Dose selection for radioiodine therapy of borderline hyperthyroid patients according to thyroid uptake of 99mTc-pertechnetate: applicability to unifocal thyroid autonomy?

PURPOSE: The aim of this study was to evaluate the feasibility of applying a previously described dose strategy based on (99m)Tc-pertechnetate thyroid uptake under thyrotropin suppression (TcTU(s)) to radioiodine therapy for unifocal thyroid autonomy. METHODS: A total of 425 consecutive patients (302 females, 123 males; age 63.1+/-10.3 years) with unifocal thyroid autonomy were treated at three different centres with (131)I, using Marinelli's formula for calculation of three different absorbed dose schedules: 100-300 Gy to the total thyroid volume according to the pre-treatment TcTU(s) (n=146), 300 Gy to the nodule volume (n=137) and 400 Gy to the nodule volume (n=142). RESULTS: Successful elimination of functional thyroid autonomy with either euthyroidism or hypothyroidism occurred at a mean of 12 months after radioiodine therapy in 94.5% of patients receiving 100-300 Gy to the thyroid volume, in 89.8% of patients receiving 300 Gy to the nodule volume and in 94.4% receiving 400 Gy to the nodule volume. Reduction in thyroid volume was highest for the 100-300 Gy per thyroid and 400 Gy per nodule strategies (36+/-19% and 38+/-20%, respectively) and significantly lower for the 300 Gy per nodule strategy (28+/-16%; p<0.01). CONCLUSION: A dose strategy based on the TcTU(s) can be used independently of the scintigraphic pattern of functional autonomous tissue in the thyroid

Breathing adapted radiotherapy: a 4D gating software for lung cancer

<p>Abstract</p> <p>Purpose</p> <p>Physiological respiratory motion of tumors growing in the lung can be corrected with respiratory gating when treated with radiotherapy (RT). The optimal respiratory phase for beam-on may be assessed with a respiratory phase optimizer (RPO), a 4D image processing software developed with this purpose.</p> <p>Methods and Materials</p> <p>Fourteen patients with lung cancer were included in the study. Every patient underwent a 4D-CT providing ten datasets of ten phases of the respiratory cycle (0-100% of the cycle). We defined two morphological parameters for comparison of 4D-CT images in different respiratory phases: tumor-volume to lung-volume ratio and tumor-to-spinal cord distance. The RPO automatized the calculations (200 per patient) of these parameters for each phase of the respiratory cycle allowing to determine the optimal interval for RT.</p> <p>Results</p> <p>Lower lobe lung tumors not attached to the diaphragm presented with the largest motion with breathing. Maximum inspiration was considered the optimal phase for treatment in 4 patients (28.6%). In 7 patients (50%), however, the RPO showed a most favorable volumetric and spatial configuration in phases other than maximum inspiration. In 2 cases (14.4%) the RPO showed no benefit from gating. This tool was not conclusive in only one case.</p> <p>Conclusions</p> <p>The RPO software presented in this study can help to determine the optimal respiratory phase for gated RT based on a few simple morphological parameters. Easy to apply in daily routine, it may be a useful tool for selecting patients who might benefit from breathing adapted RT.</p

Towards quantitative multimodality imaging in the planning, quality control, dosimetry and response assessment of therapy in oncologic and non oncologic diseases

Qualitative and quantitative multimodality imaging play a more and more important role in the planning, quality control, and assessment of response in many oncologic and non oncologic diseases. Before hybrid modalities such as SPECT/CT, PET/CT and, most recently, PET/MRI, became available, the images from the different modalities were analyzed independently or by software fusion. Nowadays, these images are most frequently acquired on hybrid modalities, allowing for so called "one-stop-shop" investigations. Depending on a static or a dynamic image acquisition, either semi or fully quantitative measurements of both structural and functional parameters are possible, allowing for multi-parametric image analysis. These qualitative and quantitative parameters can then be used for detection and assessment of extension of disease as well as for planning of therapeutic interventions or, even more interesting, for quality control, dosimetry of radionuclide therapies, assessment of response to treatment and, finally, prediction of outcome of the patients. This thesis discusses the qualitative and quantitative imaging and quantification methods available today and their potential future impact in research and clinical decision making

Molecular PET/CT imaging-guided radiation therapy treatment planning

The role of positron emission tomography (PET) during the past decade has evolved rapidly from that of a pure research tool to a methodology of enormous clinical potential. (18)F-fluorodeoxyglucose (FDG)-PET is currently the most widely used probe in the diagnosis, staging, assessment of tumor response to treatment, and radiation therapy planning because metabolic changes generally precede the more conventionally measured parameter of change in tumor size. Data accumulated rapidly during the last decade, thus validating the efficacy of FDG imaging and many other tracers in a wide variety of malignant tumors with sensitivities and specificities often in the high 90 percentile range. As a result, PET/computed tomography (CT) had a significant impact on the management of patients because it obviated the need for further evaluation, guided further diagnostic procedures, and assisted in planning therapy for a considerable number of patients. On the other hand, the progress in radiation therapy technology has been enormous during the last two decades, now offering the possibility to plan highly conformal radiation dose distributions through the use of sophisticated beam targeting techniques such as intensity-modulated radiation therapy (IMRT) using tomotherapy, volumetric modulated arc therapy, and many other promising technologies for sculpted three-dimensional (3D) dose distribution. The foundation of molecular imaging-guided radiation therapy lies in the use of advanced imaging technology for improved definition of tumor target volumes, thus relating the absorbed dose information to image-based patient representations. This review documents technological advancements in the field concentrating on the conceptual role of molecular PET/CT imaging in radiation therapy treatment planning and related image processing issues with special emphasis on segmentation of medical images for the purpose of defining target volumes. There is still much more work to be done and many of the techniques reviewed are themselves not yet widely implemented in clinical settings

Concentrations of Gd-BOPTA in cholestatic fatty rat livers: role of transport functions through membrane proteins

Gd-BOPTA (gadobenate dimeglumine) is a magnetic resonance (MR) contrast agent that, after i.v. administration, distributes within the extracellular space, enters rat hepatocytes through the sinusoidal transporters organic anion transporting peptides (Oatps) and is excreted unchanged into bile through the multidrug resistance-associated protein 2 (Mrp2). It is unclear how the hepatobiliary contrast agent would accumulate in cholestatic fatty livers from obese rats with bile flow impairment. Indeed, the expression of both Oatps and Mrp2 transporters is decreased in cholestatic hepatocytes. To assess this question, we measured on-line the hepatic concentrations of ¹⁵³Gd-BOPTA with a gamma probe placed over perfused rat livers. During the perfusion of ¹⁵³Gd-BOPTA, we obtained a similar maximal hepatic concentration in normal and fatty livers despite the decreased expression and function of membrane transporters in fatty livers. By pharmacokinetic modeling and mathematical simulations, we show how changes of transport into and out of hepatocytes modify the concentrations of ¹⁵³Gd-BOPTA within hepatocytes. Mathematical simulations help to understand how each parameter (entry into hepatocytes, bile excretion, or efflux back to sinusoids) interferes with the hepatic concentrations. The hepatic concentrations of ¹⁵³Gd-BOPTA within hepatocytes rely on the entry into hepatocytes through the sinusoidal membrane and on two paths of exit, the efflux back to sinusoids and the elimination into bile. Understanding how ¹⁵³Gd-BOPTA accumulates in hepatocytes is then complex. However, such understanding is important to analyze liver imaging with hepatobiliary contrast agents in cholestatic fatty livers

18F-DOPA PET/CT unravels malignant paraganglioma mimicking temporomandibular joint disorder

This report presents a 29-year-old patient with severe temporomandibular joint (TMJ) pain. Anamnesis and clinical examination led us to the diagnosis of TMJ disorder. He was also in control for a malignant paraganglioma originating from the right carotid body. After initial surgery 8.5 years ago and the removal of metastases 2 years ago he was deemed disease free. An (18)F-3,4-dihydroxyphenylalanine (DOPA) positron emission tomography (PET)/CT scan was obtained during follow-up 6 months before he was presented to our clinic. Suspicious of a connection between the actual pain and the tumour, we scrutinized these images. We found a tiny pathological tracer uptake in the right jugular foramen but no correlating finding in the matching CT. We repeated the DOPA PET/CT and found several metastases including the previously detected lesion. Further thin-slice CT and MRI showed a 5 mm paraganglioma located anteriorly to the jugular bulb within the jugular foramen. The lesion was in close relation to the Arnold's nerve, a branch of the vagus nerve which carries sensory information from the external tympanic membrane, external auditory canal and the external ear and explained the severe pain in our patient. He then underwent radiotherapy (45 Gy) during which the pain diminished considerably. In a variety of neuroendocrine tumours, including paraganglioma, DOPA PET/CT allows primary diagnosis, staging and restaging with a higher detection rate than conventional radiological imaging. Owing to low anatomical resolution however, high resolution contrast-enhanced CT and MRI are necessary to complete the investigations