Francesco Giuseppe Mazzei

Diffusion-weighted magnetic resonance imaging in the evaluation of renal function: a preliminary study.

PurposeMagnetic resonance diffusion-weighted imaging (MR-DWI) is useful to assess proton motion by the computation of an apparent diffusion coefficient (ADC). This property could be used to assess renal damage, with special regard to unilateral dysfunction. The aim of this study was to estimate the correlation between ADC and the stage of chronic renal failure (CRF) using a spin-echo echo-planar imaging (SE-EPI) sequence with the sensitivity encoding (SENSE) technique.Materials and methodsFourteen patients (nine men and five women, mean age 49 years, range 22–66 years) underwent an MR examination on a 1.5-T system. Seven patients had a history of hypertension or CRF, one had Takayasu disease and one had nephrovascular hypertension. Five subjects without known kidney disease were used as controls. The glomerular filtration rate (GFR) assessed by Cockcroft-Gault’s equation was used as a functional marker. The imaging protocol consisted of T1- and T2-weighted sequences followed by a SE-EPI acquisition with a diffusion gradient of 600 s/mm2 and SENSE factor 2 and pixel-by-pixel ADC map reconstruction. In five patients, the SE-EPI-DWI sequence was repeated after i.v. administration of 1 mg of furosemide.ResultsADC was of 2.44±0.24×10−3 mm2/s in patients with normal GFR and of 2.05±0.33×10−3 mm2/s (p<0.05) in subjects with altered GFR; a significant difference was found between stage III and IV (p<0.01), whereas no differences were found between stage I and II (p=0.27) and between stage II and III (p=0.39). A good correlation was found between GFR and ADC (r=0.79; p<0.01), with no significant change after furosemide administration (p=0.7).ConclusionsDWI is a feasible MR technique for assessing renal damage. Further studies with scintigraphic correlation are needed to confirm these results and to establish reference values for this imaging technique.RiassuntoScopoLa risonanza magnetica (RM) in diffusione (diffusion weighted, DW) permette di ottenere dati quantitativi sul movimento dei protoni liberi di acqua determinando il coefficiente di diffusione apparente (apparent diffusion coefficient, ADC). Questa capacità potrebbe essere usata per stabilire il danno parenchimale renale, in particolare nelle disfunzione unilaterali. Scopo del presente lavoro è quello di valutare la correlazione tra ADC e grado di insufficienza renale cronica utilizzando una sequenza SE Eco-planare (SS-EPI) a cui è stato applicato la tecnica di SENSitivity Encoding (SENSE).Materiali e metodiQuattordici pazienti (9 maschi e 5 femmine, età media 49 anni, range 22–66) sono stati sottoposti ad esame RM con sistema ad alto campo 1,5 T; in 5 pazienti non vi erano dati anamnestici e bioumorali di nefropatia, mentre in 7 era presente storia di ipertensione arteriosa e/o IRC ingravescente, in 1 di malattia di Takayasu e in 1 di ipertensione nefrovascolare. Il protocollo prevedeva acquisizioni T1 e T2 dipendenti, nonché una sequenza SE-EPI pesata in diffusione (b-factor 600 s/mm2) con fattore SENSE 2 e ricostruzione di mappe dell’ADC. In 5 casi la SS-EPI-DW è stata ripetuta dopo somministrazione di furosemide. Il filtrato glomerulare è stato ottenuto mediante metodo di Cockroft-Gault.RisultatiL’ADC nei soggetti normali ed i pazienti in stadio I è stato di 2,44±0,24×10−3 mm2/s, mentre quello dei pazienti in stadio II–IV è stato di 2,05±0,33×10−3 mm2/s (p<0,05). Non è stata rilevata una differenza significativa dell’ADC tra stadio I e stadio II (p=0,27) e tra stadio II e stadio III (p=0,39), mentre la differenza è stata significativa tra pazienti in stadio III e IV(p<0,01). Si è rilevata una significativa correlazione tra la clearance della creatinina (ClCr(CG)) e l’ ADC parenchimale (r=0,79; p<0,01). La furosemide non ha determinato modificazioni dell’ADC (p=0,7).ConclusioniLa RM-DW permette di ottenere valori quantitativi del coefficiente di diffusione correlabili con la funzione renale separata, senza somministrare mezzo di contrasto e con rapidi tempi d’esame. Ulteriori studi di correlazione con i dati scintigrafici e su più ampie casistiche sono necessari al fine di confermare tali risultati e stabilire valori di riferimento per questa metodica.

Computed tomographic evaluation of mesentery: diagnostic value in acute mesenteric ischemia.

Objective To evaluate the computed tomographic appearances of mesentery in acute mesenteric ischemia (AMI) to recognize characteristic features and their prognostic values. Methods Computed tomographic examinations of 34 patients with a confirmed diagnosis of AMI were retrospectively reviewed to evaluate the number of mesenteric vessels, diameter of the superior mesenteric artery and superior mesenteric vein, mesenteric fat stranding, mesenteric vessel pneumatosis and ascites. Results Overall, at least one of these mesenteric signs was present in all but 1 patient. In all AMI of arterial occlusive type and in 68% of nonocclusive mesenteric ischemia, the number of arterial vessels was reduced (P = 0.067). Mesenteric vessel pneumatosis and reduced number of venous vessels were significantly associated with higher mortality (P = 0.027 and P = 0.042, respectively). Reperfusion signs were associated with a reduced mortality (28.7% vs 65.5%). Conclusion Considering its characteristic features and its possible prognostic value, the evaluation of mesentery will supply additional information in the interpretation of computed tomography in AMI.

Magnetic resonance imaging: is there a role in clinical management for acute ischemic colitis?

AIM To validate the utility of magnetic resonance imaging (MRI) for the clinical management of acute ischemic colitis (IC). METHODS This is a magnetic resonance (MR) prospective evaluation of 7 patients who were proved to have acute IC on the basis of clinical, endoscopic and computed tomography (CT) findings and who were imaged in our institution between February 2011 and July 2012. The mean age of the patients was 72.28 years. Abdominal CTs were obtained using a 64-detector row configuration for all patients with un-enhanced and contrast-enhanced scans, in the late arterial phase (start delay 45-50 s) and in the portal venous phase (start delay 70-80 s). The MR examinations were performed using a 1.5T superconducting magnet, using Fast Imaging Employing Steady State Acquisition and T2-weighted fast-recovery fast-spin echo sequences in axial and coronal plane. CT and MRI examinations were analysed for the presence of colonic abnormalities and associated findings. RESULTS Segmental involvement was seen in 6 patients (85.71%), with a mean length of involvement of 412 mm (range 145.5-1000 mm). Wall thickness varied between 6 mm and 17.5 mm (mean 10.52 mm) upon CT examinations and from 5 to 15 mm (mean 8.8 mm) upon MR examinations. The MRI appearance of the colonic wall varied over the time: Type I appearance with a 3 layer sandwich sign was seen in 5 out of 12 examinations (41.66%), patients underwent MR within a mean of 36 h (ranging from 1 to 54 h) after the CT examination. Type II and III appearance with a 2 layer sign, was seen in 4 examinations (33.33%), patients underwent MR within a mean of 420.5 h (ranging from 121 to 720 h) after the CT examination. In the remaining three MRI examinations, performed within a mean of 410 h (ranging from 99.5 to 720 h) the colonic wall appeared normal. CONCLUSION MRI, only using precontrast images, may be used as a substitute for invasive procedures in diagnosis and follow-up of acute IC.

Differences in perfusion CT parameter values with commercial software upgrades: a preliminary report about algorithm consistency and stability.

Background Computed tomographic perfusion (CTp) imaging is a promising technique that allows functional imaging, as an adjunct to a morphologic CT examination, that can be used as an aid to carefully evaluate the response to therapy in oncologic patients. Considering this statement, it could be desirable that the measurements obtained with the CT perfusion software, and their upgrades, are consistent and reproducible. Purpose To determine how commercial software upgrades impact on algorithm consistency and stability among the three version upgrades of the same platform in a preliminary study. Material and Methods Blood volume (BV), blood flow (BF), mean transit time (MTT), and permeability surface area product (PS) were calculated with repeated measurements (n = 1119) while truncating the time density curve at different time values in six CT perfusion studies using CT perfusion software version 4D (CT Perfusion 4D), then repeated with the previous version (CT Perfusion 3.0 and CT Perfusion 4.0), using a fixed ROI both for arterial input and target lesion. The software upgrades were compared in pairs by applying a Kolmogorov-Smirnov test to all the parameters measured. Stability and reliability of the three versions were verified through the variation of the truncated parameters. Results The three software versions provided different parent distributions for approximately 80% of the 72 parameters measured. A complete agreement was found only for one patient in version 3.0 vs. 4.0 and 3.0 vs. 4D. Perfusion 4.0 vs. 4D: a complete agreement was found only in two cases. Parameters obtained with Perfusion 4D always showed the lowest standard deviation in all temporal intervals and also for all individual parameters. Conclusion The three versions of the same platform tested yield different perfusion measurements. Thus, our preliminary results show that Perfusion 4D version uses a stable deconvolution algorithm to provide more reliable measurements.

Reperfusion in non-occlusive mesenteric ischaemia (NOMI): effectiveness of CT in an emergency setting.

OBJECTIVE To investigate the CT features of reperfusion (presence/absence) in non-occlusive mesenteric ischaemia (NOMI) and their prognostic value in an emergency setting. METHODS A revision was undertaken of imaging from 20 patients (16 males/4 females) with a dismissal summary of NOMI. All patients had previously undergone a minimum of one multidetector CT examination, and consequently underwent surgery (n = 8), autopsy (n = 2), angiography (n = 1) or endoscopy (n = 9). An evaluation of the CT scans was conducted to determine vessels, mesentery, bowel and peritoneal cavity features. The superior mesenteric artery (SMA) average diameter of NOMI cases were compared with 30 controlled cases. Kappa, Kolmogorov-Smirnov (K-S) and Fishers exact tests were used for statistical analysis. RESULTS A mean SMA diameter significantly smaller than that of the controlled cases was found for patients with NOMI (K-S test: D = 0.75, p = 3.7 × 10-08). Fishers exact tests showed a strong connection between the presence of reperfusion and mesenteric fat stranding (p = 0.026), bowel wall thickening (p = 3.2 × 10-05) and a high attenuation of the bowel wall on unenhanced CT images (p = 2.8 × 10-04). A reduction in mortality was significantly linked to the combination of normal mesenteric vessels and wall thickening (p = 0.034). CONCLUSION Analysis of not only vessels findings but also mesentery and bowel CT features will support the identification of NOMI with or without a reperfusion event in an emergency setting. A strong correlation between some CT features and lower mortality exists. ADVANCES IN KNOWLEDGE CT features of NOMI with or without reperfusion are demonstrated. Correctly assessing the presence of reperfusion in NOMI, may allow better management of these conditions in the emergency setting.

CT Perfusion in the Characterisation of Renal Lesions: An Added Value to Multiphasic CT

Objective. To prospectively evaluate if computed tomography perfusion (CTp) could be a useful tool in addition to multiphasic CT in renal lesion characterisation. Materials and Methods. Fifty-eight patients that were scheduled for surgical resection of a renal mass with a suspicion of renal cell carcinoma (RCC) were enrolled. Forty-one out of 58 patients underwent total or partial nephrectomy after CTp examination, and a pathological analysis was obtained for a total of 49 renal lesions. Perfusion parameters and attenuation values at multiphasic CT for both lesion and normal cortex were analysed. All the results were compared with the histological data obtained following surgery. Results. PS and MTT values were significantly lower in malignant lesions than in the normal cortex (P < 0.001 and P = 0.011, resp.); PS, MTT, and BF values were also statistically different between oncocytomas and malignant lesions. According to ROC analysis, the accuracy, sensitivity, and specificity to predict RCC were 95.92%, 100%, and 66.7%, respectively, for CTp whereas they were 89.80%, 93.35%, and 50%, respectively, for multiphasic CT. Conclusion. A significant difference between renal cortex and tumour CTp parameter values may suggest a malignant renal lesion. CTp could represent an added value to multiphasic CT in differentiating renal cells carcinoma from oncocytoma.

[Quantitative CT perfusion measurements in characterization of solitary pulmonary nodules: new insights and limitations].

Although computed tomography (CT) scans remain the basis of morphologic evaluation in the characterization of solitary pulmonary nodules (SPNs), perfusion CT can represent an additional feasible technique offering reproducible measurements, at least in SPNs with a diameter >10 mm. In particular, CT perfusion could reduce the number of SPNs, diagnosed as undetermined at morphologic CT, avoiding long term follow-up CT, FDG-PET studies, biopsy or unnecessary surgery with a significant reduction in healthcare costs. In order to reduce the radiation dose, an optimization of the CT perfusion protocol could be obtained using axial mode acquisition, using shorter acquisition time and adaptative statistical iterative reconstruction algorithm.

MR lymphangiography: a practical guide to perform it and a brief review of the literature from a technical point of view

We propose a practical approach for performing high-resolution MR lymphangiography (MRL). We shall discuss and illustrate the technical approach for the visualization of lymphatic vessels in patients suffering from lymphedema, how to distinguish lymphatic vessels from veins, and MRL role in supermicrosurgery treatment planning. A brief review of literature, from a technical point of view, is also reported.

Reduced Time CT Perfusion Acquisitions Are Sufficient to Measure the Permeability Surface Area Product with a Deconvolution Method

Objective. To reduce the radiation dose, reduced time CT perfusion (CTp) acquisitions are tested to measure permeability surface (PS) with a deconvolution method. Methods and Materials. PS was calculated with repeated measurements (n = 305) while truncating the time density curve (TDC) at different time values in 14 CTp studies using CTp 4D software (GE Healthcare, Milwaukee, WI, US). The median acquisition time of CTp studies was 59.35 sec (range 49–92 seconds). To verify the accuracy of the deconvolution algorithm, a variation of the truncated PS within the error measurements was searched, that is, within 3 standard deviations from the mean nominal error provided by the software. The test was also performed for all the remaining CTp parameters measured. Results. PS maximum variability happened within 25 seconds. The PS became constant after 40 seconds for the majority of the active tumors (10/11), while for necrotic tissues it was consistent within 1% after 50 seconds. A consistent result lasted for all the observed CTp parameters, as expected from their analytical dependance. Conclusion. 40-second acquisition time could be an optimal compromise to obtain an accurate measurement of the PS and a reasonable dose exposure with a deconvolution method.

Magnetic resonance lymphangiography: How to prove it?

We found interest in the article by Mitsumori et al that reported their experience of magnetic resonance lymphangiography (MRL). We congratulate Mitsumori et al on their article on the four consecutive patients studied; however, some critical aspects in the text should be pointed out. For example, Mitsumori et al report a literature review of lymphaticovenular anastomosis (LVA) treatments, but do not report if the four patients affected by lymphedema referred to in that article were operated on with LVA, and the data regarding the postoperative outcomes are not present. MRL has been previously studied for lymphedema diagnosis and staging: Recently at the Lymphoedema Mondial Congress in Rome, 2013, and the International Lymphoedema Congress in Genova, 2014, many criticisms were raised against the use of MRL and the possible discrimination between lymphatic and venous vessels. Lohrmann et al reported the visualization of venous vessels, as contrast may be captured by both lymphatic and venous capillaries: venous vessels resulted in contrast enhancement faster than lymphatic vessels, which were slower. In a lymphedematous limb the diffusion of the contrast in the venous system may be modified due to the previous surgery. Further resonance imaging of lymphatic vessels may be even more doubtful on nonedematous limbs. Another aspect that evoked our attention in the Mitsumori et al article is their criticism of indocyanine green (ICG) lymphography: this minimally invasive imaging technique is more accepted by patients than a 2-hour MRL, it is easy to repeat, and the costs are reduced compared to MRL: further, no pain is usually referred by the patients, while Mitsumori et al report mild to moderate pain in the four patients who received the gadobenate (Gd) contrast injections. Mitsumori et al refer only to the Chang et al and Ogata et al studies regarding ICG lymphography, while recent articles reported even more advantages from the use of this technique. The main doubtful aspect of this article is their difficulty in proving that the identified vessels are really lymphatic vessels: the absence of an MRL performed on healthy limbs reduces the proof of the results of this article. In comparing ICG lymphography to MRL in a limb of healthy patients, we may observe numerous lymphatic vessels in the ICG lymphography that are not reported in the MRL (Fig. 1). To prove this theory, our multidisciplinary study group is performing a study of MRL performed on lymphedema patients enrolled for LVA and histological examination of biopsy specimens of the vessels identified at the MRL. We will soon submit this article.