Share of Diagnostic Imaging Interpretation: Radiology and Other Specialties.

PURPOSE: The aim of this study was to examine radiology's and other specialties' market shares for diagnostic imaging interpretation for Medicare fee-for-service claims by modality, body region, and place of service. METHODS: In this cross-sectional study of Physician/Supplier Procedure Summary data for 2022, the authors examined the proportion of diagnostic imaging interpretation by specialty. All claims for CT, MR, nuclear medicine (NM), ultrasound, and radiography and fluoroscopy (XR) were included. Claims were aggregated into 52 specialty groups using Medicare specialty codes. The market share for each specialty group was computed by modality, body region, and place of service. RESULTS: For Medicare fee-for-service beneficiaries, there were 122,851,716 imaging studies, of which 88,559,272 (72.1%) were interpreted by radiologists. This percentage varied by modality: 97.3% for CT, 91.0% for MR, 76.6% for XR, 50.9% for NM, and 33.9% for ultrasound. Radiologists interpreted a lower percentage of cardiac (67.6% for CT, 42.2% for MR, 11.8% for NM, and 0.4% for ultrasound) than noncardiac studies (97.6% for CT, 91.4% for MR, 95.6% for NM, and 53.0% for ultrasound). Among noncardiac studies, radiologists interpreted nearly all in the outpatient hospital, inpatient, and emergency department (99.5% for CT, 99.4% for MR, 98.9% for NM, 79.3% for ultrasound, and 97.9% for XR) compared with the office setting (84.4% for CT, 78.7% for MR, 85.4% for NM, 29.2% for ultrasound, and 43.1% for XR). CONCLUSIONS: Radiologists perform the dominant share of CT and MR interpretation and more so for noncardiac imaging and imaging performed in outpatient hospital, inpatient, and emergency department places of service.

Diagnostic Accuracy of Unenhanced Computed Tomography for Evaluation of Acute Abdominal Pain in the Emergency Department.

Importance: Intravenous (IV) contrast medium is sometimes withheld due to risk of complication or lack of availability in patients undergoing computed tomography (CT) for abdominal pain. The risk from withholding contrast medium is understudied. Objective: To determine the diagnostic accuracy of unenhanced abdominopelvic CT using contemporaneous contrast-enhanced CT as the reference standard in emergency department (ED) patients with acute abdominal pain. Design, Setting, and Participants: This was an institutional review board-approved, multicenter retrospective diagnostic accuracy study of 201 consecutive adult ED patients who underwent dual-energy contrast-enhanced CT for the evaluation of acute abdominal pain from April 1, 2017, through April 22, 2017. Three blinded radiologists interpreted these scans to establish the reference standard by majority rule. IV and oral contrast media were then digitally subtracted using dual-energy techniques. Six different blinded radiologists from 3 institutions (3 specialist faculty and 3 residents) interpreted the resulting unenhanced CT examinations. Participants included a consecutive sample of ED patients with abdominal pain who underwent dual-energy CT. Exposure: Contrast-enhanced and virtual unenhanced CT derived from dual-energy CT. Main outcome: Diagnostic accuracy of unenhanced CT for primary (ie, principal cause[s] of pain) and actionable secondary (ie, incidental findings requiring management) diagnoses. The Gwet interrater agreement coefficient was calculated. Results: There were 201 included patients (female, 108; male, 93) with a mean age of 50.1 (SD, 20.9) years and mean BMI of 25.5 (SD, 5.4). Overall accuracy of unenhanced CT was 70% (faculty, 68% to 74%; residents, 69% to 70%). Faculty had higher accuracy than residents for primary diagnoses (82% vs 76%; adjusted odds ratio [OR], 1.83; 95% CI, 1.26-2.67; P = .002) but lower accuracy for actionable secondary diagnoses (87% vs 90%; OR, 0.57; 95% CI, 0.35-0.93; P < .001). This was because faculty made fewer false-negative primary diagnoses (38% vs 62%; OR, 0.23; 95% CI, 0.13-0.41; P < .001) but more false-positive actionable secondary diagnoses (63% vs 37%; OR, 2.11, 95% CI, 1.26-3.54; P = .01). False-negative (19%) and false-positive (14%) results were common. Interrater agreement for overall accuracy was moderate (Gwet agreement coefficient, 0.58). Conclusion: Unenhanced CT was approximately 30% less accurate than contrast-enhanced CT for evaluating abdominal pain in the ED. This should be balanced with the risk of administering contrast material to patients with risk factors for kidney injury or hypersensitivity reaction.

Insulin Sensitivity After Living Donor Nephrectomy.

BACKGROUND: The kidney is essential for glucose and insulin metabolism. Living kidney donors (LKDs) experience a reduction in glomerular filtration rate of 25 to 30 mL/min after donor nephrectomy. Little is known about the effect of glomerular filtration rate decline on insulin sensitivity in LKDs. METHODS: We conducted a prospective pilot study on 9 LKDs (N = 9) who underwent dynamic metabolic testing (mixed meal tolerance test) to measure proxies of insulin sensitivity (homeostatic model assessment of insulin resistance, the area under curve [AUC] for insulin/glucose ratio, and Matsuda insulin sensitivity index) before and 3 months after donor nephrectomy. The primary outcome was the change in insulin sensitivity indices (delta [post-nephrectomy - pre-nephrectomy]). RESULTS: Four of the donors had a body mass index (BMI) between 32.0 and 36.7 predonation. Post-donor nephrectomy, compared with prenephrectomy values, median insulin AUC increased from 60.7 to 101.7 hr*mU/mL (delta median 33.3, P = .04) without significant change in median glucose AUC levels from 228.9 to 209.3 hr*mg/dL (delta median 3.2, P = .77). There was an increase in the median homeostatic model assessment of insulin resistance from 2 to 2.9 (delta median 0.8, P = .03) and the AUC insulin/glucose ratio from 30.9 to 62.1 pmol/mmol (delta median 17.5, P = .001), whereas the median Matsuda insulin sensitivity index decreased from 5.9 to 2.9 (delta median -2, P = .05). The changes were more pronounced in obese (BMI >32) donors. CONCLUSION: LKDs appear to have a trend toward a decline in insulin sensitivity post-donor nephrectomy in the short term, especially in obese donors (BMI >32). Further investigation with a larger sample size and longer follow-up is needed.

CT Volumetry of Convoluted Objects-A Simple Method Using Volume Averaging.

Accurate measurement of object volumes using computed tomography is often important but can be challenging, especially for finely convoluted objects with severe marginal blurring from volume averaging. We aimed to test the accuracy of a simple method for volumetry by constructing, scanning and analyzing a phantom object with these characteristics which consisted of a cluster of small lucite beads embedded in petroleum jelly. Our method involves drawing simple regions of interest containing the entirety of the object and a portion of the surrounding material and using its density, along with the densities of pure lucite and petroleum jelly and the slice thickness to calculate the volume of the object in each slice. Comparison of our results with the object's true volume showed the technique to be highly accurate, irrespective of slice thickness, image noise, reconstruction planes, spatial resolution and variations in regions of interest. We conclude that the method can be easily used for accurate volumetry in clinical and research scans without the need for specialized volumetry computer programs.

Relationship of Seminal Megavesicles, Prostate Median Cysts, and Genotype in Autosomal Dominant Polycystic Kidney Disease.

BACKGROUND: Autosomal dominant polycystic kidney disease (ADPKD) can involve prostate and seminal vesicles but the potential interrelationship of these findings and associations with PKD gene mutation locus and type is unknown. PURPOSE: To determine the interrelationship of seminal megavesicles (seminal vesicles with lumen diameter > 10mm) and prostatic cysts in ADPKD and to determine whether there are associations with PKD gene mutations. STUDY TYPE: Retrospective, case control. POPULATION: Male ADPKD subjects (n = 92) with mutations in PKD1 (n = 71; 77%) or PKD2 (n = 21; 23%), and age/gender-matched controls without ADPKD (n = 92). FIELD STRENGTH/SEQUENCE: 1.5T, axial/coronal T2 -weighted MR images. ASSESSMENT: Reviewers blinded to genotype independently measured seminal vesicle lumen diameter and prevalence of cysts in prostate, kidney, and liver. STATISTICAL TESTS: Nonparametric tests for group comparisons and univariate and multivariable logistic regression analyses to identify associations of megavesicles and prostate median cysts with mutations and renal/hepatic cyst burden. RESULTS: Seminal megavesicles were found in 23 of 92 ADPKD (25%) subjects with PKD1 (22/71, 31%) or PKD2 (n = 1/21, 5%) mutations, but in only two control subjects (P < 0.0001). Prostate median cysts were found in 17/92 (18%) ADPKD subjects, compared with only 6/92 (7%) controls (P = 0.01), and were correlated with seminal vesicle diameters (ρ = 0.24, P = 0.02). Nonmedian prostate cyst prevalence was identical between ADPKD and controls (7/92, 8%). After adjusting for age, estimated glomerular filtration rate, and height-adjusted total kidney volume, ADPKD subjects with megavesicles were 10 times more likely to have a PKD1 than a PKD2 mutation. Among PKD1 subjects, seminal megavesicles occurred more frequently with nontruncating mutations with less severe kidney involvement. DATA CONCLUSION: ADPKD is associated with prostate median cysts near ejaculatory ducts. These cysts correlate with seminal megavesicles (dilated to >10 mm) which predict a 10-fold greater likelihood of PKD1 vs. PKD2 mutation. Cysts elsewhere in the prostate are not related to ADPKD. LEVEL OF EVIDENCE: 2 Technical Efficacy: Stage 2 J. Magn. Reson. Imaging 2019;49:894-903.

The Role of Computed Tomography and Magnetic Resonance Imaging in Gynecologic Oncology.

This article discusses the role of Computed tomography (CT) and MR imaging in gynecologic malignancies by reviewing epidemiology, histologic subtypes, and staging systems. Imaging findings specific to different gynecologic malignancies on CT and MR imaging are reviewed and the advantages of each imaging modality discussed. Imaging of endometrial, cervical, and ovarian cancer is reviewed in depth, with a brief discussion of rare gynecologic cancers.

A Convex Hull-Based New Metric for Quantification of Bladder Wall Irregularity in Pediatric Patients With Congenital Anomalies of the Kidney and Urinary Tract.

OBJECTIVES: Early identification and quantification of bladder damage in pediatric patients with congenital anomalies of the kidney and urinary tract (CAKUT) is crucial to guiding effective treatment and may affect the eventual clinical outcome, including progression of renal disease. We have developed a novel approach based on the convex hull to calculate bladder wall trabecularity in pediatric patients with CAKUT. The objective of this study was to test whether our approach can accurately predict bladder wall irregularity. METHODS: Twenty pediatric patients, half with renal compromise and CAKUT and half with normal renal function, were evaluated. We applied the convex hull approach to calculate T, a metric proposed to reflect the degree of trabeculation/bladder wall irregularity, in this set of patients. RESULTS: The average T value was roughly 3 times higher for diseased than healthy patients (0.14 [95% confidence interval, 0.10-0.17] versus 0.05 [95% confidence interval, 0.03-0.07] for normal bladders). This disparity was statistically significant (P < .01). CONCLUSIONS: We have demonstrated that a convex hull-based procedure can measure bladder wall irregularity. Because bladder damage is a reversible precursor to irreversible renal parenchymal damage, applying such a measure to at-risk pediatric patients can help guide prompt interventions to avert disease progression.

Maximum Arterial Contrast Concentrations With Computed Tomography and Left Ventriculography: Implications for Contrast Nephrotoxicity Risk.

PURPOSE: Contrast nephropathy occurs more frequently after cardiac angiography, which usually includes left ventriculography via direct left ventricular injection, than after contrast-enhanced computed tomography (CT), despite the usually higher intravenous contrast dose used for CT. To determine whether maximum renal arterial contrast concentration is higher after left ventriculography, we assessed this parameter for both procedures. MATERIALS AND METHODS: Contrast concentration in abdominal aortic blood during contrast-enhanced CT was measured by performing CT densitometry of aortic blood before contrast, and in the arterial phase, in 100 adults undergoing abdominal CT. Densities were converted to contrast concentrations by scanning water phantoms containing 20 graded concentrations of contrast and comparing their densities to patient data. Because it was impossible to perform CT densitometry during cardiac angiography, aortic contrast concentrations were calculated from standard contrast doses and injection rates with the range of clinically encountered cardiac output rates, assuming ultimate steady state for blood/contrast mixing and normal data distribution. RESULTS: Maximum aortic (and hence renal arterial) concentrations were significantly higher (range, 6.68%-15.90%) after ventriculography than after CT (1.22%-5.80%). Because ventricular injection times are much shorter than published initial-appearance-to-maximum-concentration times after intravenous administration, the rate of change of contrast concentration is also higher after ventriculography than after CT. CONCLUSION: Higher maximum renal arterial contrast concentration may be responsible for the greater risk of nephropathy after cardiac angiography than after doses for CT. The faster rate of change of renal arterial contrast concentration after ventriculography may also increase the likelihood of renal toxicity. CLINICAL RELEVANCE/APPLICATION: Maximum renal arterial contrast concentration, and/or the rapidity of change of this parameter, may be partly responsible for the risk of nephropathy. Controlling these factors might permit reduction of nephropathy risk; they also suggest avenues of research into the pathophysiology of contrast nephropathy.

Intravenous Contrast-Induced Nephropathy-The Rise and Fall of a Threatening Idea.

Contrast-induced nephropathy (CIN) has been considered to be a cause of renal failure for over 50 years, but careful review of past and recent studies reveals the risks of CIN to be overestimated. Older studies frequently cited the use of high-osmolality contrast media, which have since been replaced by low-osmolality contrast media, which have lower risks for nephropathy. In addition, literature regarding CIN typically describes the incidence following cardiac angiography, whereas the risk of CIN from intravenous injection is much lower. Most of the early published literature also lacked appropriate control groups to compare to those that received iodinated contrast, and thus attributed rises in creatinine to intravenous contrast without considering normal creatinine fluctuations (frequent in patients with kidney disease) and other acute pathologic states such as hypotension or nephrotoxic drug administration. The aim of this paper is to review the literature detailing CIN risk, discuss why CIN risk is often overestimated and how withholding contrast can lead to misdiagnosis and delay in appropriate patient management.

Split-bolus CT urogram: Is less more?

PURPOSE: To determine the accuracy of split-bolus CT urogram (SB-CTU) without special maneuvers for ureteral distention in diagnosing upper urinary tract urothelial carcinoma (UCA). MATERIALS AND METHODS: A hospital database was searched from 1/1/10, to 9/1/15, for SB-CTU exams without special maneuvers for ureteral distention. Accuracy of SB-CTU for detecting upper and lower urinary tract UCA was computed by comparing the prospective radiology report with cystoscopy, ureteroscopy, and/or urologic clinical follow-up. Patients with less than 12 months of clinical follow-up were excluded. RESULTS: 339 studies were identified in 334 patients (60% male 40% female, avg. age 64). 119 studies were performed for microhematuria, 150 for gross hematuria, 13 for hematuria not otherwise specified, 57 for history of UCA, and one for a collecting system mass on a prior CT. There were five upper tract and 33 bladder tumors with overall prevalence of 1.5% and 9.7%, respectively. The prevalence varied significantly with patient age and clinical indication for SB-CTU. There were one false negative and four false positives for upper urinary tract UCA. Sensitivity, specificity, positive predictive value, and negative predictive value for detecting upper tract and bladder tumors were 80%, 99%, 44%, and 100%, respectively, and 55%, 98%, 78%, and 95%, respectively. CONCLUSION: Based on this study, SB-CTU without special maneuvers for ureteral distention is highly sensitive for detecting upper tract UCA, although with a low positive predictive value, false positives do occur. The clinical utility of increasing accuracy in diagnosing this low-prevalence disease through other more complex CT urogram protocols should be weighed against the added cost and radiation dose associated with these protocols.

Case 225: Leiomyoma.

A 33-year-old pregnant woman (gravida 11, para 8) presented with increasing severe abdominal pain during the first trimester of pregnancy and increasing abdominal distention out of proportion to her prior pregnancies. Ultrasonography (US) without Doppler performed at another hospital had revealed a pelvic mass; therefore, this patient had been referred to our institution for further evaluation. Unenhanced magnetic resonance (MR) imaging was then performed at 8 weeks of gestation. The main portion of the gravid uterus and the ovaries was not seen on these images, but the parts that were seen appeared normal. Diagnostic laparoscopic biopsy was performed during the first trimester, but complete removal of the mass was deferred because of fears the pregnancy would be lost. The patient was closely observed throughout the pregnancy with serial US until the 37th week of gestation, at which time the patient underwent Caesarian section. At the time of Caesarian section, the mass was noted to extend from the spleen downward deep into the pelvis. A biopsy was performed at the time of Caesarian section. Definitive removal of the mass was deferred at the time of Caesarian section to minimize postpartum blood loss and to further delineate the mass with imaging for future surgery. Intravenous contrast material-enhanced (120 mL of Omnipaque 350; Nycomed Amersham, Princeton, NJ) computed tomography (CT) was performed 3 days after Caesarian section. The cystic component measured approximately 15 HU. Repeat MR imaging 1.5 months after Caesarian section was then performed. No loss of signal intensity in the mass was seen on fat-saturated images. There was no evidence of local or distant metastatic disease. The mass abutted and displaced the uterus and the ovaries but did not distort either of these organs. Vascular anatomy was not useful in determining the origin of the mass. The comprehensive metabolic panel and complete blood count were normal throughout and after the pregnancy.

Live Donor Renal Anatomic Asymmetry and Posttransplant Renal Function.

BACKGROUND: Relationship between live donor renal anatomic asymmetry and posttransplant recipient function has not been studied extensively. METHODS: We analyzed 96 live kidney donors, who had anatomical asymmetry (>10% renal length and/or volume difference calculated from computerized tomography angiograms) and their matching recipients. Split function differences (SFD) were quantified with technetium-dimercaptosuccinic acid renography. Implantation biopsies at time 0 were semiquantitatively scored. A comprehensive model using donor renal volume adjusted to recipient weight (Vol/Wgt), SFD, and biopsy score was used to predict recipient estimated glomerular filtration rate (eGFR) at 1 year. Primary analysis consisted of a logistic regression model of outcome (odds of developing eGFR>60 mL/min/1.73 m(2) at 1 year), a linear regression model of outcome (predicting recipient eGFR at one-year, using the chronic kidney disease-epidemiology collaboration formula), and a Monte Carlo simulation based on the linear regression model (N=10,000 iterations). RESULTS: In the study cohort, the mean Vol/Wgt and eGFR at 1 year were 2.04 mL/kg and 60.4 mL/min/1.73 m(2), respectively. Volume and split ratios between 2 donor kidneys were strongly correlated (r = 0.79, P < 0.001). The biopsy scores among SFD categories (<5%, 5%-10%, >10%) were not different (P = 0.190). On multivariate models, only Vol/Wgt was significantly associated with higher odds of having eGFR > 60 mL/min/1.73 m (odds ratio, 8.94, 95% CI 2.47-32.25, P = 0.001) and had a strong discriminatory power in predicting the risk of eGFR less than 60 mL/min/1.73 m(2) at 1 year [receiver operating curve (ROC curve), 0.78, 95% CI, 0.68-0.89]. CONCLUSIONS: In the presence of donor renal anatomic asymmetry, Vol/Wgt appears to be a major determinant of recipient renal function at 1 year after transplantation. Renography can be replaced with CT volume calculation in estimating split renal function.

Comparison of Renal Parenchymal Volume Preservation Between Partial Nephrectomy, Cryoablation, and Radiofrequency Ablation Using 3D Volume Measurements.

PURPOSE: Small renal masses (SRM) can be managed via a variety of nephron-sparing procedures (NSPs), but the association between choice of NSP and renal parenchymal volume (RPV) preservation is not well understood. We sought to examine RPV preservation after partial nephrectomy (PN) performed via open, robotic, or laparoscopic approaches and thermal ablation (TA) performed via cryoablation (CA) or radiofrequency ablation (RFA). PATIENTS AND METHODS: The study was a retrospective review of three institutional databases of patients with a SRM <4 cm treated via one of the five NSPs (open PN, laparoscopic PN, robotic PN, percutaneous CA, or percutaneous RFA). The 30 most recent consecutive cases treated via each NSP were selected to obtain a total of 150 cases for analysis. Patient characteristics were obtained via manual chart review, and tumor characteristics were assessed via the R.E.N.A.L. nephrometry score. Using three-dimensional rendering software, preoperative and postoperative RPV was calculated for the tumor-bearing kidney, excluding the tumor itself (for preoperative images) or the postsurgical/ablative defect (for postoperative images). The percent change in RPV was compared between the procedure types. RESULTS: One hundred fifty cases were included in the final analysis, with 30 cases from each NSP category. While preoperative tumors were larger in the PN group, there was no difference in the mean nephrometry score between groups. The TA group was found to have a lower mean RPV loss (-8.1% vs -16.5%, p<0.005). There was no difference in the RPV loss between modalities of TA (CA vs RFA) or between approaches to PN (open, laparoscopic, robotic). Matched-pair analysis based on the tumor size and multivariate analysis indicated TA vs PN was independently associated with less RPV loss. CONCLUSIONS: TA is associated with less RPV loss than PN in the management of SRM, but there is no difference between modalities of TA (CA vs RFA) or between approaches to PN.

Multimodality imaging of the postpartum or posttermination uterus: evaluation using ultrasound, computed tomography, and magnetic resonance imaging.

Postpartum and posttermination complications are common causes of morbidity and mortality in women of reproductive age. These complications can be broadly categorized into vascular, infectious, surgical, and neoplastic etiologies, or are due to ectopic implantation of placental or endometrial tissue. Causes of postpartum vascular complications include retained products of conception, arteriovenous malformation, and pseudoaneurysm. Infectious entities include endometritis, abscess, wound cellulitis, and pelvic septic thrombophlebitis. Postsurgical complications include uterine scar dehiscence, bladder flap hematoma, and subfascial hematoma. Neoplastic complications include the spectrum of gestational trophoblastic neoplasms. Ectopic tissue implantation complications include abnormal placentation and uterine scar endometriosis. Imaging is essential for diagnosis, and radiologists must be familiar with and aware of these entities so that accurate treatment and management can be obtained. In this review, we illustrate the imaging findings of common postpartum and posttermination complications on ultrasound, computed tomography, and magnetic resonance imaging.