RF needles

RF needles can be placed under ultrasound, CT, or MRI guidance using the percutaneous approach. Ultrasound is the most common guidance method as it has real-time capabilities, allows vascular visualization, and is readily available (Rossi et al. 1998 Livraghi et al. 2000 Francica and Marone 1999 Kainuma et al. 1999). 

Rossi S, Di Stasi M, Buscarini E, Cavanna L, Quaretti P, Squassante E et al (1995) Percutaneous radiofrequency interstitial thermal ablation in the treatment of small hepatocellular carcinoma. Cancer J Sci Am 1 73 Rossi S, Buscarini E, Garbagnati F, Di Stasi M, Quaretti P, Rago M et al (1998) Percutaneous treatment of small hepatic tumors by an expandable RF needle electrode. AJR Am J Roentgenol 170 1015-1022... 

Fig. 3.3. 3a-h. RFA of a single HCC as assessed by multi-detector CT. Pre-treatment CT acquired in the arterial phase demonstrates a native tumor as a faint enhancing lesion in the axial and coronal view (a, b). Para-axial and coronal reformats of the CT scan (after TACE the day before) with the RF needle (RITA Starburst XL) in place demonstrate complete coverage of the lesion with the fully deployed hooks (c, d). The post-treatment scan the day after the RF procedure shows complete coverage of the HCC by the ablation zone (e, f). CT scan at 6 months follow-up displays in the arterial (g) as well as in the porto-venous phase (h) a well-circumscribed ablation zone, stable in size, with no evidence for local tumor recurrence... 

The level of injector fouling is most often illustrated in terms of residual flow (RF) expressed as a percentage of the flow under new conditions for a given needle lift. An RF on the order of 20% for a lift of 0.1 mm is a good compromise. This level may not be achieved with certain aromatic or naphthenic diesel fuels. The best recourse is then detergent additive addition. 

A solution of 1-phenyl-1//-pyrazolo[3,4-rf]pyridazinc-7-carbonitrilc (150 mg. 0.68 mmol) and A,A-diethyl-prop-l-ynamine(151 mg, 1.36 mmol) in l,4-dioxane(2 mL) was refluxed for 5 h. After cooling, the reaction mixture was poured onto excess ice, and extracted with CHC13. The extract was washed with H20, dried (Na2S04) and concentrated under reduced pressure. Purification by chromatography (silica gel, benzene then bcnzene/EtOAc 20 1) gave, from the benzene eluate, 6-diethylamino-1 -phenyl-1 //-indazole-7-carbo-nitrile [yield 81 mg (39 %) mp 104-105 C (benzene/petroleum ether)] as slightly yellow prisms and, from the second eluate, the diazocine 5 as yellow needles yield 90 mg (40 %) mp 121-122 C (benzene/ petroleum ether). 

The crude solid was suspended in benzene/hexanes (1 1, 100 mL), heated, and decanted after cooling. The supernatant was applied to a column of silica gel G (70 g, benzene/hexanes 1 1) to separate the benzophenone derivative from the phenyl benzoate contaminant. The column was eluted with the same solvent (250 mL), followed by benzene/hexanes (3 1, 350 mL), and finally with benzene. Fractions (50 mL) were collected. Fractions containing the component with Rf 0.14 (silica gel, benzene) were pooled and concentrated on a rotary evaporator. Recrystallization (abs EtOH) of the residue [2.4 g (15% based on starting phenol)] gave colorless needles of 94 yield 2.2 g (14%) mp 137-138°C. 

To a soln of 2-methylprop-l-ene in CH2C12 (5 mL, prepared by sparging with 2-methylprop-l-ene for 10 min) was added TMSBr (87 xL, 0.66 mmol). After 5 min, a soln of the phosphonate methyl ester 78 (100 mg, 0.13 mmol) in CH2C12 (lmL) was added to the TMSBr soln and the reaction flask was sealed with a septum. After stirring at rt for 24 h, the flask was carefully vented with a small bore needle to release excess pressure. The solvent and volatile products were removed in vacuo and the residue was reevaporated twice from CHC1> MeOH (4mL) was added, and the white solid that formed was collected and dried in vacuo to yield 79 yield 63 mg (64%) mp 225-227 °C 31P NMR (DMSO-rf , 6) 24.49. 

The crude product is dissolved in a minimum amount of dichloromethane and adsorbed onto 25 g of silica gel (32-63 micron) by subsequent evaporation of the dichloromethane under reduced pressure. The sample of dry, dark brown silica gel is added to the top of a column containing 500 g of silica gel (32-63 micron) with a mobile phase of hexanes. The polarity of the mobile phase is gradually increased from hexanes to 95 5 hexanes-ethyl acetate. The fractions containing the desired product (Rf = 0.26, 95 5 hexanes-ethyl acetate) are combined and concentrated under reduced pressure to yield 6.9 g of 3 as a yellow solid. Additional purification is required to remove traces of tin by-products. Compound 3 is dissolved in 70 mL of ethyl acetate and stirred over 70 mL of saturated, aqueous potassium fluoride for 24 hr. The two phases are separated and the organic phase is dried over magnesium sulfate, filtered, and concentrated under reduced pressure. The resulting yellow solid is recrystallized from ethyl alcohol to provide 6.1 g (48%, 2 crops) of 3 as yellow needles (Notes 17,18, and 19). 

Chiu NF, Wang JM, Yang LJ, Liao CW, Chen CH, Chen HC, Lu SS, Lin CW. An implantable multifunctional needle type biosensor with integrated RF capability. 

Reddish-brown needles from methanol. Extremely stable and may be autoclaved in solution. Very soluble in water and insoluble in most organic solvents. Rt insolvent System 1,0.28 in Solvent System 11,0.30 (149). For Rf values in other solvent systems see Ref. (46). May be extracted into benzyl alcohol from saturated ammonium sulfate solution. Gives an... 

From hot methanol in fine needles, decomp. 280°. CaTEUsOeNeFe. Insoluble in nearly all common solvents. Rf in Solvent System II, 0.59 in Solvent System III, 0.68 (8). Neutral. Absorption maximum at 4300 A... 

The first is to cover the sample lane with a glass plate and spray the standard(s) lane with the phosphorus spray. The positive spots are circled carefully (actually dotted would be better) with a thin needle. Then the plate is scanned for radioactivity as described in earlier chapters. If PAF or related derivatives are formed, then radioactivity should be located below the sphingomyelin and above the lysophosphatidylcholine at an Rf value comparable to... 

A solution of 0.5 g of ( )-1 a and 0.5 g of 85% MCPBA in 10 mL of benzene is heated under reflux for 8 h and then allowed to stand at r.t. for 12 h. The needles of 3-chlorobenzoic acid which separate are removed by filtration. The filtrate is washed with 5% aq NaHC03, with H20 and dried over Na2S04. The yellow oil obtained on removal of the solvent is dissolved in 1 mL of benzene and chromatographed on two silica gel TLC plates (100 pm, 20 x 20 cm bcnzcne/petroleum ether 1 4). The upper of three bands formed gives ail oil (242 mg) of epoxide 2a which crystallizes from petroleum ether. The middle band contains unreacted la and the third one gives a trace of oil which has the same Rf value as 3a. 

A mixture of 13 (4.5 g, 10.5 mmol), PhHgCF, (4.0 g, 11.5 mmol) and Nal (5.2 g, 34.5 mmol) in benzene (50 mL) was heated at reflux under an atmosphere of N,. After 24 h the mixture was allowed to cool to rl, then filtered and evaporated to give a yellow oil. Tile oil was chromatographed over alumina (activity 1 benzene, then benzene/MeOH). The desired product 14 obtained from the column (TLC CHCI3. Rf 0.42) was rccrystallized from 95% EtOH to give 14 as white needles yield 1.6 g (32%) mp 132 133 C. 

Fig. 12. The phase shifter/mixer unit. For each of the four rf channels the TTL logic box contains two monoflops that may activate a mixer-driver through a triple OR gate. The third input of each OR gate accepts gate pulses from the pulse programmer whose lengths are specified by software on a raster of 100 ns. The two monoflops are fired by needles from the pulse programmer and allow finely adjusted rf pulses of duration 0.3-1.5 and 0.5-3 /us, respectively, to be generated.

A mixture of 6-chloro-9-(2,3,5-tri-0-acetyI-)3-D-ribofuranosyl)purin-2-amine (0.293 g, 0.685 mmol), anhyd, distilled pentyl nitrite (1.53 mL, 11.4 mmol), and dry CCL (30 niL) was heated at reflux temperature under Nj for 24 h. The solvent was then removed and the resulting residue taken Up in CH,Cl2 (3 mL) and chromatographed (preparative layer silica gel plates, developed twice with i-PrOH/CH CL, 1 50). Elution of the only significant band Rf = 0.29) with MeOH/CH CIj gives, after crystallization (EtOH), colorless needles yield 0.2 g (66%) rap 139 -t4t°C. 

Phenyl Phenylseleno Tellurium 0.79 g (5 mmol) of benzeneselenol are dissolved in 5ml of anhydrous tetrahydrofuran. Under nitrogen, 2.6 ml of 2 molar ethyl magnesium bromide (5.2 mmol) in diethyl ether are added, the mixture is heated under reflux for 2 h, cooled to 0°, and a solution of phenyl tellurium bromide, prepared from 1.02 g (2.5 mmol) of diphenyl ditellurium and 0.40 g (2.5 mmol) of bromine in tetrahydro-furan/benzene, is added. The reaction mixture is then warmed to 20°. stirred at 20" for 30 min, then 40 ml of low-boiling petroleum ether followed by aqueous ammonium chloride solution are added. The organic layer is separated, washed with saturated aqueous sodium chloride, dried with anhydrous magnesium sulfate, filtered, and evaporated. The residue (1.38g) is plaeed on a eolumn containing 120g of silica gel G, the product (Rf 0.60) is eluted with petroleum ether, the eluate is evaporated, and reddish needles are obtained yield 1.13 g (63%) m.p, 48° (petroleum ether). 

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