Patient radiation dose at CT urography and conventional urography

Stratifying risk of disease in haematuria patients using machine learning techniques to improve diagnostics

Background

Detailed and invasive clinical investigations are required to identify the causes of haematuria. Highly unbalanced patient population (predominantly male) and a wide range of potential causes make the ability to correctly classify patients and identify patient-specific biomarkers a major challenge. Studies have shown that it is possible to improve the diagnosis using multi-marker analysis, even in unbalanced datasets, by applying advanced analytical methods. Here, we applied several machine learning algorithms to classify patients from the haematuria patient cohort (HaBio) by analysing multiple biomarkers and to identify the most relevant ones.

Materials and methods

We applied several classification and feature selection methods (k-means clustering, decision trees, random forest with LIME explainer and CACTUS algorithm) to stratify patients into two groups: healthy (with no clear cause of haematuria) or sick (with an identified cause of haematuria e.g., bladder cancer, or infection). The classification performance of the models was compared. Biomarkers identified as important by the algorithms were also analysed in relation to their involvement in the pathological processes.

Results

Results showed that a high unbalance in the datasets significantly affected the classification by random forest and decision trees, leading to the overestimation of the sick class and low model performance. CACTUS algorithm was more robust to the unbalance in the dataset. CACTUS obtained a balanced accuracy of 0.747 for both genders, 0.718 for females and 0.803 for males. The analysis showed that in the classification process for the whole dataset: microalbumin, male gender, and tPSA emerged as the most informative biomarkers. For males: age, microalbumin, tPSA, cystatin C, BTA, HAD and S100A4 were the most significant biomarkers while for females microalbumin, IL-8, pERK, and CXCL16.

Conclusions

CACTUS algorithm demonstrated improved performance compared with other methods such as decision trees and random forest. Additionally, we identified the most relevant biomarkers for the specific patient group, which could be considered in the future as novel biomarkers for diagnosis. Our results have the potential to inform future research and provide new personalised diagnostic approaches tailored directly to the needs of the individuals.

A retrospective survey to establish institutional diagnostic reference levels for CT urography examinations based on clinical indications: preliminary results

Objective. To establish institutional diagnostic reference levels (IDRLs) based on clinical indications (CIs) for three- and four-phase computed tomography urography (CTU).Methods. Volumetric computed tomography dose index (CTDIvol), dose-length product (DLP), patients' demographics, selected CIs like lithiasis, cancer, and other diseases, and protocols' parameters were retrospectively recorded for 198 CTUs conducted on a Toshiba Aquilion Prime 80 scanner. Patients were categorised based on CIs and number of phases. These groups' 75th percentiles of CTDIvoland DLP were proposed as IDRLs. The mean, median and IDRLs were compared with previously published values.Results. For the three-phase protocol, the CTDIvol(mGy) and DLP (mGy.cm) were 22.7/992 for the whole group, 23.4/992 for lithiasis, 22.8/1037 for cancer, and 21.2/981 for other diseases. The corresponding CTDIvol(mGy) and DLP (mGy.cm) values for the four-phase protocol were 28.6/1172, 30.6/1203, 27.3/1077, and 28.7/1252, respectively. A significant difference was found in CTDIvoland DLP between the two protocols, among the phases of three-phase (except cancer) and four-phase protocols (except DLP for other diseases), and in DLP between the second and third phases (except for cancer group). The results are comparable or lower than most studies published in the last decade.Conclusions. The CT technologist must be aware of the critical dose dependence on the scan length and the applied exposure parameters for each phase, according to the patient's clinical background and the corresponding imaging anatomy, which must have been properly targeted by the competent radiologist. When clinically feasible, restricting the number of phases to three instead of four could remarkably reduce the patient's radiation dose. CI-based IDRLs will serve as a baseline for comparison with CTU practice in other hospitals and could contribute to national DRL establishment. The awareness and knowledge of dose levels during CTU will prompt optimisation strategies in CT facilities.

Can 3-Phase Computed Tomography Urography Be Used to Characterize Adrenal Nodules? Results in 145 Patients

OBJECTIVE

The aim of the study is to determine whether computed tomography (CT) urography (CTU) can characterize incidental adrenal nodules.

METHODS

This retrospective cohort study was performed at an academic medical center. Patients were identified by free text search of CTU reports that contained the terms "adrenal mass" "adrenal nodule" and "adrenal lesion." Computed tomography urography technique consisted of unenhanced images and postcontrast images obtained at 100 seconds and 15 minutes. The final cohort included 145 patients with 151 adrenal nodules. Nodules were considered lipid-rich adenomas or myelolipomas based on unenhanced imaging characteristics. Absolute and relative washout values were calculated for the remaining nodules, using a cutoff of 60% and 40%, respectively, to diagnose adenomas. Reference standard for lipid-poor adenomas and malignant nodules was histopathology or imaging/clinical follow-up. Mann-Whitney U test was used for comparison of continuous variables, and Fisher exact test was used for categorical variables.

RESULTS

One hundred nodules were lipid-rich adenomas and 3 were myelolipomas. Forty-eight nodules were indeterminate at unenhanced CT, corresponding to 39 lipid-poor adenomas and 9 malignant nodules based on reference standards. Both absolute and relative washout correctly characterized 71% of nodules (34/48), with a sensitivity of 67% and specificity of 89%. Overall, 91% of all adrenal nodules (137/151) were correctly characterized by CTU alone. Lipid-poor adenomas were smaller than malignant nodules (P < 0.01) and were lower in attenuation on unenhanced and delayed images (P < 0.01).

CONCLUSIONS

Adrenal nodules detected at 3-phase CTU can be accurately characterized, potentially eliminating the need for subsequent adrenal protocol CT or magnetic resonance imaging.

Essentials of Computed Tomography Imaging of Hematuria

Hematuria is defined usually as the presence of blood in the urine, either on voiding or in a catheterized specimen. Hematuria is broadly divided into microscopic and gross hematuria and may be symptomatic or asymptomatic. The causes of hematuria include a very wide spectrum of conditions. However, here, we have filtered the causes causing gross hematuria, including calculus, trauma, tumors, vascular, and miscellaneous causes. Plain X-rays of the kidney, ureter, and bladder; ultrasound; intravenous urography; computed tomography (CT); magnetic resonance imaging; retrograde ureterography and pyelography (RGP); cystoscopy; and ureteroscopy are techniques that are useful for diagnosis. In the past, one or a combination of several techniques was used to evaluate hematuria but recently, advances in CT urography mean that it can be used alone for this task. This article briefly reviews the common causes of gross hematuria in adults and their evaluation by CT-based urography. Gross hematuria is evaluated well with CT scan urography which includes an unenhanced scan, the nephrographic phase, and the excretory phase. Unenhanced scans are routinely performed to evaluate the basic parameters such as the size, shape, position, and outline of the kidneys and calculus disease, which is the most common cause of hematuria. Renal parenchymal diseases including masses are best visualized in the nephrographic phase along with other abdominal organs. Delayed excretory phases including the kidneys, ureters, and bladder are useful for detecting urothelial diseases. CT urography's protocol permits evaluations of hematuria through a single examination.

CT-urography: a nationwide survey by the Italian Board of Urogenital Radiology

Computed tomography-urography is currently the imaging modality of choice for the assessment of the whole urinary tract, giving the possibility to detect and characterize benign and malignant conditions. In particular, computed tomography-urography takes advantage from an improved visualization of the urinary collecting system due to acquisition of delayed scan obtained after excretion of intravenous contrast medium from the kidneys. Nevertheless, the remaining scans are of great help for identification, characterization, and staging of urological tumors. Considering the high number of diseases, urinary segment potentially involved and patients' features, scanning protocols of computed tomography-urography largely vary from one clinical case to another as well as selection and previous preparation of the patient. According to the supramentioned considerations, radiation exposure is also of particular concern. Italian radiologists were asked to express their opinions about computed tomography-urography performance and about its role in their daily practice through an online survey. This paper collects and summarizes the results.

Reduced dose iterative reconstruction versus standard dose filtered back projection in detection of bladder tumors

Background

The purpose was to assess radiation dose, image quality, and diagnostic performance of reduced-dose scanning with iterative reconstruction (IR) compared with standard-dose with filtered back projection (FBP) with CT urography for detection of bladder tumor. This study was prospectively conducted on 21 patients with bladder masses. All patients were subjected to two scanning protocols: protocol A (standard dose with FBP) and protocol B (additional limited scan to the pelvis at delayed phase with low dose with IR). Based on body weight (< or > 80 kg), each protocol was subdivided into 2 protocols A1 (130 kVp) and A2 (130 kVp) and protocols B1 (80 kVp) and B2 (110 kVp). Radiation dose was assessed in terms of mean CT dose index (CTDI), Dose-length product (DLP) and effective dose (ED). Image quality and diagnostic accuracy were compared in both groups.

Results

Mean CTDI, DLP and ED were reduced by average 72.3 % in the 80 kVp protocol (B1) and by 36.3% in 110 kVp (B2) protocol compared to standard-dose protocols. There were significantly lower SNR (signal to noise ratio) between protocol A1 and B1 at aorta and psoas muscles. Subjective image quality analysis revealed no statistically significant differences between the protocol A2 and B2 whereas there were significant differences between protocol A1and B1 as regards to visual image noise and overall image quality. Diagnostic accuracy was identical among different protocols.

Conclusion

CT urography with IR scanning showed reduced radiation dose and no difference in detection of urothelial carcinomas from standard dose with FBP despite of degraded image quality in 80 kVp scanning.

Prevalence of Urologic Disease Among Patients Investigated for Hematuria With CT Urography

PURPOSE

The current study evaluated the prevalence of urologic disease among patients with hematuria referred for computerized tomography (CT) urography to determine which patients require investigation with CT urography.

METHODS

We retrospectively reviewed radiology reports of 1046 CT urograms performed for the indication of microscopic (43.7%) or gross hematuria (56.3%). Urological findings were categorized as negative, benign, or suspicious (pathologically confirmed) for malignancy.

RESULTS

Of 1046 CT urograms performed, 53.5% were negative, 36.4% were benign, and 10% were suspicious for malignancy. The most common benign finding was urolithiasis (22.3%). Overall, urinary tract malignancies were present in 3.6% of patients, and the rate was significantly higher (P < .001) for gross (5.8%) than microscopic hematuria (0.9%). CT urography identified 0.6% patients with upper urinary tract malignancies; the malignancy rate was significantly higher (P = .038) for gross (1%) than microscopic hematuria (0%), and no significant sex (P = 1.00; male = 0.6%, female = 0.6%) or age (P = .600; < 50 years = 0%, ≥ 50 years = 0.7%) differences were observed. Logistic regression revealed that being male was associated with gross hematuria (odds ratio [OR] = 2.92), and that both age and gross hematuria (ORs = 1.06 and 5.13, respectively) were associated with malignancy.

CONCLUSIONS

CT urography found no upper urinary tract malignancies in 99.4% of patients presenting with hematuria, including all patients with microscopic hematuria and those with gross hematuria <50 years old. Investigating these subgroups with CT urography may be unnecessary and result in increased patient morbidity and health-care costs.

Imaging protocols for CT urography: results of a consensus conference from the French Society of Genitourinary Imaging

OBJECTIVES

To develop technical guidelines for computed tomography urography.

METHODS

The French Society of Genitourinary Imaging organised a Delphi consensus conference with a two-round Delphi survey followed by a face-to-face meeting. Consensus was strictly defined using a priori criteria.

RESULTS

Forty-two expert uro-radiologists completed both survey rounds with no attrition between the rounds. Ninety-six (70%) of the initial 138 statements of the questionnaire achieved final consensus. An intravenous injection of 20 mg of furosemide before iodinated contrast medium injection was judged mandatory. Improving the quality of excretory phase imaging through oral or intravenous hydration of the patient or through the use of an abdominal compression device was not deemed necessary. The patient should be imaged in the supine position and placed in the prone position only at the radiologist's request. The choice between single-bolus and split-bolus protocols depends on the context, but split-bolus protocols should be favoured whenever possible to decrease patient irradiation. Repeated single-slice test acquisitions should not be performed to decide of the timing of excretory phase imaging; instead, excretory phase imaging should be performed 7 min after the injection of the contrast medium. The optimal combination of unenhanced, corticomedullary phase and nephrographic phase imaging depends on the context; suggestions of protocols are provided for eight different clinical situations.

CONCLUSION

This expert-based consensus conference provides recommendations to standardise the imaging protocol for computed tomography urography.

KEY POINTS

• To improve excretory phase imaging, an intravenous injection of furosemide should be performed before the injection of iodinated contrast medium. • Systematic oral or intravenous hydration is not necessary to improve excretory phase imaging. • The choice between single-bolus and split-bolus protocols depends on the context, but split-bolus protocols should be favoured whenever possible to decrease patient irradiation.

Feasibility of multi-contrast imaging on dual-source photon counting detector (PCD) CT: An initial phantom study

PURPOSE

Photon-counting-detector-computed tomography (PCD-CT) allows separation of multiple, simultaneously imaged contrast agents, such as iodine (I), gadolinium (Gd), and bismuth (Bi). However, PCDs suffer from several technical limitations such as charge sharing, K-edge escape, and pulse pile-up, which compromise spectral separation of multi-energy data and degrade multi-contrast imaging performance. The purpose of this work was to determine the performance of a dual-source (DS) PCD-CT relative to a single-source (SS) PCD-CT for the separation of simultaneously imaged I, Gd, and Bi contrast agents.

METHODS

Phantom experiments were performed using a research whole-body PCD-CT and head/abdomen-sized phantoms containing vials of different I, Gd, Bi concentrations. To emulate a DS-PCD-CT, the phantoms were scanned twice on the SS-PCD-CT using different tube potentials for each scan. A tube potential of 80 kV (energy thresholds = 25/50 keV) was used for low-energy tube, while the high-energy tube used Sn140 kV (Sn indicates tin filter) and thresholds of 25/90 keV. The same phantoms were scanned also on the SS-PCD-CT using the chess acquisition mode. In chess mode, the 4 × 4 subpixels within a macro detector pixel are split into two sets based on a chess-board pattern. With each subpixel set having two energy thresholds, chess mode allows four energy-bin data sets, which permits simultaneous multi-contrast imaging. Because of this design, only 50% area of each detector pixel is configured to receive photons of a pre-defined threshold, leading to 50% dose utilization efficiency. To compensate for this dose inefficiency, the radiation dose for this scan was doubled compared to DS-PCD-CT. A 140 kV tube potential and thresholds = 25/50/75/90 keV were used. These settings were determined based on the K-edges of Gd, and Bi, and were found to yield good differentiation of I/Gd/Bi based on phantom experiments and other literature. The energy-bin images obtained from each scan (scan pair) were used to generate I-, Gd-, Bi-specific image via material decomposition. Root-mean-square-error (RMSE) between the known and measured concentrations was calculated for each scenario. A 20-cm water cylinder phantom was scanned on both systems, which was used for evaluating the magnitude of noise, and noise power spectra (NPS) of I/Gd/Bi-specific images.

RESULTS

Phantom results showed that DS-PCD-CT reduced noise in material-specific images for both head and body phantoms compared to SS-PCD-CT. The noise level of SS-PCD was reduced from 2.55 to 0.90 mg/mL (I), 1.97 to 0.78 mg/mL (Gd), and 0.85 to 0.74 mg/mL (Bi) using DS-PCD. NPS analysis showed that the noise texture of images acquired on both systems is similar. For the body phantom, the RMSE for SS-PCD-CT was reduced relative to DS-PCD-CT from 10.52 to 2.76 mg/mL (I), 7.90 to 2.01 mg/mL (Gd), and 1.91 to 1.16 mg/mL (Bi). A similar trend was observed for the head phantom: RMSE reduced from 2.59 (SS-PCD) to 0.72 (DS-PCD) mg/mL (I), 2.02 to 0.58 mg/mL (Gd), and 0.85 to 0.57 mg/mL (Bi).

CONCLUSION

We demonstrate the feasibility of performing simultaneous imaging of I, Gd, and Bi materials on DS-PCD-CT. Under the condition without cross scattering, DS-PCD reduced the RMSE for quantification of material concentration in relative to a SS-PCD-CT system using chess mode.

Low-Tube-Voltage CT Urography Using Low-Concentration-Iodine Contrast Media and Iterative Reconstruction: A Multi-Institutional Randomized Controlled Trial for Comparison with Conventional CT Urography

Objective

To compare the image quality of low-tube-voltage and low-iodine-concentration-contrast-medium (LVLC) computed tomography urography (CTU) with iterative reconstruction (IR) with that of conventional CTU.

Materials and Methods

This prospective, multi-institutional, randomized controlled trial was performed at 16 hospitals using CT scanners from various vendors. Patients were randomly assigned to the following groups: 1) the LVLC-CTU (80 kVp and 240 mgI/mL) with IR group and 2) the conventional CTU (120 kVp and 350 mgI/mL) with filtered-back projection group. The overall diagnostic acceptability, sharpness, and noise were assessed. Additionally, the mean attenuation, signal-to-noise ratio (SNR), contrast-to-noise ratio (CNR), and figure of merit (FOM) in the urinary tract were evaluated.

Results

The study included 299 patients (LVLC-CTU group: 150 patients; conventional CTU group: 149 patients). The LVLC-CTU group had a significantly lower effective radiation dose (5.73 ± 4.04 vs. 8.43 ± 4.38 mSv) compared to the conventional CTU group. LVLC-CTU showed at least standard diagnostic acceptability (score ≥ 3), but it was non-inferior when compared to conventional CTU. The mean attenuation value, mean SNR, CNR, and FOM in all pre-defined segments of the urinary tract were significantly higher in the LVLC-CTU group than in the conventional CTU group.

Conclusion

The diagnostic acceptability and quantitative image quality of LVLC-CTU with IR are not inferior to those of conventional CTU. Additionally, LVLC-CTU with IR is beneficial because both radiation exposure and total iodine load are reduced.

Upper Tract Imaging in Patients with Initial or Terminal Hematuria Suggestive of Bleeding from the Lower Urinary Tract: How Often is the Upper Urinary Tract Responsible for the Hematuria?

Objectives

Visible hematuria (VH) is a common urological complaint. A history of initial or terminal VH in men is indicative of a lower urinary tract (LUT) source. A careful clinical history could limit unnecessary extensive upper tract imaging in this group of patients with VH. We conducted a single-center prospective study to examine the usefulness of investigating the upper tract in patients with a history of VH likely from a LUT source (initial and/or terminal VH) with specific reference to the incidence of demonstrable significant upper tract abnormalities.

Methods

We conducted a single-center prospective study of consecutive male patients presenting with VH over eight months. All patients underwent standard investigations including physical examination, flexible cystoscopy (FC), and radiological imaging (ultrasound scan (USS) and/or computed tomography urogram (CTU)). Those with a clear history of initial or terminal VH were identified for further scrutiny with regards to detectable upper tracts abnormalities.

Results

In total, 57 patients (aged 23-95 years) with initial or terminal VH were identified. Of these, 56 had FC and nine patients were subsequently diagnosed with a LUT malignancy. With regards to upper urinary tract (UUT), 35 patients (61.4%) had an USS, 46 (80.7%) underwent a CTU, and 25 (43.9%) patients had both. In this group, no UUT malignancy was identified on upper tract imaging.

Conclusions

Initial or terminal VH patients may not need extensive upper tract imaging. FC is recommended, but a non-invasive USS can be a safe initial investigation for the UUT, with a CTU subsequently considered in those with abnormalities on USS and those with ongoing bleeding. Further combined multicenter analysis will help corroborate these findings and could have several beneficial outcomes including a reduction in investigations cost, patient inconvenience, and ionizing radiation.

Diagnostic value of 64-slice spiral computed tomography imaging of the urinary tract during the excretory phase for urinary tract obstruction

The present study aimed to assess the diagnostic value of 64-slice spiral computed tomography (CT) imaging of the urinary tract during the excretory phase for urinary tract obstruction. CT imaging of the urinary tract during the excretory phase was performed in 46 patients that had been diagnosed with urinary tract obstruction by B-mode ultrasound imaging or clinical manifestations. It was demonstrated that out of the 46 patients, 18 had pelvic and ureteral calculi, 12 cases had congenital malformations, 3 had ureteral stricture caused by urinary tract infection and 13 cases had malignant tumors of the urinary tract. The average X-ray dose planned for the standard CT scan of the urinary tract group 1 was 14.11±5.45 mSv, while the actual X-ray dose administered for the CT scan during the excretory phase group 2 was 9.01±4.56 mSv. The difference between the two groups was statistically significant (t=15.36; P<0.01). The results of the present study indicate that CT scanning of the urinary tract during the excretory phase has a high diagnostic value for urinary tract obstruction.

Low-dose CT protocols for guiding radiofrequency ablation for the treatment of small renal cell carcinomas

OBJECTIVE

Computed tomography (CT)-guided radiofrequency ablation (RFA) results in a high radiation dose. This study aimed to assess low-dose CT protocols for guiding RFA and oncologic outcomes for the treatment of small renal cell carcinoma (RCC).

MATERIALS AND METHODS

Between December 2011 and December 2014, CT-guided RFA was performed in 31 patients with 31 biopsy-proven RCCs (median, 2.1 cm). RFA included planning, targeting, monitoring and survey phases. The dose length product (DLP), CT dose index volume (CTDIvol), effective dose, number of scans, scan range, tube current and exposure time of RFA phases were compared. The 3-year recurrence-free survival rate was recorded. Nonparametric or parametric repeated-measures ANOVA with Dunn's or Tukey-Kramer multiple comparisons and Kaplan-Meier analysis were used for statistical analysis.

RESULTS

The median total DLP, CTDIvol and effective dose of CT-guided RFA procedures per session were 1238.8 mGy (range 517.4-3391.7 mGy), 259.7 mGy (10.7-67.9 mGy) and 18.6 mSv (7.8-50.9 mSv), respectively. The median DLP, CTDIvol, effective dose, number of scans, tube current and exposure time during the targeting phase were higher than those during the other phases (p < 0.001). The scan range in the targeting phase was the same as that in the monitoring phase (p > 0.05) but smaller than those in the planning and survey phases (p < 0.001). The 3-year recurrence-free survival rate was 96.7%.

CONCLUSIONS

Low-dose CT protocols for guiding RFA may reduce radiation dose without compromising oncologic outcomes. Reducing the number of scans during the targeting phase contributes to dose reduction.

Lumbar spine evaluation: accuracy on abdominal CT

OBJECTIVE

To determine if the lumbar spine can be accurately evaluated on an abdominal CT.

METHODS

The electronic medical records at our institution were searched to find all consecutive patients who had an abdominal CT within 12 months of a lumbar spine MRI obtained between 01 November 2010 and 31 October 2015. The abdominal CT studies were retrospectively reviewed in a blinded fashion for the presence of any significant lumbar spine abnormalities. The prospective lumbar spine MRI reports were used as the standard of reference.

RESULTS

5,031 patients had lumbar spine MRI studies at our institution during the study period of 01 November 2010 to 31 October 2015. 144 patients met the inclusion criteria of our study. No patients were excluded. 107 patients had 256 abnormal findings on the lumbar spine MRI studies. The sensitivity, specificity, positive predictive value, negative predictive value and accuracy of abdominal CT in lumbar spine evaluation on a per patient/per finding basis were 89.7/95.3%, 97.3/100%, 99.0/99.2%, 76.6/99.8% and 91.7/99.8%, respectively.

CONCLUSION

Despite several limitations (e.g. spinal cord assessment, bone marrow assessment and quantum mottle) compared with evaluation of the lumbar spine using MRI, evaluation of the lumbar spine on abdominal CT studies can be accurately performed with current state of the art CT scanners. Additional prospective studies are needed for a more definitive analysis. Advances in knowledge: With recent advances in CT technology, accurate evaluation of the lumbar spine on abdominal CT studies is feasible, potentially providing significant additional information to patients without additional imaging.

Photon-counting CT for simultaneous imaging of multiple contrast agents in the abdomen: An in vivo study

PURPOSE

To demonstrate the feasibility of spectral imaging using photon-counting detector (PCD) x-ray computed tomography (CT) for simultaneous material decomposition of three contrast agents in vivo in a large animal model.

METHODS

This Institutional Animal Care and Use Committee-approved study used a canine model. Bismuth subsalicylate was administered orally 24-72 h before imaging. PCD CT was performed during intravenous administration of 40-60 ml gadoterate meglumine; 3.5 min later, iopamidol 370 was injected intravenously. Renal PCD CT images were acquired every 2 s for 5-6 min to capture the wash-in and wash-out kinetics of the contrast agents. Least mean squares linear material decomposition was used to calculate the concentrations of contrast agents in the aorta, renal cortex, renal medulla and renal pelvis.

RESULTS

Using reference vials with known concentrations of materials, we computed molar concentrations of the various contrast agents during each phase of CT scanning. Material concentration maps allowed simultaneous quantification of both arterial and delayed renal enhancement in a single CT acquisition. The accuracy of the material decomposition algorithm in a test phantom was -0.4 ± 2.2 mM, 0.3 ± 2.2 mM for iodine and gadolinium solutions, respectively. Peak contrast concentration of gadolinium and iodine in the aorta, renal cortex, and renal medulla were observed 16, 24, and 60 s after the start each injection, respectively.

CONCLUSION

Photon-counting spectral CT allowed simultaneous material decomposition of multiple contrast agents in vivo. Besides defining contrast agent concentrations, tissue enhancement at multiple phases was observed in a single CT acquisition, potentially obviating the need for multiphase CT scans and thus reducing radiation dose.

Assessment of the ability of CT urography with low-dose multi-phasic excretory phases for opacification of the urinary system

Objective

To prospectively evaluate the ability of CT urography with a low-dose multi-phasic excretory phase for opacification of the urinary system.

Materials and methods

Thirty-two patients underwent CT urography with low-dose multi-phasic s using adaptive iterative dose reduction 3D acquired at 5-, 10-, and 15-minute delays. Opacification scores of the upper urinary tracts and the urinary bladder were assigned for each excretory phase by two radiologists, who recorded whether adequate (>75%) or complete (100%) opacification of the upper urinary tract and urinary bladder was achieved in each patient. Adequate and complete opacification rates of the upper urinary tracts and the urinary bladder were compared among three excretory phases and among combined multi-phasic excretory phases using Cochran's Q test.

Results

There was no significant difference among three excretory phases with 5-, 10-, and 15-minute delays in adequate (56.3, 43.8, and 63.5%, respectively; P = 0.174) and complete opacification rates (9.3, 15.6, and 18.7%, respectively; P = 0.417) of the upper urinary tracts. Combined tri-phasic excretory phases significantly improved adequate and complete opacification rates to 84.4% and 43.8%, respectively (P = 0.002). In contrast, there were significant differences among three excretory phases for the rate of adequate (31.3, 84.4, and 93.8%, respectively; P<0.001) and complete opacification (21.9, 53.1, and 81.3%, respectively; P<0.001) of the urinary bladder. Multi-phasic excretory phases did not improve these rates because opacification was always better with a longer delay.

Conclusion

Although multi-phasic acquisition of excretory phases is effective at improving opacification of the upper urinary tracts, complete opacification is difficult even with tri-phasic acquisition.

Preliminary study on the differentiation between parapelvic cyst and hydronephrosis with non-calculous using only pre-contrast dual-energy spectral CT scans

OBJECTIVE

To investigate the value of using the quantitative parameters from only the pre-contrast dual-energy spectral CT imaging for distinguishing between parapelvic cyst and hydronephrosis with non-calculous (HNC).

METHODS

This retrospective study was approved by the institutional review board. 28 patients with parapelvic cyst and 24 patients with HNC who underwent standard pre-contrast and multiphase contrast-enhanced dual-energy spectral CT imaging were retrospectively identified. The parapelvic cyst and HNC were identified using the contrast-enhanced scans, and their CT number in the 70-keV monochromatic images, effective atomic number (Z_eff), iodine concentration (IC) and water concentration in the pre-contrast images were measured. The slope of the spectral curve (λ) was calculated. The difference in the measurements between parapelvic cyst and HNC was statistically analyzed using SPSS^® v. 19.0 (IBM Corp., New York, NY; formerly SPSS Inc., Chicago, IL) statistical software. Receiver-operating characteristic analysis was performed to assess the diagnostic performance.

RESULTS

The CT numbers in the 70-keV images, Z_eff and IC values were statistically different between parapelvic cyst and HNC (all p < 0.05). The sensitivity, specificity and accuracy of these parameters for distinguishing between parapelvic cyst and HNC were 89.2%, 73.3% and 82.1%; 86.5%, 43.3% and 67.2%; 91.9%, 40.0% and 68.7%; and 64.9%, 73.3% and 83.6%, respectively, and the combined specificity was 92.9%. There was no statistical difference in λ between the two groups (p > 0.05).

CONCLUSION

The quantitative parameters obtained in the pre-contrast dual-energy spectral CT imaging may be used to differentiate between parapelvic cyst and HNC. Advances in knowledge: The pre-contrast dual-energy spectral CT scans may be used to screen parapelvic cysts for patients who are asymptomatic, thereby avoiding contrast-enhanced CT or CT urography examination for these patients to reduce ionizing radiation dose and contrast dose.

Computed tomography and patient risk: Facts, perceptions and uncertainties

Since its introduction in the 1970s, computed tomography (CT) has revolutionized diagnostic decision-making. One of the major concerns associated with the widespread use of CT is the associated increased radiation exposure incurred by patients. The link between ionizing radiation and the subsequent development of neoplasia has been largely based on extrapolating data from studies of survivors of the atomic bombs dropped in Japan in 1945 and on assessments of the increased relative risk of neoplasia in those occupationally exposed to radiation within the nuclear industry. However, the association between exposure to low-dose radiation from diagnostic imaging examinations and oncogenesis remains unclear. With improved technology, significant advances have already been achieved with regards to radiation dose reduction. There are several dose optimization strategies available that may be readily employed including omitting unnecessary images at the ends of acquired series, minimizing the number of phases acquired, and the use of automated exposure control as opposed to fixed tube current techniques. In addition, new image reconstruction techniques that reduce radiation dose have been developed in recent years with promising results. These techniques use iterative reconstruction algorithms to attain diagnostic quality images with reduced image noise at lower radiation doses.

Dose reduction in CT urography and vasculature phantom studies using model-based iterative reconstruction

To evaluate the feasibility of radiation dose reduction using model-based iterative reconstruction (MBIR) for evaluating the ureters and vasculature in a phantom, a tissue-equivalent CT dose phantom was scanned using a 64-channel CT scan-ner. Tubes of varying diameters filled with different dilutions of a contrast agent, simulating ureters or vessels, were inserted into the center of the phantom. Each combination was scanned using an existing renal protocol at 140 kVp or 120 kVp, yielding a display volumetric CT dose index (CTDIvol) of 24 mGy. The scans were repeated using reduced scan techniques to achieve lower radiation doses down to 0.8 mGy. The images were reconstructed using filtered back-projection (FBP) and model-based iterative reconstruction (MBIR). The noise and contrast-to-noise ratio (CNR) was measured for each contrast object. Comparisons between the two reconstruction methods at different dose levels were evaluated using a factorial design. At each CTDIvol the measured image noise was lower using MBIR compared to FBP (p < 0.0001). At low doses, the percent change in measured image noise between FBP and MBIR was larger. For the 12 mm object simulating a ureter or large vessel with an HU of 600, the measured CNR using MBIR at a CTDIvol of 1.7 mGy was greater than the CNR of FBP at a CTIDvol of 24 mGy (p < 0.0001). For the 5 mm object simulating a medium-sized vessel with a HU of 250, the mea-sured CNR using MBIR at a CTDIvol of 1.7 mGy was equivalent to that of FBP at a CTDIvol of 24 mGy. For the 2 mm, 100 HU object simulating a small vessel, the measured CNR using MBIR at a CTDIvol of 1.7 mGy was equivalent to that of FBP at a CTDIvol of 24 mGy. Low-dose (3.6 mGy) CT imaging of vasculature and ureter phantoms using MBIR results in similar noise and CNR compared to FBP at approximately one-sixth the dose. This suggests that, using MBIR, a one milliSievert exam of the ureters and vasculature may be clinically possible whilst still maintaining adequate image quality.

Management of non-muscle invasive bladder cancer: A comprehensive analysis of guidelines from the United States, Europe and Asia

Bladder cancer is the 8th most common cancer with 74,000 new cases in the United States in 2015. Non-muscle invasive bladder cancer (NMIBC) accounts for 75% of all bladder cancer cases. Transurethral resection and intravesical treatments remain the main treatment modality. Up to 31-78% of cases recur, hence the need for intensive treatment and surveillance protocols which makes bladder cancer one of the most expensive cancers to manage. The purpose of this review is to compare contemporary guidelines from Europe, (European Association of Urology), the United States (National Comprehensive Cancer Network), the United Kingdom (National Institute for Health and Care Excellence), Japan (Japanese Urological Association) and the International Consultation on Bladder Cancer (ICUD). We compare and contrast the different guidelines and the evidence on which their recommendations are based.

Use of the bolus tracking technique for the tomographic evaluation of the uretero-vesicular junction in dogs and assessment of dose records

BACKGROUND

The aim of the work is the application of a bolus tracking technique for tomographic evaluation of the uretero-vesicular junction in dogs. Ten adult dogs (8-14 years) with variable body weight (2,8-32 kg) were enrolled in the prospective study. The patients were placed in sternal recumbency with a 10° elevated pelvis and the visualization of the uretero-vesicular junction was obtained with the bolus tracking technique after intravenous administration of non-ionic contrast medium. In the post-contrast late phase a region of interest was placed within the lumen of the distal ureters and the density values were monitored before starting the helical scan.

RESULTS

The uretero-vesicular junction was clearly visible in 100% of patients with the visualization of the endoluminal ureteral contrast enhancement and bladder washout. At the end of the tomographic study an evaluation of the dose records was performed and compared to human exposures reported in literature for the pelvic region. The effective dose estimated for each patient (37,5-138 mSv) proved to be elevated, when compared to those reported in human patients.

CONCLUSION

The bolus tracking technique could be applied for the visualization of the uretero-vesicular junction in non-pathological patients, placing the region of interest in the distal ureters. The high effective doses recorded in our study support the need of specific thresholds for veterinary patients, pointing out the attention for paediatric patient's exposure also in veterinary imaging.

National diagnostic reference level initiative for computed tomography examinations in Kenya

The purpose of this study was to estimate the computed tomography (CT) examination frequency, patient radiation exposure, effective doses and national diagnostic reference levels (NDRLs) associated with CT examinations in clinical practice. A structured questionnaire-type form was developed for recording examination frequency, scanning protocols and patient radiation exposure during CT procedures in fully equipped medical facilities across the country. The national annual number of CT examinations per 1000 people was estimated to be 3 procedures. The volume-weighted CT dose index, dose length product, effective dose and NDRLs were determined for 20 types of adult and paediatric CT examinations. Additionally, the CT annual collective effective dose and effective dose per capita were approximated. The radiation exposure during CT examinations was broadly distributed between the facilities that took part in the study. This calls for a need to develop and implement diagnostic reference levels as a standardisation and optimisation tool for the radiological protection of patients at all the CT facilities nationwide.

Detection of bladder cancer: comparison of low-dose scans with AIDR 3D and routine-dose scans with FBP on the excretory phase in CT urography

OBJECTIVE

To prospectively compare the detection of bladder cancer between low-dose scans with adaptive iterative dose reduction three dimensional projection (AIDR 3D) and routine-dose scans with filtered back projection (FBP) on the excretory phase (EP) in CT urography.

METHODS

42 patients were included. Routine- and low-dose EP were performed in each patient. Routine-dose images were reconstructed with FBP, and low-dose images were reconstructed with AIDR 3D. Two radiologists scored confidence levels for the presence or absence of bladder cancer using a 5-point scale. The CT dose index of each EP was measured, and the dose reduction was calculated.

RESULTS

Sensitivity, specificity and accuracy were 86.4%, 95.0% and 90.5% on routine-dose scans and were 86.4%, 90.0% and 88.1% on low-dose scans, respectively. There was no significant difference (p; not significant, 1.00 and 1.00, respectively). The average CT dose index was 8.07 and 2.63 mGy on routine- and low-dose scans, and the ratio of dose reduction was 67.6%.

CONCLUSION

The detection of bladder cancer on low-dose scans with AIDR 3D is almost equal to that on routine-dose scans with FBP on the EP, with nearly 70% dose reduction.

ADVANCES IN KNOWLEDGE

Using AIDR 3D, the radiation dose may be reduced on the EP in CT urography for the detection of bladder cancer.

Evaluation of patient effective doses in CT urography, intravenous urography and renal scintigraphy

Imaging of the renal system is performed with different techniques depending mainly on clinical symptoms and signs. This study intended to evaluate patient effective doses undergoing renal scintigraphy (technetium-99m-diethylene-triamine-pentaacetic acid), computed tomography urography (CTU) and intravenous urography (IVU). A total of 60 patients were evaluated using Orbiter 37 Gamma camera single head, dual-slice CT scanner and conventional X-ray machine with computed radiography (CR) processing unit. Patients effective dose were estimated using the administered activity, DosCal software and dose length product value for renal scan, IVU and CTU procedures, respectively. Patients' effective doses during renal scan, CTU and IVU procedures were 0.78 ± 0.18, 2.53 ± 0.94 and 1.81 ± 0.20 mSv, in that order. Patients were exposed to a higher effective dose during CTU compared with other two procedures. Patient doses depend on the size of patient, the type of scanner and the imaging protocol used. Effective doses considered low compared with previous studies.

Measurement of patient radiation doses in certain urography procedures

Patients are exposed to significant radiation doses during diagnostic and interventional urologic procedures. This study aimed to measure patient entrance surface air kerma (ESAK) and to estimate the effective dose during intravenous urography (IVU), extracorporeal shock-wave lithotripsy (ESWL), and ascending urethogram (ASU) procedures. ESAK was measured in patients using calibrated thermo luminance dosimeters, GR200A). Effective doses (E) were calculated using the National Radiological Protection Board (NRPB) software. A total of 179 procedures were investigated. 27.9 % of the patients underwent IVU procedures, 27.9 % underwent ESWL procedures and 44.2 % underwent ASU procedures. The mean ESAK was 2.1, 4.18 and 4.9 mGy for IVU, ESWL, and ASU procedures, respectively. Differences in patient ESAK for the same procedure were observed. The mean ESAK values were comparable with those in previous studies.

Dose and image quality of cone-beam computed tomography as compared with conventional multislice computed tomography in abdominal imaging

OBJECTIVES

Recent technical developments have facilitated the application of cone-beam computed tomography (CBCT) for interventional and intraoperative imaging. The aim of this study was to compare the radiation doses and image quality in CBCT with those of conventional multislice spiral computed tomography (MSCT) for abdominal and genitourinary imaging.

METHODS

Different CBCT and MSCT protocols for imaging soft tissues and hard-contrast objects at different dose levels were investigated in this study. Local skin and organ doses were measured with thermoluminescent dosimeters placed in an anthropomorphic phantom. Moreover, the contrast-to-noise ratio, the noise-power spectrum, and the high-contrast resolution derived from the modulation transfer function were determined in a phantom with the same absorption properties as those of anthropomorphic phantom.

RESULTS

The effective dose of the examined abdominal/genitourinary CBCT protocols ranged between 0.35 mSv and 18.1 mSv. As compared with MSCT, the local skin dose of CBCT examinations could locally reach much higher doses up to 190 mGy. The effective dose necessary to realize the same contrast-to-noise ratio with CBCT and MSCT depended on the MSCT convolution kernel: the MSCT dose was smaller than the corresponding CBCT dose for a soft kernel but higher than that for a hard kernel. The noise-power spectrum of the CBCT images at tube voltages of 85/90 kV(p) is at least half of that of images measured at 103/115 kV(p) at any arbitrarily chosen spatial frequency. Although the pixel size and slice thickness of CBCT were half of those of the MSCT images, high-contrast resolution was inferior to the MSCT images reconstructed with a hard convolution kernel.

CONCLUSIONS

As compared with MSCT using a medium-hard convolution kernel, CBCT produces images at medium noise levels and, simultaneously, medium spatial resolution at approximately the same dose. It is well suited for visualizing hard-contrast objects in the abdomen with relatively low image noise and patient dose. For the detection of low-contrast objects at standard tube voltages of approximately 120 kV(p), however, MSCT should be preferred.

CT urography as the first line investigation for haematuria: is it truly indicated? A single centre analysis of the use of CT urography in the haematuria clinic

Introduction:

Computed tomographic urography (CTU) is gaining popularity as the first line investigation for haematuria. It can be used to produce a ‘true’ one-stop clinical assessment. However, a large number of investigations can be negative, exposing patients to a number of risks.

Objective:

We set out to evaluate the use of CTU in our one-stop haematuria clinic to see if it supported the utilisation of CTU as a triage investigation for haematuria.

Methods:

Retrospective analysis of all CT urograms performed (508) in our trust in 2013 took place. CTUs requested from the haematuria clinic were identified and analysed further.

Results:

A total of 1086 patients attended the haematuria clinic in 2013. 168 males and 78 females (median age 64, range 25 to 90) went on to have further CTU investigation after ultrasonography (USS) and cystoscopy. Visible haematuria (VH) was reported in 95% of cases. All 9 confirmed cases of upper tract urothelial carcinoma lesions presented with VH (age > 50); 8 out of 9 had reported hydronephrosis on USS. The overall negative predictive CTU rate was 96%.

Conclusion:

Our results show that a large number of CTUs are negative. The use of risk stratification, with particular emphasis on the ultrasonography result, gives adequate guidance on the cases that require further CTU investigation, supportive of the current European Association of Urology guidelines. Our results do not support the use of CTU as a first line or triage investigation for haematuria.

When ignorance is not bliss – a study of poor awareness of radiation exposure

Introduction and objective:

Patient safety is at the forefront of quality of care. Radiation exposure secondary to diagnostic imaging is increasing rapidly. Coupled with clinicians’ lack of awareness concerning radiation, doses incurred during these common procedures mean patients are being exposed to substantial cumulative radiation. Recent publications have indicated a significant minority of cancers are secondary to medical ionising radiation. The purpose of this study was to establish physician knowledge of radiation dosages.

Methods:

Clinician knowledge of radiation doses was determined by a questionnaire distributed to 40 doctors across all specialties in a District General Hospital in England. Clinicians were asked to estimate the radiation dose incurred during common diagnostic investigations, environmental exposure and the relation to increased cancer risk. The results were correlated against seniority and previous formal education on ionising radiation.

Results:

Clinician knowledge of radiation doses was poor with a mean score of 17% (range 0–44%). There was, on average, more than a 12-fold underestimation of radiation exposure levels across all grades and specialties of doctors. Those with previous formal education outperformed those without, but not significantly ( p > 0.05).

Conclusions:

Clinician awareness surrounding radiation doses of common diagnostic modalities is poor, grossly underestimating the true values. Increasing seniority or prior formal radiology training did not significantly alter the outcome. There is a need to educate clinicians, raise radiation dose awareness and avoid the financial, medico-legal and health delivery implications of unnecessary patient exposure to radiation.

CT evaluation of the upper urinary tract in adults younger than 50 years with asymptomatic microscopic hematuria: is IV contrast enhancement needed?

OBJECTIVE

The purpose of this study is to compare CT urography (CTU) with unenhanced CT in the evaluation of upper urinary tracts in adults younger than 50 years with asymptomatic microscopic hematuria.

MATERIALS AND METHODS

In this study, 1516 CTU examinations were reviewed in adults younger than 50 years. Inclusion criteria were no significant prior urologic disease and asymptomatic microscopic hematuria with at least one urinalysis with greater than or equal to 3 RBCs/high-power field and less than or equal to 50 RBCs/high-power field. Upper urinary tract findings on CTU were classified as malignancy-related or non-malignancy-related hematuria and incidental non-hematuria-related findings. A blinded radiologist reviewed the unenhanced images, recording upper urinary tract findings and recommendations for further contrast-enhanced imaging. The modified Wald equation at a 95% CI, the "Rule of Threes" equation, and binomial distribution were used for malignancy-related findings.

RESULTS

Four hundred forty-five examinations in 442 patients met inclusion criteria. CTU reports showed zero malignancy-related hematuria findings, 64 non-malignancy-related hematuria findings (62 renal calculi and two others), and 138 incidental non-hematuria-related findings. Unenhanced CT interpretation had a sensitivity of 100% (64/64) and a specificity of 89.2% (337/378). The theoretic risk of an upper urinary tract malignancy is 0-1.1%.

CONCLUSION

CTU added no additional diagnostic benefit versus unenhanced CT in evaluating the upper urinary tracts of adults younger than 50 years with asymptomatic microscopic hematuria. Using only unenhanced CT can reduce radiation and minimize contrast agent-associated risk, with a less than 1.0% risk of missing upper urinary tract hematuria-related malignancy.

Haematuria: an imaging guide

This paper discusses the current status of imaging in the investigation of patients with haematuria. The physician must rationalize imaging so that serious causes such as malignancy are promptly diagnosed while at the same time not exposing patients to unnecessary investigations. There is currently no universal agreement about the optimal imaging work up of haematuria. The choice of modality to image the urinary tract will depend on individual patient factors such as age, the presence of risk factors for malignancy, renal function, a history of calculus disease and pregnancy, and other factors, such as local policy and practice, cost effectiveness and availability of resources. The role of all modalities, including conventional radiography, intravenous urography/excretory urography, ultrasonography, retrograde pyelography, multidetector computed tomography urography (MDCTU), and magnetic resonance urography, is discussed. This paper highlights the pivotal role of MDCTU in the imaging of the patient with haematuria and discusses issues specific to this modality including protocol design, imaging of the urothelium, and radiation dose. Examination protocols should be tailored to the patient while all the while optimizing radiation dose.

Perspectives on radiation dose in abdominal imaging

Reported instances of patients' overexposure to imaging-related radiation have spurred the radiology and medical physics communities to identify and develop methods for decreasing the amount of radiation used to achieve diagnostic-quality images. These initiatives include examining and optimizing conventional CT scanning parameters, introducing innovative scan protocols, and incorporating novel dose reduction technologies. The greatest challenge to effective dose reduction in the abdomen and pelvis remains patient size. Here, we review the state of the art in abdominopelvic CT in both adult and pediatric patients and describe some of our own efforts in dose reduction for these types of examinations.

Evaluating hematuria: impact of guideline adherence on urologic cancer diagnosis

PURPOSE

The purpose of this study was to assess physician adherence to 2001 American Urological Association (AUA) guidelines for evaluating patients with asymptomatic hematuria and its impact on the diagnosis of urologic cancer.

METHODS

In this institutional review board-approved retrospective study of patients with asymptomatic hematuria evaluated in a large academic health center in 2004 (allowing for long-term follow-up), we randomly selected 100 of 1771 patients with asymptomatic hematuria (52 men; mean age 54 years; 58 microscopic, 39 macroscopic, three unknown-type hematuria; median follow-up 89 months, interquartile range 33-97 months). Multivariate logistic regression assessed effects of age, sex, hematuria type, and physician specialty on guideline adherence, the primary outcome. Secondary outcome measures were variability in evaluation among physician specialists, and the proportion of patients developing urologic cancer.

RESULTS

Only 36 of 100 patients had a guideline-adherent evaluation, of which 5 were diagnosed with urologic cancer (median 1 month, range 0-11). No urologic cancers were diagnosed in 64 patients with nonadherent evaluations. Only evaluation by a urologist significantly predicted guideline adherence (P <.0001). Patients with gross hematuria more often underwent intravenous or computed tomography urography (P = .009); urologist evaluation more often led to intravenous or computed tomography urography (P <.0001), cystoscopy (P <.0001), cytology (P = .009), and guideline-adherent evaluation (P <.0001).

CONCLUSIONS

Although most physicians did not adhere to 2001 AUA guidelines when evaluating patients with asymptomatic hematuria, no urologic cancers were diagnosed in patients without guideline-adherent evaluation, barring the possibility of occult cancers. Evaluation by a urologist was the only predictor of a guideline-adherent evaluation. Future studies are needed to determine the optimal evaluation of patients with asymptomatic hematuria.

Lower-dose CT urography (CTU) with iterative reconstruction technique in children - initial experience and examination protocol

BACKGROUND

Conventional X-ray urography is one of the basic imaging techniques in urinary tract diseases in children. CT urography (CTU) employing standard Filtered Back Projection (FBP) reconstruction algorithms is connected with higher radiation dose. Advanced iterative reconstruction techniques enable lowering the radiation dose to the level comparable with conventional X-ray urography with better visualization of the urinary tract. Study protocol and indications for this modified technique should be discussed.

MATERIAL/METHODS

Introduction of iterative image reconstruction techniques allowed to significantly reduce the radiation dose delivered during examinations performed at our Department, including CT examinations of urinary tract in children. During the last two years, CT urography replaced conventional X-ray urography and became the basic imaging technique in our Department. We discuss the study protocol regarding pediatric CTU examinations. The main goal is to receive an optimal image quality at reduced radiation dose.

RESULTS

CTU examinations performed using the standard filtered back projection (FBP) reconstruction technique are associated with radiation doses about 1.5 times higher than those in conventional X-ray urography. Implementation of iterative reconstruction algorithms in advanced CT scanners allow to reduce the radiation dose to a level comparable or even lower than that in X-ray urography. In addition, urinary tract can be evaluated more precisely in multiplanar reformatted (MPR) and volume rendered (VR) images.

CONCLUSIONS

1. Advanced iterative reconstruction techniques allow to reduce radiation dose in CT examinations and to extend indications for CT urography in children. 2. Urinary tract can be evaluated more precisely in multiplanar reformatted and volume rendered images. 3. CTU may replace conventional X-ray urography in children.

CT urography for the diagnosis of medullary sponge kidney

BACKGROUND

Medullary sponge kidney (MSK) is characterized by malformation of the terminal collecting ducts and is associated with an increased risk of nephrolithiasis, nephrocalcinosis, urinary tract infections, renal acidification defects, and reduced bone density. It has been historically diagnosed with intravenous pyelography (IVP), which is falling out of favor as an imaging modality. CT urography (CTU) performed with multidetector CT (MDCT) has been shown to create images of the renal collecting system with similar detail as IVP; however, its utility in diagnosing MSK has not been defined.

CASE REPORT

We present the first 15 patients with recurrent symptomatic nephrolithiasis who were evaluated in our renal stone clinic with CTU. Four patients were diagnosed with MSK after visualization of the characteristic radiologic findings.

DISCUSSION

CTU effectively demonstrates the characteristic radiologic findings of MSK including collecting tubule dilatation, medullary nephrocalcinosis, nephrolithiasis, and medullary cysts. Dose reduction protocols can reduce radiation exposure below that associated with conventional IVP. We propose CTU be considered for the diagnosis of MSK.

Computed tomography urography 1: techniques and technology

Contrast-enhanced computed tomography urography has become possible because of the development of multidetector technology, which has evolved to try and increase its diagnostic efficacy and reduce the radiation exposure. This review highlights important aspects of computed tomography urography as an imaging technique.

Low-dose computed tomographic urography using adaptive iterative dose reduction 3-dimensional: comparison with routine-dose computed tomography with filtered back projection

OBJECTIVE

The aim of this study was to evaluate the image quality of low-dose computed tomographic (CT) urography using adaptive iterative dose reduction 3-dimensional (AIDR 3D) compared with routine-dose CT using filtered back projection (FBP).

METHODS

Thirty patients underwent low- and routine-dose CT scans in the nephrographic and excretory phases of CT urography. Low-dose CT was reconstructed with AIDR 3D, and routine-dose CT was reconstructed with FBP. In quantitative analyses, image noises were measured on the renal cortex, aorta, retroperitoneal fat, and psoas muscle in both CT scans and compared. Qualitative analyses of the urinary system were performed in both CT scans and compared. These results were compared on the basis of the body mass index (BMI) of the patients. The CT dose index (CTDIvol) was measured, and the dose reduction was calculated.

RESULTS

In quantitative analyses, image noises in all organs on low-dose CT were less than those on routine-dose CT in both phases independently of the patient's BMI. There were no statistical differences between low- and routine-dose CT for diagnostic acceptability on all urinary systems in both phases independently of the patient's BMI. The average CTDIvol on routine-dose CT was 14.5 mGy in the nephrographic phase and 9.2 mGy in the excretory phase. The average CTDIvol on low-dose CT was 4.2 mGy in the nephrographic phase and 2.7 mGy in the excretory phase.

CONCLUSIONS

Low-dose CT urography using AIDR 3D can offer diagnostic acceptability comparable with routine-dose CT urography with FBP with approximately 70% dose reduction.