CT‐based estimation of intracavitary gas volumes using threshold‐based segmentation: <i>In vitro</i> study to determine the optimal threshold range

McWilliams, Sebastian; O’Connor, Owen J.; McGarrigle, Anne Marie; O’Neill, Siobhán; Quigley, Eamonn Martin; Shanahan, Fergus; Maher, Michael M.

doi:10.1111/j.1754-9485.2012.02375.x

Cited by 9 publications

(5 citation statements)

References 4 publications

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“…The Draw Spline function key in the ANALYZE menu was used to mark a closed curve along the inner edge of the alar rim, the lateral edge of the nasal column, and the upper edge of the nasal threshold, and the length of the curve could be read as the nostril circumference. Second, a threshold from −1024 to −550 HU 6 was set to select the nasal vestibule target area. Then, we clicked on Mask 3D Preview to generate a 3D-reconstructed preview image, clicked on Edit Masks , selected the lasso tool, and erased the voxels out of the nostrils.…”

Section: Methodsmentioning

confidence: 99%

Three-Dimensional Computed Tomography Reconstruction and Measurement of Nasal End Deformity in Complete Unilateral Cleft Lip and Palate

Wang

Yin

et al. 2021

Ann Plast Surg

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Background The repair of nasal deformities secondary to cleft lip and palate is complex and requires reliable preoperative nasal 3-dimensional assessment. This study explored nasal end (defined as the lower third of the external nasal and vestibular parts of the nasal cavity) deformities secondary to unilateral complete cleft lip and palate. Methods Three-dimensional nasal end morphometric measurements were obtained from 48 patients who had undergone Millard cleft lip repair and reached skeletal maturity (cleft group) and from 36 age- and ethnicity-matched normal subjects (control group). For the cleft group, paired t tests and 1-way analysis of covariance were used to evaluate the internal and external morphological characteristics of the cleft and noncleft sides of the nasal end, and correlation analysis was done to evaluate the relationship between cleft-side measurements. Results In the cleft group, the cleft side showed significantly smaller nasal vestibular volume and skin area, nostril area, nasal column length, and nostril height and greater nostril base length and nasal alar length than the noncleft side (all P < 0.05). Controlling for sex, there were significant differences in the nasal vestibular volume and skin area, internal nasal valve area, long nostril diameter, nostril base length, columella length, nostril height, and nasal alar length between the cleft and control groups (all P < 0.05). On the cleft side, the area of the skin lining of the nasal vestibule positively correlated with the alar length (r = 0.67, P < 0.05). Conclusions Three-dimensional nasal end reconstruction provides a more detailed preoperative nasal end morphological evaluation than previously available techniques. Level of Evidence Level III, case-control study

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Section: Methodsmentioning

confidence: 99%

Three-Dimensional Computed Tomography Reconstruction and Measurement of Nasal End Deformity in Complete Unilateral Cleft Lip and Palate

Wang

Yin

et al. 2021

Ann Plast Surg

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“…One current limitation of MR‐CAT is that it does not account for rectal gas in the image classification. To fully elucidate the dosimetric impact of bladder and rectal status changes, the intestinal gas with each rectal contour was automatically thresholded and assigned a CT value of −350 HU based on values obtained from the literature …”

Section: Methodsmentioning

confidence: 99%

Geometric and dosimetric impact of anatomical changes for MR‐only radiation therapy for the prostate

Nejad-Davarani¹,

Sevak

Moncion

et al. 2019

J Applied Clin Med Phys

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Purpose With the move towards magnetic resonance imaging (MRI) as a primary treatment planning modality option for men with prostate cancer, it becomes critical to quantify the potential uncertainties introduced for MR‐only planning. This work characterized geometric and dosimetric intra‐fractional changes between the prostate, seminal vesicles (SVs), and organs at risk (OARs) in response to bladder filling conditions. Materials and methods T2‐weighted and mDixon sequences (3–4 time points/subject, at 1, 1.5 and 3.0 T with totally 34 evaluable time points) were acquired in nine subjects using a fixed bladder filling protocol (bladder void, 20 oz water consumed pre‐imaging, 10 oz mid‐session). Using mDixon images, Magnetic Resonance for Calculating Attenuation (MR‐CAT) synthetic computed tomography (CT) images were generated by classifying voxels as muscle, adipose, spongy, and compact bone and by assignment of bulk Hounsfield Unit values. Organs including the prostate, SVs, bladder, and rectum were delineated on the T2 images at each time point by one physician. The displacement of the prostate and SVs was assessed based on the shift of the center of mass of the delineated organs from the reference state (fullest bladder). Changes in dose plans at different bladder states were assessed based on volumetric modulated arc radiotherapy (VMAT) plans generated for the reference state. Results Bladder volume reduction of 70 ± 14% from the final to initial time point (relative to the final volume) was observed in the subject population. In the empty bladder condition, the dose delivered to 95% of the planning target volume (PTV) (D95%) reduced significantly for all cases (11.53 ± 6.00%) likely due to anterior shifts of prostate/SVs relative to full bladder conditions. D15% to the bladder increased consistently in all subjects (42.27 ± 40.52%). Changes in D15% to the rectum were patient‐specific, ranging from −23.93% to 22.28% (−0.76 ± 15.30%). Conclusions Variations in the bladder and rectal volume can significantly dislocate the prostate and OARs, which can negatively impact the dose delivered to these organs. This warrants proper preparation of patients during treatment and imaging sessions, especially when imaging required longer scan times such as MR protocols.

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“…As with many threshold region growing tools a user defined input of an upper and lower threshold of CT densities was required to commence segmentation. In a phantom study, we previously determined the most accurate range of Hounsfield units for estimating gas volume to be −1024 HU to −350 HU with less than 1% error (Figure 3) [8]. …”

Section: Methodsmentioning

confidence: 99%

Computed Tomography Colonography Technique: The Role of Intracolonic Gas Volume

McLaughlin

Murphy

Crush

et al. 2013

Radiology Research and Practice

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Introduction. Poor distention decreases the sensitivity and specificity of CTC. The total volume of gas administered will vary according to many factors. We aim to determine the relationship between the volume of retained gas at the time of image acquisition and colonic distention and specifically the presence of collapsed bowel segments at CTC. Materials and Methods. All patients who underwent CTC over a 12-month period at a single institution were included in the study. Colonic luminal distention was objectively scored by 2 radiologists using an established 4-point scale. Quantitative analysis of the volume of retained gas at the time of image acquisition was conducted using the threshold 3D region growing function of OsiriX. Results. 108 patients were included for volumetric analysis. Mean retained gas volume was 3.3 L. 35% (38/108) of patients had at least one collapsed colonic segment. Significantly lower gas volumes were observed in the patients with collapsed colonic segments when compared with those with fully distended colons 2.6 L versus 3.5 L (P = 0.031). Retained volumes were significantly higher for the 78% of patients with ileocecal reflux at 3.4 L versus 2.6 L without ileocecal reflux (P = 0.014). Conclusion. Estimation of intraluminal gas volume at CTC is feasible using image segmentation and thresholding tools. An average of 3.5 L of retained gas was found in diagnostically adequate CTC studies with significantly lower mean gas volume observed in patients with collapsed colonic segments.

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CT‐based estimation of intracavitary gas volumes using threshold‐based segmentation: In vitro study to determine the optimal threshold range

Abstract: Accurate estimation of gas volumes on CT is possible using threshold-based segmentation software with a wide range of upper thresholds. The optimal upper threshold for estimation of small volumes (1-6 mL) was -550 HU and -350 HU for volumes of 10-50 mL.

Cited by 9 publications

References 4 publications

Three-Dimensional Computed Tomography Reconstruction and Measurement of Nasal End Deformity in Complete Unilateral Cleft Lip and Palate

Three-Dimensional Computed Tomography Reconstruction and Measurement of Nasal End Deformity in Complete Unilateral Cleft Lip and Palate

Geometric and dosimetric impact of anatomical changes for MR‐only radiation therapy for the prostate

Computed Tomography Colonography Technique: The Role of Intracolonic Gas Volume

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