Experimental Observation of Proton Bunch Modulation in a Plasma at Varying Plasma Densities.

We give direct experimental evidence for the observation of the full transverse self-modulation of a long, relativistic proton bunch propagating through a dense plasma. The bunch exits the plasma with a periodic density modulation resulting from radial wakefield effects. We show that the modulation is seeded by a relativistic ionization front created using an intense laser pulse copropagating with the proton bunch. The modulation extends over the length of the proton bunch following the seed point. By varying the plasma density over one order of magnitude, we show that the modulation frequency scales with the expected dependence on the plasma density, i.e., it is equal to the plasma frequency, as expected from theory.

Experimental Observation of Plasma Wakefield Growth Driven by the Seeded Self-Modulation of a Proton Bunch.

We measure the effects of transverse wakefields driven by a relativistic proton bunch in plasma with densities of 2.1×10^{14} and 7.7×10^{14} electrons/cm^{3}. We show that these wakefields periodically defocus the proton bunch itself, consistently with the development of the seeded self-modulation process. We show that the defocusing increases both along the bunch and along the plasma by using time resolved and time-integrated measurements of the proton bunch transverse distribution. We evaluate the transverse wakefield amplitudes and show that they exceed their seed value (<15 MV/m) and reach over 300 MV/m. All these results confirm the development of the seeded self-modulation process, a necessary condition for external injection of low energy and acceleration of electrons to multi-GeV energy levels.

[Report of a rare case of Langerhans-cell histiocytosis of the skull base]. / Descrizione di un insolito caso di istiocitosi a cellule di Langerhans della base cranica.

INTRODUCTION: Langerhans cell histiocytosis, once called histiocytosis X, is a rare disease. Usually it can occur in children and is characterized by granulomas (eosinophilic granuloma and Hand-Schueller-Christian disease) or by a extensive involvement of various organs (Letterer-Siwe disease). The etiology remains uncertain and could be related to undefined immunologic disturbance. Lesions can involve bone marrow, skin, oral mucosa, retro-orbital tissue, central nervous system, lymph nodes, spleen, liver, lung, and gastroenteric tract. Surgery, radiotherapy and chemotherapy can be employed as treatment. Prognosis is different in relation to the extension of the disease. CASE REPORT: In our case (a 33 year old female) came to observation for swelling in temporal region. The patient underwent clinical and radiological examinations: the lesion involved the skull base in the right part of the sphenoid bone. CT and MRI showed a "clepsydra" lesion with wider extension to infratemporal fossa and to intracranial middle fossa and shrinking in the base of the skull; inside the lesion a lot of wider calcifications were present. A biopsy proved a diagnosis of Langerhans cell histiocytosis. No other localizations of disease were found. The patient was treated with chemotherapy followed by localized radiotherapy. Chemotherapy was performed with 3 cycles of etoposide 260 mg for 3 days every month. After this treatment a response of 25% was observed. Afterwards a radiotherapy with cobalt 60 was employed through two angled wedged fields for a total dose of 22 Gy and conventional fractionation. During the follow-up a slow, partial regression of the lesion with increase of the extension of the calcifications documented by CT and MRI was observed. After 5 years follow-up no progression of disease was observed. DISCUSSION: The usual treatment of Langerhans cell histiocytosis is surgery and eventually radiotherapy for localized disease and chemotherapy for extended disease. The prognosis is related to the number of involved organs: usually favorable with only one site of disease and unfavorable when more organs are involved. Other unfavorable prognostic factors are the age < 2 years, the presence of anemia, liver and spleen involvement and respiratory failure. In our case only one site of disease was evident and the clinical behavior has been quite favorable. The main peculiarities are the radiologic aspect and the slow, partial regression after the treatment; this fact could be related to the presence of wide calcifications inside the lesion. After 5 years follow-up it is possible to consider the absence of progression as a response to the treatment.

[Intrathoracic rupture of herniated stomach. Description of a case]. / Rottura intratoracica di stomaco erniato. Descrizione di un caso.

The authors describe a case of intrathoracic migration of the stomach consequent upon diaphragmatic laceration. Long after the traumatic event, intrathoracic stomach perforation occurred; it probably was due to stomach wall ischemia, as result of vascular compression. The lesion was diagnosed with conventional X-ray thoracic films and opacified stomach.

[The CT aspects of a case of chondromatosis of the temporomandibular joint]. / Aspetto tomodensitometrico di un caso di condromatosi dell'articolazione temporo-mandibolare.

The CT picture of a case of synovial chondromatosis of the temporomandibular joint is described. The distinctive feature of the case was the presence of ossified loose bodies surrounding the head of the condyle. Three-dimensional image reconstruction was also employed to obtain better overall visualization of the alterations.

Comparison of inter-observer reproducibility between conventional chest radiography and AMBER in the evaluation of silicosis.

The aims of this study were to test inter-observer and intraobserver agreement in the diagnosis of silicosis using conventional chest radiography and AMBER. One hundred and fifteen patients underwent chest x-rays and AMBER for the diagnosis of silicosis. Five readers blindly and independently evaluated the radiograms with standard ILO/UC classification scales. Reproducibility was assessed using ANOVA repeated measurements methods. AMBER showed a better technical quality of radiograms than conventional chest x-rays; interobserver reproducibility was high and similar (R = 0.75); intraobserver agreement between chest x-rays and AMBER was high ranging from 0.62 to 0.86 for the 5 readers. Notwithstanding the absence of standards for profusion classification, the interobserver reproducibility with AMBER was similar to that obtained with chest x-rays. Moreover, the intraobserver agreement in profusion scoring between AMBER and chest radiography was high, suggesting that AMBER and chest radiography provided similar information in the evaluation of silicosis.

CT evaluation of chondromatosis of the temporomandibular joint.

The CT findings in two cases of chondromatosis of the temporomandibular joint are described. The distinctive feature of the first case was the presence of ossified loose bodies surrounding the head of the condyle, whereas in the second there was clear evidence of arthrosis. Three-dimensional image reconstruction was also used in the first case to obtain a better overall visualization of the changes.

[Loose bodies of the temporomandibular joint. A rare pathology]. / I corpi liberi dell'articolazione temporo-mandibolare. Una patologia rara.

Loose bodies of the temporomandibular joint (TMJ) are an uncommon condition which can be caused by various complaints that can now be diagnosed with high resolution CT. The authors report on 10 cases observed from 1983 to 1992 which were studied with both conventional radiography and CT. The most common conditions were synovial chondromatosis and osteochondrosis dissecans. In the two cases of synovial chondromatosis, the demonstration of ossified loose bodies made the diagnosis easier. The cases of osteochondrosis dissecans presented with more complex diagnostic problems: in two instances the characteristic subchondral bone fragment in the condylar head was clearly visible, but in the third case this small fragment was difficult to identify as it had migrated backwards, making the disorder troublesome to diagnose. An osteophyte fracture and the presence of a bone fragment following condylar head fracture were easily diagnosed by correctly assessing the associated articular changes resulting from an arthrosic and a traumatic condition, respectively. The only case of loose body due to previous TMJ remodeling was easily diagnosed as the totally ossified formation was not seen on the preoperative X-ray film. Finally, two very similar cases, characterized by the presence of an elongated radiopaque formation in the site of the posterior meniscal ligament, were difficult to interpret as no such case is reported in the literature. In both cases an anatomical variant was presumed, characterized by posterior meniscal ligament ossification.

Radiological aspects of osteosarcoma of the jaws.

OBJECTIVES: To categorize the radiological presentation of osteosarcoma of the jaws. METHODS: Conventional radiographs and CT scans of nine patients with histologically proven osteosarcoma were reviewed. RESULTS: Five patients were men and four women, aged between 20 and 51; four lesions were in the maxilla and five in the mandible. Three radiological presentations of osteosarcoma of the jaw were identified. The first was radiolucent, characterized by a total absence of bone formation within the tumour. The second had a mottled appearance with small areas of amorphous ossification separated by non-ossified tumour tissue. The third, with lamellar ossification, was typically characterized by bony plates irradiating from a focus like a 'sunburst'. CONCLUSION: Radiological diagnosis of osteosarcoma of the jaw can be difficult because of its variable appearance. CT is particularly useful.

[Radiologic aspects of myxoma of the jaws]. / Aspetti radiologici del mixoma dei mascellari.

Four cases of jaw bones myxoma are described, laying special stress on the radiological appearance. Conventional radiogram showed a typical multilocular osteolytic lesion thinning and expanding the cortical bone. This allowed the authors to correctly diagnose the affection. On the contrary CT, showing a unilocular lesion, offered a far less typical representation of the tumor in the two patients who underwent this examination.

The computed tomographic appearances of cherubism.

The computed tomographic (CT) aspects of six cases of cherubism are described. Through its optimal representation of the lesions, CT enabled certain characteristics of this disease to be substantiated, namely, limitation of the process to the bones of the jaw and primarily superficial development of the mandibular lesions, coupled with an unusual mandibular condylar impairment. Moreover, the composition of this series permitted investigation of the condition in its several stages of progression.