Non-contrast CT at comparable dose to an abdominal radiograph in patients with acute renal colic; impact of iterative reconstruction on image quality and diagnostic performance

Evaluation, management, and analysis of demographic and radiological characteristics of patients with renal colic at a tertiary hospital in Somalia

•

Renal Colic is a common emergenbcy care complaint worldwide–but its epidemiology and strategies for evaluation and treatment have been little reported in Africa.

•

To date, there have been no studies regarding epidemiologic and radiological findings of renal colic in the emergency centre reported from Somalia.

•

Ultrasound can be the initial investigation of choice because it is safe, cheap, and may help guide for diagnosis and need for further imaging.

Background

Renal colic is a common emergency centre (EC) complaint worldwide, but its epidemiology and strategies for evaluation and treatment have been little reported in Africa. To the best of our knowledge, this is the first study aimed at evaluating the radiological investigations, management, and analysis of demographic characteristics of patients with urinary system stones who visited the EC.

Method

A 3-year retrospective study of a total of 435 patients with acute renal colic who underwent radiologic investigations was included in this study. The overall positive stone rate, stone location, size, and hydronephrosis grade were assessed. The sensitivity and specificity of ultrasound were evaluated using patients with both an ultrasound and a non-contrast CT (NCCT).

Results

The mean age of the patients was 34.7years; males accounted for 71.3% (n = 310), while females were 28.7% (n = 125). Urolithiasis was found in 63.4% of the cases, 71.3% of males and 28.7% of the females had a stone diagnosis (P < 0001). There was no statistically significant association between age and stone diagnosis (P > 0.05). The sensitivity and specificity of USG were 86.1% and 94%, respectively. Seventy-two percent of the cases had ureteral stones (29% in proximal, 25% in UVJ, 9% in mid, and 9% in distal ureter), followed by 28% having renal stones (19% calyces and 9% in renal pelvis). The mean size of the stone was 5.9±1.8, half of the cases harbour stone size <5mm, followed by 30% in 5mm-1cm.

Conclusion

Due to the scarcity of well-equipped tertiary care hospitals and the low socioeconomic status of the patients living in Sub-Saharan Africa, Ultrasound can be the initial investigation of choice because it is safe, cheap, and may help guide diagnosis and the need for further imaging. However, NCCT remains the gold standard diagnosis of choice for acute flank pain.

Ultra-low-dose non-contrast CT and CT angiography can be used interchangeably for assessing maximal abdominal aortic diameter

Background

Routine CT scans may increasingly be used to document normal aortic size and to detect incidental abdominal aortic aneurysms.

Purpose

To determine whether ultra-low-dose non-contrast CT (ULDNC-CT) can be used instead of the gold standard CT angiography (CTA) for assessment of maximal abdominal aortic diameter.

Materials and Methods

This retrospective study included 50 patients who underwent CTA and a normal-dose non-contrast CT for suspected renal artery stenosis. ULDNC-CT datasets were generated from the normal-dose non-contrast CT datasets using a simulation technique. Using the centerline technique, radiology consultants (n = 4) and residents (n = 3) determined maximal abdominal aortic diameter. The limits of agreement with the mean (LOAM) was used to access observer agreement. LOAM represents how much a measurement by a single observer may plausibly deviate from the mean of all observers on the specific subject.

Results

Observers completed 1400 measurements encompassing repeated CTA and ULDNC-CT measurements. The mean diameter was 24.0 and 25.0 mm for CTA and ULDNC-CT, respectively, yielding a significant but minor mean difference of 1.0 mm. The 95% LOAM reproducibility was similar for CTA and ULDNC-CT (2.3 vs 2.3 mm). In addition, the 95% LOAM and mean diameters were similar for CTA and ULDNC-CT when observers were grouped as consultants and residents.

Conclusions

Ultra-low-dose non-contrast CT exhibited similar accuracy and reproducibility of measurements compared with CTA for assessing maximal abdominal aortic diameter supporting that ULDNC-CT can be used interchangeably with CTA in the lower range of aortic sizes.

Application of deep learning reconstruction of ultra-low-dose abdominal CT in the diagnosis of renal calculi

BACKGROUND

Renal calculi are a common and recurrent urological disease and are usually detected by CT. In this study, we evaluated the diagnostic capability, image quality, and radiation dose of abdominal ultra-low-dose CT (ULDCT) with deep learning reconstruction (DLR) for detecting renal calculi.

METHODS

Sixty patients with suspected renal calculi were prospectively enrolled. Low-dose CT (LDCT) images were reconstructed with hybrid iterative reconstruction (LD-HIR) and was regarded as the standard for stone and lesion detection. ULDCT images were reconstructed with HIR (ULD-HIR) and DLR (ULD-DLR). We then compared stone detection rate, abdominal lesion detection rate, image quality and radiation dose between LDCT and ULDCT.

RESULTS

A total of 130 calculi were observed on LD-HIR images. Stone detection rates of ULD-HIR and ULD-DLR images were 93.1% (121/130) and 95.4% (124/130). A total of 129 lesions were detected on the LD-HIR images. The lesion detection rate on ULD-DLR images was 92.2%, with 10 cysts < 5 mm in diameter missed. The CT values of organs on ULD-DLR were similar to those on LD-HIR and lower than those on ULD-HIR. Signal-to-noise ratio was highest and noise lowest on ULD-DLR. The subjective image quality of ULD-DLR was similar to that of LD-HIR and better than that of ULD-HIR. The effective radiation dose of ULDCT (0.64 ± 0.17 mSv) was 77% lower than that of LDCT (2.75 ± 0.50 mSv).

CONCLUSION

ULDCT combined with DLR could significantly reduce radiation dose while maintaining suitable image quality and stone detection rate in the diagnosis of renal calculi.

Reducing the rate of negative ureteroscopy: predictive factors and the role of preoperative imaging

INTRODUCTION

The aim of this study was to investigate factors that may predict a negative ureteroscopy (URS) performed for ureteric calculi in prestented patients and to assess preoperative imaging in reducing the rate of negative URS.

METHODS

Data were collected on emergency stent placement for a ureteric calculus from April 2011 to February 2016 (Group A) and October 2016 to October 2019 (Group B). Data included patient demographics, indication for a stent, stone characteristics, baseline bloods, urine culture, readmission, negative URS rate and the use of pre-URS imaging. Multivariate logistic regression was used for statistical analysis.

RESULTS

Of 257 patients who underwent emergency stent insertion, 251 underwent deferred URS for a ureteric calculus and 6 avoided URS due to pre-URS imaging. Indications for stent were pain (42%), sepsis (39%) and acute kidney injury (19%). Mean stone size was 7.8mm, mean stone density was 699 Hounsfield units (HU) and the stone locations were upper (62%), mid (13%) and lower ureter (25%). The overall negative URS rate was 12%. The negative URS rate was lower in patients with pre-URS imaging compared with those with none, 6% and 14%, respectively (OR=2.33, 95% CI: 0.69-7.56, p=0.2214). Logistic regression analysis indicated stone size as the only significant predictor of a negative URS, where the greater the size of the stone the less likely URS would be negative (β=0.75, 95% CI: 0.60-0.94 p=0.011).

CONCLUSIONS

Utilising pre-URS imaging can lead to a reduction in negative URS rate. Stone size <5mm appears to be the subgroup most likely to benefit from imaging.

Ultra-low-dose CTKUB: the new standard of follow-up of ureteric calculi not visible on plain radiograph?

PURPOSE

With sensitivities over 95%, non-contrast computer tomography of kidney, ureter and bladder (CTKUB) is the investigation of choice in renal colic to diagnose or exclude ureteric calculi. CTKUB delivers an average effective radiation dose of 5.4 millisievert (mSv) and is used to follow-up calculi not visible on plain X-ray, whereas plain radiography has a radiation exposure of 0.7 mSv and is used to follow-up radio-opaque calculi. We assessed the effectiveness of using ultra-low-dose CTKUB (ULDCTKUB) for the follow-up of ureteric calculi not visible on plain radiograph of the kidneys, ureter and bladder (KUB), as an emerging option to reduce radiation exposure compared to standard dose CTKUB.

METHODS

Between 2013 and 2016 we retrospectively analysed 86 patients who underwent ULDCTKUB for CTKUB-confirmed ureteric calculi that were not visible on plain radiography. Patients were identified from our Radiology Management System with additional information from electronic patient records.

RESULTS

98% of ULDCTKUBs were of diagnostic quality; two patients required further cross-sectional imaging. 67% of patients had passed their calculi after the initial diagnostic CTKUB. In the remaining 33% who had persistent calculi on ULDCTKUB, 20% required surgical intervention and 13% required no intervention. The mean ULDCTKUB effective radiation dose was six times lower than conventional CTKUB (0.8 vs 5.4 mSv). 67% of patients had a radiation dose equivalent to X-ray KUB (< 1 mSv).

CONCLUSION

ULDCTKUB is a reliable and safe follow-up investigation of ureteric calculi and has absorbed radiation doses similar to plain radiography and lower than annual background radiation. We advocate ULDCTKUB as the primary imaging modality in the follow-up of ureteric calculi not visible on plain radiograph.

Optimization of the scan length of head traumas on the pediatric and adult CT scan and proposition of a new acquisition limit

To propose a new method of reducing the scan length of head trauma while keeping the diagnostic efficiency of the examination in order to develop DRL in an African context. This is a retrospective single-center study including 145 patients who had cranial examinations on a 64-barettes scanner. All head trauma cases were selected. The interpretations of these CT scanners by the three radiologists of the service were noted to determine the acquisition limit. All patient acquisition lengths have been recorded. The acquisition limit for head trauma ended in clinical routine at cervical spine 4 (C4). The average scan length was 23.03 cm. Out of the CT scan results for 145 patients, only 2 (1.37%) had a C3 level cervical spine fracture and 2 (1.37%) at C4. By respecting the principles of radiation protection, this result has shown us that it is possible to limit the acquisition length of the CT scanners indicated for head trauma. The limit of the optimized scan length that we proposed is at cervical spine 2 (98.62%). Now, all head trauma are limited on cervical vertebra 2 in our hospital. The use of this new method is beneficial when the clinical indication of the examination and the type of trauma (multi-trauma) are taken into account. Based on the principles of radiation protection and the clinical indication for the examination, reducing the scan length from C4 to C2 is an effective way to reduce the dose absorbed by the patient.

Accuracy of bone segmentation and surface generation strategies analyzed by using synthetic CT volumes

Different kinds of bone measurements are commonly derived from computed-tomography (CT) volumes to answer a multitude of questions in biology and related fields. The underlying steps of bone segmentation and, optionally, polygon surface generation are crucial to keep the measurement error small. In this study, the performance of different, easily accessible segmentation techniques (global thresholding, automatic local thresholding, weighted random walk, neural network, and watershed) and surface generation approaches (different algorithms combined with varying degrees of simplification) was analyzed and recommendations for minimizing inaccuracies were derived. The different approaches were applied to synthetic CT volumes for which the correct segmentation and surface geometry were known. The most accurate segmentations of the synthetic volumes were achieved by setting a case-specific window to the gray value histogram and subsequently applying automatic local thresholding with appropriately chosen thresholding method and radius. Surfaces generated by the Amira® module Generate Lego Surface in combination with careful surface simplification were the most accurate. Surfaces with sub-voxel accuracy were obtained even for synthetic CT volumes with low contrast-to-noise ratios. Segmentation trials with real CT volumes supported the findings. Very accurate segmentations and surfaces can be derived from CT volumes by using readily accessible software packages. The presented results and derived recommendations will help to reduce the measurement error in future studies. Furthermore, the demonstrated strategies for assessing segmentation and surface qualities can be adopted to quantify the performance of new segmentation approaches in future studies.

Hybrid and Model-Based Iterative Reconstruction Influences the Volumetry of Visceral and Subcutaneous Adipose Tissue on Ultra-Low-Dose CT

OBJECTIVE

The aim of this study was to compare three different reconstruction algorithms for the volumetry of the visceral adipose tissue (VAT) and subcutaneous adipose tissue (SAT) on ultra-low-dose computed tomography (CT) images.

METHODS

Thirty-seven male patients underwent ultra-low-dose CT at the level of the fourth lumbar vertebra (22.5 mm in z-axis). The acquisitions were reconstructed in 5-mm slices with 50% overlap using filtered back projection (FBP), hybrid iterative reconstruction (HIR), and iterative model-based reconstruction (IMR) techniques. The volume of VAT and SAT was measured using an interactive seed-growing segmentation and by thresholding (-30 to -190 HU).

RESULTS

The volume of SAT measured by the interactive method was smaller in FBP compared with both HIR (P = 0.0011) and IMR (P = 0.0034), and the volume of VAT was greater in IMR compared with HIR (P = 0.0253) or FBP (P = 0.0065). Using the thresholding method, IMR volumes of VAT were greater compared with HIR (P < 0.0001), and volumes of SAT were greater compared with both HIR and FBP (both P ≤ 0.0001). The VAT to SAT ratio was greater in IMR compared with HIR or FBP (both P < 0.0001).

CONCLUSIONS

There are significant differences among FBP, HIR, and IMR in the volumetry of SAT and VAT, their ratios, and attenuation measured on ultra-low-dose images.

Comparison of submillisievert CT with standard-dose CT for urolithiasis

BACKGROUND

Patients with renal stones receive multiple computed tomography (CT) examinations. We investigated whether submillisievert (sub-mSv) CT for stone detection could reduce radiation dose at exposure levels comparable to kidney, ureter, and bladder (KUB) radiography.

PURPOSE

To evaluate the radiation dose exposure, diagnostic performance, and image quality of sub-mSv non-contrast CT using advanced modelled iterative reconstruction algorithm with spectral filtration for the detection of urolithiasis.

MATERIAL AND METHODS

A total of 145 consecutive patients underwent non-contrast CT using a third-generation dual-source scanner to obtain two datasets, i.e. 16.7% (sub-mSv CT, tube detector A) and 100% (standard-dose CT, combination of tube detector A and B) tube loads with spectral filtration. The performance of sub-mSv CT for the detection of stones was analyzed by two readers and compared with that of standard-dose CT. Image quality was measured subjectively and objectively.

RESULTS

In total, 171 stones were detected in 79 patients. The mean effective radiation doses of sub-mSv CT was 0.3 mSv. The sensitivity and specificity values for diagnosis of stones measuring ≥3 mm was 95.1% and 100% for sub-mSv CT. The sensitivity and specificity for all stone detection was 74.9% and 97.8%, respectivey, for sub-mSv CT. The image quality was lower for sub-mSv CT than for standard-dose CT (P < 0.01).

CONCLUSION

Sub-mSv CT can be achieved with radiation doses close to KUB radiography. Sub-mSv CT with spectral filtration can be used to detect stones measuring ≥3 mm and be used as a follow-up imaging modality as an alternative to KUB radiography.

Strategies for dose reduction with specific clinical indications during computed tomography

Increasing integration of computed tomography (CT) into routine patient care has escalated concerns regarding associated radiation exposure. Specific patient cohorts, particularly those with cystic fibrosis (CF) and Crohn's disease, have repeat exposures and thus have an increased risk of high lifetime cumulative effective dose exposures. Thoracic CT is the gold standard imaging method in the diagnosis, assessment and management of pulmonary disease. In the setting of CF, CT demonstrates increased sensitivity compared with pulmonary function tests and chest radiography. Furthermore, in specific cases of Crohn's disease, CT demonstrates diagnostic superiority over magnetic resonance imaging (MRI) for radiological evaluation. Low dose CT protocols have proven beneficial in the evaluation of CF, Crohn's disease and renal calculi, and in the follow up of testicular cancer patients. For individuals with chronic conditions warranting frequent radiological follow up, the focus must continue to be the incorporation of appropriate CT use into patient care. This is of particular importance for the paediatric population who are most susceptible to potential radiation induced malignancy. CT technological developments continue to focus on radiation dose optimisation. This article aims to highlight these advancements, which prioritise the acquisition of diagnostically satisfactory images with the least amount of radiation possible.

The efficacy of tin-filtration for computed tomography in diagnosing urolithiasis

INTRODUCTION

The purpose of this study was to evaluate the radiation dose and image quality of computed tomography urograms (CTU) using tin-filtration compared to conventional CTU (without tin-filtration) examinations in patients with suspected urolithiasis.

METHODS

Group 1 consisted of 100 patients who were examined using the tin-filtered CTU protocols (Sn100kVp or Sn150kVp); Group 2 consisted of 100 patients who were examined using the same protocols but without tin-filtration (GE-NI41 or GE-NI43). The scanning protocol was based on the patients' body weight (<80 kg and ≥80 kg). The effective doses of all scans were compared between the two groups. Subjective image quality was evaluated by two blinded radiologists. The objective image quality was assessed for noise, signal-to-noise ratio (SNR), contrast-to-noise ratio (CNR) and figure-of-merit (FOM) using the CTU scans acquired from both the tin-filtered and non-tin-filtered protocols.

RESULTS

Tin-filtration resulted in the reduction of effective radiation dose ranging between 72% to 88% for the ≥80 kg and <80 kg patient groups respectively. For both groups, tin-filtration resulted in no significant differences in SNR and a significant increase in FOM. For the <80 kg group, tin-filtration resulted in significantly noisier images but with no significant difference in CNR. For the ≥80 kg group, tin-filtration resulted in significantly higher CNR. There was no significant difference in subjective image quality when assessed by the radiologists in terms of diagnostic confidence for urolithiasis.

CONCLUSION

Tin-filtration significantly reduces patient dose while maintaining diagnostic image quality of CTUs for patients with suspected urolithiasis.

Low-Dose Computed Tomography for the Optimization of Radiation Dose Exposure in Patients with Crohn's Disease

Magnetic resonance imaging (MRI) is the mainstay method for the radiological imaging of the small bowel in patients with inflammatory bowel disease without the use of ionizing radiation. There are circumstances where imaging using ionizing radiation is required, particularly in the acute setting. This usually takes the form of computed tomography (CT). There has been a significant increase in the utilization of computed tomography (CT) for patients with Crohn's disease as patients are frequently diagnosed at a relatively young age and require repeated imaging. Between seven and eleven percent of patients with IBD are exposed to high cumulative effective radiation doses (CEDs) (>35–75 mSv), mostly patients with Crohn's disease (Newnham E 2007, Levi Z 2009, Hou JK 2014, Estay C 2015). This is primarily due to the more widespread and repeated use of CT, which accounts for 77% of radiation dose exposure amongst patients with Crohn's disease (Desmond et al., 2008). Reports of the projected cancer risks from the increasing CT use (Berrington et al., 2007) have led to increased patient awareness regarding the potential health risks from ionizing radiation (Coakley et al., 2011). Our responsibilities as physicians caring for these patients include education regarding radiation risk and, when an investigation that utilizes ionizing radiation is required, to keep radiation doses as low as reasonably achievable: the “ALARA” principle. Recent advances in CT technology have facilitated substantial radiation dose reductions in many clinical settings, and several studies have demonstrated significantly decreased radiation doses in Crohn's disease patients while maintaining diagnostic image quality. However, there is a balance to be struck between reducing radiation exposure and maintaining satisfactory image quality; if radiation dose is reduced excessively, the resulting CT images can be of poor quality and may be nondiagnostic. In this paper, we summarize the available evidence related to imaging of Crohn's disease, radiation exposure, and risk, and we report recent advances in low-dose CT technology that have particular relevance.

Emergency Physician Interpretation of Point-of-care Ultrasound for Identifying and Grading of Hydronephrosis in Renal Colic Compared With Consensus Interpretation by Emergency Radiologists

OBJECTIVE

The ability of emergency physicians (EPs) to identify hydronephrosis using point-of-care ultrasound (POCUS) has been assessed in the past using computed tomography (CT) scans as the reference standard. We aimed to determine the ability of EPs to identify and grade hydronephrosis on POCUS using the consensus interpretation of POCUS by emergency radiologists as the reference standard.

METHODS

The study was conducted at an urban academic emergency department (ED) as a secondary analysis of previously collected ultrasound data from the EP-performed POCUS databank. Patients were eligible for inclusion if they had both POCUS and CT scanning performed during the index ED visit. Two board-certified emergency radiologists and six EPs interpreted each POCUS study independently. The interpretations were compared with the consensus interpretation by emergency radiologists. Additionally, the POCUS interpretations were also compared with the corresponding CT findings. Institutional approval was obtained for conducting this study. All the analyses were performed using Stata MP 14.0 (StataCorp).

RESULTS

A total of 651 patient image-data sets were eligible for inclusion in this study. Hydronephrosis was reported in 69.6% of POCUS examinations by radiologists and 72.7% of CT scans (p = 0.22). Using the consensus radiology interpretation of POCUS as the reference standard, EPs had an overall sensitivity of 85.7% (95% confidence interval [CI] = 84.3%-87.0%), specificity of 65.9% (95% CI = 63.1%-68.7%), positive likelihood ratio of 2.5 (95% CI = 2.3-2.7), and negative likelihood ratio of 0.22 (95% CI = 0.19-0.24) for hydronephrosis. When using CT scan as the reference standard, the EPs had an overall sensitivity of 81.1% (95% CI = 79.6% to 82.5%), specificity of 59.4% (95% CI = 56.4%-62.5%), positive likelihood ratio of 2.0 (95% CI = 1.8-2.2), and negative likelihood ratio of 0.32 (95% CI = 0.29-0.35) for hydronephrosis. The specificity of EPs was improved to 94.6% (95% CI = 93.7%-95.4%) for categorizing the degree of hydronephrosis as "moderate or severe" versus "none or mild," with positive likelihood ratio of 6.33 (95% CI = 5.3-7.5) and negative likelihood ratio of 0.69 (95% CI = 0.66-0.73).

CONCLUSIONS

Emergency physicians were found to have moderate to high sensitivity for identifying hydronephrosis on POCUS when compared with the consensus interpretation of the same studies by emergency radiologists. These POCUS findings by EPs produced more definitive results when at least moderate degree of hydronephrosis was present.

Urolithiasis: Comparison of diagnostic performance of digital tomosynthesis and ultrasound. Which one to choose and when?

OBJECTIVE

To assess the diagnostic performance of digital tomosynthesis (DT) in detecting urolithiasis and compare it with ultrasonography (USG), keeping standard volumetric multi-detector computed tomography (MDCT) as the reference.

MATERIALS AND METHODS

This prospective analytical study was approved by our institutional ethical committee. A total of 66 patients were enrolled who had either clinical suspicion of urolithiasis or history of recurrent urolithiasis. All patients underwent DT, USG and MDCT within 24 h. In all these three investigations, the calculi were categorised according to their location and size by two radiologists. Sensitivity, specificity, positive and negative predictive values of DT and USG were calculated with MDCT as a reference standard.

RESULTS

Our study comprised of 66 patients (36 males and 30 females with age range of 19-73 years). A total of 121 calculi were assessed with 52 calculi <5 mm in size, 32 calculi measuring 5-10 mm and 37 calculi >10 mm. Kappa test of agreement was used to assess the interobserver agreement for all observations. The measurement of agreement kappa value was 1. The overall sensitivity of DT and USG in detecting urolithaisis was 50% (p value <0.001) and 50.4% (p value 0.005) respectively. No statistically significant difference was noted between USG and DT in detecting urolithiasis. The sensitivity of DT and USG in detecting renal calculi was 47.1% and 50.9% respectively and the sensitivity of DT and USG in detecting ureteric calculi was 74.9% and 39.2% respectively. We observed statistically significant difference between USG and DT in detecting ureteric calculi.

CONCLUSION

In our study, there was no statistically significant difference noted between USG and DT in diagnosis of urolithiasis. DT performed significantly better than USG in detecting ureteric calculi with a higher sensitivity. Hence, we are tempted to opine that DT may be preferred over USG for initial evaluation of patients with suspected ureteric calculi. However considering the strength of ultrasound in demonstrating associated signs as hydroureteronephosis, we are still of the opinion, that both DT and USG should be used as complementary techniques in resolving these common clinical screnarios.

Low-dose CT with adaptive statistical iterative reconstruction for evaluation of urinary stone

Purpose

To prospectively determine the diagnostic performance of low-dose CT (LDCT) with adaptive statistical iterative reconstruction (ASIR) technique for the detection of urinary stone disease.

Results

The average DLP and ED was 408.16 ± 119.04 mGy and 6.12 ± 1.79 mSv in CDCT, and 138.19 ± 76.87 mGy and 2.07 ± 1.15 mSv in LDCT, respectively. The dose reduction rate of LDCT was nearly 66.1% for both DLP and ED (P < 0.05). LDCT–80% ASIR images showed great image quality (mean score = 4.09), which was similar to CDCT-FBP images (mean score = 4.17) (P > 0.05), but higher than LDCT-FBP images (mean score = 2.77) (P < 0.05).

Materials and Methods

70 consetutive patients with clinically suspected urolithiasis underwent non-enhanced CT. Followed by both conventional-dose CT (CDCT) and low-dose CT (LDCT) scans. Automatic tube current modulation (ATCM) scanning was used, with a noise index setting of 13 in CDCT and 25 in LDCT. Reconstructions were performed with filtered back projection (FBP) and different settings of adaptive statistical iterative reconstruction [ASIR(40%, 60%, 80%)]. Urinary calculi (size, location, number), image quality (scale 1–5), image noise (scale 1–3) and diagnostic confidence levels (scale 1–3) were evaluated and measured by two radiologists independently. Radiation dose was recorded by calculating dose length product (DLP) and effective dose (ED). Statistical analyses included Mann-Whitney U test and Paired t tests.

Conclusions

LDCT with ASIR can reduce the radiation dose while maintain relatively high image quality in the diagnosis of urinary stone diseases.

Advances in Pancreatic CT Imaging. AJR Am J Roentgenol. 2018;211:52-66. [PMID: 29629796 DOI: 10.2214/ajr.17.18665]

OBJECTIVE

The purpose of this article is to discuss the advances in CT acquisition and image postprocessing as they apply to imaging the pancreas and to conceptualize the role of radiogenomics and machine learning in pancreatic imaging.

CONCLUSION

CT is the preferred imaging modality for assessment of pancreatic diseases. Recent advances in CT (dual-energy CT, CT perfusion, CT volumetry, and radiogenomics) and emerging computational algorithms (machine learning) have the potential to further increase the value of CT in pancreatic imaging.

Radiation dose reduction for CT assessment of urolithiasis using iterative reconstruction: A prospective intra-individual study

Objective

To assess the performance of hybrid (HIR) and model-based iterative reconstruction (MIR) in patients with urolithiasis at reduced-dose computed tomography (CT).

Methods

Twenty patients scheduled for unenhanced abdominal CT for follow-up of urolithiasis were prospectively included. Routine dose acquisition was followed by three low-dose acquisitions at 40%, 60% and 80% reduced doses. All images were reconstructed with filtered back projection (FBP), HIR and MIR. Urolithiasis detection rates, gall bladder, appendix and rectosigmoid evaluation and overall subjective image quality were evaluated by two observers.

Results

74 stones were present in 17 patients. Half the stones were not detected on FBP at the lowest dose level, but this improved with MIR to a sensitivity of 100%. HIR resulted in a slight decrease in sensitivity at the lowest dose to 72%, but outperformed FBP. Evaluation of other structures with HIR at 40% and with MIR at 60% dose reductions was comparable to FBP at routine dose, but 80% dose reduction resulted in non-evaluable images.

Conclusions

CT radiation dose for urolithiasis detection can be safely reduced by 40 (HIR)–60 (MIR) % without affecting assessment of urolithiasis, possible extra-urinary tract pathology or overall image quality.

Key Points

• Iterative reconstruction can be used to substantially lower the radiation dose.

• This allows for radiation reduction without affecting sensitivity of stone detection.

• Possible extra-urinary tract pathology evaluation is feasible at 40–60% reduced dose.

Electronic supplementary material

The online version of this article (doi:10.1007/s00330-017-4929-2) contains supplementary material, which is available to authorized users.

Dose and Image Quality in Low-dose CT for Urinary Stone Disease: Added Value of Automatic Tube Current Modulation and Iterative Reconstruction Techniques

The aim of this study was to compare dose and image quality (IQ) of a baseline low-dose computed tomography (CT) (fix mAs) vs. an ultra-low-dose CT (automatic tube current modulation, ATCM) in patients with suspected urinary stone disease and to assess the added value of iterative reconstruction. CT examination was performed on 193 patients (103 baseline low-dose, 90 ultra-low-dose). Filtered back projection (FBP) was used for both protocols, and Sinogram Affirmed Iterative Reconstruction (SAFIRE) was used for the ultra-low-dose protocol only. Dose and ureter stones information were collected for both protocols. Subjective IQ was assessed by two radiologists scoring noise, visibility of the ureter and overall IQ. Objective IQ (contrast-to-noise ratio, CNR) was assessed for the ultra-low-dose protocol only (FBP and SAFIRE). The ultra-low-dose protocol (ATCM) showed a 22% decrease in mean effective dose (p < 0.001) and improved visibility of the pelvic ureter (p = 0.02). CNR was higher for SAFIRE (p < 0.0001). SAFIRE improves the objective IQ, but not the subjective IQ for the chosen clinical task.

Optimizing z-axis coverage of abdominal CT scans of the urinary tract: a proposed alternative proximal landmark for acquisition planning

OBJECTIVE

To evaluate an alternative method to reduce the acquisition coverage of urinary tract CT.

METHODS

This retrospective study included 365 abdominopelvic CT studies. Three radiographers simulated shortened acquisition coverages using three methods to determine the upper limit of the acquisition: Method 1 used the renal contours; Method 2 used the inferior margin of the 10th thoracic vertebra; and Method 3 used the point of intersection of the left diaphragmatic dome and the anterior margin of the vertebral bodies. Reductions in acquisition coverage and number of CT scans with a portion of the kidney excluded from the simulated reduced acquisition were compared between the three methods.

RESULTS

The mean ± standard deviation reduction of acquisition coverage for the three readers with Methods 1, 2 and 3 were 20.5 ± 4.8, 15.1 ± 6.5 and 18.2 ± 5.3%, respectively. Compared with Method 2, Method 3 allowed a mean scan length reduction of 3.6%. The proportions of CT scans with a portion of the kidney excluded from the simulated reduced acquisition with Methods 1, 2 and 3 and averaged over the three readers were 6.7, 0.7 and 1.4%, respectively, with no significant difference between Methods 2 and 3. Interreader and intrareader agreements were excellent with all methods, but interclass correlation coefficients were higher with Method 3.

CONCLUSION

The method using the renal contours should not be used owing to its high proportion of kidneys with a portion excluded from the acquisition. Using the intersection of the left diaphragmatic dome and the anterior margin of the vertebral bodies for proximal landmark for urinary tract CT represents a new alternative method with a better reduction of scan length compared with the method using the inferior margin of T10 and with no significant increase in the number of kidneys with a portion excluded from the reduced acquisition. Advances in knowledge: A new method using the point of intersection of the left diaphragmatic dome and the anterior border of the vertebral bodies on the lateral scout radiograph is introduced to reduce the z-axis coverage of urinary tract CT scans.

Radiation dosing in the investigation and follow-up of urolithiasis: Comparison between historical and contemporary practices

Purpose

Computed tomography (CT) is the gold standard imaging modality for the diagnosis and follow-up of urolithiasis. Before the use of CT, intravenous urography (IVU) was the imaging modality of choice. CT remains contentious because of the cancer risk related to radiation exposure above a threshold level. We aimed to compare the radiation exposure dose to the average patient with urolithiasis in the era of CT with that of IVU.

Materials and Methods

Our hospital medical records database was searched for patients who presented to the Emergency Department over a 1-month period in 1990 with a diagnosis of renal colic. Patients with the same presentation, from the same month, in 2013 were also identified. A total of 14 patients from each year fulfilled the inclusion criteria. The estimated effective radiation exposure dose for each patient was calculated by using data from population-based studies.

Results

The median effective radiation dose per patient in the 1990 group, for initial diagnosis and subsequent follow-up, was 4.05 mSv (interquartile range [IQR], 3.7–4.4 mSv). The corresponding median dose in the 2013 group was 4.2 mSv (IQR, 4.2–4.9 mSv), and there was no evidence of a statistical difference between the groups (p=0.8).

Conclusions

Despite the contentiousness related to the use of serial CT scanning, our study demonstrated that for radiological investigation and follow-up of urolithiasis, the estimated effective radiation exposure dose to each patient is only marginally higher than in the era of IVU, with improvements in length of hospital stay and time to definitive diagnosis.

Imaging patients with renal colic-consider ultrasound first

Renal colic is a common disease in Europe and a common cause of visit to the Emergency Department. Clinical diagnosis is usually confirmed by imaging modalities. Unenhanced computed tomography (CT) is considered the best diagnostic test due to its excellent accuracy detecting ureteral stones. However, ultrasound (US) should be considered as the primary imaging technique. It is a reproducible, non-invasive and non-expensive imaging technique, achieving accurate diagnosis in most cases without the need for radiation. Diagnosis is based on the presence of ureteral stones, but indirect findings such as the asymmetry or absence of ureteric jet, an increase of the resistive index or a colour Doppler twinkling artefact may help to suggest the diagnosis when the stone is not identified.

MAIN MESSAGES

• Renal colic diagnosis is usually confirmed by imaging modalities. • Imaging diagnosis of renal colic is based on the detection of ureteral stones. • CT is the most accurate imaging technique to identify ureteral stones. • US allows correct diagnosis in most cases without using radiation. • US should be used as the first imaging modality in patients with renal colic.

Contrast agent and radiation dose reduction in abdominal CT by a combination of low tube voltage and advanced image reconstruction algorithms

OBJECTIVES

To assess image quality in abdominal CT at low tube voltage combined with two types of iterative reconstruction (IR) at four reduced contrast agent dose levels.

METHODS

Minipigs were scanned with standard 320 mg I/mL contrast concentration at 120 kVp, and with reduced formulations of 120, 170, 220 and 270 mg I/mL at 80 kVp with IR. Image quality was assessed by CT value, dose normalized contrast and signal to noise ratio (CNRD and SNRD) in the arterial and venous phases. Qualitative analysis was included by expert reading.

RESULTS

Protocols with 170 mg I/mL or higher showed equal or superior CT values: aorta (278-468 HU versus 314 HU); portal vein (205-273 HU versus 208 HU); liver parenchyma (122-146 HU versus 115 HU). In the aorta, all 170 mg I/mL protocols or higher yielded equal or superior CNRD (15.0-28.0 versus 13.7). In liver parenchyma, all study protocols resulted in higher SNRDs. Radiation dose could be reduced from standard CTDIvol = 7.8 mGy (6.2 mSv) to 7.6 mGy (5.2 mSv) with 170 mg I/mL.

CONCLUSION

Combining 80 kVp with IR allows at least a 47 % contrast agent dose reduction and 16 % radiation dose reduction for images of comparable quality.

KEY POINTS

• There is a balance between image quality, contrast dose and radiation dose. • Iterative reconstruction has a major, positive impact on this balance. • Both contrast dose and radiation dose can be reduced in abdominal CT. • The trade-off can be quantitatively described by a 3D model. • Contrast and radiation dose can be tailored according to specific safety concerns.