Helicity-Dependent Cross Sections for the Photoproduction of π

The double-polarization observable E and helicity-dependent cross sections σ_{1/2}, σ_{3/2} have been measured for the photoproduction of π^{0} pairs off quasifree protons and neutrons at the Mainz MAMI accelerator with the Crystal Ball/TAPS setup. A circularly polarized photon beam was produced by bremsstrahlung from longitudinally polarized electrons and impinged on a longitudinally polarized deuterated butanol target. The reaction products were detected with an almost 4π covering calorimeter. The results reveal for the first time the helicity- and isospin-dependent structure of the γN→Nπ^{0}π^{0} reaction. They are compared to predictions from reaction models in view of nucleon resonance contributions and also to a refit of one model that predicted results for the proton and for the neutron target. The comparison of the prediction and the refit demonstrates the large impact of the new data.

Measurements of double-polarized compton scattering asymmetries and extraction of the proton spin polarizabilities.

The spin polarizabilities of the nucleon describe how the spin of the nucleon responds to an incident polarized photon. The most model-independent way to extract the nucleon spin polarizabilities is through polarized Compton scattering. Double-polarized Compton scattering asymmetries on the proton were measured in the Δ(1232) region using circularly polarized incident photons and a transversely polarized proton target at the Mainz Microtron. Fits to asymmetry data were performed using a dispersion model calculation and a baryon chiral perturbation theory calculation, and a separation of all four proton spin polarizabilities in the multipole basis was achieved. The analysis based on a dispersion model calculation yields γ(E1E1)=-3.5±1.2, γ(M1M1)=3.16±0.85, γ(E1M2)=-0.7±1.2, and γ(M1E2)=1.99±0.29, in units of 10(-4) fm(4).

Photoproduction of π0 mesons off neutrons in the nucleon resonance region.

Precise angular distributions have been measured for the first time for the photoproduction of π0 mesons off neutrons bound in the deuteron. The effects from nuclear Fermi motion have been eliminated by a complete kinematic reconstruction of the final state. The influence of final-state-interaction effects has been estimated by a comparison of the reaction cross section for quasifree protons bound in the deuteron to the results for free protons and then applied as a correction to the quasifree neutron data. The experiment was performed at the tagged photon facility of the Mainz Microtron MAMI with the Crystal Ball and TAPS detector setup for incident photon energies between 0.45 and 1.4 GeV. The results are compared to the predictions from reaction models and partial-wave analyses based on data from other isospin channels. The model predictions show large discrepancies among each other and the present data will provide much tighter constraints. This is demonstrated by the results of a new analysis in the framework of the Bonn-Gatchina coupled-channel analysis which included the present data.

Measurement of the 1H(γ, p)π0 reaction using a novel nucleon spin polarimeter.

We report the first large-acceptance measurement of polarization transfer from a polarized photon beam to a recoiling nucleon. The measurement pioneers a novel polarimetry technique, which can be applied to many other nuclear and hadron physics experiments. The commissioning reaction of 1H(γ, p)π0 in the range 0.4

Accurate test of chiral dynamics in the γp→π0p reaction.

A precision measurement of the differential cross sections dσ/dΩ and the linearly polarized photon asymmetry Σ≡(dσ⊥-dσ∥)/(dσ⊥+dσ∥) for the γp→π0p reaction in the near-threshold region has been performed with a tagged photon beam and almost 4π detector at the Mainz Microtron. The Glasgow-Mainz photon tagging facility along with the Crystal Ball/TAPS multiphoton detector system and a cryogenic liquid hydrogen target were used. These data allowed for a precise determination of the energy dependence of the real parts of the S- and all three P-wave amplitudes for the first time and provide the most stringent test to date of the predictions of chiral perturbation theory and its energy region of agreement with experiment.

Narrow structure in the excitation function of η photoproduction off the neutron.

The photoproduction of η mesons off nucleons bound in 2H and 3He has been measured in coincidence with recoil protons and recoil neutrons for incident photon energies from threshold up to 1.4 GeV. The experiments were performed at the Mainz MAMI accelerator, using the Glasgow tagged photon facility. Decay photons from the η→2γ and η→3π0 decays and the recoil nucleons were detected with an almost 4π electromagnetic calorimeter combining the Crystal Ball and TAPS detectors. The data from both targets are of excellent statistical quality and show a narrow structure in the excitation function of γn→nη. The results from the two measurements are consistent, taking into account the expected effects from nuclear Fermi motion. The best estimates for position and intrinsic width of the structure are W=(1670±5) MeV and Γ=(30±15) MeV. For the first time precise results for the angular dependence of this structure have been extracted.

Percutaneous microductectomy with a directional vacuum-assisted system guided by ultrasonography for the treatment of breast discharge: experience in 63 cases.

BACKGROUND: Vacuum-assisted devices are becoming a useful tool in the diagnosis and treatment of breast pathology. Recent publications show good results in percutaneous removal of benign lesions. PURPOSE: To discuss our experience in percutaneous excision of ductal lesions with a vacuum-assisted, ultrasound-guided directional system. MATERIAL AND METHODS: From January 2003 to July 2006, 63 patients with pathological nipple discharge and intraductal lesion identifiable on imaging were studied at two reference centers. Percutaneous excision with a vacuum-assisted device was offered as an alternative to surgery. RESULTS: A total of 71 lesions were diagnosed in 63 patients with a mean age of 52 years. All the patients presented nipple discharge. Mammography was normal in 65 cases (92%). Galactography showed an intraductal lesion in 67 cases (94%). Mean lesion size on ultrasonography was 7.4 mm (2-26 mm). Percutaneous excision was performed in 45 lesions (63%), while surgical excision was indicated in 26 lesions. The histopathological results in the 45 lesions biopsied demonstrated intraductal papilloma in 30 cases, dilated duct with papillomatous projections in 11, ductal ectasia with no papillary lesion in three, and a nonspecific benign result in one. Excision was considered complete in 41 lesions (91%). Clinical signs of discharge were resolved in 39 patients (95% of cases treated percutaneously). Mild complications occurred in four cases. CONCLUSION: Percutaneous excision of ductal lesions with an ultrasound-guided, vacuum-assisted device is a safe procedure with high diagnostic and therapeutic value for the management of breast discharge.

Ultrasound-guided core needle biopsy of non-palpable breast lesions: a prospective analysis in 204 cases.

PURPOSE: To assess the diagnostic value of ultrasound (US)-guided 14 G core needle breast biopsy in non-palpable suspicious breast lesions. MATERIAL AND METHODS: From August 1997 to April 2001, 198 patients with 204 suspicious non-palpable breast lesions underwent US-guided large core needle biopsy. Biopsies were performed with a free-hand technique using US equipment with a 7.5 MHz linear-array transducer; a minimum of three cores were obtained from each lesion. Pathological findings in US-guided core biopsy were correlated to findings in subsequent surgery or long-term (more than 2 years) imaging follow-up. RESULTS: Among the 204 non-palpable breast lesions for which histopathological findings were obtained by US-guided core biopsy, 118 were malignant (114 carcinoma, 2 metastasis, 1 lymphoma, and 1 malignant phyllodes tumor) and 86 were benign (4 carcinoma and 82 benign lesions confirmed at surgery or after at least 2 years of follow-up). Sensitivity, specificity, positive predictive value, and negative predictive value for diagnosis of malignancy in our series were 97%, 100%, 100%, and 95%, respectively. Diagnostic yield with 1, 2, 3, and 4 specimens per lesion was 73.5%, 88%, 94%, and 97.5%, respectively. CONCLUSION: US-guided core needle biopsy is a sensitive percutaneous biopsy method for diagnosing non-palpable breast lesions. To achieve a high diagnostic yield, a minimum number of three cores per lesion is advisable.

Sonographically guided 11-G directional vacuum-assisted breast biopsy as an alternative to surgical excision: utility and cost study in probably benign lesions.

PURPOSE: To evaluate the utility and economic costs of the 11-G vacuum-assisted biopsy probe under ultrasound (US) guidance as an alternative to surgical excision in patients with probably benign lesions. MATERIAL AND METHODS: US-guided 11-G vacuum-assisted biopsy was performed in 102 probably benign breast lesions in 97 women who refused radiological follow-up. Complete removal of the lesion was intended in all cases. Open biopsy was done if questionable pathologic findings were present. Treatment was indicated if the diagnosis was malignant. Economic costs were estimated taking into consideration monetary expenses generated to the public health system, as well as expenses for the patients receiving percutaneous and open surgical biopsy. RESULTS: Median patient age was 42 years (range 18-77). Median lesion size was 14.7 mm (range 6-30 mm). Complete removal of the lesion seen at imaging was achieved in 72.5% of cases. Adequate tissue samples for histopathological evaluation were obtained in all cases. Surgical biopsy was recommended in nine cases. One patient diagnosed with mucinous carcinoma underwent immediate surgical treatment. The remaining 87 women with 92 lesions were included in a follow-up program. Economic cost of the 11-G vacuum-assisted percutaneous biopsy was 82% lower than the surgical biopsy (total savings in this series: 136,402.84 euros). Time spent for the patient was 71% less in percutaneous biopsy than in surgery. CONCLUSION: Ultrasound-guided 11-G directional vacuum-assisted breast biopsy is an accurate and less expensive procedure that can be used as an alternative to open surgical excision in a selected group of patients.

Utility of the tumor bed marker in patients with breast cancer receiving induction chemotherapy.

PURPOSE: Induction or neoadjuvant chemotherapy is used in patients with locally advanced breast cancer to offer a higher rate of conservative surgery. The possibility of reduction in size, even in some cases complete clinical and mammographic regression, can make the localization of the tumor bed difficult at the time of surgery. The purpose of this study was to describe our experience about the utility of US-guided implantation of a metallic marker in patients with breast cancer before induction chemotherapy. MATERIAL AND METHODS: Forty-three patients with 44 masses were diagnosed with percutaneous biopsy of breast carcinoma. Before beginning of the induction chemotherapy all of them were referred for metallic marker placement. A metallic harpoon was placed under US guidance. RESULTS: One patient died during the chemotherapy. Six underwent mastectomy, and 9 still had a palpable tumor at the time of surgery. In the remaining 27 patients (with 28 lesions) pre-operative wire localization of the tumor bed was carried out: in 11 cases the harpoon was necessary for the localization of the tumor bed, in 6 the harpoon was useful, and in 11 patients the localization of the tumor could have been done without the marker. No complications were observed and the marker remained stable in all patients. CONCLUSION: In patients who undergo induction chemotherapy, the placement of a metallic harpoon under US guidance is a safe, simple and inexpensive technique for localization of the tumor bed previous to conservative surgery.

Mycotic (infected) aneurysm of the popliteal artery and arthritis following Salmonella bacteriemia.

We report a case of a mycotic (infected) aneurysm of the popliteal artery due to Salmonella enteritidis. The clinical presentation may be confused with other more common causes of diffuse swollen leg, causing a delay in the diagnosis and proper therapy. Prompt surgical resection of the infected aneurysm together with medical therapy is required for successful treatment.

[Intradural lumbar disk hernia]. / Hernia discal lumbar intradural.

Intradural disc herniation is a rare complication of degenerative disc disease. A correct diagnosis of this process is frequently difficult. If this entity is not preoperatively diagnosed and is omitted at surgery, severe neurologic sequels may be provoked. We report a case of a pathologically proven intradural disc herniation preoperatively diagnosed by MR imaging. Clinically, it was manifested by sudden onset of right leg ciatalgia and progressive right lower extremity weakness. The patient also referred a one-month history of sexual dysfunction. MR imaging revealed interruption of the low signal of the anulus fibrosus and of the posterior longitudinal ligament at L2-L3 level and a voluminous disc fragment migrated in the dural sac that showed rim enhancement with gadolinium.The clinical, neuroradiological, and surgical management of lumbar intradural disc herniation are reviewed.

Hernia discal lumbar intradural / Intradural lumbar disk hernia

La hernia intradural es una complicación infrecuente de la enfermedad degenerativa discal, de difícil diagnóstico. Si este proceso no se diagnostica preoperatoriamente y se pasa por alto en el acto quirúrgico, puede condicionar importantes secuelas neurológicas. Presentamos un caso de hernia discal intradural diagnosticado preoperatoriamente con resonancia magnética (RM). Clínicamente, se manifestaba por un cuadro de lumbociatalgia derecha de instauración súbita, disminución progresiva de la fuerza en la extremidad inferior derecha y disfunción sexual de un mes de evolución. La RM demostró interrupción de la hiposeñal normal del anillo fibroso discal y del ligamento longitudinal común posterior en L2-L3, así como un voluminoso fragmento discal migrado en el saco tecal, con realce anular tras la administración de contraste. Se revisa la nosología de la hernia discal intradural lumbar, con especial atención a los hallazgos neurorradiológicos y a su abordaje quirúrgico (AU)

Insufficiency fractures of the tibia and fibula.

OBJECTIVE: Insufficiency fractures (IF) occur when normal or physiological muscular activity stresses a bone that is deficient in mineral or elastic resistance. IF of the tibia and fibula are probably less common than IF of the ribs, vertebrae, hip, pelvis, and distal ulna, and therefore they are frequently underrecognized and mistaken for other conditions. Our aim was to analyze the main features and outcome of IF of the tibia and fibula in patients attending our Rheumatology Service. METHODS: IF was considered when occurring spontaneously or with minimal trauma. Between January 1984 and July 1997, 25 patients were diagnosed as having IF of the tibia and fibula. The main predisposing factors, clinical features, therapy, and outcome were retrospectively reviewed. RESULTS: All the patients except four were women (mean age, 66+/-12 years). Three cases were diagnosed between 1984 and 1990 (0.42 cases/year) and 22 between 1991 and 1997 (three cases/year). Eighteen patients had an underlying condition: rheumatoid arthritis (RA, 13 cases), psoriatic arthritis (2), systemic lupus erythematosus (SLE) (1), kidney transplant (1), and Crohn's disease (1). Eleven patients had osteoporotic fractures in other locations. Risk factors for osteoporosis were corticosteroids (13 cases), prolonged immobilization (10), early menopause (2), and methotrexate therapy (10). All patients had pain on weight bearing and marked functional impairment, 16 had local inflammatory signs, and 10 had deformity. In only five patients the diagnosis of IF was considered at the first examination. The diagnostic delay was 76+/-117 days (median, 21). The initial radiograph was diagnostic in 20 patients, and in the remaining the diagnosis was made by computed tomography (CT) scan (three cases), magnetic resonance imaging (MRI) (1), and bone scan (1). IF were located as follows: tibia (10 cases), fibula (seven), tibia and fibula (eight). Nineteen patients were treated with conservative management, four received no specific treatment, and two required surgery. Sixteen patients were hospitalized for a mean period of 12+/-8 days. Most patients had complete recovery. The high frequency of IF seen in RA patients is probably due to the severe disease in patients treated by our Service and that such patients have a higher risk for osteoporosis and its complications. CONCLUSIONS: IF of the tibia and fibula are probably more common than previously thought. They usually occur in patients with underlying rheumatic diseases, mainly RA, and are frequently mistaken for other joint and bone conditions. Despite a frequent delay in diagnosis, they have a good prognosis with conservative management. Nonetheless, a higher index of suspicion may avoid unnecessary investigations and treatments.

Tardive dystonia and severe tardive dyskinesia. A comparison of risk factors and prognosis.

Nine tardive dystonia cases were compared with 13 tardive dyskinesia cases selected for the severity and persistence of their involuntary movements. Both groups were neurological referrals from an identical source. While advanced age and female preponderance were prominent features in tardive dyskinesia, onset in most tardive dystonia cases occurred in young adulthood, and the sex distribution showed a slight majority of males. Other differences in the dystonia group included gait abnormalities in four cases, lower tolerance of neuroleptic discontinuance, with the reappearance of psychoses, and a poorer prognosis for reversibility after follow-up. In fact, none of the dystonia patients reversed as opposed to seven of the tardive dyskinesia patients. In order to identify the full spectrum of tardive dystonia and exclude any referral bias, systematic epidemiological studies on psychiatric populations should include young adults of both sexes.