Optical Computed Tomography Research Articles

Stray light in cone beam optical computed tomography: III. Evaluation of a redesigned large-volume commercial scanner based on a convergent light source

Optical cone beam computed tomography (CT), using a digital camera to acquire 2D projection images, provides a fast, mechanically simple method for 3D radiation dosimetry. However, original cone beam designs had poor accuracy as a result of considerable scatter/stray light reaching the camera. Previously, our group presented a redesigned convergent light source for optical cone beam CT that considerably reduced stray light contribution and improved accuracy (Dekker et al 2016 Phys. Med. Biol. 61 2910). Here, we performed an evaluation of a newly updated commercial optical cone beam CT scanner (VistaTM, ModusQA, London, Canada) based on that design. Two different light source configurations were examined: the manufacturer’s default configuration which uses a 10 cm wide, 5 cm high diffuser light source, and a smaller, 1.5 cm diameter diffuser light source that more closely aligns with our previously described design. We imaged large volume (15 cm diameter cylinders) absorbing and scattering solution phantoms as well as a 1.25 cm diameter absorber placed within 15 cm diameter gel-like scattering phantom. Optical CT reconstructions were compared against narrow-beam measurements of attenuation made by placing an aperture in the optical CT system. Our results show that considerable stray light is present when using the manufacturer’s default configuration, as cupping artifacts and large (⩾10%) discrepancies between optical CT and narrow-beam attenuation measurements occur when imaging scattering phantoms. However, when imaging is performed using the 1.5 cm diameter source, optical CT measurements agree with narrow-beam measurements within ∼3% for both absorbing and scattering objects, as well as the small absorber in a scattering medium. Using this light source will require higher optical quality vessels than are currently provided by the manufacturer.

Effect of Gold Nanoparticles on Dose Enhancement of 6 MV X-ray in MAGIC_f Polymer Gel Dosimeter

Background:Currently, the potential application of gold nanoparticles (AuNPs) to increase the efficiency of radiation therapy has been widely investigated. However, lack of an appropriate method to estimate the dose distribution in a nanoparticle-laden tissue limits the applicability of nanoparticles in radiotherapy clinics. Polymer gel dosimetry provides an accurate and precise system that facilitates the measurement of dose distribution in full three dimensions.Objective: In this study, the effect of radiation dose enhancement of AuNPs was assessed through gel dosimetry analysis.Material and Methods: For this purpose, AuNPs were integrated in MAGIC_f polymer gel dosimeter and irradiated by 6 Mv X-ray beam. The irradiated gel was then evaluated through two modalities of magnetic resonance imaging (MRI) and optical computed tomography (OCT).Result: MRI and OCT scanning of MAGIC_f gels containing 0.1 mM AuNPs demonstrated dose enhancements of 7.8% and 6.8%, respectively.Conclusion: Polymer gel dosimetry has the potential to provide a new platform for the investigation and optimization of the applicability of nanoparticles in radiation therapy.

The impact of tissue characterization for in-stent restenosis with optical coherence tomography during excimer laser coronary angioplasty

We aimed to evaluate the impact of tissue characterization for in-stent restenosis (ISR) with optical computed tomography (OCT) during excimer laser coronary angioplasty (ELCA) in the drug-eluting stent (DES) era. The effect of ELCA for ISR according to differences in tissue characteristics is unclear. Fifty-three ISR lesions (7 bare metal stents and 46 drug-eluting stents) were treated with an ELCA catheter. After ELCA, balloon dilatation with either the scoring or non-compliant balloons was conducted. The procedure was completed by applying a drug-coated balloon. Tissue characterization and lumen measurement with OCT were performed thrice: (1) before percutaneous coronary intervention (PCI), (2) after ELCA, and (3) and after the procedure. Lesions were categorized into the homogenous, layered, and mixed groups. Follow-up angiograms were conducted 6–12 months after PCI. No significant differences in minimal lumen area (MLA) were observed before PCI. A significant difference was observed in MLA after ELCA among the three groups (homogeneous group: 1.75 ± 0.84 mm2, layered group: 1.72 ± 0.45 mm2, mixed group: 2.24 ± 0.70 mm2, P = 0.048). Final MLA was larger in the mixed group than in the homogeneous group (P = 0.028). No significant difference was observed in binary restenosis in the follow-up angiogram (homogeneous group 55.5%, layered group 33.3%, mixed group 33.3%; P = 0.311) and the target lesion revascularization rate (homogeneous 30.0%, layered 23.8%, mixed 25.0%; P = 0.923). Tissue characterization by OCT may predict the efficacy of ELCA and balloon angioplasty for ISR during the acute phase.

Development of a CMOS-based optical computed tomography system (CMOS-OCT) for 3D radiotherapy dosimetry

Optical Computed Tomography (OCT) was developed as a 3D imaging system for measuring radiotherapy dose delivered to radiochromic dosimeters. The imaging system reconstructs dose distributions delivered to a radiochromic dosimeter such as PRESAGE that changes its colour when irradiated. Current optical CT systems in the market are based on CCD image sensor and have slow imaging speed. The study exploited recent advances in CMOS image sensor (CIS) technology to improve the imaging speed of the OCT system. The study characterised the components in the in-house developed CMOS-based Optical CT (CMOS-OCT) imaging system and investigates the feasibility of the system for imaging 3D radiochromic dosimeters. A green dye solution of various concentration was used to mimic colour variation in a PRESAGE radiochromic dosimeter from its response to radiation dose. The solution was filled in a plastic cylinder to study the linearity and uniformity of the system. A rotary stage was constructed using a stepper motor to hold and rotate the dosimeter between the CIS and a large area LED. The components of the imaging system were integrated and controlled using LabVIEW (National Instrument, Austin, TX). A graphical user interface (GUI) was also developed to acquire projection images of the dosimeter. The measured field of view (FOV) of the CIS is 125 mm by 90 mm that can cover the whole PRESAGE dosimeter. A projection image is captured at every 1.8 degree rotation of the dosimeter, at every second, that amounted to 200 projection images for a 360 degree rotation. Current limitation of the imaging speed is the rotation speed of the motor of 1.8 degree per second which can be improved with upgrading the stepper motor. At an imaging speed only limited by the maximum sensor frame rate of 28.5 fps, the scanning time will be reduced to 7 s compared to 200 s. The results show that the system is capable of capturing the projection images of a 3D translucent object with good linearity and uniformity. Further experiments will be carried out to optimise the development of the system to reconstruct dose distributions in 3D from a PRESAGE dosimeter.

Fixed, object-specific intensity compensation for cone beam optical CT radiation dosimetry

Optical cone beam computed tomography (CT) scanning of radiochromic gel dosimeters, using a CCD camera and a low stray light convergent source, provides fast, truly 3D radiation dosimetry with high accuracy. However, a key limiting factor in radiochromic gel dosimetry at large (⩾10 cm diameter) volumes is the initial attenuation of the dosimeters. It is not unusual to observe a 5–10× difference in signal intensity through the dosimeter center versus through the surrounding medium in pre-irradiation images. Thus, all dosimetric information in a typical experiment is measured within the lower 10%–20% of the camera sensor’s range, and re-use of gels is often not possible due to a lack of transmission.To counteract this, in this note we describe a simple method to create source compensators by printing on transparent films. This technique, which is easily implemented and inexpensive, is an optical analogue to the bowtie filter in x-ray CT. We present transmission images and solution phantom reconstructions to demonstrate that (1) placing compensators beyond the focal zone of the imaging lens prevents high spatial frequency features of the printed films from generating reconstruction artifacts, and (2) object-specific compensation considerably reduces the range of intensities measured in projection images. This will improve the measurable dose range in optical CT dosimetry, and will enable imaging of larger gel volumes (∼15 cm diameter). Additionally, it should enable re-use of dosimeters by printing a new compensator for a second experiment.

Recent advances in Optical Computed Tomography (OCT) imaging system for three dimensional (3D) radiotherapy dosimetry

Radiotherapy delivery techniques for cancer treatment are becoming more complex and highly focused, to enable accurate radiation dose delivery to the cancerous tissue and minimum dose to the healthy tissue adjacent to tumour. Instrument to verify the complex dose delivery in radiotherapy such as optical computed tomography (OCT) measures the dose from a three-dimensional (3D) radiochromic dosimeter to ensure the accuracy of the radiotherapy beam delivery to the patient. OCT measures the optical density in radiochromic material that changes predictably upon exposure to radiotherapy beams. OCT systems have been developed using a photodiode and charged coupled device (CCD) as the detector. The existing OCT imaging systems have limitation in terms of the accuracy and the speed of the measurement. Advances in on-pixel intelligence CMOS image sensor (CIS) will be exploited in this work to replace current detector in OCT imaging systems. CIS is capable of on-pixel signal processing at a very fast imaging speed (over several hundred images per second) that will allow improvement in the 3D measurement of the optical density. The paper will review 3D radiochromic dosimeters and OCT systems developed and discuss how CMOS based OCT imaging will provide accurate and fast optical density measurements in 3D. The paper will also discuss the configuration of the CMOS based OCT developed in this work and how it may improve the existing OCT system.

Dual-modal photoacoustic/CT imaging system

Photoacoustic (PA) tomography (PAT) breaks the barrier for high-resolution optical imaging in a strong light-scattering medium, having a great potential for both clinical implementation and small animal studies. However, many organs and tissues lack enough PA contrast or even hinder the propagation of PA waves. Therefore, it is challenging to interpret pure PAT images, especially three-dimensional (3D) PA images for deep tissues, without enough structural information. To overcome this limitation, in this study, we integrated PAT with X-ray computed tomography (CT) in a standalone system. PAT provides optical contrast and CT gives anatomical information. We performed agar, tissue phantom, and animal studies, and the results demonstrated that PAT/CT imaging systems can provide accurate spatial registration of important complementary contrasts.

On the use of a novel Ferrous Xylenol-orange gelatin dosimeter for HDR brachytherapy commissioning and quality assurance testing

PurposeTo evaluate a commercially available Ferrous-Xylenol Orange-Gel (FXG) dosimeter (TrueView™) coupled with Optical-Computed Tomography (OCT) read out, for 3D dose verification in an Ir-192 superficial brachytherapy application. MethodsTwo identical polyethylene containers filled with gel from the same batch were used. One was irradiated with an 18 MeV electron field to examine the dose-response linearity and obtain a calibration curve. A flap surface applicator was attached to the other to simulate treatment of a skin lesion. The dose distribution in the experimental set up was calculated with the TG-43 and the model based dose calculation (MBCA) algorithms of a commercial treatment planning system (TPS), as well as Monte Carlo (MC) simulation using the MCNP code. Measured and calculated dose distributions were spatially registered and compared. ResultsApart from a region close to the container’s neck, where gel measurements exhibited an over-response relative to MC calculations (probably due to stray light perturbation), an excellent agreement was observed between measurements and simulations. More than 97% of points within the 10% isodose line (80 cGy) met the gamma index criteria established from uncertainty analysis (5%/2 mm). The corresponding passing rates for the comparison of experiment to calculations using the TG-43 and MBDCA options of the TPS were 57% and 92%, respectively. ConclusionTrueView™ is suitable for the quality assurance of demanding radiotherapy applications. Experimental results of this work confirm the advantage of the studied MBDCA over TG-43, expected from the improved account of scatter radiation in the treatment geometry.

Dosimetric characterisation of anthropomorphic PRESAGE® dosimeter and EBT2 film for partial breast radiotherapy

AbstractPurposeWhole-breast external beam radiotherapy results in significant reduction in the risk for breast cancer-related death, but this may be offset by an increase in deaths from other causes and toxicity to surrounding organs. Partial breast irradiation techniques are approaches that treat only the lumpectomy area rather than the whole breast. Quality assurance in the radiation therapy treatment planning process is essential to ensure accurate dose delivery to the patient. For this purpose, this article compares the results from an anthropomorphic PRESAGE® dosimeter, radiation treatment planning system and from the GAFCHROMIC® EBT2 film.Materials and methodsA breast dosimeter was created and a three-field partial plan was generated in the Pinnacle3 treatment planning system. Dose distribution comparisons were made between Pinnacle3 treatment planning system, GAFCHROMIC® EBT2 film and PRESAGE® dosimeter. Dose–volume histograms (DVHs), gamma maps and line profiles were used to evaluate the comparison.ResultsDVHs of gross tumour volume, clinical tumour volume and planning tumour volume for the PRESAGE® dosimeter and Pinnacle3 treatment planning system shows that both measured and calculated statistics were in agreement, with a value of 97.8% of the prescribed dose. Gamma map comparisons showed that all three distributions passed 95% at the ±3%/±3 mm criteria. Comparisons of isodose line distribution between the PRESAGE® dosimeter, EBT2 film and planning system demonstrated agreement, with an average difference of 1.5%.ConclusionsThis work demonstrated the feasibility of PRESAGE® to function as an anthropomorphic phantom and laid the foundation for research studies in PRESAGE®/optical-computed tomography three-dimensional dosimetry with the most complex anthropomorphic phantoms.

Mussel-Inspired Polydopamine-Coated Lanthanide Nanoparticles for NIR-II/CT Dual Imaging and Photothermal Therapy.

Nanomedicine has attracted substantial attention for the accurate diagnosis or treatment of carcinoma in recent years. Nd3+-doped lanthanide nanophosphor-based near-infrared-II (NIR-II) optical imaging is widely used for deep penetration tissue imaging while X-ray computed tomography (CT) is well-suited for in vivo imaging. Polymer-coated lanthanide nanophosphors are increasingly used in both diagnostics and therapies for tumor in vivo. However, the biocompatibility of nanocomposites and the efficiency of tumor ablation should be taken into consideration when constructing a nanotheranostic probe. In this article, we have fabricated polydopamine (PDA)-coated NaYF4:Nd3+@NaLuF4 nanocomposites using the reverse microemulsion approach. The thickness of the PDA shell can be precisely modulated from ∼1.5 to ∼18 nm, endowing the obtained NaYF4:Nd3+@NaLuF4@PDA with an excellent colloidal stability and considerable biocompatibility. The photothermal conversion efficiency of the resultant nanocomposites was optimized and maximized by the increase of the PDA shell thickness. Because of the remarkable photothermal conversion efficiency, the mice xenograft tumors were completely eradicated after NIR irradiation. Given the considerable photoluminescence and X-ray attenuation efficiency, the performance of NaYF4:Nd3+@NaLuF4@PDA for NIR-II optical imaging and X-ray CT dual imaging of the tumor in vivo was evaluated. All of the results above highlight the great potential of PDA-based NaYF4:Nd3+@NaLuF4 nanocomposites as a novel multifunctional nanotheranostic agent.

Application of negative molds technology based on three-dimensional printing in digital maxillofacial prostheses

Objective: To explore a digital negative molds technique based on three-dimensional (3D) printing to assist in the manufacture of maxillofacial prostheses, and to improve the deficiency of the current clinical treatment. Methods: Seventeen patients with maxillofacial defects (including nasal defects, orbital defects, cheek defects, auricle defect) were scanned by means of facial optical scanning and computer tomography (CT). The 3D models were then reconstructed and global registration was made to merge the reconstructed models into a new digital model for 3D design. The 3D design of the prostheses was implemented in software. The mechanical connection structure was designed by forward engineering technology for 3 patients with intra-oral defects in maxilla who needed to make removable partial dentures, so that the silicone prostheses and removable partial denture could be combined. The removable partial dentures were made by conventional method and connected with the prostheses. According to the 3D data of the prostheses, the digital negative molds were designed, and the 3D printing technology was used to finish the processing of the resin molds. Silicone for prostheses were filled and cured in the resin molds to fabricate the clinical restorations for the patients. The margin adaptation and retention of the prostheses was detected. Results: Twenty patients with varying degrees of maxillofacial defects were rehabilitated using the courses developed in the study. All patients reported no pain or discomfort during the treatment; and they were satisfied with the final prostheses of the shape, color, retention, stability, etc. Eighteen of the prostheses showed good marginal adaptation, and sixteen of the prostheses showed good retention effect. Conclusions: The digital negative molds technique used in this study could greatly reduce the intensity of manual operation and provided a good therapeutic effect for patients with maxillofacial defects.

Three-dimensional finite-element based deformable image registration for evaluation of pleural cavity irradiation during photodynamic therapy.

Photodynamic therapy (PDT) is used after surgical resection to treat the microscopic disease for malignant pleural mesothelioma and to increase survival rates. As accurate light delivery is imperative to PDT efficacy, the deformation of the pleural volume during the surgery is studied on its impact on the delivered light fluence. In this study, a three-dimensional finite element-based (3D FEM) deformable image registration is proposed to directly match the volume of lung to the volume of pleural cavity obtained during PDT to have accurate representation of the light fluence accumulated in the lung, heart and liver (organs-at-risk) during treatment. A wand, comprised of a modified endotrachial tube filled with Intralipid and an optical fiber inside the tube, is used to deliver the treatment light. The position of the treatment is tracked using an optical tracking system with an attachment comprised of nine reflective passive markers that are seen by an infrared camera-based navigation system. This information is used to obtain the surface contours of the plural cavity and the cumulative light fluence on every point of the cavity surface that is being treated. The lung, heart, and liver geometry are also reconstructed from a series of computed tomography (CT) scans of the organs acquired in the same patient before and after the surgery. The contours obtained with the optical tracking system and CTs are imported into COMSOL Multiphysics, where the 3D FEM-based deformable image registration is obtained. The delivered fluence values are assigned to the respective positions (x, y, and z) on the optical tracking contour. The optical tracking contour is considered as the reference, and the CT contours are used as the target, which will be deformed. The data from three patients formed the basis for this study. The physical correspondence between the CT and optical tracking geometries, taken at different times, from different imaging devices was established using the 3D FEM-based image deformable registration. The volume of lung was matched to the volume of pleural cavity and the distribution of light fluence on the surface of the heart, liver and deformed lung volumes was obtained. The method used is appropriate for analyzing problems over complicated domains, such as when the domain changes (as in a solid-state reaction with a moving boundary), when the desired precision varies over the entire domain, or when the solution lacks smoothness. Implementing this method in real-time for clinical applications and in situ monitoring of the under- or over- exposed regions to light during PDT can significantly improve the treatment for mesothelioma.

How and when to suspect spontaneous coronary artery dissection: novel insights from a single-centre series on prevalence and angiographic appearance.

Spontaneous coronary artery dissection (SCAD) is an underdiagnosed entity of acute coronary syndrome (ACS). Its prevalence remains unclear due to a challenging diagnosis, particularly in instances of intramural haematoma without intimal rupture. In the present study, we aimed to: 1) estimate the prevalence of SCAD among acute coronary syndrome (ACS) patients managed in a French coronary care centre, 2) demonstrate the value of specific angiographic signs for diagnosing SCAD, and 3) confirm the incremental value of intracoronary imaging in ambiguous cases. From 1999 to 2014, 55 cases of SCAD (all women, mean age 50.1 years) were diagnosed. Ignoring age, 51 (92.7%) had ≤2 cardiovascular risk factors. Thirty-six were diagnosed prospectively during the latter period (2012-2014). Among these, SCAD accounted for 35.7% of ACS (20/56) in women <60 years with ≤1 cardiovascular risk factor. Upon close investigation, five angiographic features commonly observed with SCAD were identified: 1) absence of atheroma on other coronary arteries, 2) radiolucent flap(s), 3) contrast dye staining of the arterial wall, 4) starting and/or ending of the angiographic ambiguity on a side branch, 5) long narrowing of lumen calibre: smooth and linear, or stenosis of varying severity mimicking a "stick insect" or "radish" aspect. Three of the above five signs were present in 51 (92.7%) cases. Optical computed tomography (OCT) was performed in 19 cases with no complication. All explored arteries had evidence of intramural haematoma and/or intimomedial membrane separation. An intimal rupture was observed in 10 (52.6%) patients. The diseased segment initiated or ended on a side branch in 14 (73.7%) patients. SCAD accounts for approximately one third of ACS in young women with ≤1 CRF. The combination of specific angiographic signs and OCT imaging facilitates the diagnosis of ambiguous cases without intimal rupture.

Scanning laser optical computed tomography system for large volume 3D dosimetry

Stray light causes artifacts in optical computed tomography (CT) that negatively affect the accuracy of radiation dosimetry in gels or solids. Scatter effects are exacerbated by a large dosimeter volume, which is desirable for direct verification of modern radiotherapy treatment plans such as multiple-isocenter radiosurgery. The goal in this study was to design and characterize an optical CT system that achieves high accuracy primary transmission measurements through effective stray light rejection, while maintaining sufficient scan speed for practical application. We present an optical imaging platform that uses a galvanometer mirror for horizontal scanning, and a translation stage for vertical movement of a laser beam and small area detector for minimal stray light production and acceptance. This is coupled with a custom lens-shaped optical CT aquarium for parallel ray sampling of projections. The scanner images 15 cm diameter, 12 cm height cylindrical volumes at 0.33 mm resolution in approximately 30 min. Attenuation coefficients reconstructed from CT scans agreed with independent cuvette measurements within 2% for both absorbing and scattering solutions as well as small 1.25 cm diameter absorbing phantoms placed within a large, scattering medium that mimics gel. Excellent linearity between the optical CT scanner and the independent measurement was observed for solutions with between 90% and 2% transmission. These results indicate that the scanner should achieve highly accurate dosimetry of large volume dosimeters in a reasonable timeframe for clinical application to radiotherapy dose verification procedures.

Optical Computed Tomography for Polymer Gel Dosimetry

This article describes an optical computed tomography (OCT) for polymer gel dosimetry, focusing on two systems recently constructed by us. The first OCT system, which is categorized as a first-generation system, comprised a single He-Ne laser, photodiode, and mechanical stages for moving and turning gel dosimeter. Projection data per angle are acquired from turned gel dosimeter. In this system, the reconstructed image is obtained using filtered back-projection (FBP) method from projection data. The second OCT system is a 2D-OCT scanner that utilizes a light panel and a camera detector. The dose-response relationship between the optical density and radiation dose reconstructed from the scanning images is comparable to that obtained using magnetic resonance imaging. Although there is much room for improvement in the image artifacts due to reflection and refraction of light and so on, OCT is expected as a modality for the future polymer gel dosimetry as the rapid, high-resolution, highly accurate evaluation tool.

Evaluation of Radiochromic Gel Dosimeter and Optical CT

Three-dimensional (3D) radiation dosimeter has received growing interest with the implementation of highly conformal radiotherapy treatments. Optical Computed tomography (CT) scanners have been developed for 3D quantitative measurement of optical attenuation. Malachite green and Leuco Crystal Violet (LCV) dye radiochromic gels were recently developed as radiation dosimeters in combination with optical CT scanners. Malachite green and LCV are colorless dyes and they become green or violet after irradiation, respectively. The dyes mixed with gelatin and surfactant became hardened and can be used as a 3D gel dosimeter. The radiochromic gels dosimeter with optical CT scanners provides many of desired features such as: low cost, easy to fabricate, low toxicity and fast readout. In this article, the fundamental characteristics of radiochromic gel dosimeter with optical CT scanners are reviewed.

Fricke Gel Dosimeters

Fricke gel dosimeters are based on the aqueous ferrous sulfate solution that has been used as a reliable chemical dosimeter for more than 90 years. The amount of radiation-induced oxidation of ferrous ions to ferric ions could be evaluated three-dimensionally via optical computed tomography (OCT) or magnetic resonance imaging (MRI). Three-dimensional dosimetry is expected to be a useful tool, in particular, for the verification of complex radiation dose planning in advanced radiation cancer therapy. Compared with other 3D gel dosimeters, there are several problems such as retention of dose distribution or dose sensitivity; however, they can easily be prepared in a chemistry laboratory. In addition, a unique gel dosimeter was also reported for heavy-ion beam irradiation. In this review, recent papers concerning the Fricke gel dosimeter and its application in 3D dosimetry are summarized.

Optical computed tomography in PRESAGE® three-dimensional dosimetry: Challenges and prospective.

With the advent of new complex but precise radiotherapy techniques, the demands for an accurate, feasible three-dimensional (3D) dosimetry system have been increased. A 3D dosimeter system generally should not only have accurate and precise results but should also feasible, inexpensive, and time consuming. Recently, one of the new candidates for 3D dosimetry is optical computed tomography (CT) with a radiochromic dosimeter such as PRESAGE®. Several generations of optical CT have been developed since the 90s. At the same time, a large attempt has been also done to introduce the robust dosimeters that compatible with optical CT scanners. In 2004, PRESAGE® dosimeter as a new radiochromic solid plastic dosimeters was introduced. In this decade, a large number of efforts have been carried out to enhance optical scanning methods. This article attempts to review and reflect on the results of these investigations.

A prototype of high resolution parallel beam Optical Computed Tomography scanner

Introduction There is a pressing need for a three-dimensional (3D) dosimetry system, appropriate for clinical use, to enable comprehensive verification of the dose distributions typical of modern radiation therapy. Purpose For this aim we introduced a dosimetry system that consist of a polymer gel dosimeter (MAGIC-F) and a prototype of laboratory dedicated level Optical Computed Tomography (OCT) scanner. Materials and methods The OCT was designed and constructed based on a broad beam visible light source and a two-dimensional charge-coupled device (CCD) detector. In this study spatial resolution parameter was determined. One of the methods for evaluating the spatial resolution of an optical CT scanner is to calculate the modulation transfer function (MTF). Results The system could scan a sample around 25 min completely then a set of cross sectional images is reconstructed from projections. The reconstructed images from optical scanner were analyzed to evaluate spatial resolution. The result indicated 10% modulation was 3.6 cycle/mm. That is means the system has sub millimeter resolution. Conclusion It has been observed that the prototype Optical parallel beam scanner is reliable the perspective of resolution for scanning gels for radiotherapy applications. The cost of fabrication scanner is lower than the commercial models. This scanner is a laboratory dedicated level Optical Computed Tomography of course it can be improved and develop in future.

Vorinostat differentially alters 3D nuclear structure of cancer and non-cancerous esophageal cells.

The histone deacetylase (HDAC) inhibitor vorinostat has received significant attention in recent years as an ‘epigenetic’ drug used to treat solid tumors. However, its mechanisms of action are not entirely understood, particularly with regard to its interaction with the aberrations in 3D nuclear structure that accompany neoplastic progression. We investigated the impact of vorinostat on human esophageal epithelial cell lines derived from normal, metaplastic (pre-cancerous), and malignant tissue. Using a combination of novel optical computed tomography (CT)-based quantitative 3D absorption microscopy and conventional confocal fluorescence microscopy, we show that subjecting malignant cells to vorinostat preferentially alters their 3D nuclear architecture relative to non-cancerous cells. Optical CT (cell CT) imaging of fixed single cells showed that drug-treated cancer cells exhibit significant alterations in nuclear morphometry. Confocal microscopy revealed that vorinostat caused changes in the distribution of H3K9ac-marked euchromatin and H3K9me3-marked constitutive heterochromatin. Additionally, 3D immuno-FISH showed that drug-induced expression of the DNA repair gene MGMT was accompanied by spatial relocation toward the center of the nucleus in the nuclei of metaplastic but not in non-neoplastic cells. Our data suggest that vorinostat’s differential modulation of 3D nuclear architecture in normal and abnormal cells could play a functional role in its anti-cancer action.