Dmitry Khrichenko

Functional analysis in MR urography — made simple

MR urography (MRU) has proved to be a most advantageous imaging modality of the urinary tract in children, providing one-stop comprehensive morphological and functional information, without the utilization of ionizing radiation. The functional analysis of the MRU scan still requires external post-processing using relatively complex software. This has proved to be a limiting factor in widespread routine implementation of MRU functional analysis and use of MRU functional parameters similar to nuclear medicine. We present software, developed in a pediatric radiology department, that not only enables comprehensive automated functional analysis, but is also very user-friendly, fast, easily operated by the average radiologist or MR technician and freely downloadable at www.chop-fmru.com. A copy of IDL Virtual Machine is required for the installation, which is obtained at no charge at www.ittvis.com. The analysis software, known as “CHOP-fMRU,” has the potential to help overcome the obstacles to widespread use of functional MRU in children.

Dynamic Gadolinium-Enhanced MRI of the Proximal Femur: Preliminary Experience in Healthy Children

OBJECTIVE The purpose of this study is to use dynamic contrast-enhanced MRI to evaluate the perfusion characteristics of the proximal femur in the growing skeleton. MATERIALS AND METHODS We evaluated 159 subjects (mean age, 5.67 years) who underwent a well-controlled protocol of contrast-enhanced MRI of the abdomen and hips. Perfusion and permeability parameters (enhancement ratio peak, AUC, time to peak, and rate of extraction) for six regions of the proximal femur were calculated. RESULTS A decrease with age was found for all contrast kinetics parameters in all regions (p < 0.001). Perfusion parameters differed between the regions (p < 0.001). The highest perfusion and permeability parameters were found in the metaphyseal spongiosa, metaphyseal marrow, and periosteum. The metaphyseal spongiosa had a highly vascular pattern of enhancement and showed the highest enhancement ratio peak, AUC, and rate of extraction and the lowest time to peak. The metaphyseal marrow showed a vascular pattern of enhancement with a lower peak compared with the metaphyseal spongiosa. The periosteum showed prompt nonvascular contrast enhancement that reached a plateau that remained elevated. CONCLUSION The highest enhancement was seen in areas involved with growth: the metaphyseal spongiosa, which is related to endochondral ossification, and the periosteal cambium, which is related to membranous ossification. The enhancement characteristics are radically different: in the spongiosa; enhancement is brisk and declines, with a vascular pattern, whereas contrast uptake increases with time in the periosteum. Recognition of normal enhancement patterns of the proximal femur is important for distinguishing normal development from pathologic processes.

Central pontine myelinolysis: A case report and clinical-pathological review

Cui R, Fayek S, Rand EB, Feygin T, Khrichenko D, Shaked A. Central pontine myelinolysis: A case report and clinical–pathological review. Pediatr Transplantation 2011.

Role of magnetic resonance urography in pediatric renal fusion anomalies

Renal fusion is on a spectrum of congenital abnormalities that occur due to disruption of the migration process of the embryonic kidneys from the pelvis to the retroperitoneal renal fossae. Clinically, renal fusion anomalies are often found incidentally and associated with increased risk for complications, such as urinary tract obstruction, infection and urolithiasis. These anomalies are most commonly imaged using ultrasound for anatomical definition and less frequently using renal scintigraphy to quantify differential renal function and assess urinary tract drainage. Functional magnetic resonance urography (fMRU) is an advanced imaging technique that combines the excellent soft-tissue contrast of conventional magnetic resonance (MR) images with the quantitative assessment based on contrast medium uptake and excretion kinetics to provide information on renal function and drainage. fMRU has been shown to be clinically useful in evaluating a number of urological conditions. A highly sensitive and radiation-free imaging modality, fMRU can provide detailed morphological and functional information that can facilitate conservative and/or surgical management of children with renal fusion anomalies. This paper reviews the embryological basis of the different types of renal fusion anomalies, their imaging appearances at fMRU, complications associated with fusion anomalies, and the important role of fMRU in diagnosing and managing children with these anomalies.

Detection of renal crossing vessels in MR urography made simple

Sir, Parikh et al. [1] published the interesting article “Pediatric ureteropelvic junction obstruction: can magnetic resonance urography identify crossing vessels?” in the November 2015 issue of Pediatric Radiology. This was followed by a thoughtprovoking letter to the editor – “Direct visualization of crossing renal vessels on MRU achieved by splitting intravenous contrast dose” – that described a novel protocol for contrast administration during magnetic resonance urography (MRU) [2]. The study by Parikh et al. [1] included 25 MRUs of patients diagnosed with ureteropelvic junction obstruction who underwent surgery. Crossing vessels were identified on 10 of the MRUs and 9 were confirmed surgically (ĸ=0.92). We published a similar study of 41 MRUs in patients with ureteropelvic junction obstruction [3]. Crossing vessels were identified on 17MRUs and 15 were confirmed intraoperatively. Ureteral obstruction by the crossing vessel was visualized on the MRUs in only 9/17 cases. In our series, the sensitivity and specificity of MRU to detect renal crossing vessels in the setting of ureteropelvic obstruction was 88.2% and 91.7%, respectively. Thus, these two studies demonstrate the value of MR urography to diagnose crossing vessels with a single bolus post-contrast dynamic series. Proposed split-bolus MRU allows simultaneous visualization of the renal vessels and the collecting system [2]. In their pictorial essay, Battal et al. [4] presented the utility of splitbolus MRU in a number of vascular anomalies related to the urinary tract, including crossing vessels [4]. However, to date, there is no systematic evaluation of using this method to diagnose crossing vessels. Split-bolus MRU requires careful real-time monitoring in order to time the second contrast injection. The additional procedural step and monitoring increase unnecessarily the scan time and add complexity to the examination. We would like to point out a simple way to get concurrent images of the renal angiographical and excretory phases using the single-bolus contrast technique. The freeware “CHOPfMRU,” available at www.chop-fmru.com, utilized in studies by Parikh et al. [1] and Weiss et al. [3], has built-in capabilities to do so [5]. The CHOP-fMRU software has a maximum intensity projection (MIP) time feature that allows the user to view any given slice of a dynamic sequence with maximum enhancement at every pixel. Accordingly, the user is not limited to specific timing of the injections for image acquisition as in the split-bolus technique. The maximally enhanced pixels can be selected simultaneously from the entire dynamic data set including the kidneys, ureters and vessels. The only limitation to MIP reconstruction is significant patient motion. Generating the combined angiographical and excretory images using the CHOP-fMRU software is simple. The step-bystep instructions had previously been described in the appendix part (Step 8) of the publication by Khrichenko et al. [5]. * Kassa Darge darge@email.chop.edu

Abstract C108: An expanded imaging cohort of pazopanib in children and adolescents with relapsed or refractory soft tissue sarcoma (ADVL0815): A Children's Oncology Group phase I consortium trial.

Background: Pazopanib (NCT00929903) is an orally available small molecule inhibitor of VEGFR 1–3, PDGFR α/β, and c-kit, which has been shown to prolong progression free survival in adults with soft tissue sarcoma (STS). Following a standard phase I dose escalation trial to determine the pediatric maximum tolerated dose (MTD), an expanded cohort of children and adolescents with relapsed and refractory STS and at least one lesion amenable to dynamic contrast enhanced MRI (DCE-MRI) was studied to explore changes in tumor blood volume and vascular permeability following initiation of pazopanib, and to correlate these changes with clinical outcome. Methods: Oral pazopanib was administered at 450mg/m2 once daily in 28 day cycles, for up to 24 cycles. DCE-MRI scans were obtained at baseline and within 15 × 2 days after initiation of pazopanib. DCE-MRI data sets were analyzed using a two compartment kinetic model yielding estimates of fractional blood volume and the permeability transfer constant (Ki). Results: 10 subjects were enrolled [5 male; median age 17 yrs (range, 8–23)], of whom 8 had paired DCE-MRI scans of sufficient quality to be evaluable. Subjects received a median of 4 cycles (range 1–7; 3 remain on study receiving courses 6, 7 and 8). One subject had a dose limiting toxicity of Gr3 back and extremity pain with Gr3 sensory neuropathy. Other non-dose limiting toxicities occurring in >10% of subjects (n=10) during the first cycle included mild myelosuppression, sinus bradycardia, fatigue, diarrhea, nausea, vomiting, anorexia, dehydration, dizziness, headache, liver transaminase elevation and hyperglycemia. All subjects with evaluable DCE-MRI (n=8) experienced a decrease in tumor blood volume following initiation of pazopanib, with a mean pre-treatment level of 16% (range 1–29%) versus 7% (0–15%) post-treatment (p Conclusions: DCE-MRI changes in tumor blood volume and Ki in pediatric and adolescent patients with soft tissue sarcoma are supportive of physiological activity and the antiangiogenic mechanism of pazopanib. Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the AACR-NCI-EORTC International Conference: Molecular Targets and Cancer Therapeutics; 2011 Nov 12-16; San Francisco, CA. Philadelphia (PA): AACR; Mol Cancer Ther 2011;10(11 Suppl):Abstract nr C108.