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Alterations in hepatic uptake and distribution of organ-specific superparamagnetic MRI contrast media: clinical findings and classification according to pathogenesis
No full textPurpose. The aim of this study was to classify the alterations
in the liver uptake and distribution of superparamagnetic
contrast media that could potentially lead
to diagnostic errors. These alterations, referred to as
SPIO-LUDA for convenience,may be caused by a variety
of disorders, such as cirrhosis, vascular thrombosis,
hepatitis and liver steatosis, that interfere with the
normal uptake of the contrast material. These conditions
can give rise to focal or diffuse areas of hyperintensity
or hypointensity which may mimic the presence
of neoplastic lesions or hinder the detection or
characterisation of neoplasms.
Materials and methods.We retrospectively reviewed
the hepatic MR examinations of 412 patients performed
to detect hepatocellular carcinoma in 349 cases and
metastases in 63 cases, with the aim of identifying conditions
corresponding to the definition of SPIO-LUDA.
All the examinations were performed using a 1.5 Tesla
MR unit with SE and GE sequences, T1 and T2 weighted
images, and SPIO as a contrast agent, in 402 cases
ferumoxide (Endorem, Guerbet) and in 10 cases SHU-
555-A (Resovist, Schering). The SPIO-LUDA were
classed into two groups: due to reduced uptake (cell
replacement, reduced vascular flow and cellular inhibition)
and due to increased uptake (Kupffer cell hyperactivity
or increased vascularity). From a quantitative
point of view we evaluated the percentage of signal
loss (PSIL) of the SPIO-LUDA relative to the surrounding
healthy parenchyma, as an expression of
increase or reduced uptake of contrast material.
Results. In 54 patients we identified potentially misleading
SPIO-LUDA: 41 were due to reduced uptake
and 13 to increased uptake. In 16 cases, all of which
cases of reduced uptake, the alteration significantly
limited the diagnostic effectiveness of the MR examination.
The reduced-uptake SPIO-LUDA were caused
by fibrosis in 31 cases, by portal vein thrombosis in 3,
by suprahepatic vein thrombosis in 2, by peritumoural
vascular shunts in 3 and by hepatitis in 2. The
increased-uptake SPIO-LUDA were caused by focal
steatosis in 2 cases and by dysplastic nodules in cirrhosis
in 11. The reduced-uptake SPIO-LUDA exhibited
30% lower PSIL values than the normal liver (range
15-45%); the increased-uptake SPIO-LUDA displayed
19% higher PSIL values than the surrounding liver
(range 15-23%). Out of a total of 412 patients, the alteration
of SPIO uptake was so severe as to prevent detection
or exclusion of focal lesions in 4% of cases.
Conclusions. SPIO-LUDA constitute a diagnostic challenge. The recognition and correct interpretation of
these alterations are fundamental for avoiding confusion
with other diseases and to obtain further clues for
the interpretation of abnormal patterns detected at MRI
or other imaging modalities
MRI in ACL reconstructive surgery with PDLLA bioabsorbable interference screws: evaluation of degradation and osteointegration processes of bioabsorbable screws]
No full textPurpose. Anterior cruciate ligament (ACL) reconstructive
surgery has seen significant progress since bioabsorbable
interference screws have replaced synthetic
metallic screws for ligament graft fixation within the
femoral and tibial osseous tunnel. Our study compared
the MR images of patients who underwent ACL reconstruction
using bioabsorbable interference screws with
those of patients who underwent ACL reconstruction
using metallic screws to evaluate the MR aspects of
degradation and osteointegration processes of bioabsorbable
interference screws post-operatively.
Materials and methods. Between September 1999 and
December 2002 we performed MRI on 40 patients who
underwent arthroscopic ACL reconstruction with patellar
tendon auto-graft using PDLLA bioabsorbable screws
in 35 cases and metallic screws in 5 cases. After surgery,
all patients underwent an intensive rehabilitation
programme along with clinical evaluation using the
standard knee ligament evaluation form of the
International Knee Documentation Committee (IKDC)
and radiological examinations. MR studies were performed
1, 2 and 3 years post-operatively using a 0.5-
Tesla MR scanner with T1- and T2*-weighted and STIR
sequences.
Results. Thirty-three patients were clinically classified
as group A IKDC (full return to sports activity) and 7
patients as group B IKDC. No foreign-body reaction
was found in patients treated with bioabsorbable interference
screws, both from a clinical point of view and
from laboratory exams. Ferromagnetic artefacts were
found in all patients treated with metallic interference
screws. In patients with bioabsorbable interference
screws, degradation of the screws and absence of significant
artefacts allowed correct evaluation of the signal
of the reconstructed ligament throughout its length,
the osseous tunnels and the joint cavity. In 34 of 35
patients with bioabsorbable interference screws, the
screw could not be detected due to complete degradation.
In 8, 12 and 4 cases, a small cyst-like formation
due to screw hydrolysis was present at the screw site
within 1, 2 and 3 years from surgery respectively. Only
in 4 cases was the process of osteointegration of the
screw and bone plug complete 3 years after the operation,
with consequent restoration of bone morphology.
Discussion and conclusions. The use of bioabsorbable
interference screws is a valuable alternative to synthetic
metallic fixation implants as the absence of artefacts
allows correct post-operative MR follow-up. MRI is the
only technique able to visualize all the portions of the
transplant and to evaluate the healing process.
Bioabsorbable interference screws usually degrade with-in one year. However, full osteointegration requires a
long time and may not be complete 3 years after surgery.
The presence of cyst-like formations at the screw
site has to be regarded as a normal feature of the screw
degradation process. Therefore, the use of bioabsorbable
interference screws is recommended as it enables
MR follow-up of the knee after ACL reconstruction
Evaluation of patellar chondromalacia with MR: Comparison between T2-weighted FSE SPIR and GE MTC [Valutazione della condropatia rotulea con RM: Confronto tra sequenze FSE SPIR T2 e GE MTC]
No full textGoing Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Aspects of magnetic resonance in the surgical treatment of osteochondral lesions of the knee [Aspetti RM dei trattamenti chirurgici delle lesioni osteocondrali del ginocchio]
No full textValutazione RM dei noduli displasici e degli epatocarcinomi nel fegato cirrotico: ruolo dei mezzi di contrasto superparamagnetici.
No full textVariations on the Author
Full text link“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
Appropriate Similarity Measures for Author Cocitation Analysis
Full text linkWe provide a number of new insights into the methodological discussion about author cocitation analysis. We first argue that the use of the Pearson correlation for measuring the similarity between authors’ cocitation profiles is not very satisfactory. We then discuss what kind of similarity measures may be used as an alternative to the Pearson correlation. We consider three similarity measures in particular. One is the well-known cosine. The other two similarity measures have not been used before in the bibliometric literature. Finally, we show by means of an example that our findings have a high practical relevance.information science;Pearson correlation;cosine;similarity measure;author cocitation analysis
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