Canadian Association of Radiologists Guidance on Contrast Associated Acute Kidney Injury.

Iodinated contrast media (ICM) is one of the most frequently administered pharmaceuticals. In Canada, over 5.4 million computed tomography (CT) examinations were performed in 2019, of which 50% were contrast enhanced. Acute kidney injury (AKI) occurring after ICM administration was historically considered a common iatrogenic complication which was managed by screening patients, prophylactic strategies, and follow up evaluation of renal function. The Canadian Association of Radiologists (CAR) initially published guidelines on the prevention of contrast induced nephropathy in 2007, with an update in 2012. However, new developments in the field have led to the availability of safer contrast agents and changes in clinical practice, prompting a complete revision of the earlier recommendations. This revised guidance document was developed by a multidisciplinary CAR Working Group of radiologists and nephrologists, and summarizes changes in practice related to contrast administration, screening, and risk stratification since the last guideline. It reviews the scientific evidence for contrast associated AKI and provides consensus-based recommendations for its prevention and management in the Canadian healthcare context. This article is a joint publication in the Canadian Association of Radiologists Journal and Canadian Journal of Kidney Health and Disease, intended to inform both communities of practice.

Correction to: Correlation of 3T multiparametric prostate MRI using prostate imaging reporting and data system (PIRADS) version 2 with biopsy as reference standard.

Unfortunately the article was published with a spell error in the co-author name "Hassan Maan". The correct co-author name should be "Hassaan Maan".

Detection of Relapse by Low-dose Computed Tomography During Surveillance in Stage I Testicular Germ Cell Tumours.

BACKGROUND: Standard-dose computed tomography (SDCT) scans are associated with radiation exposure during stage I testicular cancer surveillance. OBJECTIVE: To evaluate low-dose CT (LDCT) for clinical use. DESIGN, SETTING, AND PARTICIPANTS: In this single-arm prospective study, patients on surveillance for stage I testicular germ cell tumour underwent SDCT and LDCT scans on their first visit after enrolment. The adequacy of LDCT image quality was assessed for subsequent use. Patients were followed with LDCT only and suspected relapse was confirmed by SDCT. OUTCOME MEASURES AND STATISTICAL ANALYSIS: We assessed whether initial LDCT scans were of sufficient quality for routine clinical use. We compared mean differences in nodal size at relapse between LDCT and SDCT using a one-sample paired t test. The relapse free-rate was calculated using the Kaplan-Meier method. RESULTS AND LIMITATIONS: Of 257 patients, one was excluded because of inadequate image quality. At median follow-up of 5.25 yr, 35 patients had relapsed, 33 with retroperitoneal lymphadenopathy. The 2- and 5-yr relapse-free rates were 89.5% and 85.3%, respectively. The mean size of retroperitoneal nodal relapse was 17.3 and 17.5mm on the short axis, 23.2 and 22.7mm on the long axis, and 26.1 and 26.7mm on craniocaudal length for LDCT and SDCT, respectively. The mean difference between LDCT and SDCT was 0.14mm (p=0.55) short axis, -0.54mm (p=0.092) long axis, and -0.51mm (p=0.086) length. A limitation was the lack of a control arm. CONCLUSIONS: LDCT image quality was adequate for clinical use, and retroperitoneal nodal relapse was detected with minimal differences seen between LD and SDCT. LDCT can be safely adopted and will decrease overall radiation exposure in stage I germ cell tumour surveillance. PATIENT SUMMARY: We studied the use of low-dose computed tomography scans for detecting testicular cancer recurrence in lymph nodes of the abdomen and pelvis and found that they were safe, effective and would potentially reduce overall X-ray exposure. This trial is registered at ClinicalTrials.gov as NCT03142802.

Correlation of 3T multiparametric prostate MRI using prostate imaging reporting and data system (PIRADS) version 2 with biopsy as reference standard.

OBJECTIVE: To correlate the findings on 3T multiparametric prostate MRI using PIRADS version 2 with prostate biopsy results as the standard of reference. MATERIALS AND METHODS: 134 consecutive treatment naive patients (mean age 64 years, range 41-82 years) underwent MRI-directed prostate biopsy. MRI-TRUS fusion biopsy was used for 77 (77/134 = 57.5%) patients, cognitive fusion for 51 (51/134 = 38.0%) patients, and 6 patients (6/134 = 4.5%) without a target nodule had systematic biopsy only. Out of the 1676 biopsy sites, 237 (237/1676 = 14.1%) were positive on MRI for a PIRADS 3, 4, or 5 nodule. Fifty-eight (58/134, 43.3%) patients had clinically significant prostate cancer (csPCa). The findings on MRI using PIRADS version 2 were correlated with the biopsy results. RESULTS: The accuracy, sensitivity, specificity, positive predictive value, and negative predictive value of PIRADS ≥ 3 for csPCa were 89%, 76.5%, 89.7%, 31.7%, and 98.4%, respectively. The detection rates of csPCa for PIRADS 3, 4, and 5 nodules were 6.1% (4/66), 33.3% (42/126), and 64.4% (29/45), respectively. MRI did not identify a nodule in 23/1676 (1.4%) biopsy sites that contained csPCa. The MRI reader, biopsy operator, method of fusion biopsy, and zonal location of prostate nodule did not significantly affect the odds of having a biopsy result positive for csPCa. CONCLUSION: PIRADS ≥ 3 had high specificity and high negative predictive value for csPCa using biopsy results as the standard of reference. The presence of csPCa from a biopsy site was highly unlikely in the absence of a corresponding PIRADS ≥ 3 nodule.

Primary perivascular epithelioid cell tumors of the liver: CT/MRI findings and clinical outcomes.

OBJECTIVES: The purpose of our study was to describe the CT and MRI features of primary PEComas of the liver and to document the associated clinical outcomes. METHODS: Retrospective study included 20 patients with primary hepatic perivascular epithelioid cell tumors (PEComa) with pathology and clinical outcomes for correlation. RESULTS: Study group included 20 patients: 16 women, 4 men; mean age 53 (range 35-77) years. Initial pathology diagnoses were classic angiomyolipoma (AML) (n = 11), epithelioid AML (n = 7), and PEComa not otherwise specified (n = 2). Mean tumor size was 5.1 (range 1.3-15.0) cm. CT/MRI features included well-defined margins 20/20 (100%), arterial enhancement 18/19 (95%), subcapsular location 17/20 (85%), heterogeneous 16/20 (80%), dysmorphic vessels 14/20 (70%), fat 13/20 (65%), hemorrhage 4/20 (20%), cystic components 4/20 (20%), and calcification 1/20 (5%). At the time of discovery, 18 patients were asymptomatic and their tumors were incidentally detected on imaging, and 2 patients were symptomatic. Ultimately, 18 tumors were benign and 2 developed metastases. CONCLUSIONS: On CT/MRI, most primary hepatic PEComas were well-defined, arterial enhancing, subcapsular, heterogeneous masses that often had dysmorphic vessels and contained fat. Most tumors were benign but complications included local symptoms, bleeding, and malignant change.

CT following US for possible appendicitis: anatomic coverage.

OBJECTIVE: To determine superior-inferior anatomic borders for CT following inconclusive/nondiagnostic US for possible appendicitis. METHODS: Ninety-nine patients with possible appendicitis and inconclusive/nondiagnostic US followed by CT were included in this retrospective study. Two radiologists reviewed CT images and determined superior-inferior anatomic borders required to diagnose or exclude appendicitis and diagnose alternative causes. This "targeted" coverage was used to estimate potential reduction in anatomic coverage compared to standard abdominal/pelvic CT. RESULTS: The study group included 83 women and 16 men; mean age 32 (median, 29; range 18-73) years. Final diagnoses were: nonspecific abdominal pain 50/99 (51%), appendicitis 26/99 (26%), gynaecological 12/99 (12%), gastrointestinal 9/99 (10%), and musculoskeletal 2/99 (2%). Median dose-length product for standard CT was 890.0 (range, 306.3 - 2493.9) mGy.cm. To confidently diagnose/exclude appendicitis or identify alternative diagnoses, maximum superior-inferior anatomic CT coverage was the superior border of L2-superior border of pubic symphysis, for both reviewers. Targeted CT would reduce anatomic coverage by 30-55% (mean 39%, median 40%) compared to standard CT. CONCLUSIONS: When CT is performed for appendicitis following inconclusive/nondiagnostic US, targeted CT from the superior border of L2-superior border of pubic symphysis can be used resulting in significant reduction in exposure to ionizing radiation compared to standard CT. KEY POINTS: • When CT is used following inconclusive/ nondiagnostic ultrasound, anatomic coverage can be reduced. • CT from L2 to pubic symphysis can be used to diagnose/exclude appendicitis. • Reduced anatomic coverage for CT results in reduced exposure to ionizing radiation.

Canadian Association of Radiologists Radiation Protection Working Group: Automated Patient-Specific Dose Registries­What Are They and What Are They Good for?

Medical radiation should be used appropriately and with a dose as low as reasonably achievable. Dose monitoring technologies have been developed that automatically accumulate patient dose indicators, providing effective dose estimates and patient-specific dose histories. Deleterious radiation related events have prompted increased public interest in the safe use of medical radiation. Some view individualized patient dose histories as a tool to help manage the patient dose. However, it is imperative that dose monitoring technologies be evaluated on the outcomes of dose reduction and effective patient management. Patient dose management needs to be consistent with the widely accepted linear no-threshold model of stochastic radiation effects. This essay reviews the attributes and limitations of dose monitoring technologies to provoke discussion regarding resource allocation in the current fiscally constrained health care system.

Assessment of feasibility of running RSNA's MIRC on a Raspberry Pi: a cost-effective solution for teaching files in radiology.

PURPOSE: The value of a teaching case repository in radiology training programs is immense. The allocation of resources for putting one together is a complex issue, given the factors that have to be coordinated: hardware, software, infrastructure, administration, and ethics. Costs may be significant and cost-effective solutions are desirable. METHODS: We chose Medical Imaging Resource Center (MIRC) to build our teaching file. It is offered by RSNA for free. For the hardware, we chose the Raspberry Pi, developed by the Raspberry Foundation: a small control board developed as a low cost computer for schools also used in alternative projects such as robotics and environmental data collection. Its performance and reliability as a file server were unknown to us. For the operational system, we chose Raspbian, a variant of Debian Linux, along with Apache (web server), MySql (database server) and PHP, which enhance the functionality of the server. A USB hub and an external hard drive completed the setup. Installation of software was smooth. RESULTS: The Raspberry Pi was able to handle very well the task of hosting the teaching file repository for our division. Uptime was logged at 100 %, and loading times were similar to other MIRC sites available online. We setup two servers (one for backup), each costing just below $200.00 including external storage and USB hub. CONCLUSION: It is feasible to run RSNA's MIRC off a low-cost control board (Raspberry Pi). Performance and reliability are comparable to full-size servers for the intended purpose of hosting a teaching file within an intranet environment.

Imaging of abdominal complications associated with hematopoietic stem cell transplantation.

Complications associated with hematopoietic stem cell transplantation are common and frequently involve the gastrointestinal tract and other abdominal organs. Imaging is often used to help to confirm or exclude a suspected complication and to facilitate management. In this article, we review the imaging findings of abdominal complications related to hematopoietic stem cell transplantation.

Small renal oncocytomas: is segmental enhancement inversion a characteristic finding at biphasic MDCT?

OBJECTIVE: The purpose of this study was to retrospectively determine whether segmental enhancement inversion was a common and characteristic finding in small (≤ 4 cm) renal oncocytomas on biphasic contrast-enhanced CT. MATERIALS AND METHODS: This retrospective case-control study included 16 patients with 16 renal oncocytomas and 15 control patients with 15 renal cell carcinomas (RCCs), matched for age and sex, who underwent biphasic contrast-enhanced MDCT at our institution. Three reviewers independently analyzed each tumor for enhancement patterns on MDCT, including the presence or absence of segmental enhancement inversion, homogeneity, and phase of peak enhancement. RESULTS: The mean and median sizes of the oncocytomas were 2.5 and 2.4 cm, respectively (range, 1.1-3.9 cm), and the mean and median sizes of the RCCs were both 2.6 cm (range, 1.4-3.9 cm). There was no significant difference in the size of the renal masses between the two groups (p = 0.50). For two reviewers, segmental enhancement inversion was not present in any of the renal masses; for one reviewer, segmental enhancement inversion was present in one oncocytoma (6%) and one RCC (7%). For all reviewers, there was no feature or enhancement pattern that was statistically significantly associated with renal oncocytoma or RCC (p < 0.05). CONCLUSION: Segmental enhancement inversion was not a common or characteristic CT finding for renal oncocytoma and was not helpful in differentiating small renal oncocytomas from RCC.

Detection of urothelial tumors: comparison of urothelial phase with excretory phase CT urography--a prospective study.

PURPOSE: To compare contrast material-enhanced computed tomographic (CT) urography 60 seconds after injection of contrast material (urothelial phase [UP]) after intravenous administration of a diuretic with the standard 5-minute delayed excretory phase (EP) in a high-risk population for upper tract tumors. MATERIALS AND METHODS: Institutional review board approval and informed consent were obtained. Eighty CT urographic examinations in 77 patients known to have or at high risk for urothelial malignancy were included. After intravenous administration of a diuretic, dual-phase CT urography was performed at 60 seconds (UP) and 5 minutes (EP) after intravenous administration of contrast material. Two experienced abdominal radiologists independently interpreted each phase more than 1 month apart to minimize recall bias. Urinary tract distention and location and size of all lesions suspected of being urothelial tumors were recorded. Standard of reference was obtained from prospective study interpretation and surgical histopathologic findings. Generalized estimating equations for logistic regression were used to compare performance measures and adjust for the correlation of repeated measures within patients. RESULTS: There were 23 upper and 61 lower urinary tract tumors confirmed in 15 and 32 patients, respectively. For detection of bladder tumors, there was higher sensitivity for the UP than the EP (89.3% [109 of 122] vs 70.5% [86 of 122], respectively; P<.0001). For detection of upper tract tumors, there was higher sensitivity for the UP than the EP (82.6% [38 of 46] vs 69.6% [32 of 46], respectively; P=.0194). Distention of all upper urinary tract segments was better during the EP than the UP (P<.0001). CONCLUSION: UP CT urography after injection of a diuretic has a higher lesion detection rate than the EP for both upper and lower urinary tract tumors, which suggests its possible use as a single-phase protocol for evaluation of the entire urinary tract in patients at high risk for urothelial tumors.

Comparison of low dose with standard dose abdominal/pelvic multidetector CT in patients with stage 1 testicular cancer under surveillance.

PURPOSE: To compare the image quality and acceptability of a low dose with those of standard dose abdominal/pelvic multidetector CT in patients with stage 1 testicular cancer managed by surveillance. METHODS: One hundred patients (median age 31 years; range 19-83 years), 79 with seminoma and 21 with non-seminoma, underwent abdominal/pelvic imaging with low and standard dose protocols on 64-slice multidetector CT. Three reviewers independently evaluated images for noise and diagnostic quality on a 5-point scale and for diagnostic acceptability. RESULTS: On average, each reader scored noise and diagnostic quality of standard dose images significantly better than corresponding low dose images (p < 0.0001). One reader found all CT examinations acceptable; two readers each found 1/100 (1%) low dose examinations unacceptable. Median and mean dose-length product for low and standard dose protocols were 416.0 and 452.2 (range 122.9-913.4) and 931.9 and 999.8 (range 283.8-1,987.7) mGy cm, respectively. CONCLUSIONS: The low dose protocol provided diagnostically acceptable images for at least 99% of patients and achieved mean dose reduction of 55% compared with the standard dose protocol.

Split-bolus MDCT urography: Upper tract opacification and performance for upper tract tumors in patients with hematuria.

OBJECTIVE: Our purpose was to assess upper urinary tract opacification and the performance of split-bolus MDCT urography for upper tract tumors in patients with hematuria. MATERIALS AND METHODS: Between January 2004 and December 2006, we identified 200 patients (119 men, 81 women; median age, 58 years, age range, 18-89 years) who underwent MDCT urography for hematuria. MDCT urography included unenhanced and combined nephrographic and excretory phase imaging of the urinary tract. Images were independently reviewed by two radiologists blinded to the final diagnosis. The degree of upper urinary tract opacification and the diagnosis were recorded. Prospective interpretations were also reviewed. The standard of reference included all available clinical, imaging, and laboratory data for up to 12 months after MDCT urography. Sensitivity, specificity, accuracy, and positive and negative predictive values were calculated for upper tract tumors for prospective and retrospective interpretations. RESULTS: For reviewers 1 and 2, 85.1% and 84.5% of segments were at least 50% opacified, respectively. Final diagnoses for hematuria were no cause, 123 (61.5%); urothelial cancer, 27 (13.5%); nonmalignant, 46 (23%) and indeterminate, four patients (2%). There were nine upper tract cancers. Sensitivity, specificity, and accuracy for upper tract cancers for prospective interpretation, reviewer 1 and reviewer 2, were 100%, 99%, 99%; 100%, 99.5%, 99.5%; and 88.9%, 99.0%, 98.5%, respectively. CONCLUSION: Split-bolus MDCT urography provided at least 50% opacification of the majority of upper urinary tract segments and had high sensitivity, specificity, and accuracy for the detection of upper urinary tract tumors.

Primary gastrointestinal lymphoma: spectrum of imaging findings with pathologic correlation.

Gastrointestinal lymphoma is an uncommon disease but is the most frequently occurring extranodal lymphoma and is almost exclusively of non-Hodgkin type. Primary gastrointestinal lymphoma most commonly involves the stomach but can involve any part of the gastrointestinal tract from the esophagus to the rectum. Risk factors for the development of gastrointestinal lymphoma include Helicobacter pylori infection, immunosuppression after solid organ transplantation, celiac disease, inflammatory bowel disease, and human immunodeficiency virus infection. Although gastrointestinal lymphoma has a wide variety of imaging appearances and definitive diagnosis relies on histopathologic analysis, certain findings (eg, a bulky mass or diffuse infiltration with preservation of fat planes and no obstruction, multiple site involvement, associated bulky lymphadenopathy) can strongly suggest the diagnosis. Imaging also plays an important role in the detection of complications such as perforation, obstruction, and fistulization. The most commonly used imaging modalities are barium examination and computed tomography (CT). These modalities are complementary, although CT provides a better overall assessment of the disease stage.

Adverse events with universal use of iodixanol for CT: comparison with iohexol.

OBJECTIVE: To evaluate the incidence of adverse events with the universal use of iodixanol for computed tomography (CT) and compare it with periods when iohexol was used exclusively. METHODS: Iodixanol was used for CT in 15,142 consecutive patients and compared with 22,044 patients who received iohexol. RESULTS: Adverse events were observed in 116 patients (0.77%) who received iodixanol and in 54 patients (0.25%) who received iohexol (P < 0.001). Immediate and delayed adverse events were seen in 76 and 40 patients (0.50% and 0.26%, respectively) who received iodixanol and in 52 and 2 patients (0.24% and 0.01%, respectively) who received iohexol, respectively (immediate, P = 0.002; delayed, P < 0.001). Adverse events with iodixanol and iohexol were as follows: mild, 89% and 98%; moderate, 10% and 2%; and severe, 1% and 0%, respectively. CONCLUSIONS: Adverse events occurred in less than 1% of patients receiving either contrast agent. However, the incidence of immediate and delayed adverse events was significantly higher with iodixanol than iohexol.

CT of pheochromocytoma and paraganglioma: risk of adverse events with i.v. administration of nonionic contrast material.

OBJECTIVE: When pheochromocytoma or paraganglioma is suspected, many institutions perform only unenhanced CT because of a perceived risk of inducing a hypertensive crisis with i.v. administration of contrast material. The purpose of this study was to review our experience with the use of nonionic i.v. contrast material for CT of patients with pheochromocytoma or paraganglioma. The specific goal was to determine whether adverse events occurred. MATERIALS AND METHODS: A retrospective review of radiology records identified 25 patients (17 women, eight men; mean age, 43 years; age range, 27-70 years) with 40 pathologically proven pheochromocytomas or paragangliomas who received nonionic i.v. contrast material for CT. There were 16 adrenal pheochromocytomas, 12 abdominal paragangliomas, five neck paragangliomas, and seven metastatic lesions. Medical records were reviewed to determine whether the tumors were sporadic or associated with a syndrome, incidentally detected, or biochemically active; and whether patients were taking alpha-blocking medication at the time of CT. Adverse events were documented. RESULTS: Nineteen patients had 23 sporadic tumors, and six patients had 17 tumors associated with a syndrome. In 12 (48%) of the 25 patients the diagnosis was clinically unsuspected at the time of CT. Elevated levels of urinary catecholamines or their metabolites were found in 19 (90%) of the 21 patients for whom this test was performed. No patients were taking alpha-blocking medication at the time of CT. No adverse events occurred in association with i.v. administration of nonionic contrast material. CONCLUSION: I.v. administration of nonionic contrast material for CT is a safe practice for patients with pheochromocytoma and related tumors even without alpha-blocking medication.

Value of the unenhanced phase for detection of hepatocellular carcinomas 3 cm or less when performing multiphase computed tomography in patients with cirrhosis.

OBJECTIVE: To determine whether unenhanced images are of added benefit to dual-phase computed tomography (CT) for detection of hepatocellular carcinomas (HCCs) 3 cm or less. METHODS: Thirty-six patients with cirrhosis underwent unenhanced, arterial and portal venous phase CT, 17 with pathologically proven HCCs 3 cm or less and 19 without HCC. Two radiologists reviewed dual-phase images with and without unenhanced images. Presence or absence of HCC in each segment (n = 324) and subjective added benefit of unenhanced images were recorded. RESULTS: For readers 1 and 2, unenhanced CT was subjectively helpful in 16 (5%) of 324 and 23 (7%) of 324 segments. Sensitivity and area under the receiver operating characteristic curve were identical for dual-phase versus triple-phase images for reader 1 (82.4% and 0.882) and reader 2 (100% and 0.997). CONCLUSIONS: Addition of unenhanced to dual-phase CT does not statistically significantly increase the diagnostic accuracy or sensitivity for HCCs 3 cm or less.

Variability in size measurement of renal masses smaller than 4 cm on computerized tomography.

PURPOSE: We assessed the degree of interobserver and intra-observer variability in the size measurement of small renal tumors with computerized tomography. MATERIALS AND METHODS: A total of 29 renal masses from 21 patients were reviewed independently by 3 radiologists on computerized tomography performed with 5 mm collimation and a reconstruction interval of 2.5 mm. Measurements were made of the largest axial dimension (X), perpendicular axial dimension (Y) and slice direction (Z) with double reads performed in a subset of patients. The predicted 95% CI was calculated for each measure, assuming different readers and the same reader. RESULTS: The predicted error bounds for a single renal mass measurement in the X axis were +/-3.1 mm when considering multiple readers and +/-2.3 mm for a single reader. In the X axis 78 of the 87 measurements (90%) were within 2 mm of the average measure. Smaller variances in measurements were seen with single reader repeat measurements than with multiple readers. Highest variances were seen in the Z axis. Measurements of volume and cross-sectional area showed a higher degree of variance. CONCLUSIONS: When comparing independent computerized tomography readings done with 5 mm collimation and a 2.5 mm reconstruction interval, a size change in the largest axial dimension of a renal mass of less than 3.1 mm between different radiologists and less than 2.3 mm for the same radiologist should be viewed with caution because it is within the range of measurement variability.