Respiratory-gated Scans Research Articles

No diagnostic impact of routinely use of respiratory gating to characterize lung nodules with 18F-FDG PET/CT

PurposeTo evaluate diagnostic impact of routinely use of respiratory gated (RG) 18FDG PET/CT to distinguish benign and malignant lung nodules. MethodsWe analyzed retrospectively data of 76 patients referred for metabolic characterization of lung nodules who underwent whole body 18FDG PET/CT scan followed by RG PET/CT (deep-inspiration breath-hold, DIBH). RG was prospectively planned without knowledge of WB PET/CT results. Independent reading of PET/CT scans with or without respiratory gating was separately conducted by two nuclear medicine physicians. Uptake of lung nodules was evaluated visually (positive if nodule's uptake superior to pulmonary background uptake), and quantitatively (SUVmax, SUVmean, metabolic volume, tumor to background ratio). Reference standard was obtained for all patients by histology (n=37) or clinico-radiological follow-up (n=39). Sub-groups were also evaluated (nodule<15mm, lower lobe nodules). ResultsNodules were classified positives without RG scans in 43/76 (59.7%) patients and with RG scans in 41/75 (54.6%) patients. Results were discordant for 5/75 (6.7%) patients. According to the reference standard, 35/39 cancers were correctly identified by PET/CT without RG, and 34/38 by RG PET/CT. Without RG PET, sensitivity, specificity and accuracy were 89.7%, 78.4% and 84.2% respectively. With RG PET, sensitivity, specificity and accuracy were 89.5%, 81.1% and 85.3% respectively, not statistically different. Concerning quantitative analysis, results were not statistically better with RG than without RG and were not better than visual analysis. Sub-groups analysis showed no added value of RG scans in specific groups (lower lobes and smaller nodules). ConclusionRoutinely use of RG did not help in the diagnosis of neoplastic lung nodules. Others evaluations are needed to assess the contribution of RG for others selective indications (therapeutic evaluation, radiotherapy planning, characterization of liver lesions).

Evaluation of image quality of DWIBS versus DWI sequences in thoracic MRI at 3 T

PurposeTo compare diffusion weighted imaging with background suppression (DWIBS) sequence with classic spectral diffusion sequence (DWI) with and without respiratory gating in mediastinal lymph node analysis at 3T. Materials and methods26 patients scheduled for mediastinoscopic lymph node analysis, prospectively undergone a thoracic 3T MRI with DWIBS (FatSat=STIR; TR/TE=6674.1/44.7ms; IR=260ms) and DWI sequences (FatSat=SPIR; TR/TE=1291/59.6ms) (b=0-400-800s/mm2) with and without (free breathing) respiratory gating.Images at b=800 were analyzed by two radiologists. They performed qualitative analysis of fat-sat homogeneity and motion artifacts, rated from 0 to 4, and quantitative evaluation by studying signal to background (STB) of lymph nodes. ResultsQuality of fat suppression was significantly higher for DWIBS than for DWI both for free-breathing (score 3.48±0.65 vs. 1.76±0.96, p<0.0001) and respiratory-gated scans (3.17±0.77 vs. 1.72±0.73, p=0.0001). Similarly, artifacts were reduced with DWIBS (3.16±0.47 vs. 1.76±0.59, p<0.0001; 3.0±0.73 vs. 2.04±0.53, p=0.0001). Quantitative analysis showed higher STB with DWIBS (3.26±1.83 vs. 0.98±0.44, p<0.0001; 3.56±, 2.09 vs. 0.92±0.59, p<0.0001). Gating did not improve image quality and STB on DWIBS (p>0.05). ConclusionIn thoracic MRI, ungated DWIBS sequence improves fat-sat homogeneity, reduces motion artifacts and increases STB of lymph nodes. Respiratory gating does not improve DWIBS image quality.

The effect of respiratory gated PET/CT on SUV of lung nodules

Objective To analyze the difference of SUV between respiratory gated (RG) and nongated PET/CT scans,and to investigate the trend of SUV change in different respiratory phases.Methods Fourteen patients (6 male,8 female,age range:29 to 80 years,average age:63.7 ± 7.1 years) with pulmonary nodules who had undergone both RG and non-gated PET/CT between May 2010 to March 2011 were enrolled in the study.A total of 37 pulmonary nodules were identified.Both PET and CT gated data were divided into 6 phases.PET images were matched with CT at different respiratory phases.Each nodule was measured 7 times including gated data of 6 phases and non-gated data.The t-test,rank-sum test and Spearman correlation analysis were used.Results The SUVmax and SUVmean of RG PET/CT ( 13.69 ± 6.70 and 8.56 ±4.11,respectively) were higher than those of non-gated PET/CT ( 12.76 ± 6.74 and 7.66 ±4.00,respectively) (t =3.475,Z =- 3.661,both P ＜ 0.001 ).The two sets were correlated with each other (r =0.971 and 0.969,both P ＜ 0.05).SUVmax was the highest at phase 1 ( end of expiration) and lowest at phase 4 (end of inspiration).In non-gated scans,there were 4 nodules with SUVmax ＜ 2.5,including 1 nodule with a higher SUV of 2.52 in the RG scan than SUV of 2.13 in the non-gated scan.Conclusions SUV of lung nodules in RG scans is higher than that in non-gated scans.The highest SUVmax could be obtained at the end of expiration.RG scans might improve the detection of lung nodules with low-grade FDG uptake. Key words: Lung neoplasms ; Tomography, emission-computed; Tomography, X-ray computed; Deoxyglucose

Respiratory gated multidetector computed tomography: Applicable for diagnostic abdominal imaging?

Purpose To evaluate the ability and accuracy of a respiratory gated technique used with contrast enhanced MDCT of the upper abdomen with focus on diagnostic image quality and depiction of organs and major vessels. Materials and methods Forty-five adult patients who were referred to our institution for follow-up dynamic contrast enhanced abdominal CT imaging were included in this study. Respiratory gated CT scans were performed with the use of a dedicated hardware. A multiphasic CT scan was performed for each patient. Respiratory gated images were obtained between early arterial and portal venous phases during free breathing. Images of respiratory gated (RG) and breathhold (BH) phases were compared qualitatively and quantitatively by two radiologists. Definitive statistical methods were used for evaluating the scoring data, while Mann Whitney U test was used for comparison. Statistical significance was accepted for p values <0.05. Results Statistical significant difference was found for comparison of scores regarding luminal opacification and contoural integrity of intrahepatic vascular structures with scores of RG scans rated poor to moderate (e.g. 2.86 ± 1.07 for luminal opacification of intrahepatic portal veins as well as border detectability) in comparison to scores of BH scans rated good to excellent (e.g. 1.37 ± 1.31 for luminal opacification, 1.35 ± 1.28 for border detectability of intrahepatic portal veins, p < 0.001). Furthermore, statistical significant differences were found for general image noise levels ( p < 0.001). Conclusions Further technical advances of RG technique could enable routine use of this technique for selected patient groups.