Biomedical subjects

Aaron Fenster

Publications and source records attributed to Aaron Fenster.

At least 19 recordsLinked to original sources

PubMed2006

Prostate contouring uncertainty in megavoltage computed tomography images acquired with a helical tomotherapy unit during image-guided radiation therapy.

PURPOSE: To evaluate the image-guidance capabilities of megavoltage computed tomography (MVCT), this article compares the interobserver and intraobserver contouring uncertainty in kilovoltage computed tomography (KVCT) used for radiotherapy planning with MVCT acquired with helical tomotherapy. METHODS AND MATERIALS: Five prostate-cancer patients were evaluated. Each patient underwent a KVCT and an MVCT study, a total of 10 CT studies. For interobserver variability analysis, four radiation oncologists, one physicist, and two radiation therapists (seven observers in total) contoured the prostate and seminal vesicles (SV) in the 10 studies. The intraobserver variability was assessed by asking all observers to repeat the contouring of 1 patient's KVCT and MVCT studies. Quantitative analysis of contour variations was performed by use of volumes and radial distances. RESULTS: The interobserver and intraobserver contouring uncertainty was larger in MVCT compared with KVCT. Observers consistently segmented larger volumes on MVCT where the ratio of average prostate and SV volumes was 1.1 and 1.2, respectively. On average (interobserver and intraobserver), the local delineation variability, in terms of standard deviations [Deltasigma = radical(sigma2MVCT-sigma2KVCT)], increased by 0.32 cm from KVCT to MVCT. CONCLUSIONS: Although MVCT was inferior to KVCT for prostate delineation, the application of MVCT in prostate radiotherapy remains useful.

Humans↗

PubMed2006

Prostate segmentation by feature enhancement using domain knowledge and adaptive region based operations.

Estimation of prostate location and volume is essential in determining a dose plan for ultrasound-guided brachytherapy, a common prostate cancer treatment. However, manual segmentation is difficult, time consuming and prone to variability. In this paper, we present a semi-automatic discrete dynamic contour (DDC) model based image segmentation algorithm, which effectively combines a multi-resolution model refinement procedure together with the domain knowledge of the image class. The segmentation begins on a low-resolution image by defining a closed DDC model by the user. This contour model is then deformed progressively towards higher resolution images. We use a combination of a domain knowledge based fuzzy inference system (FIS) and a set of adaptive region based operators to enhance the edges of interest and to govern the model refinement using a DDC model. The automatic vertex relocation process, embedded into the algorithm, relocates deviated contour points back onto the actual prostate boundary, eliminating the need of user interaction after initialization. The accuracy of the prostate boundary produced by the proposed algorithm was evaluated by comparing it with a manually outlined contour by an expert observer. We used this algorithm to segment the prostate boundary in 114 2D transrectal ultrasound (TRUS) images of six patients scheduled for brachytherapy. The mean distance between the contours produced by the proposed algorithm and the manual outlines was 2.70 +/- 0.51 pixels (0.54 +/- 0.10 mm). We also showed that the algorithm is insensitive to variations of the initial model and parameter values, thus increasing the accuracy and reproducibility of the resulting boundaries in the presence of noise and artefacts.

Algorithms↗

PubMed2005

Disparate associations of a functional promoter polymorphism in PCK1 with carotid wall ultrasound traits.

BACKGROUND AND PURPOSE: Cytosolic phosphoenolpyruvate carboxykinase (PEPCK; EC 4.1.1.32), encoded by PCK1, catalyzes the first committed step in gluconeogenesis. We previously showed that a -232C>G promoter polymorphism within a cis-acting element required for basal and cAMP-mediated PCK1 gene transcription results in loss of negative regulation by insulin, contributing to worsened metabolic control in the context of insulin resistance. We hypothesized that this polymorphism would be associated with carotid atherosclerosis in a sample of 150 aboriginal Canadians. METHODS: Dependent variables were 2 distinct carotid traits, namely intima-media thickness (IMT) assessed using B-mode ultrasound and total carotid plaque volume (TPV) assessed using 3D ultrasound. RESULTS: Multivariate analysis showed significant but opposite associations of PCK1 genotype with these traits. Specifically, subjects with the PCK1-232G/G genotype had more carotid IMT (0.80+/-0.02 versus 0.73+/-0.03 mm; P=0.007) but less TPV (0.10+/-0.09 versus 0.38+/-0.13; P=0.03) than subjects with other genotypes. CONCLUSIONS: The findings connect the key enzyme in gluconeogenesis with atherosclerosis. The meaning of the opposing associations of PCK1 genotype with IMT and TPV is unclear; more work is required to confirm whether these might be distinct quantitative traits with different biological determinants.

Adolescent↗

PubMed2005

Establishment of a serum tumor marker for preclinical trials of mouse prostate cancer models.

Current prostate cancer research in both basic and preclinical trial studies employ genetically engineered mouse models. However, unlike in human prostate cancer patients, rodents have no counterpart of prostatic-specific antigen (PSA) for monitoring prostate cancer initiation and progression. In this study, we established a mouse serum tumor marker from a mouse homologue of human prostate secretory protein of 94 amino acids (PSP94). Immunohistochemistry studies on different histologic grades from both transgenic and knock-in mouse prostate cancer models showed the down-regulation of tissue PSP94 expression (P < 0.001), the same as for PSA and PSP94 in humans. The presence of mouse serum PSP94 was shown by affinity column and immunoprecipitation purification using a polyclonal mouse PSP94 antibody. A competitive ELISA protocol was established to quantify serum PSP94 levels with a sensitivity of 1 ng/mL. Quantified serum levels of mouse PSP94 ranged from 49.84 ng/mL in wild-type mice to 113.86, 400.45, and 930.90 ng/mL in mouse prostatic intraepithelial neoplasia with microinvasion, well differentiated, moderately differentiated, and poorly differentiated prostate cancer genetically engineered prostate cancer mice, respectively (P < 0.01, n = 68). This increase in serum PSP94 is also well correlated with age and tumor weight. Through longitudinal monitoring of serum PSP94 levels of castrated mice (androgen ablation therapy), we found a correlation between responsiveness/refractory prostate tissues and serum PSP94 levels. The utility of mouse serum PSP94 as a marker in hormone therapy was further confirmed by three-dimensional ultrasound imaging. The establishment of the first rodent prostate cancer serum biomarker will greatly facilitate both basic and preclinical research on human prostate cancer.

Animals↗

PubMed2005

3D ultrasound measurement of change in carotid plaque volume: a tool for rapid evaluation of new therapies.

BACKGROUND AND PURPOSE: New therapies are being developed that are antiatherosclerotic but that lack intermediate end points, such as changes in plasma lipids, which can be measured to test efficacy. To study such treatments, it will be necessary to directly measure changes in atherosclerosis. The study was designed to determine sample sizes needed to detect effects of treatment using 3D ultrasound (US) measurement of carotid plaque. METHODS: In 38 patients with carotid stenosis >60%, age+/-SD 69.42+/-7.87 years, 15 female, randomly assigned in a double-blind fashion to 80 mg atorvastatin daily (n=17) versus placebo (n=21), we measured 3D plaque volume at baseline and after 3 months by disc segmentation of voxels representing carotid artery plaque, after 3D reconstruction of parallel transverse duplex US scans into volumetric 3D data sets. RESULTS: There were no significant differences in baseline risk factors. The rate of progression was 16.81+/-74.10 mm3 in patients taking placebo versus regression of -90.25+/-85.12 mm3 in patients taking atorvastatin (P<0.0001). CONCLUSIONS: 3D plaque volume measurement can show large effects of therapy on atherosclerosis in 3 months in sample sizes of approximately 20 patients per group. Sample sizes of 22 per group would be sufficient to show an effect size of 25% that of atorvastatin in 6 months. This technology promises to be very useful in evaluation of new therapies.

Aged↗

PubMed2005

A new three-dimensional ultrasound microimaging technology for preclinical studies using a transgenic prostate cancer mouse model.

Prostate cancer is the most common cancer in adult men in North America. Preclinical studies of prostate cancer employ genetically engineered mouse models, because prostate cancer does not occur naturally in rodents. Widespread application of these models has been limited because autopsy was the only reliable method to evaluate treatment efficacy in longitudinal studies. This article reports the first use of three-dimensional ultrasound microimaging for measuring tumor progression in a genetically engineered mouse model, the 94-amino acid prostate secretory protein gene-directed transgenic prostate cancer model. Qualitative comparisons of three-dimensional ultrasound images with serial histology sections of prostate tumors show the ability of ultrasound to accurately depict the size and shape of malignant masses in live mice. Ultrasound imaging identified tumors ranging from 2.4 to 14 mm maximum diameter. The correlation coefficient of tumor diameter measurements done in vivo with three-dimensional ultrasound and at autopsy was 0.998. Prospective tumor detection sensitivity and specificity were both >90% when diagnoses were based on repeated ultrasound examinations done on separate days. Representative exponential growth curves constructed via longitudinal ultrasound imaging indicated volume doubling times of 5 and 13 days for two prostate tumors. Compared with other microimaging and molecular imaging modalities, the application of three-dimensional ultrasound imaging to prostate cancer in mice showed advantages, such as high spatial resolution and contrast in soft tissue, fast and uncomplicated protocols, and portable and economical equipment that will likely enable ultrasound to become a new microimaging modality for mouse preclinical trial studies.

Adenocarcinoma↗

PubMed2005

Three-dimensional high-frequency ultrasound imaging for longitudinal evaluation of liver metastases in preclinical models.

Liver metastasis is a clinically significant contributor to the mortality associated with melanoma, colon, and breast cancer. Preclinical mouse models are essential to the study of liver metastasis, yet their utility has been limited by the inability to study this dynamic process in a noninvasive and longitudinal manner. This study shows that three-dimensional high-frequency ultrasound can be used to noninvasively track the growth of liver metastases and evaluate potential chemotherapeutics in experimental liver metastasis models. Liver metastases produced by mesenteric vein injection of B16F1 (murine melanoma), PAP2 (murine H-ras-transformed fibroblast), HT-29 (human colon carcinoma), and MDA-MB-435/HAL (human breast carcinoma) cells were identified and tracked longitudinally. Tumor size and location were verified by histologic evaluation. Tumor volumes were calculated from the three-dimensional volumetric data, with individual liver metastases showing exponential growth. The importance of volumetric imaging to reduce uncertainty in tumor volume measurement was shown by comparing three-dimensional segmented volumes with volumes estimated from diameter measurements and the assumption of an ellipsoid shape. The utility of high-frequency ultrasound imaging in the evaluation of therapeutic interventions was established with a doxorubicin treatment trial. These results show that three-dimensional high-frequency ultrasound imaging may be particularly well suited for the quantitative assessment of metastatic progression and the evaluation of chemotherapeutics in preclinical liver metastasis models.

Animals↗

PubMed2005

A comparison of ultrasound measurements to assess carotid atherosclerosis development in subjects with and without type 2 diabetes.

BACKGROUND: Subjects with type 2 diabetes are at an increased risk of vascular complications. The use of carotid ultrasound remains an attractive, non-invasive method to monitor atherosclerotic disease progression and/or response to treatment in patients with type 2 diabetes, with intima-media thickness routinely used as the gold standard to detect pathology. However, alternative measurements, such as plaque area or volume, may represent a potentially more powerful approach. Thus, the objective of this study was to compare the traditional intima-media thickness measurement against the novel total plaque volume measurement in analyzing carotid atherosclerosis development in individuals with type 2 diabetes. METHODS: The case-control study included 49 Oji-Cree adults with diabetes or impaired glucose tolerance, aged 21-69, and 49 sex- and age-matched normoglycemic subjects. At baseline, metabolic variables were measured, including body mass index, waist circumference, total cholesterol: high density lipoprotein ratio, plasma triglycerides, plasma glucose, and serum insulin. Carotid ultrasound measurements, 7 years later, assessed carotid arterial intima-media thickness and total plaque volume. RESULTS: At baseline, the two groups were well matched for smoking habits, hypertension, body mass index, and waist circumference. Differences were noted in baseline measurements of total cholesterol:high density lipoprotein (P = 0.0006), plasma triglycerides (P < 0.0001) and fasting glucose (P < 0.0001). After seven years, carotid ultrasound scans revealed that total plaque volume measurements (P = 0.037), but not intima-media thickness measurements, were higher in subjects with diabetes/impaired glucose tolerance compared to the normoglycemic controls. Correlation between intima-media thickness and total plaque volume was moderate. Based on our study findings, to achieve power levels > 0.70 when comparing intima-media thickness measurements for diabetics versus non-diabetics, thousands of study subjects are required. For comparing total plaque volume measurements, only hundreds of study subjects are required. CONCLUSION: The development of atherosclerotic plaque is greater in subjects with diabetes/impaired glucose tolerance. Total plaque volume appears to capture the atherosclerotic disease burden more effectively in subjects with type 2 diabetes, and would be an appropriate outcome measure for studies aimed at changing the diabetic milieu.

Adult↗

PubMed2005

Registration of two-dimensional cardiac images to preprocedural three-dimensional images for interventional applications.

PURPOSE: To evaluate the accuracy and efficiency of rigid-body registration of two-dimensional fast cine and real-time cardiac images to high-resolution and SNR three-dimensional preprocedural reference volumes for application during MRI-guided interventional procedures. MATERIALS AND METHODS: Mutual information (MI) and correlation ratio (CR) similarity measures were evaluated. The dependence of registration accuracy and efficiency on different resolution and SNR parameters, and also on cardiac-phase differences was evaluated in a porcine model. Two-dimensional images were initially misoriented at distances (d) of 2-10 mm, and rotations of +/-5 degrees about all axes. Registration error and computation time were evaluated, and performance was also assessed visually. RESULTS: The maximum registration error using MI (<2.7 mm and <3.6 degrees ) occurred for d = 10 mm, misrotation of +/-5 degrees , and relative SNR = 1. The computation time was 15 seconds for MI and 10 seconds for CR. CONCLUSION: Registration accuracy was not highly dependent on the relative timing, within the cycle, between the two-dimensional and three-dimensional images. Registration using CR was faster than that using MI, although accuracy was marginally higher with MI. J.

Algorithms↗

PubMed2005

3D TRUS guided robot assisted prostate brachytherapy.

This paper describes a system for dynamic intraoperative prostate brachytherapy using 3D ultrasound guidance with robot assistance. The system consists of 3D transrectal ultrasound (TRUS) imaging, a robot and software for prostate segmentation, 3D dose planning, oblique needle segmentation and tracking, seed segmentation, and dynamic re-planning and verification. The needle targeting accuracy of the system was 0.79 mm +/- 0.32 mm in a phantom study.

Algorithms↗

PubMed2005

Differences between carotid wall morphological phenotypes measured by ultrasound in one, two and three dimensions.

Ultrasound measurements are both surrogate markers and risk factors for atherosclerosis end points. Carotid intima-media thickness (IMT) is most commonly used, but ultrasound can also define structures in higher spatial dimensions, such as total plaque area (TPA) and total plaque volume (TPV). Because there are minimal data regarding the relationship between IMT, TPA and TPV, we measured these variables in 272 Oji-Cree subjects. We found pairwise correlations for IMT:TPA, IMT:TPV and TPA:TPV of 0.507, 0.588 and 0.846, respectively (transformed variables, all P <0.0001). In a subset of 168 subjects with complete cardiovascular risk factor data, we performed multivariate regression analysis to identify sources of variation for IMT, TPA and TPV. We found that the ultrasound traits showed different correlations with individual cardiovascular risk factors. In particular, IMT was significantly associated with hypertension, TPA with smoking and plasma cholesterol, and TPV with diabetes. Therefore, these ultrasound measures of carotid artery morphology, while somewhat correlated, likely represent distinctive quantitative traits with different biological determinants, as underscored by different risk factor associations in the multivariate regression analysis. Because the measurements have different implications and determinants, investigators might need to be selective about the particular measurements they choose for specific applications.

Adult↗

PubMed2005

Image-based cardiac gating for three-dimensional intravascular ultrasound imaging.

Three-dimensional (3-D) intravascular ultrasound (US), or IVUS, provides valuable insight into the tissue characteristics of the coronary wall and plaque composition. However, artefacts due to cardiac motion and vessel wall pulsation limit the accuracy and variability of coronary lumen and plaque volume measurement in 3-D IVUS images. ECG-gated image acquisition can reduce these artefacts but it requires recording the ECG signal and may increase image acquisition time. The goal of our study was to reconstruct a 3-D IVUS image with negligible cardiac motion and vessel pulsation artefacts, by developing an image-based gating method to track 2-D IVUS images over the cardiac cycle. Our approach involved selecting 2-D IVUS images belonging to the same cardiac phase from an asynchronously-acquired series, by tracking the changing lumen contour over the cardiac cycle. The algorithm was tested with IVUS images of a custom-built coronary vessel phantom and with patient images. The artefact reduction achieved using the image-gating approach was > 86% in the in vitro images and > 80% in the in vivo images in our study. Our study shows that image-based gating of IVUS images provides a useful method for accurate reconstruction of 3-D IVUS images with reduced cardiac motion artefact.

Algorithms↗

PubMed2005

Quantification of carotid plaque volume measurements using 3D ultrasound imaging.

An accurate and reliable technique used to quantify carotid plaque volume has practical importance in research and patient management. In this study, we develop and investigate a theoretical description of carotid plaque volume measurements made using three-dimensional (3D) ultrasound (US) images and compare it with experimental results. Multiple observers measured 48 3D US patient images of carotid plaque (13.2 to 544.0 mm(3)) by manual planimetry. Coefficients of variation in the measurement of plaque volume were found to decrease with increasing plaque size for both inter- (90.8 to 3.9%) and intraobserver (70.2 to 3.1%) measurements. Plaque volume measurement variability was found to increase with interslice distance (ISD), while the relative measurement accuracy remained constant for ISDs between 1.0 and 3.0 mm and then decreased. Root-mean-square (RMS) difference between our theoretical description of plaque volume measurement variance and the experimental results was 5.7%. Thus, our results support the clinical utility of measuring carotid plaque volume by manual planimetry noninvasively using 3D US.

Aged↗

PubMed2005

Three-dimensional ultrasound biomicroscopy for xenograft growth analysis.

We reported the use of high-frequency ultrasound biomicroscopy (UBM) in the quantitative analysis of early tumor growth in mice bearing melanoma xenografts in a noninvasive longitudinal assay. Initially, measurements of tumor width, depth and length were obtained using on-screen UBM calipers in real time and tumor volume was calculated with the standard ellipsoid formula w d l pi/6. We were able to detect initiating minute tumor nodules, with the lower limit of detection at approximately 0.01 mm(3) in volume. Successive parallel cross-sectional UBM images (33 microm step) encompassing the complete length of these tumors were also obtained and reconstructed into 3-D representations. Subsequent segmentational volumetric analysis provided a measure of tumor volume. Volume measurements using the two techniques were highly correlated when all 33 xenografts were studied (r = 0.9813, p < 0.0001) and a lower degree of correlation was measured with a subset of early small tumors (r = 0.7973, n = 16, p = 0.0004). Further analysis demonstrated that 3-D segmentational volumetric analysis yielded volume estimates that were often smaller than the caliper-and-formula calculation for most early developing xenografts. Thus, 3-D UBM imaging and segmentation is expected to be especially valuable for small tumors that were observed to grow in irregular shapes other than ellipsoids.

Animals↗

PubMed2005

Brachytherapy needle deflection evaluation and correction.

In prostate brachytherapy, an 18-gauge needle is used to implant radioactive seeds. This thin needle can be deflected from the preplanned trajectory in the prostate, potentially resulting in a suboptimum dose pattern and at times requiring repeated needle insertion to achieve optimal dosimetry. In this paper, we report on the evaluation of brachytherapy needle deflection and bending in test phantoms and two approaches to overcome the problem. First we tested the relationship between needle deflection and insertion depth as well as whether needle bending occurred. Targeting accuracy was tested by inserting a brachytherapy needle to target 16 points in chicken tissue phantoms. By implanting dummy seeds into chicken tissue phantoms under 3D ultrasound guidance, the overall accuracy of seed implantation was determined. We evaluated methods to overcome brachytherapy needle deflection with three different insertion methods: constant orientation, constant rotation, and orientation reversal at half of the insertion depth. Our results showed that needle deflection is linear with needle insertion depth, and that no noticeable bending occurs with needle insertion into the tissue and agar phantoms. A 3D principal component analysis was performed to obtain the population distribution of needle tip and seed position relative to the target positions. Our results showed that with the constant orientation insertion method, the mean needle targeting error was 2.8 mm and the mean seed implantation error was 2.9 mm. Using the constant rotation and orientation reversal at half insertion depth methods, the deflection error was reduced. The mean needle targeting errors were 0.8 and 1.2 mm for the constant rotation and orientation reversal methods, respectively, and the seed implantation errors were 0.9 and 1.5 mm for constant rotation insertion and orientation reversal methods, respectively.

Agar↗

PubMed2005

Oblique needle segmentation and tracking for 3D TRUS guided prostate brachytherapy.

An algorithm was developed in order to segment and track brachytherapy needles inserted along oblique trajectories. Three-dimensional (3D) transrectal ultrasound (TRUS) images of the rigid rod simulating the needle inserted into the tissue-mimicking agar and chicken breast phantoms were obtained to test the accuracy of the algorithm under ideal conditions. Because the robot possesses high positioning and angulation accuracies, we used the robot as a "gold standard," and compared the results of algorithm segmentation to the values measured by the robot. Our testing results showed that the accuracy of the needle segmentation algorithm depends on the needle insertion distance into the 3D TRUS image and the angulations with respect to the TRUS transducer, e.g., at a 10 degrees insertion anglulation in agar phantoms, the error of the algorithm in determining the needle tip position was less than 1 mm when the insertion distance was greater than 15 mm. Near real-time needle tracking was achieved by scanning a small volume containing the needle. Our tests also showed that, the segmentation time was less than 60 ms, and the scanning time was less than 1.2 s, when the insertion distance into the 3D TRUS image was less than 55 mm. In our needle tracking tests in chicken breast phantoms, the errors in determining the needle orientation were less than 2 degrees in robot yaw and 0.7 degrees in robot pitch orientations, for up to 20 degrees needle insertion angles with the TRUS transducer in the horizontal plane when the needle insertion distance was greater than 15 mm.

Agar↗

PubMed2004

Prostate segmentation algorithm using dyadic wavelet transform and discrete dynamic contour.

Knowing the location and the volume of the prostate is important for ultrasound-guided prostate brachytherapy, a commonly used prostate cancer treatment method. The prostate boundary must be segmented before a dose plan can be obtained. However, manual segmentation is arduous and time consuming. This paper introduces a semi-automatic segmentation algorithm based on the dyadic wavelet transform (DWT) and the discrete dynamic contour (DDC). A spline interpolation method is used to determine the initial contour based on four user-defined initial points. The DDC model then refines the initial contour based on the approximate coefficients and the wavelet coefficients generated using the DWT. The DDC model is executed under two settings. The coefficients used in these two settings are derived using smoothing functions with different sizes. A selection rule is used to choose the best contour based on the contours produced in these two settings. The accuracy of the final contour produced by the proposed algorithm is evaluated by comparing it with the manual contour outlined by an expert observer. A total of 114 2D TRUS images taken for six different patients scheduled for brachytherapy were segmented using the proposed algorithm. The average difference between the contour segmented using the proposed algorithm and the manually outlined contour is less than 3 pixels.

Algorithms↗

PubMed2004

Genetic variation in PPARG encoding peroxisome proliferator-activated receptor gamma associated with carotid atherosclerosis.

BACKGROUND AND PURPOSE: Peroxisome proliferator-activated receptor gamma is a crucial molecule in atherogenesis because it is associated with metabolic risk factors such as obesity and diabetes and also plays a key role in subcellular metabolism of arterial wall macrophage foam cells. Genetic variation in PPARG has been associated with metabolic and cardiovascular end points. METHODS: We investigated the relationship between 2 common PPARG polymorphisms, namely P12A and c.1431C>T, and carotid atherosclerosis in a sample of 161 Canadian aboriginal people. Dependent variables were carotid intima media thickness (IMT), assessed using B-mode ultrasonography, and total carotid plaque volume (TPV), assessed using 3D ultrasound. RESULTS: Using multivariate analysis, we found that subjects with > or =1 PPARG A12 allele had less carotid IMT than others (0.72+/-0.03 versus 0.80+/-0.02 mm; P=0.0045), with no between-genotype difference in TPV. In contrast, subjects with the PPARG c.1431T allele had greater TPV than others (124+/-18.4 versus 65.1+/-23.7 mm3; P=0.0079), with no between-genotype difference in IMT. CONCLUSIONS: The findings show an association between PPARG genotypes and carotid arterial phenotypes, and further reflect the prevailing view that the PPARG A12 allele protects against deleterious phenotypes. Also, whereas IMT and TPV are somewhat correlated with each other, they might also represent distinct traits with discrete determinants representing different stages of atherogenesis.

Adult↗