Intraprocedural Ablation Margin Assessment by Using Ammonia Perfusion PET during FDG PET/CT-guided Liver Tumor Ablation: A Pilot Study.

Purpose To prospectively determine whether nitrogen 13 (13N) ammonia perfusion positron emission tomography (PET) during fluorine 18 fluorodeoxyglucose (FDG) PET/computed tomography (CT)-guided liver tumor ablation can be used to intraprocedurally assess ablation margins. Materials and Methods Eight patients (five women and three men; age range, 36-74 years; mean age, 57 years) were enrolled in this pilot study and underwent FDG PET/CT-guided microwave ablation of 11 FDG-avid liver metastases (mean diameter, 22 mm; range, 11-34 mm). All procedures were performed between March 2014 and December 2016. Complete ablation margin visibility and minimum ablation margin thickness were assessed by using intraprocedural 13N-ammonia perfusion PET compared with 24-hour postprocedural MR imaging by two independent blinded radiologists. Local tumor progression for each ablated tumor was assessed at follow-up imaging for 3-38 months (median, 17.6 months). Descriptive analysis was performed. Results Eleven of 11 (100%) ablation margins were fully assessable by using intraprocedural perfusion PET by both readers; six of eleven (55%) margins were fully assessable by both readers at postprocedural 24-hour MR imaging. By using perfusion PET, one tumor that had been judged by both readers to have a minimum margin of 0 mm progressed locally. No tumors judged to have a minimum margin greater than 0 mm at perfusion PET progressed locally. Conclusion 13N-ammonia perfusion PET during FDG PET/CT-guided liver tumor ablations can potentially be used to intraprocedurally assess the entire ablation margin, including the minimum margin. © RSNA, 2018.

Bladder cancer diagnosis with CT urography: test characteristics and reasons for false-positive and false-negative results.

PURPOSE: To determine test characteristics of CT urography for detecting bladder cancer in patients with hematuria and those undergoing surveillance, and to analyze reasons for false-positive and false-negative results. METHODS: A HIPAA-compliant, IRB-approved retrospective review of reports from 1623 CT urograms between 10/2010 and 12/31/2013 was performed. 710 examinations for hematuria or bladder cancer history were compared to cystoscopy performed within 6 months. Reference standard was surgical pathology or 1-year minimum clinical follow-up. False-positive and false-negative examinations were reviewed to determine reasons for errors. RESULTS: Ninety-five bladder cancers were detected. CT urography accuracy: was 91.5% (650/710), sensitivity 86.3% (82/95), specificity 92.4% (568/615), positive predictive value 63.6% (82/129), and negative predictive value was 97.8% (568/581). Of 43 false positives, the majority of interpretation errors were due to benign prostatic hyperplasia (n = 12), trabeculated bladder (n = 9), and treatment changes (n = 8). Other causes include blood clots, mistaken normal anatomy, infectious/inflammatory changes, or had no cystoscopic correlate. Of 13 false negatives, 11 were due to technique, one to a large urinary residual, one to artifact. There were no errors in perception. CONCLUSION: CT urography is an accurate test for diagnosing bladder cancer; however, in protocols relying predominantly on excretory phase images, overall sensitivity remains insufficient to obviate cystoscopy. Awareness of bladder cancer mimics may reduce false-positive results. Improvements in CTU technique may reduce false-negative results.

Immune-related tumour response assessment criteria: a comprehensive review.

Growing emphasis on precision medicine in oncology has led to increasing use of targeted therapies that encompass a spectrum of drug classes including angiogenesis inhibitors, immune modulators, signal transduction inhibitors, DNA damage modulators, hormonal agents etc. Immune therapeutic drugs constitute a unique group among the novel therapeutic agents that are transforming cancer treatment, and their use is rising. The imaging manifestations in patients on immune therapies appear to be distinct from those typically seen with conventional cytotoxic therapies. Patients on immune therapies may demonstrate a delayed response, transient tumour enlargement followed by shrinkage, stable size, or initial appearance of new lesions followed by stability or response. These newer patterns of response to treatment have rendered conventional criteria such as World Health Organization and response evaluation criteria in solid tumours suboptimal in monitoring changes in tumour burden. As a consequence, newer imaging response criteria such as immune-related response evaluation criteria in solid tumours and immune-related response criteria are being implemented in many trials to effectively monitor patients on immune therapies. In this review, we discuss the traditional and new imaging response criteria for evaluation of solid tumours, review the outcomes of various articles which compared traditional criteria with the new immune-related criteria and discuss pseudo-progression and immune-related adverse events.

Interreader Agreement of Prostate Imaging Reporting and Data System Version 2 Using an In-Bore MRI-Guided Prostate Biopsy Cohort: A Single Institution's Initial Experience.

OBJECTIVE: The purpose of this study is to determine the interobserver agreement of the Prostate Imaging Reporting and Data System version 2 (PI-RADSv2) for diagnosing prostate cancer using in-bore MRI-guided prostate biopsy as the reference standard. MATERIALS AND METHODS: Fifty-nine patients underwent in-bore MRI-guided prostate biopsy between January 21, 2010, and August 21, 2013, and underwent diagnostic multiparametric MRI 6 months or less before biopsy. A single index lesion per patient was selected after retrospective review of MR images. Three fellowship-trained abdominal radiologists (with 1-11 years' experience) blinded to clinical information interpreted all studies according to PI-RADSv2. Interobserver agreement was assessed using Cohen kappa statistics. RESULTS: Thirty-eight lesions were in the peripheral zone and 21 were in the transition zone. Cancer was diagnosed in 26 patients (44%). Overall PI-RADS scores were higher for all biopsy-positive lesions (mean ± SD, 3.9 ± 1.1) than for biopsy-negative lesions (3.1 ± 1.0; p < 0.0001) and for clinically significant lesions (4.2 ± 1.0) than for clinically insignificant lesions (3.1 ± 1.0; p < 0.0001). Overall suspicion score interobserver agreement was moderate (κ = 0.45). There was moderate interobserver agreement among overall PI-RADS scores in the peripheral zone (κ = 0.46) and fair agreement in the transition zone (κ = 0.36). CONCLUSION: PI-RADSv2 scores were higher in the biopsy-positive group. PI-RADSv2 showed moderate interobserver agreement among abdominal radiologists with no prior experience using the scoring system.

Imaging appearance of topical haemostatic agents: pictorial review.

Topical haemostatic agents have become an essential tool to assist with the control of bleeding during surgery as well as to facilitate wound closure. The imaging appearance of these agents can overlap that of abscess or tumour. Knowledge of the appearance of these various agents on ultrasound and CT is crucial to avoid misdiagnosing pathology, potentially resulting in unnecessary interventional procedures.

CT restaging of testicular germ cell tumors: The incidence of isolated pelvic metastases.

PURPOSE: We determined the incidence of isolated pelvic metastases at restaging computed tomography (CT) in patients with testicular germ cell tumors to consider if imaging the pelvis could be omitted. METHODS: After receiving IRB approval for this HIPAA-compliant retrospective study, medical records of 560 men (mean age 32.8) with 583 testicular germ cell tumors who underwent 3683 restaging CT scans of the abdomen and pelvis were reviewed to determine the proportion of patients with metastatic disease in the pelvis alone, as verified by histology or by resolution after therapy. Chi-square statistical analysis tested the association between factors currently thought to predispose patients to pelvic metastases. Patients were also categorized by clinical stage, tumor histology, and initial treatment. RESULTS: Isolated pelvic metastases were detected in nine (1.6%) of 560 men. Neither bulky abdominal disease (p=0.85) nor extratesticular invasion by the primary tumor (p=0.37) were statistically significant in predicting which patients were more likely to have isolated pelvic metastases. Among the nine patients with isolated pelvic recurrence, only three (0.7%) of 408 men with no known pelvic disease at initial staging and no tumor marker elevation at restaging had isolated pelvic metastases. Isolated pelvic recurrence was not statistically different when analyzed by initial stage and treatment. CONCLUSION: The incidence of isolated pelvic metastases in testicular germ cell tumors at restaging CT is low, but no group of patients was found to be without risk. Therefore, given the small, if any, risk of radiation-induced harm, the decision about whether to include routine pelvic CT in surveillance protocols should be individualized.

Radiogenomics of clear cell renal cell carcinoma: preliminary findings of The Cancer Genome Atlas-Renal Cell Carcinoma (TCGA-RCC) Imaging Research Group.

PURPOSE: To investigate associations between imaging features and mutational status of clear cell renal cell carcinoma (ccRCC). MATERIALS AND METHODS: This multi-institutional, multi-reader study included 103 patients (77 men; median age 59 years, range 34-79) with ccRCC examined with CT in 81 patients, MRI in 19, and both CT and MRI in three; images were downloaded from The Cancer Imaging Archive, an NCI-funded project for genome-mapping and analyses. Imaging features [size (mm), margin (well-defined or ill-defined), composition (solid or cystic), necrosis (for solid tumors: 0%, 1%-33%, 34%-66% or >66%), growth pattern (endophytic, <50% exophytic, or ≥50% exophytic), and calcification (present, absent, or indeterminate)] were reviewed independently by three readers blinded to mutational data. The association of imaging features with mutational status (VHL, BAP1, PBRM1, SETD2, KDM5C, and MUC4) was assessed. RESULTS: Median tumor size was 49 mm (range 14-162 mm), 73 (71%) tumors had well-defined margins, 98 (95%) tumors were solid, 95 (92%) showed presence of necrosis, 46 (45%) had ≥50% exophytic component, and 18 (19.8%) had calcification. VHL (n = 52) and PBRM1 (n = 24) were the most common mutations. BAP1 mutation was associated with ill-defined margin and presence of calcification (p = 0.02 and 0.002, respectively, Pearson's χ (2) test); MUC4 mutation was associated with an exophytic growth pattern (p = 0.002, Mann-Whitney U test). CONCLUSIONS: BAP1 mutation was associated with ill-defined tumor margins and presence of calcification; MUC4 mutation was associated with exophytic growth. Given the known prognostic implications of BAP1 and MUC4 mutations, these results support using radiogenomics to aid in prognostication and management.

Yield of urinary tract cancer diagnosis with repeat CT urography in patients with hematuria.

OBJECTIVE. The purpose of this study was to evaluate the yield of repeat CT urography (CTU) in detecting urinary tract malignancies in patients with hematuria. MATERIALS AND METHODS. A review of 5525 patients who underwent CTU between 2000 and 2011 revealed 751 (13.6%) patients who underwent repeat CTU. We excluded 127 patients with more than 3 years between examinations, 409 with nonhematuria indications, and 13 with less than 1 year of follow-up from a negative repeat examination. An additional 54 patients with malignancy diagnosed on the initial evaluation were excluded, leaving 148 patients in the study cohort (77 men and 71 women; mean age, 57 years). Patients were categorized on the basis of the presence or absence of findings suspicious for malignancy on initial CTU reports. Repeat CTU reports were correlated with cystoscopy, pathology, and clinical follow-up to determine the incidence of malignancy. Examinations negative for malignancy were confirmed with at least 1 year of clinical follow-up. CTU examinations of patients diagnosed with malignancy on repeat examination were reviewed by two radiologists in consensus. RESULTS. Initial CTU showed no findings suspicious for malignancy in 103 (70%) of 148 patients; of these, none had malignancy identified on repeat CTU. Among 45 (30%) patients with suspicious initial CTU findings, four malignancies were identified on repeat CTU (8.9%). Three were incidental to the initial suspicious finding; in retrospect, two were present on the initial CTU examination. CONCLUSION. In patients with hematuria, repeat CTU within 3 years is unlikely to show a urinary tract malignancy. These results support currently published guidelines.

A prospective feasibility study of radiation and concurrent bevacizumab for recurrent endometrial cancer.

OBJECTIVES: To determine the toxicity and survival rates in a trial of concurrent bevacizumab and external beam radiation (EB) for patients with recurrent endometrial or ovarian cancer. METHODS: Nineteen women with recurrent endometrial (n = 15) or ovarian (n = 4) cancer with gross disease involving the vaginal cuff, and/or pelvic nodes and/or para-aortic nodes, cancer were enrolled between 2008 and 2010. All patients received bevacizumab during radiation. Toxicity was assessed at baseline, weekly during treatment and every 3 months for at least 1 year after treatment. RESULTS: All patients completed EB on schedule. For the 15 patients with recurrent endometrial cancer, the 1- and 3-year progression-free survival (PFS was) 80%/67% and overall survival (OS) was 93%/80%. Patients that had a vaginal cuff recurrence alone had a 1- and 3-year PFS of 75%/63% and OS of 100%/75%. Two patients with pelvic node involvement did not recur throughout the entire follow-up period. The 5 patients with para-aortic node involvement had a 1- and 3-year PFS of 80%/60% and OS of 80%/80%. Of the 4 ovarian cancer patients 3 relapsed with 1- and 3-year PFS of 80%/40% and OS of 100%/60%. Toxicities included thrombosis and 1 embolic event in the setting of metastatic disease. No gastrointestinal perforations were noted. CONCLUSIONS: Delivering bevacizumab with concurrent radiation provides excellent local tumor control and survival for women with recurrent endometrioid endometrial cancer, particularly those with unresectable nodes. Caution must be used in those at highest risk of developing metastatic disease given the increased risk of thromboembolic events. This regimen may be considered for recurrent gynecologic malignancies in future trials.

Imaging female infertility.

The purpose of this pictorial review is to discuss causes of female infertility, in particular, those etiologies in which imaging plays a key role in detection. Included are disorders of cervical, ovarian, fallopian tube, and uterine origin. We also discuss the role of various imaging modalities including hysterosalpingography, pelvic ultrasonography, hysterosonography, and pelvic MR imaging in elucidating the cause of female infertility. Radiologists need to know the conditions to be aware of when these patients are sent for diagnostic imaging, as well as how to direct further management, if necessary, should an abnormality be detected.

Surveillance of patients with bladder cancer following cystectomy: yield of CT urography.

PURPOSE: To determine the yield of CT urography (CTU) in the surveillance of patients with bladder cancer following cystectomy. MATERIALS AND METHODS: In this IRB-approved, HIPAA-compliant, retrospective study of 5,404 CT urograms performed at our institution between March 2000 and February 2011, 225 CT urograms were performed in 105 patients [79 men, 26 women; mean age 65 years (43-85)] following cystectomy for bladder cancer. Median follow-up after cystectomy was 63 months (range 1-234), median time between cystectomy and CTU was 39 months (range 0-229), median follow-up after CTU was 34 months (range 1-111). CTU examinations were reviewed by two radiologists in consensus and findings were categorized into those related to surgery, locoregional recurrence, metastases, or metachronous upper tract urothelial tumor (UTT). FINDINGS: Findings were present in 69 (65.7 %) of 105 patients, including findings related to surgery in 60 (57.1 %) patients, locoregional recurrence or metastatic disease in 21 (20 %) patients, and UTT in 3 (2.9 %) patients. Of surgery-related findings, hydronephrosis (23/105, 21.9 %) and parastomal hernia (17/105, 16.2 %) were the most common findings. Visceral metastases (16/105, 15.2 %) and lymph node metastases (13/105, 12.4 %) were the most common manifestations of recurrent disease. CONCLUSION: CTU findings in the surveillance of patients with bladder cancer after cystectomy are common and include those related to surgery, spread of the disease, and metachronous tumors. Our study supports current published guidelines on the use of CTU in these patients.

Body CT scanning in young adults: examination indications, patient outcomes, and risk of radiation-induced cancer.

PURPOSE: To quantify patient outcome and predicted cancer risk from body computed tomography (CT) in young adults and identify common indications for the imaging examination. MATERIALS AND METHODS: This retrospective multicenter study was HIPAA compliant and approved by the institutional review boards of three institutions, with waiver of informed consent. The Research Patient Data Registry containing patient medical and billing records of three university-affiliated hospitals in a single metropolitan area was queried for patients 18-35 years old with a social security record who underwent chest or abdominopelvic CT from 2003 to 2007. Patients were analyzed according to body part imaged and scanning frequency. Mortality status and follow-up interval were recorded. The Biologic Effects of Ionizing Radiation VII method was used to calculate expected cancer incidence and death. Examination indication was determined with associated ICD-9 diagnostic code; 95% confidence intervals for percentages were calculated, and the binomial test was used to compare the difference between percentages. RESULTS: In 21 945 patients, 16 851 chest and 24 112 abdominopelvic CT scans were obtained. During the average 5.5-year (± 0.1 [standard deviation]) follow-up, 7.1% (575 of 8057) of chest CT patients and 3.9% (546 of 13 888) of abdominal CT patients had died. In comparison, the predicted risk of dying from CT-induced cancer was 0.1% (five of 8057, P < .01) and 0.1% (eight of 12 472, P < .01), respectively. The most common examination indications were cancer and trauma for chest CT and abdominal pain, trauma, and cancer for abdominopelvic CT. Among patients without a cancer diagnosis in whom only one or two scans were obtained, mortality and predicted risk of radiation-induced cancer death were 3.6% (215 of 5914) and 0.05% (three of 5914, P < .01) for chest CT and 1.9% (219 of 11 291) and 0.1% (six of 11 291, P < .01) for abdominopelvic CT. CONCLUSION: Among young adults undergoing body CT, risk of death from underlying morbidity is more than an order of magnitude greater than death from long-term radiation-induced cancer.

MRI assessment of percutaneous ablation of liver tumors: value of subtraction images.

PURPOSE: To evaluate the value of subtraction images when using MRI to assess liver tumors treated with percutaneous ablation. MATERIALS AND METHODS: Following percutaneous ablation of 35 liver tumors, two abdominal radiologists, blinded to outcomes, independently reviewed follow-up MRI examinations for tumoral enhancement suggestive of residual/recurrent tumor and rated their confidence level. After one year, the readers reviewed the same examinations with added subtraction images. Accuracy of the detection of residual/recurrent tumor and contrast-to-noise ratios (CNR; for tumoral enhancement-to-liver, tumoral enhancement-to-ablation zone, and ablation zone-to-liver) were calculated with and without subtraction images and compared using Wilcoxon signed rank test. Interobserver variability was computed using Kappa (κ) statistics. RESULTS: Residual/recurrent tumor was present in 8 (23.5%) of 34 tumors. Accuracy of detecting residual/recurrent tumor with subtraction images and interobserver agreement (κ = 0.72, good) were better than accuracy of detecting residual/recurrent tumor and interobserver agreement (κ = 0.57, moderate) of enhanced MR images without subtraction. Mean CNR of subtraction images was significantly higher than that of enhanced MR images for tumoral enhancement-to-liver (0.2 ± 5 versus 11.6 ± 14.4, P = 0.03), tumoral enhancement-to-ablation zone (10.1 ± 12.5 versus 34.4 ± 29.4, P = 0.02), and ablation zone-to-liver (11.8 ± 13.3 versus 102.5 ± 238.4, P = 0.03). CONCLUSION: When using MRI, subtraction images help both detect and exclude residual/recurrent tumor following percutaneous liver ablations.

Renal cell carcinoma containing abundant non-calcified fat.

Renal masses found to contain macroscopic fatty elements on CT or MRI imaging can generally be classified as benign angiomyolipomas. Rarely, renal cell carcinomas may also contain evidence of macroscopic fat. When true adipocytic elements are present, this is generally due to a process of osseous metaplasia in which both fat cells and calcification are co-localized within the mass. We present a patient with a large papillary renal cell carcinoma containing abundant fat with sparse, punctate calcification remote from the fatty elements on imaging. This report highlights the need for radiologists to maintain caution when diagnosing renal angiomyolipomas on the basis of macroscopic fat and reviews the current literature on fat-containing renal masses.

Duodenal and other gastrointestinal toxicity in cervical and endometrial cancer treated with extended-field intensity modulated radiation therapy to paraaortic lymph nodes.

PURPOSE: To characterize the rates of acute and late duodenal and other gastrointestinal (GI) toxicities among patients treated for cervical and endometrial cancers with extended-field intensity modulated radiation therapy (EF-IMRT) to the paraaortic nodes and to analyze dose-volume relationships of GI toxicities. METHODS AND MATERIALS: Fifty-three patients with endometrial or cervical cancer underwent EF-IMRT to the paraaortic nodes, of whom 46 met the inclusion criteria for GI toxicity and 45 for duodenal toxicity analysis. The median prescribed dose to the paraaortic nodes was 54 Gy (range, 41.4-65 Gy). The 4 duodenal segments, whole duodenum, small bowel loops, peritoneum, and peritoneum plus retroperitoneal segments of colon were contoured retrospectively, and dosimetric analysis was performed to identify dose-volume relationships to grade ≥3 acute (<90 day) and late (≥90 day) GI toxicity. RESULTS: Only 3/46 patients (6.5%) experienced acute grade ≥3 GI toxicity and 3/46 patients (6.5%) experienced late grade ≥3 GI toxicity. The median dose administered to these 6 patients was 50.4 Gy. One of 12 patients who received 63 to 65 Gy at the level of the renal hilum experienced grade 3 GI toxicity. Dosimetric analysis of patients with and without toxicity revealed no differences between the mean absolute or fractional volumes at any 5-Gy interval between 5 Gy and the maximum dose. None of the patients experienced duodenal toxicity. CONCLUSIONS: Treatment of paraaortic nodes with IMRT is associated with low rates of GI toxicities and no duodenal-specific toxicity, including patients treated with concurrent chemotherapy. This technique may allow sufficient dose sparing of the bowel to enable safe dose escalation to at least 65 Gy.

Mucinous tubular and spindle cell carcinoma of the kidney: imaging features.

This article describes the features on sonography, computed tomography (CT) and magnetic resonance imaging (MRI) of mucinous tubular and spindle cell carcinoma of the kidney. Six pathologically proven cases of mucinous tubular and spindle cell carcinoma of the kidney were identified (5 females, 1 male); all patients underwent preoperative imaging. The mean age of the patients was 58.5 years. Thirteen imaging studies were available for review: 2 sonograms, 1 unenhanced CT scan, 5 contrast-enhanced CT scans, 1 unenhanced magnetic resonance imaging (MRI) examination, and 4 contrast-enhanced MRI examinations. Two abdominal radiologists evaluated all images retrospectively on a PACS workstation using a standardized data collection sheet until consensus was reached. All mucinous tubular and spindle cell carcinomas presented as well-marginated, small (mean 2.6 cm, range 1.9-3.2 cm) predominantly solid masses. No intratumoral fat or calcification was identified. Unenhanced CT and MRI appearances were variable as was the degree of enhancement following intravenous contrast material administration. There was no evidence of perinephric extension, renal vein involvement or metastatic disease in any of the cases. The radiological appearance of mucinous tubular and spindle cell carcinoma is diverse and therefore indistinguishable from the more common subtypes of renal cell carcinoma.

Sonographic and magnetic resonance imaging findings in uterine incarceration.

We show the sonographic and magnetic resonance imaging features of uterine incarceration. Clinical data and imaging findings were retrospectively reviewed for 8 confirmed cases identified by sonography from 2000 to 2010. Two patients had magnetic resonance imaging. Seven of 8 patients (87.5%) presented with abdominal pain; 4 of 8 (50.0%) also had urinary symptoms. All had a retroverted uterus with an elongated anterosuperiorly displaced or poorly visualized cervix on sonography. Magnetic resonance imaging showed similar features, but in both cases, the placental position was misinterpreted because of severe uterine retroversion. Radiologists should be aware of this condition and its imaging features to reduce associated morbidity and mortality.

Diagnostic yield of CT urography in the evaluation of young adults with hematuria.

OBJECTIVE: CT urography is increasingly used as the initial imaging test in patients with hematuria. The aim of our study was to determine the yield of CT urography in young adults with hematuria to see whether single phase unenhanced CT would have been sufficient. MATERIALS AND METHODS: We reviewed medical records of consecutive patients undergoing CT urography between March 2000 and July 2009 at our tertiary medical center. Of 5400 CT urograms performed, 375 (6.9%) in 359 patients aged 40 years or younger with hematuria were included in the study. Urographic findings were tabulated according to their clinical significance. CT images were reviewed to see whether contrast-enhanced images were necessary for diagnosis. RESULTS: A clinically significant source was found in 83 of 375 examinations (22.1%), including 42 of 142 (29.6%) for gross hematuria, 29 of 181 (16.0%) for microscopic hematuria, and 12 of 52 (23.1%) for hematuria of unspecified subtype. The most common clinically significant findings were renal or ureteral calculi (n = 73 [75.3%]); four malignancies were also detected. Ninety-two (94.8%) of 97 clinically significant findings were evident on unenhanced images. All significant findings that required contrast-enhanced images for diagnosis occurred in patients with predisposing medical conditions. CONCLUSION: A clinically significant source of hematuria was detected in 22.1% of CT urograms of young adults. However, an unenhanced CT alone may be sufficient in patients without additional predisposing medical conditions, thereby reducing radiation dose in this radiosensitive population.

Feasibility of low-tube-voltage excretory phase images during CT urography: assessment using a dual-energy CT scanner.

OBJECTIVE: The purpose of this study is to assess the feasibility of low-tube-voltage images during excretory phase CT urography. MATERIALS AND METHODS: In this retrospective study, we examined 70 consecutive CT urograms (35 men and 35 women; mean age, 58.5 years) performed on a dual-energy CT scanner and compared excretory phase images obtained at 80 kVp and 340 mAs with blended images (0.3 × 140 kVp and 80 mAs; and 0.7 × 80 kVp and 340 mAs). Quantitative measurements of urinary system opacification (Hounsfield units), image noise (Hounsfield units), and effective dose (millisieverts) were compared using Student paired t test. Image noise was correlated with patient thickness. Two independent blinded readers qualitatively assessed opacification, image quality (both compared using Wilcoxon test), overall acceptability (compared using McNemar test), and detectability of urinary and extraurinary findings. RESULTS: The 80-kVp images yielded significantly higher opacification of renal pelvis (p < 0.0001), ureter (p < 0.0001), bladder (p < 0.0001), and aorta (p < 0.0001); higher image noise (p < 0.0001); and lower radiation dose (5.2 vs 11.9 mSv). Image noise increased along with increasing patient thickness (r = 0.86 for 80-kVp images). Qualitative opacification scores were better only in the bladder on 80-kVp images (p = 0.002). Although 80-kVp image quality was lower (p < 0.0001), the overall acceptability was similar. Of 42 urinary findings, 40 were detected on 80-kVp images (< 2-mm calyceal calculus and tiny foci of collecting system gas were missed in one patient each, both large patients). Of 137 extraurinary findings, 130 were detected on 80-kVp images (no findings of high clinical significance were missed). CONCLUSION: Low tube voltage (80 kVp) during excretory phase CT urography is feasible, with improved urinary system opacification, acceptable image quality, and lower radiation dose.