Purpose To develop a fast and accurate mono-exponential fitting algorithm based on AutoRegression on Linear Operations (ARLO) of data, and to validate its accuracy and computational speed by comparing it with the conventional Levenberg-Marquardt (LM) and Log-Linear (LL) algorithms. Methods ARLO, LM and LL performances for T2* mapping were evaluated in simulation and in vivo imaging of liver (n=15) and myocardial (n=1) iron overload patients and the brain (2 healthy volunteers). Results In simulations, ARLO consistently delivered accuracy similar to LM and significantly superior to LL. In in vivo mapping of T2* values, ARLO showed excellent agreement with LM, while LL showed only limited agreements with ARLO and LM. Compared to LM and LL in the liver, ARLO was 125 and 8 times faster using our Matlab implementations, and 156 and 13 times faster using our C++ implementations. In C++ implementations, ARLO reduced the online whole-brain processing time from 9 min 15 sec of LM and 35 sec of LL to 2.7 sec, providing T2* maps approximately in real time. Conclusion Due to comparable accuracy and significantly higher speed, ARLO can be considered as a valid alternative to the conventional LM algorithm for online T2* mapping.

Dynamic QSM can be used to perform 4D mapping of contrast agent concentration in contrast-enhanced magnetic resonance imaging. The perfusion parameters derived from this 4D contrast agent concentration map were in good agreement with those obtained using arterial spin labeling.

Background: The purpose of this study was to evaluate breast tissue expanders with magnetic ports for safety in patients undergoing abdominal/pelvic magnetic resonance angiography before autologous breast reconstruction. Methods: Magnetic resonance angiography of the abdomen and pelvis at 1.5 T was performed in 71 patients in prone position with tissue expanders with magnetic ports labeled “MR Unsafe” from July of 2012 to May of 2014. Patients were monitored during magnetic resonance angiography for tissue expander–related symptoms, and the chest wall tissue adjacent to the tissue expander was examined for injury at the time of tissue expander removal for breast reconstruction. Retrospective review of these patients’ clinical records was performed. T2-weighted fast spin echo, steady-state free precession and gadolinium-enhanced spoiled gradient echo sequences were assessed for image artifacts. Results: No patient had tissue expander or magnetic port migration during the magnetic resonance examination and none reported pain during scanning. On tissue expander removal (71 patients, 112 implants), the surgeons reported no evidence of tissue damage, and there were no operative complications at those sites of breast reconstruction. Conclusion: Magnetic resonance angiography of the abdomen and pelvis in patients with certain breast tissue expanders containing magnetic ports can be performed safely at 1.5 T for pre–autologous flap breast reconstruction perforator vessel mapping. CLINICAL QUESTION/LEVEL OF EVIDENCE: Therapeutic, IV.

Purpose:To define the magnetic resonance (MR) imaging prevalence of pancreatic cysts in a cohort of patients with autosomal dominant polycystic kidney disease (ADPKD) compared with a control group without ADPKD that was matched for age, sex, and renal function. Materials and Methods:In this HIPAA-compliant, institutional review board-approved study, all patients with ADPKD provided informed consent; for control subjects, informed consent was waived. Patients with ADPKD (n = 110) with mutations identified in PKD1 or PKD2 and control subjects without ADPKD or known pancreatic disease (n = 110) who were matched for age, sex, estimated glomerular filtration rate, and date of MR imaging examination were evaluated for pancreatic cysts by using axial and coronal single-shot fast spin-echo T2-weighted images obtained at 1.5 T. Total kidney volume and liver volume were measured. Univariate and multivariable logistic regression analyses were conducted to evaluate potential associations between collected variables and presence of pancreatic cysts among patients with ADPKD. The number, size, location, and imaging characteristics of the cysts were recorded. Results:Patients with ADPKD were significantly more likely than control subjects to have at least one pancreatic cyst (40 of 110 patients [36%] vs 25 of 110 control subjects [23%]; P = .027). In a univariate analysis, pancreatic cysts were more prevalent in patients with ADPKD with mutations in PKD2 than in PKD1 (21 of 34 patients [62%] vs 19 of 76 patients [25%]; P = .0002). In a multivariable logistic regression model, PKD2 mutation locus was significantly associated with the presence of pancreatic cysts (P = .0004) and with liver volume (P = .038). Patients with ADPKD and a pancreatic cyst were 5.9 times more likely to have a PKD2 mutation than a PKD1 mutation after adjusting for age, race, sex, estimated glomerular filtration rate, liver volume, and total kidney volume. Conclusion:Pancreatic cysts were more prevalent in patients with ADPKD with PKD2 mutation than in control subjects or patients with PKD1 mutation.q RSNA, 2016

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Imaging is needed for diagnosis, treatment planning, and follow-up of patients with pathologies affecting upper extremity vasculature. With growth and evolution of imaging modalities [especially CT angiography (CTA) and MR angiography (MRA)], there is need to recognize the advantages and disadvantages of various modalities and obtain the best possible imaging diagnostic test. Understanding various limitations and pitfalls as well as the best practices to minimize and manage these pitfalls is very important for the diagnosis. This article reviews the upper extremity arterial vascular anatomy, discusses the CTA and MRA imaging, various pitfalls, and challenges and discuss imaging manifestations of upper extremity arterial pathologies.

Perforator flap-based breast reconstruction in a post mastectomy patient requires dissection of the artery-vein bundle (perforators) responsible for perfusion of the subcutaneous fat and skin of the flap. Traditionally, these reconstructions were performed with the transverse rectus abdominis myocutaneous (TRAM) flap, but autologous breast reconstruction using muscle sparing free flaps has become steadily more popular in recent years. Preoperative imaging to locate and evaluate candidate perforators has become an essential step before patients undergo the microsurgical procedure. Preoperative mapping assists with operative planning, reduces operating times, and brings anatomical variations to their attention. Pre-operative imaging also assists in choosing the appropriate donor site for harvesting flaps. Computed tomography angiography (CTA) and magnetic resonance angiography (MRA) have been widely used for this type of preoperative imaging. Both MRA and CTA have their inherent advantages and disadvantages, and the preferred modality for this purpose varies by institution based on factors such as scanner availability, radiologist and surgeon experience, and comfort in interpreting the images. Concerns over excessive exposure to ionizing radiation and poor iodinated contrast agent enhancement of the intramuscular perforator course has made MRA the first-choice imaging modality in many centers. The purpose of the article is to review technique and protocols for the pre-operative CTA/MRA in patients who are being considered for a deep inferior epigastric artery perforator (DIEP) or profunda artery perforator (PAP) flap and to familiarize the reader with the normal and variant anatomic features of the deep inferior epigastric and PAP vessels along with the anatomic and surgical considerations used in the selection of perforator flap donor site for breast reconstruction post mastectomy.

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