In vitro blood sample assessment: investigating correlation of laboratory hemoglobin and spectral properties of dual-energy CT measurements (ρ/Z).

OBJECTIVES: Our study comprised a single-center retrospective in vitro correlation between spectral properties, namely ρ/Z values, derived from scanning blood samples using dual-energy computed tomography (DECT) with the corresponding laboratory hemoglobin/hematocrit (Hb/Hct) levels and assessed the potential in anemia-detection. METHODS: DECT of 813 patient blood samples from 465 women and 348 men was conducted using a standardized scan protocol. Electron density relative to water (ρ or rho), effective atomic number (Zeff), and CT attenuation (Hounsfield unit) were measured. RESULTS: Positive correlation with the Hb/Hct was shown for ρ (r-values 0.37-0.49) and attenuation (r-values 0.59-0.83) while no correlation was observed for Zeff (r-values -0.04 to 0.08). Significant differences in attenuation and ρ values were detected for blood samples with and without anemia in both genders (p value < 0.001) with area under the curve ranging from 0.7 to 0.95. Depending on the respective CT parameters, various cutoff values for CT-based anemia detection could be determined. CONCLUSION: In summary, our study investigated the correlation between DECT measurements and Hb/Hct levels, emphasizing novel aspects of ρ and Zeff values. Assuming that quantitative changes in the number of hemoglobin proteins might alter the mean Zeff values, the results of our study show that there is no measurable correlation on the atomic level using DECT. We established a positive in vitro correlation between Hb/Hct values and ρ. Nevertheless, attenuation emerged as the most strongly correlated parameter with identifiable cutoff values, highlighting its preference for CT-based anemia detection. CLINICAL RELEVANCE STATEMENT: By scanning multiple blood samples with dual-energy CT scans and comparing the measurements with standard laboratory blood tests, we were able to underscore the potential of CT-based anemia detection and its advantages in clinical practice. KEY POINTS: Prior in vivo studies have found a correlation between aortic blood pool and measured hemoglobin and hematocrit. Hemoglobin and hematocrit correlated with electron density relative to water and attenuation but not Zeff. Dual-energy CT has the potential for additional clinical benefits, such as CT-based anemia detection.

Towards universal comparability of pericoronary adipose tissue attenuation: a coronary computed tomography angiography phantom study.

OBJECTIVES: Different computed tomography (CT) scanners, variations in acquisition protocols, and technical parameters employed for image reconstruction may introduce bias in the analysis of pericoronary adipose tissue (PCAT) attenuation derived from coronary computed tomography angiography (CCTA). Therefore, the aim of this study was to establish the effect of tube voltage, measured as kilovoltage peak (kVp), and iterative reconstruction on PCAT mean attenuation (PCATMA). METHODS: Twelve healthy ex vivo porcine hearts were injected with iodine-enriched agar-agar to allow for ex vivo CCTA imaging on a 256-slice CT and a dual-source CT system. Images were acquired at tube voltages of 80, 100, 120, and 140 kVp and reconstructed by using both filtered back projection and iterative reconstruction algorithms. PCATMA was measured semi-automatically on CCTA images in the proximal segment of coronary arteries. RESULTS: The tube voltage showed a significant effect on PCATMA measurements on both the 256-slice CT scanner (p < 0.001) and the dual-source CT system (p = 0.013), resulting in higher attenuation values with increasing tube voltage. Similarly, the use of iterative reconstructions was associated with a significant increase of PCATMA (256-slice CT: p < 0.001 and dual-source CT: p = 0.014). Averaged conversion factors to correct PCATMA measurements for tube voltage other than 120 kVp were 1.267, 1.080 and 0.947 for 80, 100, and 140 kVp, respectively. CONCLUSION: PCATMA values are significantly affected by acquisition and reconstruction parameters. The same tube voltage and reconstruction type are recommended when PCAT attenuation is used in multicenter and longitudinal studies. KEY POINTS: • The tube voltage used for CCTA acquisition affects pericoronary adipose tissue attenuation, resulting in higher attenuation values of fat with increasing tube voltage. • Conversion factors for pericoronary adipose tissue attenuation values could be used to adjust for differences in attenuation between scans performed at different tube voltages. • In longitudinal CCTA studies employing pericoronary adipose tissue attenuation as imaging endpoint, it is recommended to maintain tube voltage and image reconstruction type constant across serial scans.

Quantifying image quality in chest computed tomography angiography: Evaluation of different contrast-to-noise ratio measurement methods.

BACKGROUND: Contrast-to-noise ratio is used to objectively evaluate image quality in chest computed tomography angiography (CTA). Different authors define and measure contrast-to-noise ratio using different methods. PURPOSE: To summarize and evaluate the different contrast-to-noise ratio calculation formulas in the current literature. MATERIAL AND METHODS: A systematic review of the recent literature for studies using contrast-to-noise ratio was performed. Contrast-to-noise ratio measurement methods reported by the different authors were recorded and reproduced in three patients who underwent chest CTA in our department for exploring variations among the different measurement methods. RESULTS: The search resulted in 109 articles, of which 26 were included. The studies involved 69 different measurements and overall, three different formula patterns. In all three, aorta and pulmonary arteries comprised the objects of interest in the numerator. In the denominator, standard deviation of the attenuation of the object of interest itself or of another background were used to reflect image noise. Some authors averaged the ratio values at different levels to obtain global ratio values. Using the object of interest itself for image noise calculation in the denominator compared to the usage of another background caused the most prominent variances of contrast-to-noise ratio between the two different protocols used for the reproduction of the measurements. CONCLUSION: We recommend using the standard deviation of the attenuation of a background indicator as image noise rather than the object of interest itself for more reliable and comparative values. Global contrast-to-noise ratios based on averaging the values of different measurement levels should be avoided.

Gadolinium Distribution in Cerebrospinal Fluid after Administration of a Gadolinium-based MR Contrast Agent in Humans.

Purpose To evaluate whether gadolinium penetrates human cerebrospinal fluid (CSF) after MR imaging (MRI) with a gadolinium-based contrast agent (GBCA). Materials and Methods For this retrospective study, the authors analyzed 60 CSF samples from 57 patients (median age, 50 years; range, 3-92 years) who underwent one contrast material-enhanced MRI examination with gadoterate meglumine within 60 days of CSF extraction between January and December 2016. CSF samples from patients who underwent MRI without contrast material administration (n = 22) or those who underwent contrast-enhanced MRI at least 1 year before extraction (n = 2) were analyzed and used as control samples. CSF measurements were performed with inductively coupled plasma mass spectrometry by monitoring the gadolinium 158 isotope. Statistical analyses were performed by using a preliminary Kruskal-Wallis test. Results Higher CSF gadolinium concentrations were detected within the first 8 hours after GBCA administration (mean concentration, 1152 ng/mL ± 734.6). Concentrations were lower between 8 and 48 hours (872 ng/mL ± 586). After 48 hours, gadolinium was almost completely cleared from CSF (121 ng/mL ± 296.3). All but two samples from the 24 control patients (median age, 60.5 years; range, 19-79 years) were negative for the presence of gadolinium. Those samples were from patients who had undergone GBCA-enhanced MRI examination more than a year before CSF extraction (0.1 and 0.2 ng/mL after 1 and 3 years, respectively). The concentrations in patients with chronic renal insufficiency (n = 3), cerebral toxoplasmosis (n = 1), and liver cirrhosis (n = 1) were higher than the mean concentrations. Conclusion Gadoterate meglumine can be detected in human CSF after intravenous administration.

Application of Cinematic Rendering in Clinical Routine CT Examination of Ankle Sprains.

OBJECTIVE: Cinematic rendering technique is used to generate almost photorealistic 3D reconstructions of volumetric data. The purpose of this study was to evaluate the feasibility of cinematically rendered reconstructions in routine CT examinations of ankle sprains. CONCLUSION: Cinematic rendering technique may be primarily used to deliver visual information to patients, physicians, and virtual anatomy classes. Postprocessing requires more time than traditional methods do, which can be a hindrance in clinical work.

Organ-based tube current modulation in a clinical context: Dose reduction may be largely overestimated in breast tissue.

OBJECTIVES: Organ-based tube current modulation aims to reduce exposure to radiosensitive organs like the breasts by considering their anatomical location and altering tube current during rotation. Former phantom studies demonstrated a dose reduction of 20-37 %. Our study aimed to estimate the potential of dose reduction with this technique in relation to the actual location of breast tissue in a large clinical cohort. METHODS: A 1-year cohort of chest CTs of females (N=1,263) was retrospectively evaluated. To estimate the relative dose effect, breast location was analysed by measuring the angle range of glandular tissue within the different dose zones. Relative exposure compared with constant tube current was calculated. Descriptive statistics and Wilcoxon-test were applied. RESULTS: Only 63 % of angle range of glandular breast tissue was found inside the reduced dose zone. The estimated mean relative dose reduction was lower than observed in former phantom studies(16 % vs. 20-37 %) but still significant compared to constant tube current (p<0.0001). CONCLUSIONS: Although organ-based tube current modulation results in a significant reduction of breast exposure compared to non-modulated irradiation, the technique cannot unfold its full potential, because breast tissue is often located outside the reduced dose zone, resulting in significantly lower dose reduction than expected. KEY POINTS: • OBTCM results in significant dose reduction compared to constant tube current scans. • A substantial portion of glandular tissue lies outside the reduced dose zone. • Potential dose reduction using organ-based tube current modulation may be overestimated.

Estimated risk of radiation-induced cancer from paediatric chest CT: two-year cohort study.

BACKGROUND: The increasing absolute number of paediatric CT scans raises concern about the safety and efficacy and the effects of consecutive diagnostic ionising radiation. OBJECTIVE: To demonstrate a method to evaluate the lifetime attributable risk of cancer incidence/mortality due to a single low-dose helical chest CT in a two-year patient cohort. MATERIALS AND METHODS: A two-year cohort of 522 paediatric helical chest CT scans acquired using a dedicated low-dose protocol were analysed retrospectively. Patient-specific estimations of radiation doses were modelled using three different mathematical phantoms. Per-organ attributable cancer risk was then estimated using epidemiological models. Additional comparison was provided for naturally occurring risks. RESULTS: Total lifetime attributable risk of cancer incidence remains low for all age and sex categories, being highest in female neonates (0.34%). Summation of all cancer sites analysed raised the relative lifetime attributable risk of organ cancer incidence up to 3.6% in female neonates and 2.1% in male neonates. CONCLUSION: Using dedicated scan protocols, total lifetime attributable risk of cancer incidence and mortality for chest CT is estimated low for paediatric chest CT, being highest for female neonates.

Pediatric chest CT at 70 kVp: a feasibility study in 129 children.

BACKGROUND: Before introducing 70-kVp settings in the low-kilovoltage strategies for pediatric examinations, it was mandatory to demonstrate, at similar dose levels, an equivalence of image quality at 70 kVp and 80 kVp. OBJECTIVE: To assess image quality of chest CT examinations acquired at 70 kVp in comparison with standard scanning at 80 kVp. MATERIALS AND METHODS: We prospectively evaluated 129 children with a 70-kVp scanning protocol (group 1). All scanning parameters were kept similar to those usually selected for pediatric standard 80-kVp protocols, except the milliamperage increased by a factor of 1.6 to maintain comparable radiation dose. Image quality of group 1 examinations was compared to that of a paired population scanned at 80 kVp (group 2). The noninferiority hypothesis was fixed at 10% of the mean level of image noise. RESULTS: There was no significant difference in the mean dose length product (DLP) and the volume computed tomography dose index (CTDIvol) between the groups (DLP: 20.5 ± 5.8 mGy.cm [group 1] vs. 19.7 ± 7.6 mGy.cm [group 2]; P = 0.06) (CTDIvol: 0.8 ± 0.1 mGy [group 1] vs. 0.8 ± 0.18 mGy [group 2]; P = 0.94). The mean of differences in image noise between group 1 and group 2 examinations was -1.38 (-2.59; -0.18), verifying the noninferiority hypothesis. Subjective image quality did not significantly differ between group 1 and group 2 examinations (P = 0.18). CONCLUSION: At equivalent radiation dose levels, 70-kVp protocols provide similar image quality to that achievable at 80 kVp.

A Simple and Safe Method for Checking the Position of Central Venous Catheters-A New and Reliable Threshold for Right Atrial Swirl Sign in Microbubbles Tests.

Background: Central venous catheters (CVCs) are indispensable tools in intensive care and emergency medicine. CVC malpositions still occur frequently and can cause various complications leading to increased patient mortality. A microbubbles test (MBT) can be used to confirm correct CVC positioning. However, there is serious doubt regarding whether the currently applied threshold of a 2 s push-to-bubbles time (PTB time) for rapid atrial swirl sign (RASS) in an MBT is reliable and accurate. The aim of the present study was to prove the quality of a new threshold: 1 s. Methods: Consecutive patients who were admitted to the intensive care unit (ICU) in a German neurological specialist hospital from 1 March 2021 to 20 July 2022 were enrolled. After ultrasound-guided CVC insertion, an MBT was performed, PTB time was measured, and RASS was interpreted. Additionally, a chest X-ray (CXR) was requested to check CVC position. Results: A total of 102 CVCs (98% jugular and 2% subclavian) were inserted in 102 patients (38% female and 62% male; median age: 66 years). Negative RASS (PTB time > 1 s) was observed in 2 out of 102 patients, resulting in an echocardiographic malposition rate of 2.0%. CXR confirmed the echocardiographic results. After correcting CVC position in the initially malpositioned CVCs, the PTB time was <1 s (positive RASS). The MBT protocol took about 0.5 min on average, while the CXR results were all available within 30 min. Sensitivity, specificity, and positive and negative predictive value were each 100% for the detection of CVC malpositions via an MBT using a threshold of 1 s compared to CXR. Conclusions: A new threshold of a 1 s PTB time for RASS in an MBT could detect CVC malpositions with excellent quality compared to CXR. Since the MBT was fast and safe and could be performed at the bedside, we propose that an MBT with the new and reliable threshold of 1 s should be routinely used in patient care.

The Transabdominal Lumbar Approach (TALA) for Robotic Renal Surgery-A Retrospective Single-Center Comparative Study and Step-by-Step Description of a Novel Approach.

The transperitoneal approach (TP) and the retroperitoneal approach (RP) are two common methods for performing nephrectomy or partial nephrectomy. However, both approaches face difficulties, such as trocar placement and limited working space (RP). TP is impaired in the case of dorsal tumors and dissection of the renal artery can be challenging due to the anatomic localization dorsally to the renal vein. A hybrid approach that combines both methods has been previously reported in a case series, but not evaluated systematically. This study proposes a modified hybrid approach, which we call the transabdominal lumbar approach (TALA), involving late robotic docking after elaborating the retroperitoneum using conventional laparoscopy. The study compares the last 20 consecutive patients who underwent RP and the last 20 patients who underwent TALA at our institution. The investigated variables include operative time and amount of blood loss, hospitalization duration, postoperative analgesia requirement, and postoperative complications. The study found no significant difference in operative time, blood loss, ischemia time, or hospital stay between the two groups. The TALA group had fewer complications regarding Clavien-Dindo category 3, but one complication of category 4. In Conclusion, TALA is a safe and promising approach that combines the advantages of RP and TP.

Clinical evaluation of automatic tube voltage selection in chest CT angiography.

OBJECTIVE: To evaluate the clinical impact of automatic tube voltage selection on chest CT angiography (CTA). METHODS: Ninety-three patients were prospectively evaluated with a CT protocol aimed at comparing two successive CTAs acquired under similar technical conditions except for the kV selection: (1) the initial CTA was systematically obtained at 120 kVp and 90 ref mAs; (2) the follow-up CTA was obtained with an automatic selection of the kilovoltage (Care KV; Siemens Healthcare) for optimised CTA. RESULTS: At follow-up, 90 patients (97 %) underwent CTA with reduced tube voltage, 100 kV (n = 26; 28 %) and 80 kV (n = 64; 69 %), resulting in a significant dose-length-product reduction (follow-up: 87.27; initial: 141.88 mGy.cm; P < 0.0001; mean dose reduction: 38.5 %) and a significant increase in the CNR at follow-up (follow-up: 11.5 ± 3.5 HU; initial: 10.9 ± 3.7 HU; P = 0.03). The increase in objective image noise at follow-up (follow-up: 23.2 ± 6.7 HU vs. 17.8 ± 5.1 HU; P < 0.0001) did not alter the diagnostic value of images. CONCLUSION: Automatic tube voltage selection reduced the radiation dose delivered during chest CT angiograms by 38.5 % while improving the contrast-to-noise ratio of the examinations. KEY POINTS: • As low a dose as possible must be used for CT angiography. • Automatic tube voltage selection permits reduced patient exposure. • Lowering the kVp enables increased intravascular attenuation. • Automatic tube voltage selection does not compromise the overall image quality.

Assessment of Image Quality in Chest CT With Precision Matrix and Increased Framing Rate Using Single Source CT: A Phantom Study.

BACKGROUND/AIM: The aim was to evaluate the effect of a combined precision matrix and high sampling rate on the delineation of anatomical structures and objective image quality in single source CT in a qualitative approach. MATERIALS AND METHODS: An anthropomorphic thoracic phantom was used to evaluate the objective image quality parameters, including image noise, noise power spectrum, image stepness and Q for different CT scanners including high/standard matrix and framing frequency setups. Scan parameters were standardized over all scanners. Additional subjective quality assessment was also performed. RESULTS: A linear mixed effects model was used to determine the effect of sampling rate and image matrix on objective image quality parameters. Noise power spectrum and image noise were significantly influenced by both framing frequency and image matrix. There were significant differences between high and standard frequency/matrix acquisitions. CONCLUSION: Higher framing frequency and image matrix allows for improved image noise texture and objective image quality in CT.

Evaluation of Image Quality of Overweight and Obese Patients in CT Using High Data Rate Detectors.

BACKGROUND/AIM: To evaluate the impact of high data rate and sampling frequency detector technology compared to standard scan equipment on the image quality in abdominal computed tomography (CT) of overweight and obese patients. PATIENTS AND METHODS: A total of 173 patients were retrospectively included in this study. Objective image quality in abdominal CT was evaluated using comparative analysis with new detector technology prior to market launch and standard CT equipment. Contrast noise ratio (CNR), image noise, volumetric computed tomography dose index (CTDIVol), and figures of merit (Q and Q1) were assessed for all patients. RESULTS: Image quality was superior in the new detector technology for all parameters evaluated. The dose dependent parameters Q and Q1 showed a significant difference (p<0.001). CONCLUSION: A significant increase in objective image quality could be demonstrated using a new generation detector setup with increased frequency transfer in abdominal CT of overweight patients.

Analysis of Diagnostic Modalities in Hospital-admitted Patients Evaluated for COVID-19.

BACKGROUND/AIM: To assess the diagnostic performance of reverse transcriptase polymerase chain reaction (RT-PCR), low-dose chest computed tomography (CT), and serological testing, alone and in combinations, as well as routine inflammatory markers in patients evaluated for COVID-19 during the first wave in early 2020. PATIENTS AND METHODS: We retrospectively analyzed data of all patients who were admitted to the emergency department due to fever and/or respiratory symptoms. CT scans were rated using the COVID-19 Reporting and Data System (CO-RADS) suspicion score. True disease status (COVID-19 - positive vs. negative) was adjudicated by two independent clinicians. Receiver-operating characteristic curves and areas under the curves were calculated for inflammatory markers. Sensitivities and specificities were calculated for RT-PCR, CT, and serology alone, as well as the combinations of RT-PCR+CT, RT-PCR+serology, CT+serology, and all three modalities. RESULTS: Of 221 patients with a median age of 72 years, 113 were classified as COVID-19 positive. Among 180 patients from which data on CT and RT-PCR were available, RT-PCR had the highest sensitivity to detect COVID-19 (0.87; 95%CI=0.78-0.93). Notably, the addition of CT in the analysis increased sensitivity to 0.89 (95%CI=0.8-0.94), but lowered specificity from 1 (95%CI=0.96-1) to 0.9 (95%CI=0.83-0.95). The combination of RT-PCR, CT and serology (n=60 patients with complete dataset) yielded a sensitivity of 0.83 (95%CI=0.61-0.94) and specificity of 0.86 (95%CI=0.72-0.93). CONCLUSION: RT-PCR was the best single test in patients evaluated for COVID-19. Conversely, the routine performance of chest CT adds little sensitivity and decreases specificity.

Influence of Radiation Dose, Photon Energy, and Reconstruction Kernel on rho/z Analysis in Spectral Computer Tomography: A Phantom Study.

BACKGROUND/AIM: The effective atomic number (Zeff) and electron density relative to water (ρe or Rho) of elements can be derived in dual-energy computed tomography (DECT). The aim of this phantom study was to investigate the effect of different photon energies, radiation doses, and reconstruction kernels on Zeff and Rho measured in DECT. MATERIALS AND METHODS: An anthropomorphic head phantom including five probes of known composition was scanned under three tube-voltage combinations in DECT: Sn140/100 kV, 140/80 kV and Sn140/80 kV with incremented radiation doses. Raw data were reconstructed with four reconstruction kernels (I30, I40, I50, and I70). Rho and Zeff were measured for each probe for all possible combinations of scan and reconstruction parameters. RESULTS: DECT-based Rho and Zeff closely approached the reference values with a mean and maximum error of 1.7% and 6.8%, respectively. Rho was lower for 140/80 kV compared with Sn140/100 kV and Sn140/80 kV with differences being 0.009. Zeff differed among all tube voltages with the most prominent difference being 0.28 between 140/80 kV and Sn140/100 kV. Zeff was lower in I70 compared with those of I30 and I40 with a difference of 0.07. Varying radiation dose yielded a variation of 0.0002 in Rho and 0.03 in Z, both considered negligible in practice. CONCLUSION: DECT comprises a feasible method for the extraction of material-specific information. Slight variations should be taken into account when different radiation doses, photon energies, and kernels are applied; however, they are considered small and in practice not crucial for an effective tissue differentiation.

Development and In Vitro Assessment of a Novel Vacuum-Based Tissue-Holding Device for Laparoscopic and Robotic Kidney Cancer Operations.

In this paper, we describe the development and evaluation of a novel tissue-holding device (THD) for use during robotic-assisted laparoscopic partial nephrectomy. The THD is a vacuum-based apparatus made of either 3D-printed polyethylene or stainless steel. The proximal end connects to suction tubing routed outside the body, while the distal end is conically shaped and designed to firmly interface with the tumor. Device feasibility studies were performed on six porcine kidneys, two porcine livers, and two embalmed human cadavers. A Likert-scale rating was used to assess device setup, suction, and tissue handling. Additional tests were performed using the daVinci Xi® robotic system. Finally, the holding force of the THD was assessed using different standard vacuum systems and pressure settings. In porcine tissue, the device setup, tissue suction, and handling were rated as "good". THD insertion and removal was uncomplicated. In a simulated transabdominal approach on fixed human cadavers, the device setup, suction, and tissue handling were also rated as "good". No macroscopic tissue compromise or device deterioration was noted. The handling and holding abilities using the daVinci Xi® robotic system were also rated "good". The device was able to successfully hold over 300 g of tissue at a suction pressure of -600 mmHg. The preliminary evaluation of the THD demonstrated satisfactory results.

Quantifying and Statistically Modeling Residual Pneumoperitoneum after Robotic-Assisted Laparoscopic Prostatectomy: A Prospective, Single-Center, Observational Study.

BACKGROUND: Laparoscopic surgery (LS) requires CO2 insufflation to establish the operative field. Patients with worsening pain post-operatively often undergo computed tomography (CT). CT is highly sensitive in detecting free air-the hallmark sign of a bowel injury. Yet, the clinical significance of free air is often confounded by residual CO2 and is not usually due to a visceral injury. The aim of this study was to attempt to quantify the residual pneumoperitoneum (RPP) after a robotic-assisted laparoscopic prostatectomy (RALP). METHODS: We prospectively enrolled patients who underwent RALP between August 2018 and January 2020. CT scans were performed on postoperative days (POD) 3, 5, and 7. To investigate potential factors influencing the quantity of RPP, correlation plots were made against common variables. RESULTS: In total, 31 patients with a mean age of 66 years (median 67, IQR 62-70.5) and mean BMI 26.59 (median 25.99, IQR: 24.06-29.24) underwent RALP during the study period. All patients had a relatively unremarkable post-operative course (30/31 with Clavien-Dindo class 0; 1/31 with class 2). After 3, 5, and 7 days, 3.2%, 6.4%, and 32.3% were completely without RPP, respectively. The mean RPP at 3 days was 37.6 mL (median 9.58 mL, max 247 mL, IQR 3.92-31.82 mL), whereas the mean RPP at 5 days was 19.85 mL (median 1.36 mL, max 220.77 mL, IQR 0.19-5.61 mL), and 7 days was 10.08 mL (median 0.09 mL, max 112.42 mL, IQR 0-1.5 mL). There was a significant correlation between RPP and obesity (p = 0.04665), in which higher BMIs resulted in lower initial insufflation volumes and lower RPP. CONCLUSIONS: This is the first study to systematically assess RPP after a standardized laparoscopic procedure using CT. Larger patients tend to have smaller residuals. Our data may help surgeons interpreting post-operative CTs in similar patient populations.