François Terrier

In vivo human gastrocnemius architecture with changing joint angle at rest and during graded isometric contraction

1. Human gastrocnemius medialis architecture was analysed in vivo, by ultrasonography, as a function of joint angle at rest and during voluntary isometric contractions up to the maximum force (MCV). maximum force (MVC). 2. At rest, as ankle joint angle increased from 90 to 150 deg, pennation increased from 15.8 to 27.7 deg, fibre length decreased from 57.0 to 34.0 mm and the physiological cross‐sectional area (PCSA) increased from 42.1 to 63.5 cm2. 3. From rest to MVC, at a fixed ankle joint angle of 110 deg, pennation angle increased from 15.5 to 33.6 deg and fibre length decreased from 50.8 to 32.9 mm, with no significant change in the distance between the aponeuroses. As a result of these changes the PCSA increased by 34.8%. 4. Measurements of pennation angle, fibre length and distance between the aponeuroses of the gastrocnemius medialis were also performed by ultrasound on a cadaver leg and found to be in good agreement with direct anatomical measurements. 5. It is concluded that human gastrocnemius medialis architecture is significantly affected both by changes of joint angle at rest and by isometric contraction intensity. The remarkable shortening observed during isometric contraction suggests that, at rest, the gastrocnemius muscle and tendon are considerably slack. The extrapolation of muscle architectural data obtained from cadavers to in vivo conditions should be made only for matching muscle lengths.

Long-Term Outcome of Mesocolic and Pelvic Diverticular Abscesses of the Left Colon: A Prospective Study of 73 Cases

PURPOSEThe aim of of this study was to evaluate prospectively the long-term outcome of mesocolic and pelvic diverticular abscesses of the left colon.METHODSBetween October 1986 and October 1997, a total of 465 patients urgently admitted to our hospital with a suspected diagnosis of acute left-sided colonic diverticulitis had a CT scan. Of 76 patients (17 percent) who had an associated mesocolic or pelvic abscess, 3 were lost to follow-up. The remaining 73 patients (45 with a mesocolic abscess and 28 with a pelvic abscess) were followed for a median of 43 months.RESULTSof the 45 patients with a mesocolic abscess, 7 (15 percent) required surgery during their first hospitalization versus 11 (39 percent) of the 28 patients with a pelvic abscess (P = 0.04). At the end of follow-up, 22 (58 percent) of the 38 patients with a mesocolic abscess who had successful conservative treatment during their first hospitalization did not need surgical treatment vs. 8 (47 percent) of the 17 who had a pelvic abscess. Altogether, 51 percent of the patients with a mesocolic abscess had surgical treatment versus 71 percent of those with a pelvic abscess (P = 0.09).CONCLUSIONSConsidering the poor outcome of pelvic abscess associated with acute left-sided colonic diverticulitis, percutaneous drainage followed by secondary colectomy seems justified. Mesocolic abscess by itself is not an absolute indication for colectomy.

Blunt abdominal trauma in adults: role of CT in the diagnosis and management of visceral injuries Part 1: Liver and spleen

Abstract. Computed tomography is now widely used in the initial diagnostic workup of adult trauma victims with suspected intra-abdominal injuries. We review the role of CT in the detection and management of blunt visceral injuries in two parts. In the first part we discuss general aspects of performing CT in the setting of abdominal trauma and the diagnostic findings of intra-abdominal hemorrhage and blunt hepatic and splenic injuries. Hepatic and splenic injuries can be detected by means of CT with a high accuracy. The vast majority of hepatic injuries can be successfully managed conservatively, even when CT demonstrates parenchymal damage of more than three segments and major hemoperitoneum. Delayed complications, e. g., formation of biloma or a false aneurysm, can be readily detected on repeat CT studies, although they are quite uncommon. The outcome of conservative treatment of splenic injuries remains unpredictable because delayed splenic rupture may occur even when initial CT shows only minor parenchymal lesions and little or no intraperitoneal hemorrhage.

Acute left colonic diverticulitis—compared performance of computed tomography and water-soluble contrast enema

PURPOSE: The most valuable radiologic examination to be done initially when acute left colonic diverticulitis is suspected is still a matter of controversy. This study compares the performance between water-soluble contrast enema and computed tomography. METHODS: From 1986 to 1997, all patients admitted in our emergency center with clinically suspected left-colonic diverticulitis had a contrast enema and a computed tomography within 72 hours of their admission, unless clinical findings required immediate laparotomy. They were prospectively included in the study if one or both radiologic examinations showed signs of acute diverticulitis or diverticulitis was surgically removed and histologically proven or both. Diverticulitis was considered moderate when computed tomography showed localized thickening of the colonic wall (5 mm or more) and inflammation of pericolic fat and contrast enema showed segmental lumen narrowing and tethered mucosa; it was considered severe when abscess or extraluminal air or contrast or all three were observed on computed tomography and when one or both of the last two signs were seen on contrast enema. Of 542 patients, 420 who had both computed tomography and contrast enema entered the study. RESULTS: The performance of computed tomography was significantly superior to contrast enema in terms of sensitivity (98vs. 92 percent;P=0.01), which was calculated from patients who had their colon removed and whose diverticulitis was histologically proven, and in the evaluation of the severity of the inflammation (26vs. 9 percent;P=0.02). Moreover, of 69 patients who had an associated abscess seen on computed tomography, only 20 (29 percent) had indirect signs of this complication on contrast enema. CONCLUSIONS: In the diagnostic evaluation of acute left-colonic diverticulitis, computed tomography should be preferred to contrast enema as the initial radiologic examination because of its statistically significant superiority in sensitivity and for its significantly better performance in the detection of severe infection, especially when an abscess is associated with the disease.

Absolute renal blood flow quantification by dynamic MRI and Gd-DTPA

Abstract. The aim of this study was to demonstrate the feasibility of the absolute renal blood flow quantification using MRI and injection of contrast media. Using a T1-weighted fast gradient sequence following an intravenous bolus injection of Gd-DTPA, dynamic images of the kidney were obtained in patients with well-functioning native kidneys (n = 7) or transplant (n = 9), with significant renal artery stenosis (n = 4) and with renal failure (n = 7). After signal intensity calibration, the absolute renal perfusion was equal to the wash-in slope of the renal transit curve divided by the contrast medium concentration at the peak of the bolus in the aorta. The cortical blood flow was 2.54 ± 1.16 ml/min per gram in well-functioning kidneys decreasing to 1.09 ± 0.75 ml/min per gram in case of renal artery stenosis (p = 0.04) and to 0.51 ± 0.34 ml/min per gram in case of renal failure (p < 0.001). These measurements were in agreement with previous results obtained by other methods. A standard MRI imaging sequence and a simple model can provide realistic quantitative data on renal perfusion. This work justifies further studies to compare this model with a gold standard for renal blood flow measurements.

Long-term results of the Simon nitinol inferior vena cava filter

The aim of this study was to evaluate the clinical efficacy, mechanical stability, and safety of the Simon nitinol inferior vena cava filter (SNF). The SNF was inserted in 114 consecutive patients at two institutions for prophylaxis of pulmonary embolism (PE). Clinical follow-up data were obtained retrospectively on all patients, and 38 patients underwent a dedicated radiologic follow-up protocol consisting of abdominal radiography, Doppler sonography, and CT. There was no immediate complication following filter insertion. Fifty patients died, on average, 5.6 (1–23) months after filter insertion, and 64 patients were alive, on average, 27 (3–62) months after filter insertion. Recurrent pulmonary embolism was documented in 5 patients (4.4 %) but originated distal to the filter in 1 patient. Deep venous thrombosis (DVT) was documented in 5.3 %, thrombosis at the access site in 3.5 %, and thrombosis of the inferior vena cava in 3.5 %. The rate of thromboembolic complications was similar in patients who did receive long-term anticoagulation and in those who did not. Radiologic follow-up showed no filter migration after, on average, 32 (5–62) months. A CT examination showed that struts of the SNF had penetrated the vena cava in 95 %, and were in contact with adjacent organs in 76 %; however, there were no clinical symptoms attributable to the filter. Filters were in an eccentric position in 63 % and partial filter disruption was found in 16 %; however, this did not affect filter function. The rate of recurrent pulmonary embolism after insertion of the SNF is 2.4 % per patient per year. Regardless of long-term anticoagulation, the rate of caval thrombosis is acceptably low. Except for occasional access-site thrombosis, no other filter-related morbidity was observed.

Blunt abdominal trauma in adults: role of CT in the diagnosis and management of visceral injuries. Part 2: Gastrointestinal tract and retroperitoneal organs

Abstract. Computed tomography plays an important role in the detection and management of blunt visceral injuries in adults. Current standard examination techniques enable detection of the majority of perforating or devascularizing bowel injuries, although diagnostic findings are often subtle and meticulous inspection is required. Computed tomography may demonstrate pancreatic contusions and lacerations and help in distinguishing minor traumatic lesions without involvement of the pancreatic duct (organ injury scale, grades I and II) from deep lacerations with ductal involvement (grades III and V). Computed tomography enables distinguishing renal contusions and minor cortical lacerations that can usually be managed conservatively (injuries of grades I–III) from corticomedullary lacerations and injuries of the major renal vessels (grades IV and V) that have a less favorable prognosis and more commonly require surgical repair. In addition, CT is well suited for the detection of active renal hemorrhage and guidance of transcatheter embolization treatment and delineation of preexisting benign or malignant pathologies that may predispose to posttraumatic hemorrhage. The radiologists awareness of the diagnostic CT findings of abdominal visceral injuries as well as their clinical and surgical implications are important prerequisites for optimal patient management.

MR cholangiopancreatography: technique, potential indications, and diagnostic features of benign, postoperative, and malignant conditions

Abstract. The objective of this article is to review technical aspects, discuss potential clinical indications for MR cholangiopancreatography (MRCP) and demonstrate the spectrum of diagnostic findings in benign, postoperative, and malignant conditions. We describe our current imaging protocol in comparison with other available techniques. Using a non-breath-hold, heavily T2-weighted fast-spin-echo (FSE) sequence with or without respiratory gating we obtained coronal and axial source images and maximum intensity projections (MIPs) in 102 patients with suspected abnormalities of the biliary or pancreatic ducts. Based on this series we demonstrate the diagnostic appearance of a variety of benign, postoperative, and malignant conditions of the biliary and pancreatic ducts and discuss potential clinical indications for MRCP. The non-breath-hold FSE technique enables a consistent image quality even in patients who cannot cooperate well. Respiratory gating increased the rate of diagnostic examinations from 79 to 95 %. Acquisition of coronal and axial source images enables detection of bile duct stones as small as 2 mm, although calculi that are impacted and not surrounded by hyperintense bile may sometimes be difficult to detect. The MIP reconstructions help to determine the level of obstruction in malignant jaundice, delineate anatomical variants and malformations, and to diagnose inflammatory conditions, e. g., sclerosing cholangitis, the Mirizzi syndrome and inflammatory changes in the main pancreatic duct. The MRCP technique also correctly demonstrates the morphology of bilio-enteric or bilio-biliary anastomoses. Because MRCP provides sufficient diagnostic information in a wide range of benign and malignant biliary and pancreatic disorders, it could obviate diagnostic endoscopic retrograde cholangiopancreatography (ERCP) in many clinical settings. The ERCP technique may be increasingly reserved for patients in whom nonsurgical interventional procedures are anticipated.

Noninvasive measurement of absolute renal perfusion by contrast medium-enhanced magnetic resonance imaging

Objective:The aim of this study was to validate the quantification of absolute renal perfusion (RP) determined by dynamic magnetic resonance imaging (MRI) and contrast media using an experimental model in the rabbit and a transit-timed ultrasound flow probe around the left renal artery as comparison. Material and Methods:An MR-compatible ultrasonic time-of-flight flow-probe was placed around the left renal artery in 9 new Zealand white rabbits. Absolute RP in basal state, after mechanical renal artery stenosis, intravenous dopamine, angiotensin II, or colloid infusion was measured using dynamic MRI and intravenous injection of gadoteridol. The results were correlated to the renal artery flow measured inside the magnet with the transit-timed flow-probe. For the signal intensity concentration conversion, we applied different calibrations according to various velocities measured in the aorta by a phase contrast sequence to correct for inflow effect. MRI-derived RP (in mL/min) was calculated by the maximum upslope method, where RP/volume was defined as the ratio of the cortex contrast enhancement slope over the maximum of the arterial input function determined in the aorta. Results:Reproducible arterial and renal transit curve with excellent contrast to noise ratio were obtained. The MRI derived perfusion was systematically underestimated by comparison to the ultrasonic transit-timed flow-probe but was linearly correlated with these measures (r = 0.80, P < 0.001). Conclusions:Using a flow-sensitive calibration, an accurate arterial input function can be measured from the blood MR signal and used in a realistic model to assess the RP. There was a good correlation between the MR-derived RP and the renal artery blood flow measured by the flow-meter. This experimental study validates absolute RP quantification by MRI and contrast media injection and justifies further clinical studies.

Second-generation three-dimensional reconstruction for rotational three-dimensional angiography.

RATIONALE AND OBJECTIVES The purpose of this study was to assess the feasibility and accuracy of three-dimensional (3D) reconstruction techniques for digital subtraction angiography (DSA) in planning and evaluation of minimally invasive image-controlled therapy. MATERIALS AND METHODS Using a standard, commercially available system, the authors acquired DSA images and corrected them for inherent distortions. They designed and implemented parallel and multiresolution versions of cone-beam reconstruction techniques to reconstruct high-resolution targeted volumes in a short period of time. Testing was performed on anatomically correct, calibrated in vitro models of a cerebral aneurysm. These models were used with a pulsatile circulation circuit to allow for blood flow simulation during DSA, computed tomographic (CT) angiography, and magnetic resonance (MR) angiography image acquisitions. RESULTS The multiresolution DSA-based reconstruction protocol and its implementation allowed the authors to achieve reconstruction times and levels of accuracy for the volume measurement of the aneurysmal cavities that were considered compatible with actual clinical practice. Comparison with data obtained from other imaging modalities shows that, besides vascular tree depiction, the DSA-based true 3D technique provides volume estimates at least as good as those obtained from CT and MR angiography. CONCLUSION The authors demonstrated the feasibility and potential of true 3D reconstruction for angiographic imaging with DSA. On the basis of the model testing, this work addresses both the timing and quantification required to support minimally invasive image-controlled therapy.