Automatic Lung Cancer Segmentation in 18 FFDG PET/CT Using a Two-Stage Deep Learning Approach / 대한핵의학회잡지

Purpose@#Since accurate lung cancer segmentation is required to determine the functional volume of a tumor in [ 18 F]FDG PET/CT, we propose a two-stage U-Net architecture to enhance the performance of lung cancer segmentation using [ 18 F]FDG PET/CT. @*Methods@#The whole-body [ 18 F]FDG PET/CT scan data of 887 patients with lung cancer were retrospectively used for network training and evaluation. The ground-truth tumor volume of interest was drawn using the LifeX software. The dataset was randomly partitioned into training, validation, and test sets. Among the 887 PET/CT and VOI datasets, 730 were used to train the proposed models, 81 were used as the validation set, and the remaining 76 were used to evaluate the model. In Stage 1, the global U-net receives 3D PET/CT volume as input and extracts the preliminary tumor area, generating a 3D binary volume as output. In Stage 2, the regional U-net receives eight consecutive PET/CT slices around the slice selected by the Global U-net in Stage 1 and generates a 2D binary image as the output. @*Results@#The proposed two-stage U-Net architecture outperformed the conventional one-stage 3D U-Net in primary lung cancer segmentation. The two-stage U-Net model successfully predicted the detailed margin of the tumors, which was determined by manually drawing spherical VOIs and applying an adaptive threshold. Quantitative analysis using the Dice similarity coefficient confirmed the advantages of the two-stage U-Net. @*Conclusion@#The proposed method will be useful for reducing the time and effort required for accurate lung cancer segmentation in [ 18 F]FDG PET/CT.

Effect of Ultra-high-definition Television on Ocular Surface and Fatigue

Purpose@#To investigate the effects of watching ultra-high-definition television (UHD TV) on subjective ocular fatigue and objective ocular surface indices. @*Methods@#A total of 76 volunteers were recruited for this study. Subjects watched UHD TV for 10 minutes at a viewing distance of 110 cm. Best-corrected visual acuity, refractive errors, tear break-up time, corneal staining grading, conjunctival redness grading by slit-lamp examination, tear meniscus measurement by anterior segment optical coherence tomography, and ocular symptom scores were obtained before and immediately after watching UHD TV. Subgroup analyses were conducted according to participant age (old age group >50 years vs. young age group ≤50 years) and dry-eye syndrome (presence vs.absence). The relationship between subjective and objective indices was evaluated. @*Results@#The mean age of subjects was 39.6 ± 12.4 years. Watching UHD TV induced a decrease in tear break-up time in the non-dry-eye group (p < 0.001) but not in the dry-eye group (p= 0.726). Corneal staining grades increased in all subgroups, and the changes were particularly larger in the older group (p = 0.038). The increase in ocular symptom scores was larger in the dry-eye group (p = 0.08) and in the older group (p = 0.016). The decrease in tear break-up time and ocular symptom scores after watching UHD TV was significantly correlated with tear break-up time. @*Conclusions@#Tear break-up time significantly decreased in non-dry-eye subjects after watching UHD TV. Subjective ocular discomfort increased significantly in subjects over the age of 50 and in participants with dry-eye syndrome.

Comparison of Blinking Patterns When Watching Ultra-high Definition Television: Normal versus Dry Eyes

PURPOSE: To analyze blinking patterns when watching an ultra-high definition (UHD) television and to compare the results between normal eyes and dry eyes. METHODS: A total of 59 participants aged from 13 to 69 years were instructed to watch a colorful and dynamic video on a UHD television for 10 minutes. Before and after watching the UHD television, we measured the best corrected visual acuities, autorefraction, tear-break-up-time, degree of corneal erosion and conjunctival hyperemia via slit lamp biomicroscopy. In addition, questionnaires for the evaluation of eye fatigue and symptoms of a dry eye were completed. The definition of dry eye syndrome was that the tear-break-up-time of one of the eyes was less than 5 seconds, conjunctival injection, or marked corneal erosion. The number of blinks and the duration of blinking were both measured and analyzed at the early and late phases of video-watching. RESULTS: After watching the UHD television in the normal eye group, the tear-break-up-time was significantly decreased (p < 0.001) and the degree of corneal erosion was significantly increased (p = 0.023). However, the subjective symptoms of participants were not aggravated (p = 0.080). There were no significant differences in blinking patterns in the dry eye group. On the other hand, in the normal eye group, the mean blinking time was significantly increased (p = 0.030). CONCLUSIONS: Watching an UHD television changes the tear-break-up-time, degree of corneal erosion, and blinking pattern in normal eyes, which may increase the risk of dry eye syndrome.

The Inhibitory Effect of Myopic and Astigmatic Progression by Orthokeratology Lens

PURPOSE: To investigate the clinical effects of orthokeratology lens wear on inhibition of the progression of Korean myopia and astigmatism. METHODS: The authors reviewed out-patient records of 144 eyes of 74 patients wearing orthokeratology lenses. The cycloplegic refraction and keratometry before and after wearing the lens were compared. The 190 eyes wearing spectacles were included into the control group. We evaluated the relationship between orthokeratology lens wear and control group according to age, initial myopia, initial astigmatism, myopic progression, astigmatic progression and duration of orthokeratology lens wearing. RESULTS: The mean cycloplegic refractive error of spherical equivalent was -3.36 +/- 1.96 diopters (D) in the patients wearing orthokeratology lenses, the mean astigmatism was -0.86 +/- 0.72 D, and the mean wearing period was 3.41 +/- 1.5 years. The mean myopic progression was 0.25 +/- 0.31 D in lens wearing, and 0.62 +/- 0.39 D in glasses wearing, respectively. There were statistically significant differences between lens and glasses wearing group (t-test, p 0.01). CONCLUSIONS: The orthokeratology lens was found to be effective in suppression of the progression of Korean myopia and astigmatism, compared with the glasses.

Hereditary and Clinical Features of Retinitis Pigmentosa in Koreans

There has been no report about hereditary and clinical features of retinitis pigmentosa (RP) in Koreans. To evaluate these, data were collected from 365 RP patients including age, gender, visual acuity (VA), spherical equivalent (SE) of refractive errors, funduscopic findings, color vision test, visual field score (VFS) obtained from Goldmann perimetry, and the inheritance patterns from pedigrees. Simplex RP was the most common inheritance pattern (61.9%); followed by autosomal recessive RP (17.3%), autosomal dominant RP (12.1%) and X-linked recessive RP (8.8%). Myopia was the most common refractive errors (77.5%) including 16.1% of high myopia. The most common cataract type was posterior subcapsular cataract (25.8%). Observed retinal findings included changes of retinal pigment epithelium (88.8%), bony spicule-like pigmentation (79.7%), attenuation of retinal vessel (76.2%), waxy disc pallor (12.6%), golden ring around optic disc (2.2%), epiretinal membrane (0.8%) and cystoid macular edema (0.5%). Corrected VA and refractive errors did not show any significant difference between the inheritance patterns. VFS was significantly worse in autosomal recessive RP than in autosomal dominant RP. Color vision defect was noted in 66.1% on Hardy-Rand-Rittlers color vision test. In conclusion, Korean RP patients have the indigenous hereditary and clinical features as well as the ordinary ones.

Analysis of Electrically Evoked Potential in Rabbits with Polyimide Retinal Stimulator

PURPOSE: Electrically evoked potential (EEP) was recorded in rabbits with polyimide-based, multichannel, microelectrode array (MEA) in their eyes, and was compared with the visual evoked potential (VEP) by flash light. METHODS: VEP was recorded under full-field flash light stimulation by 0. 6 J at 2 Hz, while EEP was recorded under electrical current stimulation of the retina by MEA. Latencies and shapes of N1, P100 and N2 in each evoked potential were compared. RESULTS: EEP was recorded in four of six rabbits. N1, P100 and N2 were observed in EEP on the electrical retina stimulation over 2.5 mA, and they resembled those of VEP. However, N1, P100 and N2 of EEP showed shorter latencies than those of VEP, by 15.1 msec (32.9%), 76.8 msec (38.3%) and 99.7 msec (60.1%) respectively. CONCLUSIONS: EEP by electrical retina stimulation with MEA was similar to VEP, indicating that MEA is suitable for the development of the artificial retina prototype. The shorter latencies of EEP should be considered in the parameters of the electrical stimulation of the retina.

Expression of Hypoxia-Inducible Factor-1alpha(HIF-1alpha) in the Experimental Model of Choroidal Neovascularization

PURPOSE: The expression of hypoxia-inducible factor-1alpha(HIF-1alpha) in the choroidal neovascular membrane (CNV) was investigated. METHODS: CNV was induced in the eyes of Brown Norway rats by 545 nm argon laser photocoagulation into the eye, and fluorescein angiography (FAG) was performed to identify the early hyperfluorescence and the late leakage after 2 weeks of the photocoagulation. Three days after FAG, the eyeball was harvested and the expression of vascular endothelial growth factor (VEGF) and HIF-1alpha was identified by immunohistochemical methods. RESULTS: Twenty-nine of 37 photocoagulation sites of the eyes showed CNV formation on FAG. Immunohistochemical staining of the laser photocoagulation-induced CNV tissues revealed the expression of VEGF and HIF-1alpha in the sites. CONCLUSIONS: These results suggest the possibility of the involvement of HIF-1alpha in the VEGF expression and the pathogenesis of CNV in the laser photocoagulation-induced CNV rat model.

Protective Effect of Ginkgo biloba Extract (Ginexin(R)) on a Variety of Damage on Cultured RPE

PURPOSE: The protective effect of the Ginkgo biloba extract (EGb) on the retinal pigment epithelia (RPE) against ultraviolet, oxidative, and hypoxic damage was investigated. METHODS: Cultured RPE was exposed to ultraviolet B, oxidative damage and hypoxic culture condition after treating with EGb, Vitamin E and red ginseng. Viable RPE after the application of stress was determined by trypan blue assay or MTT assay, and the apoptosis was determined by flow cytometry. Protective effect against the stress by each agent was compared. RESULTS: The group treated with EGb or Vitamin E 1 hour prior to UVB exposure showed a better survival rate than the control group did, and there was no difference in the best survival rate between EGb and Vitamin E. EGb treatment 1 hour before oxidative damage positively affected the survival rate of the RPE. EGb, Vitamin E and red ginseng showed the strongest protective effect against hypoxic damage at the concentration of 0.5 mg/ml, 0.1 mM and 1 mg/ml respectively, with the protective effect of EGb being superior to that of the rest. CONCLUSIONS: These results show that EGb prevents cell death by a variety of damage on RPE, and support the possibility for EGb as a therapeutic agent in the diseases in which RPE damage plays an important role in the pathogenesis.

A New Rapid and Non-radioactive Assay for Monitoring and Determining the Proliferation of Retinal Pigment Epithelial Cells

AlamarBlue is used to induce color and fluorescence in the microenvironment of activated cells. The alamarBlue assay was studied to determine if it could be used as a method of evaluating the number of retinal pigment epithelial (RPE) cells. A series of two-fold dilutions of RPE cells were placed into 96-well culture plates. The alamarBlue was added to the culture media after attaching the cells. The absorbance and fluorescence were measured consecutively at various intervals over a period of 24 hr. Cell viability were evaluated by means of the trypan blue exclusion method and flow cytometry using a combination of propidium iodide and annexin V was done to prove the safety of alamarBlue assay to the cells. Both the absorbance and the fluorescence had a linear relationship with the number of RPE cells. Exposing the RPE cells to alamarBlue was not detrimental to the cells. In conclusion, the alamarBlue assay constitutes a one-step, extremely simple, reproducible, economical and non-toxic procedure for evaluating the number of viable RPE cells.

Correction of with-the-rule Astigmatism by Superior Clear Corneal Incision and Transverse Keratotomy in Cataract Surgery

PURPOSE: The effect of superior clear corneal incision and transverse astigmatic keratotomy on the with-the-rule astigmatism in sutureless, small incision cataract surgery was evaluated. METHODS: The postoperative keratometric changes were evaluated in 18 eyes with more than 1.4 diopter (D) of preoperative with-the-rule astigmatism, having sutureless, superior clear corneal incision phacoemulsification. Five eyes over 2.8 D with-the-rule astigmatism also had transverse corneal relaxing incision. Keratometric readings were done within 1 month preoperatively, 1 day and 2 months postoperatively and the changes were statistically analyzed. Simple subtraction method and Cravy method were used for the analysis of astigmatic changes. RESULTS: The mean astigmatism showed decreasing trend, 2.08, 2.25, 1.12 D, within preoperative 1 month, at postoperative 1 day and 2 months respectively and 3.70, 2.48, 2.06 D respectively when transverse keratotomy was added. The reduction of astigmatism was statistically significant at postoperative 2 months (P<0.05; Wilcoxon rank-sum test) and it was more significant with transverse astigmatic keratotomy (P<0.05, Mann-Whitney U test). CONCLUSIONS: The with-the-rule astigmatism over 1.40 D could be reduced in cataract surgery by sutureless, superior clear corneal incision and transverse corneal relaxing keratotomy.

The Usefulness of the PCL Power Calculation Computer Program: 'POWER!'

PURPOSE: To assess the usefulness and reliability of the IOL power calculation computer program ('POWER!'). METHODS: Calculation times and projected postoperative refractive values of 100 patients with 'POWER!' program were compared with those of the program mounted on the Humphrey R A/B scan system (model 820) by SRK-II and SRK/T formula. RESULTS: There was no significant difference between the projected postoperative refractive values of 'POWER!' program and Humphrey R A/B scan system (paired-t test, p>0.05). Calculation time of 'POWER!' was shorter than that of the program mounted on the Humphrey R A/B scan system incalculating more than 3 sets of IOL (paired-t test, P0.05). CONCLUSIONS: 'POWER!' is a useful and reliable program for IOL power calculation using SRK-II and SRK/T formula.

Geometric changes of the eye with an encircling scleral buckle

PURPOSE: To investigate the postoperative changes and the mechanism of retinal reattachment, the geometric changes of the eye with an encircling scleral buckle was analyzed using a simplified eye model. METHODS: The simplified eye model is an inelastic sphere with an external diameter of 25 mm and an internal diameter of 23.6 millimeters. With an encircling scleral buckle, it was assumed that the circumference of the eyeball would decrease, and in particular with tightening of the buckle, the cross-section of eyeball would be deformed to an ellipsoid shape. The changes in radius, internal surface area, and volume of the eyeball in relationship to the changes in height and span of the silicone buckle were estimated. RESULTS: The radius of eyeball decreased by 0.19-0.90 mm with an encircling scleral buckle, and varied according to the increment of the tightening of the encircling band. The axial length of the eye increased and the volume of the eye decreased also with increased tightening of the band. The scleral arc of the buckle was shorter than the retinal arc of the buckle by 0.09-0.55 mm and the scleral surface area of the buckle was smaller than the retinal area of the buckle by 56-219 mm 2 ; therefore the retina would be redundant. CONCLUSIONS: An encircling scleral buckle changes the axial length and decreases the volume and internal surface area of the eye, making the retina redundant. This redundancy helps resolve or alleviate the problem of a foreshortened retina in retinal reattachment procedures.

Apnea Associated with General Anesthesia in the Surgical Treatment of Retinopathy of Prematurity and its Risk Factors

We evaluated the relationship between preoperative risk factors[gestational age, birth weight, postconceptual age and weight at operation, duration of operation, duration of anesthesia, abnormalities in neurosonogram, bronchopulmonary dysplasia]and apnea with or without bradycardia, for which mechanical ventilation was necessary after general anesthesia in the surgical treatment of retinopathy of prematurity[ROP]. Thirty-eight patients [21%]developed apnea and thirteen patients[7%]had bradycardia out of 183 patients. Retrospective study was performed and risk factors were analyzed by logistic regression. Gestational age, birth weight, postconceptual age and weight at operation and bronchopulmonary dysplasia showed the positive correlation with postanesthetic apnea and bradycardia. Duration of operation showed the positive correlation with postanesthetic apnea but not with postanesthetic bradycardia. In logistic regression without confoundings, weight at operation and bronchopulmonary dysplasia were correlated with postanesthetic apnea. Receiver operating characteristic curve analysis revealed that patients with weight under 2, 600gm at operation suffered from apnea more frequently than those with weight over 2, 600gm. In conclusion, patients with weight under 2600gm or bronchopulmonary dysplasia are at greater risk for postanesthetic apnea and optimal pre-and postanesthetic management should be prepared for these patients.

The Relationship between the Mean Height of Contour of the Retinal Surface at the Temporal Disc Margin and the Reference Height in Analyzing Optic Disc using Heidelberg Retina Tomograph

The relationship between the amount of posterior displacement of the retinal surface at the temporal disc margin and the reference height(HRef)in analyzing optic disc using Heidelberg Retina Tomograph(HRT;Heidelberg Engineering, Heidelberg, Germany)was evaluated. The displacement was measured as mean height of contour(MHC)in the temporal 40degrees C segment(20degrees C superior and 20degrees C inferior to the horizontal midline)of optic disc. HRef is a value representing the location of the standard reference plane. The accordances of HRef and stereometric parameters between right and left disc were also evaluated. MHC in the temporal 40 degrees C and nasal 40 degrees C segment, HRef, and stereometric parameters of optic disc were measured with the HRT in 244 eyes of 122 subjects. HRef was 0.376+/-0.099 mm in the right disc and 0.385+/-0.090 mm in the left disc. There was good correlation between HRef and MHC in the temporal 40degrees C segment(r=0.97, p<0.01), but poor in the nasal 40 degrees C segment(r=0.29, p<0.01). The accordances of HRef and stereometric parameters increased as the difference of MHC in the temporal 40degrees C segment between right and left disc decreased. HRef was affected by the amount of posterior displacement of the retinal surface at the temporal disc margin, which occurs in instances such as a tilted disc. We should find the method to adjust stereometric parameters to the amount of disc tilt.

Diagnosis of Ictal Hyperperfusion Using Subtraction Image of Ictal and Interictal Brain Perfusion SPECT / 대한핵의학회잡지

A robust algorithm to disclose and display the difference of ictal and interictal perfusion may facilitate the detection of ictal hyperfusion foci. Diagnostic performance of localizing epileptogenic zones with subtracted SPECT images was compared with the visual diagnosis using ictal and interictal SPECT, MR, or PET. Ictal and interictal Tc-99m-HMPAO cerebral perfusion SPECT images of 48 patients(pts) were processed to get parametric subtracted images. Epileptogenic foci of all pts were diagnosed by seizure free state after resection of epileptogenic zones. In subtraction SPECT, we used normalized difference ratio of pixel counts((ictal-interictal)/interictalx100%) after correcting coordinates of ictal and interictal SPECT in semi-automatized 3-dimensional fashion. We found epileptogenic zones in subtraction SPECT and compared the performance with visual diagnosis of ictal and interictal SPECT, MR and PET using post-surgical diagnosis as gold standard. The concordance of subtraction SPECT and ictal-interictal SPECT was moderately good(kappa=0.49). The sensitivity of ictal-interictal SPECT was 73% and that of subtraction SPECT 58%. Positive predictive value of ictal-interictal SPECT was 76% and that of subtraction SPECT was 64%. There was no statistical difference between sensitivity or positive predictive values of subtraction SPECT and ictal-interictal SPECT, MR or PET. Such was also the case when we divided patients into temporal lobe epilepsy and neocortical epilepsy. We conclude that subtraction SPECT we produced had equivalent diagnostic performance compared with ictal-interictal SPECT in localizing epileptogenic zones. Additional value of these subtraction SPECT in clinical interpretation of ictal and interictal SPECT should be further evaluated.