P Hajek’s research while affiliated with University of Vienna and other places

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Publications (79)


Magnetic resonance in lesions of the parotid gland
  • Article

July 1991

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17 Reads

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31 Citations

International Journal of Oral and Maxillofacial Surgery

M Traxler

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P Hajek

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In a prospective study the relevance of magnetic resonance (MR) for the diagnoses of tumors of the parotid gland has been evaluated. Due to the excellent soft tissue contrast and also the possibility of imaging in various planes and sections and to the high resolution achieved by surface coils, it was possible to visualize the lesions and the surrounding anatomy in great detail. MR combines the advantages of ultrasound and computed tomography and is indicated if a tumor cannot be defined sharply by using ultrasound or CT.


The Effect of Intra-Articular Gadolinium-DTPA on Synovial Membrane and Cartilage

March 1990

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49 Reads

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49 Citations

Investigative Radiology

PAUL C. HAJEK

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DAVID J. SARTORIS

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VICTORIA GYLYS-MORIN

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[...]

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DONALD RESNICK

This investigation evaluated the potential effect of gadolinium (Gd)-DTPA-dimeglumine on synovial membrane and joint cartilage, using macroscopic, microscopic, and x-ray fluorescent spectroscopic techniques. Thirteen New Zealand white rabbits (26 knees) were used in this study, ten receiving 500 micromolar injections of Gd-DTPA-dimeglumine in their right knees; the remainder of the knees served as controls. One injected knee had minimal joint effusion and one had mild hyperemia. Microscopically four knees exhibited mild focal hyperplasia of the synovium, another three minimal focal mononuclear cell infiltration. X-ray fluorescent spectroscopy demonstrated no evidence of Gd-DTPA-dimeglumine in the synovium or articular cartilage. Neither macroscopic nor microscopic evaluation detected any Gd-DTPA-dimeglumine related effects. Gd-DTPA-dimeglumine was found to be safe for intra-articular injection in this animal model.


Primary malignant fibrous histiocytoma of a metacarpal bone: A new localization
  • Article
  • Full-text available

November 1989

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23 Reads

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10 Citations

The British journal of radiology

Malignant fibrous histiocytoma (MFH) is a common tumour of the soft tissues (Ros et al, 1984); it is rare in bone but the predilection sites in bone are the distal metaphysis of the femur and the proximal metaphysis of the tibia. We present a patient with MFH of a metacarpal bone. A 72-year-old man presented with pain in his right second metacarpal region. Duration of symptoms was 5 months with increasing swelling in the past 4 weeks. There was no history of previous trauma or malignancy. Clinical examination revealed a tender second metacarpal of the right hand.

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Carpal tunnel syndrome: Morphologic changes after release of the transverse carpal ligament

October 1989

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33 Reads

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188 Citations

The Journal Of Hand Surgery

We describe the morphologic changes that follow division of the transverse carpal ligament in patients with carpal tunnel syndrome. Fifteen hands in 12 patients with carpal tunnel syndrome were studied with magnetic resonance imaging before operation and for 6 weeks after operation. Eight hands were studied at 8 months after operation. Carpal arch width, anterior displacement of the carpal canal contents, and carpal canal volume were measured by use of multiplanar reformation and three-dimensional reconstruction of magnetic resonance images. There was a 24.2 +/- 11.6% increase in carpal canal volume 6 weeks after carpal tunnel release (p less than 0.001). This difference persisted at 8-month follow-up. There was an anterior displacement of carpal canal contents 3.5 +/- 1.9 mm from its original position 6 weeks after operation (p less than 0.001). This palmar displacement persisted at the 8-month follow-up. There was no statistically significant increase in carpal arch width 8 months after carpal tunnel release. We believe that division of the transverse carpal ligament restores median nerve function by increasing the volume of the carpal canal. This volumetric increase results from an anterior displacement of the newly formed transverse carpal ligament and not from a widening of the bony carpal arch.


[Gd-DTPA in the MR diagnosis of pituitary adenomas]

April 1989

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12 Reads

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9 Citations

RöFo - Fortschritte auf dem Gebiet der R

25 Patienten mit chirurgisch (n = 14) und/oder biochemisch (n = 20) verifizierten Hypophysenadenomen wurden mit einem 1,5-T-MR-Tomographen mittels Spinechotechnik, 3 mm Schichtdicke und einer 256 × 256 Bildmatrix untersucht. T1-gewichtete sagittale und koronale Bilder wurden vor und nach Gd-DTPA-Bolusinjektion (0,1 mmol/kg KG) angefertigt. Es wurden 13 Mikroadenome und 12 Makroadenome nachgewiesen. Nativ waren 48 % der Adenome isointens, 48 % hypointens und 4 % hyperintens. 58 % zeigten im Vergleich zum normalen Hypophysengewebe eine verminderte, 15 % eine verstärkte Anfärbung. 12 % wiesen isointenses Anfärbeverhalten auf, und 15 % hatten sowohl hypointense als auch hyperintense Areale. Bei 3 Patienten (12 %) war das Adenom nur anhand der KM-Serie erkennbar. Die Abgrenzung der Adenome vom Sinus cavernosus wurde durch Gd-DTPA von 25 auf 95 % verbessert. Summary 25 patients with surgically (n = 14) and/or biochemically (n = 20) confirmed pituitary adenomas were examined on a 1.5 T superconducting MR system by means of multislice spin-echo technique, 3 mm thick sections and a 256 × 256 matrix. T1-weighted sagittal and coronal sections were obtained before and after administration of Gd-DTPA (O.1 mmol./kg. BW). 13 microadenomas and 12 macroadenomas were found. In unenhanced T1-weighted images 48 % of the adenomas were isointense, 48 % were hypointense and 4 % were hyperintense. 58 % of the adenomas enhanced to a lesser degree, 15 % enhanced to a higher degree than the normal pituitary gland. 12 % showed equal enhancement and 15 % showed hypointense and hyperintense areas simultaneously. In 3 patients (12 %) there was evidence of adenoma only in the enhanced images. The delineation of the adenoma from the cavernous sinus was possible in 95 % of the enhanced, but only in 25 % of the native scans.


[Intratemporal course of the facial nerve in magnetic resonance imaging]

February 1989

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10 Reads

HNO

MR images of the intratemporal portion of the facial nerve were obtained with a 1.5 Tesla permanent magnet whole-body imaging system. The facial nerve was followed from the internal auditory through the temporal bone to the styloid foramen. MR promises to be a sensitive method for the evaluation of intratemporal facial nerve diseases.


Radiologic search for embolized leaflets of prosthetic heart valves: A report of two cases

January 1989

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6 Reads

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4 Citations

CardioVascular and Interventional Radiology

In a radiologic search for embolized leaflets of Edwards-Duromedics bileaflet valves in 2 patients, the embolized fragments were localized in the iliac vessels using computed tomography. Sonography was successful in one case and standard X-ray films of the abdomen were negative in both cases. In vitro investigations with Björk-Shiley and Edwards-Duromedics leaflets suggested that standard X-ray films of the abdomen and pelvis should be considered as the first investigational technique. If negative, computed tomography of the lower abdomen should be done.


Detection of Testicular Torsion by Magnetic Resonance Imaging in a Rat Model

December 1988

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17 Reads

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16 Citations

The Journal of Urology

Testicular torsion is one of the most common pediatric urological emergencies. Incorrect or delayed diagnosis contributes significantly to morbidity. We previously have shown that magnetic resonance displays scrotal contents with great detail using hydrogen concentration weighted and T2 weighted images. Sprague-Dawley rats underwent either unilateral 720-degree testicular torsion or a sham procedure. Magnetic resonance images were obtained at intervals with a 3 or 5-inch surface coil. Scans after surgical torsion showed a characteristic spiral distortion of the fascial planes of the spermatic cord, not seen in the sham animals, as well as a decrease in testicular size with prolonged torsion.


Fig. 2.-2000/20 
A wire-sheath system for MR-guided biopsy and drainage: Laboratory studies and experience in 10 patients

November 1988

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30 Reads

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45 Citations

American Journal of Roentgenology

On the basis of laboratory experiments, we devised a wire-sheath system for MR-guided biopsy and drainage and then evaluated that system in 10 patients. The localizing system consisted of a 20-gauge plastic sheath into which a stainless-steel alloy wire had been inserted. In laboratory studies, we compared this wire-sheath assembly with other materials to determine its optimal visualization on MR images. We then used the same wire-sheath system to perform 16 procedures (in 10 patients), including six biopsies, five diagnostic fluid aspirations, and five catheter drainages of infected and noninfected fluid collections. The laboratory results showed that the wire-sheath assembly cast a 7-mm artifact, was visualized well on all pulse sequences, and was safe within the magnet (minimal attraction). The assembly was visualized well in each patient and provided adequate localization. MR-guided biopsy and drainage can be performed with high-resolution detail by using this wire-sheath system. Potential uses of this system include (1) treatment of lesions that can be seen on MR images only (or that can be seen to significantly better advantage on MR images than on sonograms or CT scans), and (2) treatment of patients in whom avoidance of the radiation delivered by CT is imperative.


MR Imaging of brain contusions: A comparative study with CT

June 1988

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24 Reads

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111 Citations

American Journal of Roentgenology

Ninety-eight brain contusions in 17 patients served as a data base for a comparative study of MR and CT for defining brain contusions. MR was the more sensitive technique, detecting 98% of the brain contusions compared with only 56% by CT. CT was slightly better for showing hemorrhagic components, documenting 77% of hemorrhages compared with 71% for MR. The appearance of the contusions on MR was variable, depending on the T1- and T2-weighting of the images and the constituents of the contusions, such as edema, hemorrhage, and encephalomalacia. On MR, hemorrhagic components appeared as high signal on T1-weighted images and as either low or high signal on T2-weighted images, depending on the age of the hemorrhage. The approximate ages of hemorrhagic contusions were often suggested by their appearance on T1- and T2-weighted images. CT is very effective for evaluating acute head trauma, but MR is recommended for documenting brain contusions during the subacute and chronic stages of head injuries.


Citations (34)


... Ultrasound (US) is a rapid non-invasive technique that can be used to visualize all of the submandibular and sublingual salivary glands as well as the entire parotid gland (except of the portion obscured by the acoustic shadow of the mandible) [18,19]. In recent years, publications have discussed the diagnostic value of parotid sonography in the detection of gland involvement in SS, but opinions in the validity of this method were contradictory [20][21][22][23][24][25]. ...

Reference:

Quantitative ultrasonography and magnetic resonance imaging of the parotid gland: Can they replace the histopathologic studies in patients with Sjogren's syndrome?
Sonographische Halsanatomie und ihre Bedeutung beim Lymphknotenstaging von Kopf-Hals-Malignomen
  • Citing Article
  • January 1987

RöFo - Fortschritte auf dem Gebiet der R

... Some studies used hypoxia and preterm methods to establish NHP CP models [10,11]. Near-total birth asphyxia was used in neonatal rhesus macaques (Macaca mulatta) and pigtailed macaques (Macaca nemestrina) to study the effects of hypoxia as a cause of neurological deficits [5,[12][13][14]. ...

Cerebral palsy in a macaque monkey
  • Citing Article
  • January 1988

American Journal of Primatology

... a Axial T1 w image shows Bankart lesion (arrow); b axial T1 w SPIR image showing Perthes lesion (arrow); c axial T1w and d coronal T1w images showing ALPSA lesion (arrows); e axial T1 w SPIR image shows the glenoid labrum ovoid mass sign (GLOM) that indicates a torn anterior glenoid labrum that is retracted medially (arrow); f axial T1w SPIR image shows posterior labrum tear (arrow). See Fig. 4 for a schematic view of labral lesions accurate technique for the evaluation of the extent of damage [70][71][72]. ...

Potential Contrast Agents for MR Arthrography: In Vitro Evaluation and Practical Observations
  • Citing Article
  • July 1987

American Journal of Roentgenology

... This is primarily based on the finding that time-signal intensity curves (TICs) for malignant tumors and the two commonest benign lesions, pleomorphic adenomas (PAs) and WTs, differ markedly, especially in terms of the time to peak enhancement (T peak ) and washout rate values (WR). According to literature, PAs show a gradual enhancement (high T peak ) followed by a slow contrast washout (low WR) 14,[16][17][18] . In contrast, WTs and malignant lesions are characterized by an early enhancement (low T peak ) followed by a rapid 17,19,20 or gradual washout, respectively 21,22 , which results in high or low WR. ...

Magnetic resonance in lesions of the parotid gland
  • Citing Article
  • July 1991

International Journal of Oral and Maxillofacial Surgery

... An early study by Engel et al. [11] demonstrated retention of Gd into the synovial membrane after IA injection of gadopentetate dimeglumine (Magnevist) into human knees, and transient retention into the articular cartilage in rabbits. Swift elimination of Gd from the joint, generally over several hours, has been shown in a study in rabbits [12]. Similar rapid elimination is suggested in humans, with studies demonstrating no MR signal alteration from IA GBCA 6 h after injection, presumably due to systemic absorption via the joint synovium [10,13,14]. ...

The Effect of Intra-Articular Gadolinium-DTPA on Synovial Membrane and Cartilage
  • Citing Article
  • March 1990

Investigative Radiology

... The promising results, with accuracy levels to distinguish responders from nonresponders of 85.7-100 %, can largely be explained by the pos- sibility of dynamic MRI to depict tissue vascular- ization. Other successful methods, such as angiography, color Doppler flow imaging, and blood-pool scintigraphy with technetium-99 m diphosphonate (99mTc-labeled MDP), are also based on the demonstration of a significant decrease in tumor vascularization and perfusion in responders [46,[61][62][63][64]. ...

The angiographic response of osteosarcoma following pre-operative chemotherapy
  • Citing Article
  • February 1986

Skeletal Radiology

... High-resolution MRI before and after gadolinium (Gd) injection is believed to be the most sensitive imaging method for diagnosis of pituitary microadenomas [1][2][3][4][5][6][7][8][9]. The utility of three-dimensional (3D) fast low-angle shot (FLASH) in the diagnosis of microadenomas has also been reported: using both coronal Tl-weighted spin-echo (SE) and 3D FLASH before and after intravenous Gd, 90 % sensitivity was achieved in 21 patients with surgical correlation [10]. ...

[Gd-DTPA in the MR diagnosis of pituitary adenomas]
  • Citing Article
  • April 1989

RöFo - Fortschritte auf dem Gebiet der R

... Our explanation is supported by two studies that reported a significant increase in the intraductal pressure of both the carpal and Guyon's tunnels in patients with idiopathic CTS, with a subsequent significant reduction in their pressure after a surgical section of the transverse carpal ligament (TCL) [46,47]. Moreover, morphological evaluation by magnetic resonance imaging (MRI) demonstrated that Guyon's canal, which had a triangular shape before surgery, turned into an oval or rounded shape after the surgical release of CTS [48,49]. Unfortunately, no studies were available to demonstrate abnormal sonographic findings of the ulnar nerve secondary to its entrapment in Guyon's canal due to the rarity of such a condition. ...

Carpal tunnel syndrome: Morphologic changes after release of the transverse carpal ligament
  • Citing Article
  • October 1989

The Journal Of Hand Surgery

... -la scoliose. Une diminution de la masse osseuse est observée dans la scoliose, avec des remplacements focaux de MO hématopoïétique plus fréquents que dans la MO de sujets normaux (166). Les MSCs des patients scoliotiques ont une capacité de différenciation ostéogénique diminuée en comparaison au groupe contrôle, alors que leur potentiel de différenciation adipogénique est similaire (167). ...

Focal fatty deposits in spinal bone marrow--MR findings. MRI of focal fatty deposits
  • Citing Article
  • February 1988

RöFo - Fortschritte auf dem Gebiet der R

... Baastrup's disease is characterized by degenerative changes of both spinous processes and interspinous soft tissues between two adjacent vertebrae [2]. Although several etiologies have been described for Baastrup's, it is thought that repetitive lumbar spinal movements in the sagittal plane predisposes injury of the posterior elements of the spine [3,4]. Chronic flexion and extension strain the interspinous ligament, causing the neighboring spinous processes to adjoin [3,5]. ...

Magnetic resonance imaging of the lumbar spinous processes and adjacent soft tissues: Normal and pathologic appearances
  • Citing Article
  • September 1987

The Journal of Rheumatology