PET/CT: combining function and morphology.
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Heart Diseases↗
Biomedical subjects
T F Hany
Publications and source records attributed to T F Hany.
How much intravenous contrast is needed in FDG-PET/CT?
Intravenous, iodinated contrast agents are used routinely for CT (ceCT) imaging but only applied reluctantly for FDG-PET/CT due to possible artefacts. Only for few oncological PET/CT indications, the role of IV contrast agent has been clarified. Essentially, if any knowledge regarding vascular structures or tumour invasion into adjacent structures are needed, a ceCT as part of the combined PET/CT exam should be implemented. However, for some indications like lymphoma, contrast seems not to be necessary. Therefore, imaging procedures for the use of IV contrast for PET/CT have to be adapted individually for each FDG-PET/CT indication to especially reduce unnecessary radiation burden to the patient.
Contrast Media↗
The value of PET, CT and in-line PET/CT in patients with gastrointestinal stromal tumours: long-term outcome of treatment with imatinib mesylate.
PURPOSE: Gastrointestinal stromal tumours (GIST) are mesenchymal neoplasms of the gastrointestinal tract that are unresponsive to standard sarcoma chemotherapy. Imaging of GIST patients is done with structural and functional methods such as contrast-enhanced helical computed tomography (ceCT) and positron emission tomography (PET) with 18F-fluorodeoxyglucose (FDG). The aim of this study was to compare the prognostic power of PET and ceCT and to evaluate the clinical role of PET/CT imaging. METHODS: All patients with GIST undergoing PET or PET/CT examinations were prospectively included in this study, and the median overall survival, time to progression and treatment duration were documented. The prognostic significance of PET and ceCT criteria of treatment response was assessed and PET/CT was compared with PET and ceCT imaging. Data for 34 patients (19 male, 15 female, 21-76 years) undergoing PET or PET/CT for staging or restaging were analysed. RESULTS: In 28 patients, PET/CT and ceCT were available after introduction of treatment with the tyrosine kinase inhibitor imatinib mesylate (Gleevec; Novartis, Basel, Switzerland). Patients without FDG uptake after the start of treatment had a better prognosis than patients with residual activity. In contrast, ceCT criteria provided insufficient prognostic power. However, more lesions were found on ceCT images than on PET images, and FDG uptake was sometimes very variable. PET/CT delineated active lesions better than did the combination of PET and ceCT imaging. CONCLUSION: Both PET and PET/CT provide important prognostic information and have an impact on clinical decision-making in GIST patients. PET/CT precisely delineates lesions and thus allows for the correct planning of surgical interventions.
Adult↗
Fusion PET-CT imaging of neurolymphomatosis.
In a patient suffering from peripheral neuropathy due to neurolymphomatosis, fused PET-CT imaging, performed on a novel in-line PET-CT system, showed multiple small nodular lesions extending along the peripheral nerves corresponding to an early relapse of a transformed B-cell non-Hodgkin's lymphoma.
Aged↗
The effect of injection rate on time-resolved contrast-enhanced peripheral MRA.
In contrast-enhanced (CE) magnetic resonance (MR) angiography (MRA), lower injection rates of a fixed contrast agent dose provide longer contrast agent bolus at the expense of lower intravascular signal. This study evaluated the effect of different injection rates in imaging of the vasculature of the lower extremities with time-resolved, CE MRA. In three volunteers, injection rates of 0.5, 1.5 and 3.0 mL/second were administered in a randomized order and imaged in two separate sessions. Contrast agent bolus dynamics measured in volunteers were used in computer simulations to confirm variations in contrast agent concentration as a source of vessel ringing and blurring artifacts. To validate the effect of injection rate in pathologic vessels, 37 patients with peripheral vascular disease were imaged with a time-resolved technique using an injection rate of 0.5 mL/second or 1.5 mL/second and retrospectively divided into two groups. In volunteers, higher injection rates caused a stronger modulation of k-space and resulted in increased ringing artifacts in time-resolved CE MRA. These results were reproduced with computer simulations. In the qualitative patient study, significantly less vessel blurring was observed using a lower injection-rate, without a significant loss of vessel contrast.
Adult↗
Aorta and runoff vessels: single-injection MR angiography with automated table movement compared with multiinjection time-resolved MR angiography--initial results.
The authors compared two techniques for performing runoff, contrast material-enhanced magnetic resonance (MR) angiography. Multiinjection time-resolved imaging of contrast kinetics (TRICKS) and single-injection bolus-chase MR angiographic examinations were performed in 10 volunteers and 10 patients. Image quality and venous overlay of the major blood vessels of the abdomen, thigh, and calf were evaluated. Significantly more (P <.05) vessels were depicted with diagnostic quality on multiinjection TRICKS than on single-injection bolus-chase MR angiographic images.
Adult↗
Pelvic and lower extremity arterial imaging: diagnostic performance of three-dimensional contrast-enhanced MR angiography.
OBJECTIVE: The diagnostic performance of a three-dimensional MR angiography-based strategy was assessed with regard to its ability to characterize the arterial vasculature from the aortic bifurcation to the lower extremity runoff vessels. A single-injection, two-station protocol in combination with a lower-extremity vascular coil was used. SUBJECTS AND METHODS: Both conventional digital subtraction angiography and three-dimensional contrast-enhanced MR angiography with a dedicated peripheral vascular coil were performed in 61 patients with suspected peripheral vascular disease. In a prospective analysis, one reviewer evaluated the digital subtraction angiographic images and a second reviewer evaluated the MR angiographic images; both were unaware of the results of the other imaging technique. Each vascular segment (29 segments per patient) was evaluated for the presence of occlusive vessel disease. The following grading system was applied: 0, normal; 1, vessel irregularity with a luminal reduction of less than 10%; 2, mild stenosis (lumen reduction, 10-49%); 3, severe stenosis (lumen reduction, 50-99%); and 4, occlusion (lumen reduction, 100%). In 11 patients surgical graft patency was assessed. RESULTS: MR angiography provided an image quality comparable with that of digital subtraction angiography. Overall sensitivity and specificity for MR angiography were 92% and 96.6%, respectively, for the detection of hemodynamically significant disease and 92.3% and 99.4%, respectively, for the detection of occlusions. CONCLUSION: Two-station contrast-enhanced three-dimensional MR angiography with a dedicated lower-extremity vascular coil proved effective enough to consider it as a noninvasive alternative to digital subtraction angiography in the assessment of the pelvic and lower extremity arterial vasculature.
Adult↗
3D MR gastrography: exoscopic and endoscopic analysis of the stomach.
The aim of this study was to evaluate the feasibility of MR gastrography, based on 3D MRI following the oral administration of Gd-DOTA-enriched blueberry juice, in order to depict alterations of the gastric wall. The stomachs of three volunteers and three patients were examined on a 1.5-T MR system. Following ingestion of 400 ml of blueberry juice spiked with 2 ml of Gd-DOTA, each subject underwent 3D MR imaging in three positions: 45 degrees left lateral decubitus, supine, and 45 degrees right lateral decubitus. In each position, a coronal 3D SPGR acquisition consisting of 60 continuous 2-mm slices was acquired over a 35-s breathhold (TR/TE = 4.0/1.8 ms, 40 degrees flip angle, 0.5 excitations, voxel size of 1.25 x 1.66 x 2.00 mm). Multiplanar reformats (MPR), maximum intensity projections (MIP), surface shaded displays (SSD), and virtual intraluminal endoscopic views (VIE) were calculated. Magnetic resonance gastroscopy was tolerated well by all subjects without adverse effects. Based on the 3D MRI data sets acquired in various patient positions, all regions of the stomach and the proximal duodenum were visualized to good advantage. Whereas MPR and MIP provided a morphologic overview, SSD and VIE images permitted analysis of the gastric mucosa. Normal mucosa could be differentiated from the course and irregular pattern characterizing carcinomatous infiltration. The 3D SPGR data sets acquired following ingestion of oral Gd-DOTA-spiked blueberry juice permits exoscopic and virtual endoscopic viewing of the stomach.
Adult↗
Magnetic resonance angiography versus duplex sonography for diagnosing renovascular disease.
Noninvasive testing for renovascular disease is required to identify patients who may benefit from revascularization procedures without exposing an unnecessary amount of patients to the risks of catheter angiography. All available methods of diagnosing renal artery stenosis have significant limitations. We compared a new technique, contrast-enhanced magnetic resonance angiography, with an established technique, duplex ultrasonography, for the detection of renal artery stenosis using catheter angiography as the standard of reference. Eighty-nine patients with clinically suspected renovascular disease underwent duplex renal scanning and contrast-enhanced magnetic resonance angiography. Sixty of these also underwent catheter angiography. All studies were interpreted for the presence of renal artery stenosis blinded to the results of the other imaging modalities. For detection of hemodynamically significant (>/=60% diameter reduction) main renal artery stenosis, sensitivity and specificity were 90% and 86%, respectively, for magnetic resonance angiography and 81% and 87% for duplex sonography. Most false readings involved differential grading of stenoses detected with all 3 techniques. When patients with fibromuscular dysplasia were excluded from the analysis, the sensitivity of magnetic resonance angiography increased to 97%, with a negative predictive value of 98%. Magnetic resonance angiography detected 96% and duplex 5% of accessory renal arteries seen at catheter angiography. Contrast-enhanced magnetic resonance angiography is a useful technique for diagnosing atherosclerotic renovascular disease. It overcomes the major limitations of duplex renal scanning. However, duplex has the advantage of providing hemodynamic information and appears better suited for the assessment of patients with suspected fibromuscular dysplasia.
Adult↗
[Clinical use of contrast-enhanced MR angiography].
Compared to other non-invasive MR-angiography techniques, contrast-enhanced MR angiography is a robust imaging technique in the assessment of the arterial vascular system. This is due to the use of three-dimensional data acquisition, non-nephrotoxic paramagnetic contrast and short acquisition times. Clinical applications include the evaluation of the thoracic and abdominal arterial vessels. With the refinement of this technique also small peripheral arteries of the extremities can be imaged and an entire non-invasive diagnostic work-up of the peripheral arteries will be possible.
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MR-based assessment of vascular morphology and function.
Initially, time-of-flight angiography found its way into clinical routine for imaging vascular morphology. In conjunction with phase-contrast imaging, functional and morphological assessment of vascular pathology became possible. The flow dependence and associated artifacts inherent to these techniques have restricted the clinical use of these magnetic resonance angiography (MRA) techniques to the extra- and intracranial arterial, as well as the systemic and portal, venous systems. With the advent of high-performance gradient systems a new, promising MRA strategy has been developed: contrast-enhanced 3D MR angiography. It is based on the combination of rapid 3D imaging and the T1-shortening effect of intravenously infused paramagnetic contrast. This review provides a technical overview and critically discusses the clinical application for the different MRA techniques regarding morphological as well as functional assessment of the vascular system.
Adult↗
Optimization of contrast dosage for gadolinium-enhanced 3D MRA of the pulmonary and renal arteries.
To determine the minimal contrast dosage required for diagnostic contrast-enhanced three-dimensional (3D) magnetic resonance angiography (MRA) image quality of the pulmonary (PAs) or renal arteries (RAs). In 12 volunteers (10 females, 2 males; mean age 24 years) imaging was performed with 4 different dosages: 0.05, 0.1, 0.2 and 0.3 mmol/kg of body weight (BW) 0.5 M gadolinium (Gd) contrast agent. The PAs and RAs were evaluated separately each in groups of six volunteers. Qualitative and quantitative signal-to-noise ratio (SNR) image analysis was performed. For the PAs, the increases in signal-to-noise ratio were paralleled by increases in image quality ratings. For the PAs, with the use of 0.05 mmol/kg, only 50.3% of all segments were rated diagnostic, whereas with higher dosages the percentage rose to 89.2% for 0.1 mmol/kg, 98.2% for 0.2 mmol/kg. and 99.1% for 0.3 mmol/kg. For the RAs, 0.3 mmol/kg provided no significant increase in singal-to-noise ratio compared to 0.2 mmol/kg (p = 0.4). Only by a dosage of 0.2 and 0.3 mmol/kg, all evaluated segments were diagnostic evaluable. A dose of 0.2 mmol/kg is required for proper assessment of the RAs or PAs.
Adult↗
Contrast-enhanced magnetic resonance angiography of the renal arteries. Original investigation.
RATIONALE AND OBJECTIVES: The authors determine the value of contrast-enhanced, three-dimensional (3D) magnetic resonance angiography (MRA) in the assessment of the renal arteries in comparison with conventional arteriography (CA). METHODS: One hundred three patients (71 m, 32 f) were evaluated with both CA and 3D MRA. The 3D MRA data set consisted of 44 contiguous sections, acquired in apnea (23-28 seconds) using the following parameters: TR/TE 3.9/1.5 milliseconds, flip angle 40 degrees to 50 degrees, 3/4 k-space acquisition. A bolus of 0.3 mmol/kg BW gadolinium-DTPA was administered intravenously, using an automated injector. A test bolus method was used for timing of the bolus relative to the beginning of the data acquisition. Intra-arterial CA was used as the standard of reference in all patients. Separate interpretations of the CA and MRA results were made by two different pairs of radiologists, who were each blinded to the results of the other exam. RESULTS: In all, 31 of 33 accessory renal arteries were correctly identified. All 205 main renal arteries were seen with MRA. Of 65 significant stenoses identified on CA, 61 were correctly identified and graded by MRA. Sensitivity and specificity values for the assessment of significant renal arterial lesions were 93% and 90%, respectively. CONCLUSIONS: Breath-hold, contrast-enhanced 3D MRA allows for the reliable assessment of renal arterial morphology and pathologic states.
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Contrast-enhanced three-dimensional magnetic resonance angiography of the splanchnic vasculature before and after caloric stimulation. Original investigation.
RATIONALE AND OBJECTIVES: To develop a comprehensive noninvasive magnetic resonance angiography (MRA) strategy for the morphologic and functional assessment of the splanchnic arteries, based on a combination of breath-held contrast-enhanced 3D MRA and segmented k-space 2D phase-contrast acquisitions acquired before and after caloric stimulation. METHODS: Ten healthy volunteers were examined twice: once in the fasting state (6 hours with no food intake) and a second time following caloric stimulation with a standard 475-kcal meal. Flow in the superior mesenteric artery (SMA) and vein (SMV) was quantitated using a 2D breath-held, segmented k-space phase-contrast (PC) acquisition in a plane perpendicular to the axis of the vessels, while vascular morphology was displayed with a contrast-enhanced 3D MRA acquisition consisting of 44 contiguous 2-mm sections, acquired in apnea (28 seconds). For comparative analysis, the splanchnic vasculature was divided into 11 segments and evaluated on a 2-point scale (cannot exclude pathology, can exclude pathology). RESULTS: Flow volume in the SMA increased from 2.3 ml/min/kg (+/- 0.9 ml/min kg) to 7.3 ml/min kg (+/- 4.7 ml/min kg) following caloric stimulation (P < 0.05). Flow in the SMV exceeded flow in the SMA and increased from 3.4 ml/min/kg (+/- 0.3 ml/min kg) to 9.1 ml/min/kg (+/- 4.8 ml/min/kg) following stimulation. Flow volume of SMV correlated better with SMA flow after stimulation. Caloric stimulation significantly improved visualization of the splanchnic arterial vasculature (P < 0.05). Only 5 of 110 evaluated arterial segments (4.5%) remained inadequately seen to exclude vascular pathology. CONCLUSION: Magnetic resonance imaging offers a comprehensive assessment of the splanchnic arterial vasculature based on 3D display of vessel morphology and analysis of flow function. While the most relevant proximal vessel segments are visible even under fasting conditions, caloric stimulation enhances visualization of small vessels.
Adult↗
Dynamic MR defecography with a superconducting, open-configuration MR system.
PURPOSE: To evaluate dynamic magnetic resonance (MR) defecography performed with a superconducting, open-configuration system in diagnosis of defecation disorders. MATERIALS AND METHODS: Five healthy volunteers and 15 patients with defecation disorders were studied with MR defecography performed with a superconducting, open-configuration system; the patients also underwent fluoroscopic defecography. Before MR imaging, the rectum was filled with 300 mL of mashed potatoes mixed with 1.5 mL of gadopentetate dimeglumine. T1-weighted gradient-echo images were acquired every 2 seconds in the midsagittal plane with the patient at rest, at maximal contraction of the anal sphincter, during straining, and during defecation. RESULTS: MR defecography permitted analysis of the anorectal angle, anal canal, puborectal muscle, and descent of the pelvic floor. Owing to the high signal intensity of the intraluminal contrast material, the rectal walls were well demonstrated on the MR images, permitting visualization of intussusception and rectocele. Concomitant demonstration of structures surrounding the anorectal canal was helpful in assessment of spastic pelvic floor syndrome and descending perineum syndrome. MR defecography was superior to fluoroscopic defecography and allowed detection of all clinically relevant pathologic conditions except for one. CONCLUSION: Dynamic MR defecography is an attractive alternative for evaluation of defecation disorders.
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Diagnostic impact of four postprocessing techniques in evaluating contrast-enhanced three-dimensional MR angiography.
OBJECTIVE: The purpose of this study was to determine the added diagnostic value of various three-dimensional (3D) data viewing techniques when analyzing contrast-enhanced 3D MR angiography. MATERIALS AND METHODS: Twenty patients (mean age, 62 years) with symptomatic peripheral vascular disease were assessed with breath-hold, contrast-enhanced 3D MR angiography and catheter angiography, which served as the standard of reference. After an initial interpretation of the 3D MR angiographic data sets based only on standardized maximum intensity projections (MIP), the diagnostic gain of the stepwise addition of interactive multiplanar reformations, shaded-surface displays (SSD), and virtual intraarterial endoscopy (VIE) images was calculated. Time required for each step of postprocessing was measured. RESULTS: Pathologic changes were revealed by catheter angiography in 60 vascular segments (50 severe stenoses, seven aneurysms, and three occlusions). The average postprocessing times were MIP, 8 min (range, 5-12 min); multiplanar reformations, 9 min (range, 3-11 min); SSD, 15 min (range, 8-25 min); and VIE, 40 min (range, 18-63 min). Addition of multiplanar reformations to MIPs resulted in the greatest gain of diagnostic accuracy, from 92% to 96%, and diagnostic confidence. When analysis was based on all four techniques, receiver operating characteristic curve analysis revealed only minimal improvements in diagnostic confidence, whereas diagnostic accuracy remained unchanged at 96%. CONCLUSION: Accurate and time-effective analysis of contrast-enhanced 3D MR angiography should be based on MIP algorithms and multiplanar reformations. Additional evaluation with VIE or SSD techniques is time-consuming and provides little diagnostic gain.
Adult↗
Virtual MR cholangiography.
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Adolescent↗
[Value of contrast-enhanced 3D magnetic resonance angiography of the renal arteries].
PURPOSE: To determine the value of gadolinium-enhanced, three-dimensional breath-hold Magnetic Resonance Angiography (MRA) in the assessment of the aorta and renal arteries in comparison to conventional arteriography (CA). PATIENTS AND METHODS: 49 patients were evaluated with both CA and 3D MRA. 0.3 mmol/kg BW gadolinium-DTPA was administered intravenously in a bolus, using an automated injector. A test bolus method was used for timing of the bolus and beginning of the data acquisition. The intraarterial CA was used as the gold standard. RESULTS: MRA-based assessment of renal artery stenosis was identical with CA in 31 of 45 stenoses (68.8%). Sensitivity and specificity for assessment of renal arterial disease by MRA were 84% and 96%; for clinically relevant lesions they amounted to 90% and 98%. CONCLUSION: The presented contrast-enhanced 3D MRA technique allows for the reliable assessment of renal arterial morphology and pathology.
Adult↗