Hyperpolarized (3)He magnetic resonance imaging: comparison with four-dimensional x-ray computed tomography imaging in lung cancer

RATIONALE AND OBJECTIVES

Pulmonary functional imaging using four-dimensional x-ray computed tomographic (4DCT) imaging and hyperpolarized (3)He magnetic resonance imaging (MRI) provides regional lung function estimates in patients with lung cancer in whom pulmonary function measurements are typically dominated by tumor burden. The aim of this study was to evaluate the quantitative spatial relationship between 4DCT and hyperpolarized (3)He MRI ventilation maps.

MATERIALS AND METHODS

Eleven patients with lung cancer provided written informed consent to 4DCT imaging and MRI performed within 11 ± 14 days. Hyperpolarized (3)He MRI was acquired in breath-hold after inhalation from functional residual capacity of 1 L hyperpolarized (3)He, whereas 4DCT imaging was acquired over a single tidal breath of room air. For hyperpolarized (3)He MRI, the percentage ventilated volume was generated using semiautomated segmentation; for 4DCT imaging, pulmonary function maps were generated using the correspondence between identical tissue elements at inspiratory and expiratory phases to generate percentage ventilated volume.

RESULTS

After accounting for differences in image acquisition lung volumes ((3)He MRI: 1.9 ± 0.5 L ipsilateral, 2.3 ± 0.7 L contralateral; 4DCT imaging: 1.2 ± 0.3 L ipsilateral, 1.3 ± 0.4 L contralateral), there was no significant difference in percentage ventilated volume between hyperpolarized (3)He MRI (72 ± 11% ipsilateral, 79 ± 12% contralateral) and 4DCT imaging (74 ± 3% ipsilateral, 75 ± 4% contralateral). Spatial correspondence between 4DCT and (3)He MRI ventilation was evaluated using the Dice similarity coefficient index (ipsilateral, 86 ± 12%; contralateral, 88 ± 12%).

CONCLUSIONS

Despite rather large differences in image acquisition breathing maneuvers, good spatial and significant quantitative agreement was observed for ventilation maps on hyperpolarized (3)He MRI and 4DCT imaging, suggesting that pulmonary regions with good lung function are similar between modalities in this small group of patients with lung cancer.

Proton therapy radiation pneumonitis local dose-response in esophagus cancer patients

PURPOSE

This study quantifies pulmonary radiation toxicity in patients who received proton therapy for esophagus cancer.

MATERIALS/METHODS

We retrospectively studied 100 esophagus cancer patients treated with proton therapy. The linearity of the enhanced FDG uptake vs. proton dose was evaluated using the Akaike Information Criterion (AIC). Pneumonitis symptoms (RP) were assessed using the Common Toxicity Criteria for Adverse Events version 4.0 (CTCAEv4). The interaction of the imaging response with dosimetric parameters and symptoms was evaluated.

RESULTS

The RP scores were: 0 grade 4/5, 7 grade 3, 20 grade 2, 37 grade 1, and 36 grade 0. Each dosimetric parameter was significantly higher for the symptomatic group. The AIC winning models were 30 linear, 52 linear quadratic, and 18 linear logarithmic. There was no significant difference in the linear coefficient between models. The slope of the FDG vs. proton dose response was 0.022 for the symptomatic and 0.012 for the asymptomatic (p=0.014). Combining dosimetric parameters with the slope did not improve the sensitivity or accuracy in identifying symptomatic cases.

CONCLUSIONS

The proton radiation dose response on FDG PET/CT imaging exhibited a predominantly linear dose response on modeling. Symptomatic patients had a higher dose response slope.

Pre-hospital electrocardiography by emergency medical personnel: effects on scene and transport times for chest pain and ST-segment elevation myocardial infarction patients

OBJECTIVES

This study sought to measure the impact of pre-hospital (PH) electrocardiography (ECG) on scene-to-hospital time for patients with chest pain of cardiac origin and those with ST-segment elevation myocardial infarction (STEMI).

BACKGROUND

Pre-hospital ECG decreases door-to balloon (D2B) time for STEMI patients. However, obtaining a PH ECG might prolong scene time. We investigated the impact of obtaining a PH ECG on both scene and transport times for patients with chest pain suspected of cardiac origin.

METHODS

City of San Diego Emergency Medical System runsheets of patients with chest pain from January 2003 to April 2008 were analyzed. The scene times and transport times were compared before (from January 2003 to December 2005) and after (from January 2006 to April 2008) implementation of the PH ECG. Among patients with a PH ECG, median scene times and transport times were compared in patients with and without STEMI.

RESULTS

There were 21,742 patients evaluated for chest pain during the study period. Implementation of PH ECG resulted in minimal increases in median scene time (19 min, 10 s vs. 19 min, 28 s, p = 0.002) and transport time (13 min, 16 s vs. 13 min, 28 s, p = 0.007). However, compared with chest pain patients, in STEMI patients (n = 303), shorter median scene time (17 min, 51 s vs. 19 min, 31 s, p < 0.001), transport time (12 min, 34 s vs. 13 min, 31 s, p = 0.006), and scene-to-hospital time was observed (30 min, 45 s vs. 33 min, 29 s, p < 0.001).

CONCLUSIONS

Obtaining a PH ECG for patients with chest pain minimally prolongs scene and transport times. Further, for STEMI patients, both scene times and transport times are actually reduced leading to a potential reduction in total ischemic time.

Least median of squares filtering of locally optimal point matches for compressible flow image registration

Compressible flow based image registration operates under the assumption that the mass of the imaged material is conserved from one image to the next. Depending on how the mass conservation assumption is modeled, the performance of existing compressible flow methods is limited by factors such as image quality, noise, large magnitude voxel displacements, and computational requirements. The Least Median of Squares Filtered Compressible Flow (LFC) method introduced here is based on a localized, nonlinear least squares, compressible flow model that describes the displacement of a single voxel that lends itself to a simple grid search (block matching) optimization strategy. Spatially inaccurate grid search point matches, corresponding to erroneous local minimizers of the nonlinear compressible flow model, are removed by a novel filtering approach based on least median of squares fitting and the forward search outlier detection method. The spatial accuracy of the method is measured using ten thoracic CT image sets and large samples of expert determined landmarks (available at www.dir-lab.com). The LFC method produces an average error within the intra-observer error on eight of the ten cases, indicating that the method is capable of achieving a high spatial accuracy for thoracic CT registration.

Use of weekly 4DCT-based ventilation maps to quantify changes in lung function for patients undergoing radiation therapy

PURPOSE

A method has been proposed to calculate ventilation maps from four-dimensional computed tomography (4DCT) images. Weekly 4DCT data were acquired throughout the course of radiation therapy for patients with lung cancer. The purpose of our work was to use ventilation maps calculated from weekly 4DCT data to study how ventilation changed throughout radiation therapy.

METHODS

Quantitative maps representing ventilation were generated for six patients. Deformable registration was used to link corresponding lung volume elements between the inhale and exhale phases of the 4DCT dataset. Following spatial registration, corresponding Hounsfield units were input into a density-change-based model for quantifying the local ventilation. The ventilation data for all weeks were registered to the pretreatment ventilation image set. We quantitatively analyzed the data by defining regions of interest (ROIs) according to dose (V(20)) and lung lobe and by tracking the weekly ventilation of each ROI throughout treatment. The slope of the linear fit to the weekly ventilation data was used to evaluate the change in ventilation throughout treatment. A positive slope indicated an increase in ventilation, a negative slope indicated a decrease in ventilation, and a slope of 0 indicated no change. The dose ROI ventilation and slope data were used to study how ventilation changed throughout treatment as a function of dose. The lung lobe ROI ventilation data were used to study the impact of the presence of tumor on pretreatment ventilation. In addition, the lobe ROI data were used to study the impact of tumor reduction on ventilation change throughout treatment.

RESULTS

Using the dose ROI data, we found that three patients had an increase in weekly ventilation as a function of dose (slopes of 1.1, 1.4, and 1.5) and three patients had no change or a slight decrease in ventilation as a function of dose (slopes of 0.3, -0.6, -0.5). Visually, pretreatment ventilation appeared to be lower in the lobes that contained tumor. Pretreatment ventilation was 39% for lobes that contained tumor and 54% for lobes that did not contain tumor. The difference in ventilation between the two groups was statistically significant (p = 0.017). When the weekly lobe ventilation data were qualitatively observed, two distinct patterns emerged. When the tumor volume in a lobe was reduced, ventilation increased in the lobe. When the tumor volume was not reduced, the ventilation distribution did not change. The average slope of the group of lobes that contained tumors that shrank was 1.18, while the average slope of the group that did not contain tumors (or contained tumors that did not shrink) was -0.32. The slopes for the two groups were significantly different (p = 0.014).

CONCLUSIONS

We did not find a consistent pattern of ventilation change as a function of radiation dose. Pretreatment ventilation was significantly lower for lobes that contained tumor, due to occlusion of the central airway. The weekly lobe ventilation data indicated that when tumor volume shrinks, ventilation increases, and when the thoracic anatomy is not visibly changed, ventilation is likely to remain unchanged.

The kinetoplastid chemotherapy revisited: current drugs, recent advances and future perspectives

Leishmaniasis, African sleeping sickness and Chagas disease, caused by the kinetoplastid parasites Leishmania spp, Trypanosoma brucei and Trypanosoma cruzi, respectively, are among the most important parasitic diseases, affecting millions of people and considered to be within the most relevant group of neglected tropical diseases. The main alternative to control such parasitosis is chemotherapy. Nevertheless, the current chemotherapeutic treatments are far from being satisfactory. This review outlines the current understanding of different drugs against leishmaniasis, African sleeping sickness and Chagas disease, their mechanism of action and resistance. Recent approaches in the area of anti-leishmanial and trypanocidal therapies are also enumerated, new modulators from the mode of action, development of new formulations of old drugs, therapeutic switching and "in silico" drug design.

Reliability of the MODS assay decentralisation process in three health regions in Peru

OBJECTIVE

To deliver rapid isoniazid (INH) and rifampicin (RMP) drug susceptibility testing (DST) close to the patient, we designed a decentralisation process for the microscopic observation drug susceptibility (MODS) assay in Peru and evaluated its reliability.

METHODS

After 2 weeks of training, laboratory staff processed ≥ 120 consecutive sputum samples each in three regional laboratories. Samples were processed in parallel with MODS testing at an expert laboratory. Blinded paired results were independently analysed by the Instituto Nacional de Salud (INS) according to pre-determined criteria: concordance for culture, DST against INH and RMP and diagnosis of multidrug-resistant tuberculosis (MDR-TB) ≥ 95%, McNemar's P > 0.05, kappa index (κ) ≥ 0.75 and contamination 1-4%. Sensitivity and specificity for MDR-TB were calculated.

RESULTS

The accreditation process for Callao (126 samples, 79.4% smear-positive), Lima Sur (n = 130, 84%) and Arequipa (n = 126, 80%) took respectively 94, 97 and 173 days. Pre-determined criteria in all regional laboratories were above expected values. The sensitivity and specificity for detecting MDR-TB in regional laboratories were >95%, except for sensitivity in Lima Sur, which was 91.7%. Contamination was 1.0-2.3%. Mean delay to positive MODS results was 9.9-12.9 days.

CONCLUSION

Technology transfer of MODS was reliable, effective and fast, enabling the INS to accredit regional laboratories swiftly.

Effect of bovine lactoferrin addition to milk in yogurt manufacturing

The aim of this work was to study the effect of milk supplementation with lactoferrin of different iron saturation on the manufacturing and characteristics of yogurt. Bovine lactoferrin was added at concentrations of 0.5, 1, and 2 mg/mL in the holo (iron saturated) and apo (without iron) forms. Some physicochemical properties, such as pH, concentration of lactic acid, and texture of supplemented yogurts, were determined throughout the shelf-life period storage (28 d) at 4°C. We also evaluated the stability of lactoferrin in supplemented yogurt throughout the storage time. The supplementation of milk with bovine lactoferrin did not greatly affect the physical properties of the yogurt, though apo-lactoferrin slightly delayed the decrease of pH. This could be attributed to the partial inhibition observed on the growth of Streptococcus thermophilus. The integrity and immunoreactive concentration of lactoferrin, determined by Western blotting and noncompetitive ELISA, respectively, remained constant throughout the shelf life of yogurt.

MODS accreditation process for regional reference laboratories in Peru: validation by GenoType® MTBDRplus

SETTING

Although considerable effort has been put into the development and evaluation of new diagnostics for tuberculosis (TB) and multidrug-resistant TB (MDR-TB), little attention has thus far been paid to the technical aspects of initiating quality-assured routine service use. For implementation of the microscopic-observation drug susceptibility (MODS) methodology in the Peruvian reference laboratory network, a laboratory accreditation process was devised; MODS results from an expert reference laboratory (Universidad Peruana Cayetano Heredia [UPCH]) were used as the standard against which implementing laboratory MODS results were judged to ensure that, prior to use for patient care, implementing laboratories achieved the same high performance with MODS as previously demonstrated in the research laboratory.

OBJECTIVE

To evaluate the validity of MODS-based accreditation and the concordance of MODS drug susceptibility testing (DST) with molecular testing.

DESIGN

Head-to-head comparison of MODS DST results from implementing Peruvian regional reference laboratories and the accrediting expert MODS laboratory (UPCH) with GenoType® MTBDRplus DST.

RESULTS

The concordance of phenotypic MODS rifampicin (RMP) DST with GenoType MTBDRplus was respectively 97.4%, 97.9% and 97.1% for the two implementing regional laboratories and UPCH, and respectively 94.7%, 95.7% and 94.6% for isoniazid (INH) DST.

CONCLUSION

High and consistent levels of MODS/MTBDRplus concordance for INH and RMP DST confirm the validity of the use of rapid methods as reference standards for accreditation.

Ventilation from four-dimensional computed tomography: density versus Jacobian methods

Two calculation methods to produce ventilation images from four-dimensional computed tomography (4DCT) acquired without added contrast have been reported. We reported a method to obtain ventilation images using deformable image registration (DIR) and the underlying CT density information. A second method performs the ventilation image calculation from the DIR result alone, using the Jacobian determinant of the deformation field to estimate the local volume changes resulting from ventilation. For each of these two approaches, there are variations on their implementation. In this study, two implementations of the Jacobian-based methodology are evaluated, as well as a single density change-based model for calculating the physiologic specific ventilation from 4DCT. In clinical practice, (99m)Tc-labeled aerosol single photon emission computed tomography (SPECT) is the standard method used to obtain ventilation images in patients. In this study, the distributions of ventilation obtained from the CT-based ventilation image calculation methods are compared with those obtained from the clinical standard SPECT ventilation imaging. Seven patients with 4DCT imaging and standard (99m)Tc-labeled aerosol SPECT/CT ventilation imaging obtained on the same day as part of a prospective validation study were selected. The results of this work demonstrate the equivalence of the Jacobian-based methodologies for quantifying the specific ventilation on a voxel scale. Additionally, we found that both Jacobian- and density-change-based methods correlate well with global measurements of the resting tidal volume. Finally, correlation with the clinical SPECT was assessed using the Dice similarity coefficient, which showed statistically higher (p-value < 10(-4)) correlation between density-change-based specific ventilation and the clinical reference than did either Jacobian-based implementation.

Diagnostic accuracy of contrast-enhanced magnetic resonance angiography and duplex ultrasound in patients with peripheral vascular disease

INTRODUCTION

Noninvasive techniques such as duplex ultrasound (DU) and contrast-enhanced magnetic resonance angiography (CE-MRA) are valid alternatives in the preoperative evaluation of such patients. Our aim is to assess the diagnostic accuracy of CE-MRA and DU in patients with peripheral arterial disease (PAD).

METHODS

Forty consecutive patients underwent DU, hybrid CE-MRA, and digital subtraction angiography (DSA). Magnetic resonance angiography and DSA images were evaluated independently and in a blinded fashion. Every segment was graded as normal, stenosed less than 50%, stenosed more than 50%, or occluded.

RESULTS

There were 1720 segments for analysis. Duplex ultrasound depicting stenosis >50% demonstrated a sensitivity (S) 81.4%, specificity (E) 99%, positive predictive value (PPV) 96.2%, and negative predictive value (NPV) 94.8%. Occlusions showed S 90%, E 97%, PPV 98.1%, and NPV 88.4%. Magnetic resonance angiography depicting stenosis >50% demonstrated a S 91%, E 99%, PPV 96.7%, and NPV 97.6%. Occlusions showed S 95.4%, E 98%, PPV 98.4%, and NPV 94.7%.

CONCLUSION

Combined CE-MRA and DU is the first diagnostic approach in the preoperative assessment of PAD, leading to the use of DSA for selected cases.

Implementation and evaluation of various demons deformable image registration algorithms on a GPU

Online adaptive radiation therapy (ART) promises the ability to deliver an optimal treatment in response to daily patient anatomic variation. A major technical barrier for the clinical implementation of online ART is the requirement of rapid image segmentation. Deformable image registration (DIR) has been used as an automated segmentation method to transfer tumor/organ contours from the planning image to daily images. However, the current computational time of DIR is insufficient for online ART. In this work, this issue is addressed by using computer graphics processing units (GPUs). A gray-scale-based DIR algorithm called demons and five of its variants were implemented on GPUs using the compute unified device architecture (CUDA) programming environment. The spatial accuracy of these algorithms was evaluated over five sets of pulmonary 4D CT images with an average size of 256 x 256 x 100 and more than 1100 expert-determined landmark point pairs each. For all the testing scenarios presented in this paper, the GPU-based DIR computation required around 7 to 11 s to yield an average 3D error ranging from 1.5 to 1.8 mm. It is interesting to find out that the original passive force demons algorithms outperform subsequently proposed variants based on the combination of accuracy, efficiency and ease of implementation.

Four-dimensional deformable image registration using trajectory modeling

A four-dimensional deformable image registration (4D DIR) algorithm, referred to as 4D local trajectory modeling (4DLTM), is presented and applied to thoracic 4D computed tomography (4DCT) image sets. The theoretical framework on which this algorithm is built exploits the incremental continuity present in 4DCT component images to calculate a dense set of parameterized voxel trajectories through space as functions of time. The spatial accuracy of the 4DLTM algorithm is compared with an alternative registration approach in which component phase to phase (CPP) DIR is utilized to determine the full displacement between maximum inhale and exhale images. A publically available DIR reference database (http://www.dir-lab.com) is utilized for the spatial accuracy assessment. The database consists of ten 4DCT image sets and corresponding manually identified landmark points between the maximum phases. A subset of points are propagated through the expiratory 4DCT component images. Cubic polynomials were found to provide sufficient flexibility and spatial accuracy for describing the point trajectories through the expiratory phases. The resulting average spatial error between the maximum phases was 1.25 mm for the 4DLTM and 1.44 mm for the CPP. The 4DLTM method captures the long-range motion between 4DCT extremes with high spatial accuracy.