high proportion of oxidized proteins; (ii) since there is no evidence for increased protein oxidative damage or decreased tissue antioxidant levels in ICH, therapeutic strategies aimed at salvage of potentially viable tissue would not benefit from inclusion of protein protecting antioxidants.

Continuous monitoring of ICP and CPP following ICH and its relationship to clinical, radiological and surgical parameters

Sixty-two patients with a spontaneous supratentorial haemorrhage had continuous Intracranial Pressure (ICP) and Cerebral Perfusion Pressure (CPP) monitoring. In addition to the recordings of physiological data their past medical history, presenting neurological state, Computed Tomograph (CT) findings, daily Glasgow Coma Score (GCS) and outcome were noted. The mean age was 57.6 years (sd 13.3). Onset of recording, after ictus was at a mean of 32.6 hours (sd 26.0). Average length of recording was 62.0 hours (sd 39.8). Thirty-one patients had evacuation of haematoma, 6 insertion of External Ventricular Drain (EVD). Preoperative measures of ICP were significantly related to delayed neurological deterioration, death within three days and Glasgow Outcome Scale (GOS) at neurosurgical discharge. No such relationships existed with preoperative measures of CPP and neither ICP nor CPP was related to outcome at 6 months. Post-operative measures of both ICP and CPP demonstrated a significant relationship with death within three days of ictus and GOS at neurosurgical discharge. Again no relationship existed with these parameters and outcome at six months. Surgical evacuation of haematoma acted to significantly reduce ICP and improve CPP. Given that these factors seem to be related to deterioration, death and early outcome, it would seem that surgery could play a role in reducing mortality and improving outcome following Intra cerebral Haemorrhage (ICH).