Rapid Standardized CT-Based Method to Determine Lean Body Mass SUV for PET-A Significant Improvement Over Prediction Equations.

Unlabelled: In F-fluorodeoxyglucose (F-FDG) positron emission tomography (PET) studies, maximum standardized uptake value (SUV) is the parameter commonly used to provide a measurement of the metabolic activity of a tumor. SUV normalized by body mass is affected by the proportions of body fat and lean tissue, which present high variability in patients with cancer. SUV corrected by lean body mass (LBM), denoted as SUL, is recommended to provide more accurate, consistent, and reproducible SUV results; however, LBM is frequently estimated rather than measured.

131I-MIBG Therapy in a Metastatic Small Bowel Neuroendocrine Tumor Patient Undergoing Hemodialysis.

Systemic radioisotope therapy with I-metaiodobenzylguanidine (I-MIBG) is an effective form of targeted therapy for neuroendocrine tumors. One of the absolute contraindications to administering I-MIBG therapy listed in the 2008 European Association of Nuclear Medicine guidelines is renal insufficiency requiring dialysis, although this contraindication is not evidence based. We describe a 68-year-old woman with a metastatic small bowel neuroendocrine tumor who developed renal insufficiency requiring hemodialysis.

Ectopic Corticotropin-Producing Neuroendocrine Tumor of the Pancreas Treated With 177Lu DOTATATE Induction and Maintenance Peptide Receptor Radionuclide Therapy.

A 57-year-old woman diagnosed with ectopic Cushing syndrome was found to have a 111In-octreotide-avid corticotropin-producing pancreatic neuroendocrine tumor with liver metastases. She was treated with 4 induction and 4 maintenance cycles of 177Lu-DOTATATE, which normalized her serum corticotropin levels and dramatically reduced the size of the pancreatic primary and liver metastases.

Resolution of Hyperreninemia, Secondary Hyperaldosteronism, and Hypokalemia With 177Lu-DOTATATE Induction and Maintenance Peptide Receptor Radionuclide Therapy in a Patient With Pancreatic Neuroendocrine Tumor.

A 54-year-old woman presented with a history of nausea, vomiting, diarrhea, and recurrent episodes of severe hypokalemia requiring hospitalization. Imaging revealed a pancreatic mass with liver metastases, histologically confirmed to be a neuroendocrine tumor. Elevated active renin and aldosterone levels were identified, and the patient was treated with 4 induction cycles of Lu-DOTATATE, which resolved the diarrhea, nausea, and hypokalemia, and normalized the renin and aldosterone levels.

Chest X-ray Artifact Caused by Bilateral 99mTc-Antimony Trisulfite Injection for Sentinel Node Imaging in a Patient With Breast Cancer.

A 52-year-old woman diagnosed with invasive ductal carcinoma of both breasts had a chest x-ray for preoperative assessment. A striking artifact was noted by the x-ray technologist, who, as a result, became very concerned about radiation exposure from the patient. The patient had undergone bilateral sentinel lymph node injections in the nuclear medicine department with Tc-antimony trisulfite colloid just 2 hours before the chest x-ray.

Glucagonoma Pancreatic Neuroendocrine Tumor Treated With 177Lu DOTATATE Induction and Maintenance Peptide Receptor Radionuclide Therapy.

A 56-year-old man presented with a history of 2 prior resections of a recurrent pancreatic glucagonoma in the past 4 years. Workup revealed new liver and abdominal nodal metastases with a rising serum glucagon level. He was started on peptide receptor radionuclide therapy with Lu DOTATATE, and his disease stabilized, while his glucagon levels decreased and also stabilized.

Assessment of a commercially available automatic deformable registration system.

In recent years, a number of approaches have been applied to the problem of deformable registration validation. However, the challenge of assessing a commercial deformable registration system - in particular, an automatic registration system in which the deformable transformation is not readily accessible - has not been addressed. Using a collection of novel and established methods, we have developed a comprehensive, four-component protocol for the validation of automatic deformable image registration systems over a range of IGRT applications.

Prostate positioning errors associated with two automatic registration based image guidance strategies.

Daily image guidance for helical tomotherapy prostate patients is based on the registration of pre-treatment megavoltage CT (MVCT) images and the original planning CT. The goal of registration, whether manual or automatic, is the overlap of the prostate; otherwise prostate misplacement may compromise the efficacy of treatment or lead to increased toxicity. A previous study demonstrated that without the aid of implanted fiducials, manual registration results in inaccurate prostate positioning.

Initial results of hypoxia imaging using 1-alpha-D: -(5-deoxy-5-[18F]-fluoroarabinofuranosyl)-2-nitroimidazole ( 18F-FAZA).

Purpose: Tumour hypoxia is thought to play a significant role in the outcome of solid tumour therapy. Positron emission tomography (PET) is the best-validated noninvasive technique able to demonstrate the presence of hypoxia in vivo. The locally developed PET tracer for imaging hypoxia, 1-alpha-D: -(5-deoxy-5-[(18)F]-fluoroarabinofuranosyl)-2-nitroimidazole ((18)F-FAZA), has been shown to accumulate in experimental models of tumour hypoxia and to clear rapidly from the circulation and nonhypoxic tissues.

A review of basic principles of fractals and their application to pharmacokinetics.

Pharmacokinetic models play a crucial role in analyzing and assessing the results of in vitro and in vivo studies. In this review, comparative analysis of pharmacokinetic models under homogeneous and heterogeneous conditions is performed, placing special focus on the role of fractal theory. The concept of fractals provides a new perspective from which processes occurring in heterogeneous, confined, or poorly mixed environments can be modeled.

Use of a simulated annealing algorithm to fit compartmental models with an application to fractal pharmacokinetics.

Increasingly, fractals are being incorporated into pharmacokinetic models to describe transport and chemical kinetic processes occurring in confined and heterogeneous spaces. However, fractal compartmental models lead to differential equations with power-law time-dependent kinetic rate coefficients that currently are not accommodated by common commercial software programs. This paper describes a parameter optimization method for fitting individual pharmacokinetic curves based on a simulated annealing (SA) algorithm, which always converged towards the global minimum and was independent of the initial parameter values and parameter bounds.

Modeling fractal-like drug elimination kinetics using an interacting random-walk model.

We introduce an interacting random-walk model to describe the residence time of drug molecules undergoing a series of sojourn times in the body before being permanently eliminated under either homogeneous or heterogeneous conditions. We show that short-term correlations between drug molecules lead to Michaelis-Menten kinetics while long-term correlations lead to transient fractal-like kinetics. By combining both types of correlation, fractal-like Michaelis-Menten kinetics are achieved, and the simulations confirm previous analytical results.

Monte Carlo investigation of single cell beta dosimetry for intraperitoneal radionuclide therapy.

Single event spectra for five beta-emitting radionuclides (Lu-177, Cu-67, Re-186, Re-188, Y-90) were calculated for single cells from two source geometries. The first was a surface-bound isotropically emitting point source and the second was a bath of free radioactivity in which the cell was submerged. Together these represent a targeted intraperitoneal radionuclide therapy.

A numerical approach to non-circular birdcage RF coil optimization: verification with a fourth-order coil.

It is demonstrated that birdcage resonators, satisfying conditions of quadrature operation and radiofrequency field homogeneity, can be realized in practice on formers of non-circular cross section described by an equation of the form (x/a)n + (y/b)n = 1 where a and b are constants and n > or = 2 is an integer. Using a ladder network analogous to that of a conventional circular birdcage, optimization algorithms were employed to determine the elemental current distribution on the non-circular cylindrical surfaces. A comparison of circular, elliptical, symmetric and asymmetric fourth-order (n = 4) section birdcage current distributions is presented.

Approximate 3D iterative reconstruction for SPECT.

Compared with slice-by-slice approaches for SPECT reconstruction, three-dimensional iterative methods provide a more accurate physical model and an improved SPECT image. Clinical application of these methods, however, is limited primarily to their computational demands. This paper investigates the methods for approximate 3D iterative reconstruction that greatly reduce this demand by excluding from the reconstruction the smaller magnitude elements of the system matrix.

Experimental and numerical investigation of the 3D SPECT photon detection kernel for non-uniform attenuating media.

Experimental tests for non-uniform attenuating media are performed to validate theoretical expressions for the photon detection kernel, obtained from a recently proposed analytical theory of photon propagation and detection for SPECT. The theoretical multi-dimensional integral expressions for the photon detection kernel, which are computed numerically, describe the probability that a photon emitted from a given source voxel will trigger detection of a photon at a particular projection pixel. The experiments were performed using a cylindrical water-filled phantom with large cylindrical air-filled inserts to simulate inhomogeneity of the medium.

Photon propagation and detection in single-photon emission computed tomography--an analytical approach.

An analytical theory of photon propagation and detection in single-photon emission computed tomography (SPECT) for collimated detectors is developed from first principles. The total photon detection kernel is expressed as a sum of terms due to the primary and the Compton scattered photons. The primary as well as contributions due to every order of Compton scattering are calculated separately.