Tight Margins Research Articles

SU‐E‐T‐318: The Effect of Patient Positioning Errors On Target Coverage and Cochlear Dose in Stereotactic Radiosurgery Treatment of Acoustic Neuromas

Purpose:Setup errors on the order of millimeters may cause under‐dosing of targets and significant changes in dose to critical structures especially when planning with tight margins in stereotactic radiosurgery. This study evaluates the effects of these types of patient positioning uncertainties on planning target volume (PTV) coverage and cochlear dose for stereotactic treatments of acoustic neuromas.Methods:Twelve acoustic neuroma patient treatment plans were retrospectively evaluated in Brainlab iPlan RT Dose 4.1.3. All treatment beams were shaped by HDMLC from a Varian TX machine. Seven patients had planning margins of 2mm, five had 1–1.5mm. Six treatment plans were created for each patient simulating a 1mm setup error in six possible directions: anterior‐posterior, lateral, and superiorinferior. The arcs and HDMLC shapes were kept the same for each plan. Change in PTV coverage and mean dose to the cochlea was evaluated for each plan.Results:The average change in PTV coverage for the 72 simulated plans was −1.7% (range: −5 to +1.1%). The largest average change in coverage was observed for shifts in the patient's superior direction (−2.9%). The change in mean cochlear dose was highly dependent upon the direction of the shift. Shifts in the anterior and superior direction resulted in an average increase in dose of 13.5 and 3.8%, respectively, while shifts in the posterior and inferior direction resulted in an average decrease in dose of 17.9 and 10.2%. The average change in dose to the cochlea was 13.9% (range: 1.4 to 48.6%). No difference was observed based on the size of the planning margin.Conclusion:This study indicates that if the positioning uncertainty is kept within 1mm the setup errors may not result in significant under‐dosing of the acoustic neuroma target volumes. However, the change in mean cochlear dose is highly dependent upon the direction of the shift.

SU-E-T-57: Brain SRS Dose Variations Due to TrueBeam STx Isocenter Uncertainty

Purpose: Stereotactic Radiosurgery (SRS) is a valuable option for treatment of cranial melignancies. Well defined isocenter position (uncertainty <1 mm) of Varian TrueBeam STx, HD MLC, linac allows for tighter PTV margins(1mm). We report the effect of daily isocenter fluctuations established by Winston-Lutz test on target and cranial organ at risk (OAR) dosimetric parameters. Methods: 10 patient treatments were prepared using BrainLab iPlan softare. GTV and critical structures were contoured by neurosurgeon. A uniform margin of 1mm was used to expand GTV to PTV. Dose of 18 to 20Gy was prescribed to cover 99% of PTV volume using 3 or 4 dynamic arcs. Winston-Lutz test was performed daily to monitor linac isocenter stability, with 8 images (4 for various gantry angles, 4 for couch angles) analyzed by Standard Imaging PIPSpro software. Singular Value Decomposition method is used to determine the values for isocenter x, y and z coordinate offset, subsequently fed into treatment planning software to evaluate changes in dose coverage. Results: The average displacement (distance from lightfield center) of linac isocenter during 3 months of daily observations was 0.42±0.12mm (max observed displacement 0.656mm), with the average displacement of 0.27mm ptsuperior, 0.22mm pt-right, 0.04mm pt-posterior direction. With all plans normalized (PTV V100=99%) the daily isocenter walk resulted in average loss of V100PTV volume coverage of 4.2%. PTV Dmin dropped 8.9%, while GTV Dmin was 3.1% lower (108.1% planned) on average. Changes for PTV and GTV Dmean and Dmax parameters were less than 1%. Most of the cases showed insignificant changes in OAR dose coverage, with exception of vermis lesion where brainstem Dmax changed 2.4%. Conclusion: Daily monitoring of TrueBeam STx linac isocenter showed that GTV V100 remained at 100% of target volume in all cases. The effect of isocenter uncertainty could be further reduced by Brainlab ExacTrac Xray imaging.

Analysis of cervical pedicle with reconstructed computed tomography imaging in Korean population: feasibility and surgical anatomy.

We analyzed the anatomy of C3-C6 cervical pedicles with reconstructed computed tomography images. The objective of the study was to estimate the feasibility and to understand the surgical anatomy in order to reduce pedicle penetration. It is necessary to minimize pedicle penetration by anatomic analysis of cervical pedicles. Many studies have been conducted on cervical pedicle anatomy and cervical pedicle screw fixation, yet there are debates about the feasibility and surgical anatomy. Oblique axial and oblique sagittal images were reconstructed from a 1 mm cut computed tomography image. The pedicle transverse diameter, pedicle length, pedicle convergence angle (CA), and pedicle distance were measured on the oblique axial images. The pedicle sagittal diameter, pedicle sagittal angle (SA), and lateral mass index were measured on the oblique sagittal images. The multiple t test was used for statistical analysis. The averages of the pedicle transverse diameter ranged from 5.79 to 6.19 mm, the pedicle length ranged from 16.24 to 17.56 mm, the CA ranged from 47.49 to 48.86 degrees, the pedicle distance ranged from 22.67 to 24.93 mm, the SA ranged from -15.43 to 19.98 degrees, and the lateral mass index ranged from 0.64 to 1.25. Because of a tight safe margin, to reduce pedicle penetration the screw should be inserted along the pedicle. With regard to SA, C3 and C4 have a risk of upper end plate penetration. However, C5 and C6 have a risk of facet joint violation, which needs C4 and C5 inferior articular process removal for screw placement. The entry point at C3 and C4 is near one third of the lateral mass height from the posterior border of the superior articular process at the posterolateral border of the lateral mass. The entry point at C5 is near the posterolateral border of the superior articular process and that at C6 is superior to the posterior border of the superior articular process at a line medial to the posterolateral border of the C5 lateral mass. During insertion, not only CA but even SA should be considered carefully to reduce pedicle penetration.

Market Power and Prudence in Dynamic Banking: The Charter Value Theory Revisited

Conventional wisdom suggests that fiercer competition for deposits tends to undermine bank prudence. We build a dynamic model of banking and show that the traditional view neglects that banks, when facing tighter margins, also have less room to take reckless risks. As a result, heightened competition can entail more, rather than less, prudence. Yet, at the same time, it tends to make banks more fragile. This is because the direct, destabilizing effect of higher deposit rates outweighs the prudence effect, and, moreover, a substantial rise in competition can reduce banks’ incentive to build precautionary capital buffers. A key implication is that the effects of competition on bank risk-taking and, respectively, failure risk can move in opposite directions.

Change in prostate volume during extreme hypo-fractionation analysed with MRI

BackgroundHypo-fractionated external beam radiotherapy with narrow CTV-PTV margins is increasingly applied for prostate cancer. This demands a precise target definition and knowledge on target location and extension during treatment. It is unclear how increase in fraction size affects changes in prostate volume during treatment. Our aim was to study prostate volume changes during extreme hypo-fractionation (7 × 6.1 Gy) by using sequential MRIs.MethodsTwenty patients treated with extreme hypo-fractionation were recruited from an on-going prospective randomized phase III trial. An MRI scan was done before start of treatment, at mid treatment and at the end of radiotherapy. The prostate was delineated at each MRI and the volume and maximum extension in left-right, anterior-posterior and cranial-caudal directions were measured.ResultsThere was a significant increase in mean prostate volume (14%) at mid treatment as compared to baseline. The prostate volume remained enlarged (9%) at the end of radiotherapy. Prostate swelling was most pronounced in the anterior-posterior and cranial-caudal directions.ConclusionsExtreme hypo-fractionation induced a significant prostate swelling during treatment that was still present at the time of last treatment fraction. Our results indicate that prostate swelling is an important factor to take into account when applying treatment margins during short extreme hypo-fractionation, and that tight margins should be applied with caution.

Results of patient specific quality assurance for patients undergoing stereotactic ablative radiotherapy for lung lesions

Hypofractionated image guided radiotherapy of extracranial targets has become increasingly popular as a treatment modality for inoperable patients with one or more small lesions, often referred to as stereotactic ablative body radiotherapy (SABR). This report details the results of the physical quality assurance (QA) program used for the first 33 lung cancer SABR radiotherapy 3D conformal treatment plans in our centre. SABR involves one or few fractions of high radiation dose delivered in many small fields or arcs with tight margins to mobile targets often delivered through heterogeneous media with non-coplanar beams. We have conducted patient-specific QA similar to the more common intensity modulated radiotherapy QA with particular reference to motion management. Individual patient QA was performed in a Perspex phantom using point dose verification with an ionisation chamber and radiochromic film for verification of the dose distribution both with static and moving detectors to verify motion management strategies. While individual beams could vary by up to 7%, the total dose in the target was found to be within ±2% of the prescribed dose for all 33 plans. Film measurements showed qualitative and quantitative agreement between planned and measured isodose line shapes and dimensions. The QA process highlighted the need to account for couch transmission and demonstrated that the ITV construction was appropriate for the treatment technique used. QA is essential for complex radiotherapy deliveries such as SABR. We found individual patient QA helpful in setting up the technique and understanding potential weaknesses in SABR workflow, thus providing confidence in SABR delivery.

Green Train concept and interior design

In the Green Train research programme, the objective is to develop an attractive train concept in the form of a concept proposal based on economic assessments. Green Train is to be an attractive express train for both business and leisure-time travellers. High standards of comfort can be motivated by passengers’ willingness to pay. One fundamental idea is the wide carbody for services in Scandinavia to achieve lower total costs for train traffic than a carbody with a normal, quite narrow European continental profile. The trains are thereby made shorter and 2 + 3 seating arrangements are optimised for optimal comfort. Another principle is that the train must be designed to allow punctual station stops, also during periods of peak load. Boarding and alighting must take place within very tight margins, which means that doors, entrances and luggage racks must be in well-considered locations and correctly dimensioned.

Financer les PME en France : encore un « papier » !

Comment comprendre le financement des PME en France et en Europe ? Est-ce que tout va aussi bien que le disent les enquetes (faites par les banquiers eux-memes) ou pas si bien que cela si l’on prend les chiffres d’encours de credit (avec pourtant les taux d’interet les plus bas de la zone euro) et si l’on entend les plaintes des entreprises (PME, TPE, start-up...) ? Cote banque, les regles prudentielles, la surveillance bancaire europeenne (avec l’union bancaire en preparation) et la concurrence interbancaire rendent l’octroi de credit plus difficile, avec des marges plus faibles. En meme temps, le monde bancaire voit la montee de la titrisation et de la desintermediation permise pour les nouvelles technologies, souhaitee par des gestionnaires d’actifs et les assureurs, encouragee par les regulateurs et acceptee par les banques. Alors : un grand changement en cours, a un taux d’interet superieur ? Il faut d’ores et deja s’y preparer, tous.Classification JEL : G21, G23, G28, L25.

Low-cost Extension of Information Transparency Throughout the Product Life-cycle via Optical Identification and Quality Indication

Growing needs for data transparency are experienced in production networks, calling for individual product traceability and accurate information on actual state, quality or history of the individual product. Special challenges arise when “low-tech” network members, retailers or customers are likewise to be served during the product life-cycle, or in case low unit prices or tight profit margins require highly cost-efficient solutions. In line with the latter, the paper examines the integration of optical identifiers with optically perceptible quality indicators as an alternative to sensor-equipped RFID, including new designs not yet covered by implemented solutions. Following a separate survey of the two combined technological domains, possibilities of synthesis are examined from the point of view of optical codes, as their (semi)automatic acquisition and subsequent processing presents the key value added to most present-day indicator-only labels. As different targeted application ranges, e.g., supply chain members of different size, may require different pre-implementation surveys, the paper includes a collection of acceptance aspects for all of the identified user groups.

Dose variations caused by setup errors in intracranial stereotactic radiotherapy: A PRESAGE study

Stereotactic radiotherapy (SRT) requires tight margins around the tumor, thus producing a steep dose gradient between the tumor and the surrounding healthy tissue. Any setup errors might become clinically significant. To date, no study has been performed to evaluate the dosimetric variations caused by setup errors with a 3-dimensional dosimeter, the PRESAGE. This research aimed to evaluate the potential effect that setup errors have on the dose distribution of intracranial SRT. Computed tomography (CT) simulation of a CIRS radiosurgery head phantom was performed with 1.25-mm slice thickness. An ideal treatment plan was generated using Brainlab iPlan. A PRESAGE was made for every treatment with and without errors. A prescan using the optical CT scanner was carried out. Before treatment, the phantom was imaged using Brainlab ExacTrac. Actual radiotherapy treatments with and without errors were carried out with the Novalis treatment machine. Postscan was performed with an optical CT scanner to analyze the dose irradiation. The dose variation between treatments with and without errors was determined using a 3-dimensional gamma analysis. Errors are clinically insignificant when the passing ratio of the gamma analysis is 95% and above. Errors were clinically significant when the setup errors exceeded a 0.7-mm translation and a 0.5° rotation. The results showed that a 3-mm translation shift in the superior-inferior (SI), right-left (RL), and anterior-posterior (AP) directions and 2° couch rotation produced a passing ratio of 53.1%. Translational and rotational errors of 1.5mm and 1°, respectively, generated a passing ratio of 62.2%. Translation shift of 0.7mm in the directions of SI, RL, and AP and a 0.5° couch rotation produced a passing ratio of 96.2%. Preventing the occurrences of setup errors in intracranial SRT treatment is extremely important as errors greater than 0.7mm and 0.5° alter the dose distribution. The geometrical displacements affect dose delivery to the tumor and the surrounding normal tissues.

Causes of missed synchronous gastric epithelial neoplasms with endoscopic submucosal dissection: a multicenter study

Objective. Unlike surgery, endoscopic submucosal dissection (ESD) removes gastric epithelial neoplasms within a tight margin, leaving most normal tissue around the neoplasm intact, thus resulting in a high risk for missed synchronous gastric epithelial neoplasms (mSGENs). The purpose of this study was to evaluate the characteristics and risk factors of mSGENs (mSGENs) compared to simultaneously identified SGENs (siSGENs) in patients who underwent ESD. Materials and methods. The authors have retrospectively examined 312 SGENs from 275 patients treated with ESD at three hospitals in Korea between January 2004 and May 2011. The incidence and clinicopathological features of SGENs, mSGENs, and siSGENs were investigated. Any second epithelial neoplasm found within 1 year of the first ESD procedure was defined as an mSGEN and any neoplasm detected simultaneously with the first neoplasm was defined as a siSGEN. Results. The overall incidence of ESD patients with SGENs was 9.1% (275 of 3018 patients). Of the SGENs, 45.2% were siSGENs and 54.8% were mSGENs. Independent risk factors for mSGENs were adenoma as the first gastric lesion (Exp (B) = 2.154, 95% CI: 1.282–3.262) and duration of endoscopic examination before the first ESD (Exp (B) = 1.074, 95% CI: 1.001–1.141). The results suggest that 33% of mSGENs could have been identified during the endoscopic examination prior to ESD. Conclusion. Additional effort needs to be expended in identifying siSGENs, particularly prior to ESD for less serious adenomas. This should include sufficient time for endoscopic examination, prior to ESD, to ensure a thorough examination for siSGENs.

Continuous Threshold-Based Monitoring Versus Periodic Surveillance for Prostate Intrafraction Motion Management

Continuous Threshold-Based Monitoring Versus Periodic Surveillance for Prostate Intrafraction Motion Management

Creating Guidelines for Reactive and Prophylactic Enteral Feeding in Definitive (Chemo) IMRT for Head-and-Neck Cancer

course were consistent within 5% and 1.5% of the planned mean doses for PTvs and CTvs, respectively. For the tighter margin plans, the cumulative mean dose ratios were consistent within 4.3% and 2.3% of the planned mean doses for CTV2 and CTV3, respectively. No significant changes in D95 and D90 for the CTV2/3 cumulative doses in both reference and tighter margin plans were observed. While interfraction anatomical changes introduced minor variations in delivered target doses, improved normal structure sparing was observed in plan_0margin. The averaged planned cord maximum doses in Plan_0margin was 7.6% lower, and the parotid mean doses were 18.9% lower than plan_Ref. Similar dose variations of the delivered dose were seen for the reference and tighter margin plans. The delivered maximum and mean doses for the cord were 20% and 10% higher than the planned doses; a 3.6% higher cumulative mean dose for the parotids was also observed for the delivered dose than the planned doses in both plans. Conclusions: The GPU-based image framework enables real-time dose verification, accumulation and documentation. By imposing tighter PTV margins for level 2 and 3 targets for HN Varian Medical Systems, Inc. F. Honoraria; Accuray Inc., Siemens Medical Solutions, Viewray Inc. M. Steinberg: None. D. Low: None. S. Lee: None.

Minimal medium for optimal growth and lipid production of the microalgae Scenedesmus dimorphus

The culture of Scenedesmus dimorphus at the laboratory scale has often been in standard microalgae media, such as 3N‐Basal Bold medium (3N‐BB), which contains 15 different chemicals. Given the extremely tight profit margins of large‐scale production of biofuel from microalgae, it is important to identify the minimally sufficient quantities of nutrients necessary to maximize lipid productivity. The individual and interactive effects of six groupings of the components of 3N‐BB medium on growth rate, lipid content, and total biomass yield of S. dimorphus were determined. Trace metal and vitamin concentrations were reduced to 1/6 the level of 3N‐BB medium without adversely affecting growth rates and biomass concentration, while concentrations of CaCl2 and K2HPO4/KH2PO4 were reduced to 1/10 that of 3N‐BB without adversely affecting biomass and lipid concentrations. Both lipid productivity and lipid content were maximized at the lowest NaNO3 concentration (1/10 that in 3N‐BB) and independent of MgSO4 concentration, while the interaction of these two chemicals enhanced biomass concentration. © 2013 American Institute of Chemical Engineers Environ Prog, 32: 937–945, 2013

Laser Doppler imaging of skin microcirculation under fiber-reinforced composite framework of facial prosthesis

Objective. Glass-fiber reinforced composite has been suggested to be used as framework material in silicone elastomer facial prostheses. The glass-fiber reinforced framework makes it possible to make the margin of the prosthesis very tight, so that it will lean tightly against the skin even during facial expressions and jaw movements. The purpose of this study was to study how the compression of the glass-fiber reinforced framework would affect the microcirculation of the facial skin. Materials and methods. A face mask, with a compression pad corresponding to the outer margin of a glass fiber-reinforced composite framework beam of a facial prosthesis, was used to apply pressure on the facial skin of healthy volunteers. The skin blood flow during touch, light and moderate compression of the skin was measured by laser Doppler imaging technique. Results. None of the compressions had any marked effects on local skin blood flow. No significant differences between the blood flow of the compressed skin, compared to the baseline values, were found. Conclusions. The pressure applied to the skin by the tight margins of a facial prosthesis, fabricated with a framework of glass-fiber reinforced composite, does not remarkably alter the skin blood flow.

SU‐E‐T‐412: What Is the Benefit of Fiducial Marker Implantation for Pancreatic SBRT?

Purpose: Localization of pancreatic tumors during Stereotactic Body Radiation Therapy (SBRT) is difficult due to the poor soft‐tissue contrast of abdominal cone‐beam CT (CBCT). The purpose of this study was to measure the increased accuracy of pancreas localization when radiopaque fiducial markers (RFM) are implanted into the tumor and peri‐pancreatic tissue to facilitate a reduction of margins and escalation of dose. Methods: 15 CBCT scans were acquired of patients implanted with RFM enrolled in a prospective study involving SBRT for pancreatic cancer, receiving 30 Gy in five fractions with PTV margins of 3–5 mm. In order to quantify the effect of RFM, matching sets of markerless CBCT images were created. An automated tracking algorithm was developed to identify the location of markers in each CBCT projection, and 2D Gaussian fitting was used to filter these markers from the images. The 3D dataset was re‐reconstructed using these filtered projections, yielding a CBCT image of the same patient geometry with no RFM. These markerless images were aligned to the reference CT images using the anterior vertebral surface/aorta and the pancreatic stent as a guide. Using the RFM images as a gold standard, the differences in position represent the error in localization due to the lack of RFM information. Results: The automated algorithm successfully yielded CBCT images without RFM, star artifacts due to markers, or artifacts due to the filtration process. When the vertebral bodies and aorta were used for localization, the average error (compared to RFM images) was 15.0±7.4 mm. When a pancreatic stent was used for localization, the average error was 3.9±2.1 mm. Conclusion: Implantation of RFM increases localization accuracy by 4–15 mm compared to conventional techniques. Marker implantation is necessary when using tight margins and/or increasing tumor dose, and can be used to increase the therapeutic ratio.

TU‐E‐108‐06: Investigation of Prostate Deformation and Associated Dosimetric Implications in IMRT of the Prostate

Purpose: Prostate deformation is generally considered a secondary correction and is consequently often ignored in planning margin design. In this study we estimated prostate deformation and investigate the associated dosimetric impact on target coverage. Methods: A cohort of ten prostate cancer patients were retrospectively selected for the study, each with three fiducial markers implanted in the prostate. All CBCT images were registered to respective planning CT images using the Velocity AI deformable image registration (B‐spline‐based) software. For cases with accurate prostate registrations (defined by mean marker misalignments of &lt;1.5 mm), deformation‐vector‐fields (DVFs) of the prostate and seminal vesicles (SVs) were quantified using deformation‐volume histograms. For the case with the largest prostate deformation, target coverage degradation was analyzed in each of three treatment plans with PTV margins of 10, 5, and 3 mm. Results: Deformation of the prostate and SVs was most significant in the anterior‐posterior (AP) direction. Maximum prostate deformation of &gt; 10mm, 5mm, and 3mm occurred in 0.5%, 10.0%, and 68.5% of cases, respectively. Based on the deformation‐volume histograms, DVF magnitudes greater than 5mm and 3mm occurred in 2% and 27% of cases, respectively. In general, SV deformation was larger than that of the prostate. For the case with the largest prostate deformation, prostate coverage (D95%) was reduced by 0.5%, 9.0%, and 17.0% for 10mm, 5mm, and 3mm margin plans respectively. Conclusion: These preliminary results are suggestive that prostate deformation over a course of fractionated prostate radiotherapy may not be insignificant, and thereby that proper margin design may be necessary to account for deformation. A consequence of these results is that use of tight planning margins of (e.g. less than 5 mm) must be viewed with severe caution.

Large‐scale production of diesel‐like biofuels – process design as an inherent part of microorganism development

Industrial biotechnology is playing an important role in the transition to a bio-based economy. Currently, however, industrial implementation is still modest, despite the advances made in microorganism development. Given that the fuels and commodity chemicals sectors are characterized by tight economic margins, we propose to address overall process design and efficiency at the start of bioprocess development. While current microorganism development is targeted at product formation and product yield, addressing process design at the start of bioprocess development means that microorganism selection can also be extended to other critical targets for process technology and process scale implementation, such as enhancing cell separation or increasing cell robustness at operating conditions that favor the overall process. In this paper we follow this approach for the microbial production of diesel-like biofuels. We review current microbial routes with both oleaginous and engineered microorganisms. For the routes leading to extracellular production, we identify the process conditions for large scale operation. The process conditions identified are finally translated to microorganism development targets. We show that microorganism development should be directed at anaerobic production, increasing robustness at extreme process conditions and tailoring cell surface properties. All the same time, novel process configurations integrating fermentation and product recovery, cell reuse and low-cost technologies for product separation are mandatory. This review provides a state-of-the-art summary of the latest challenges in large-scale production of diesel-like biofuels.

Radiotherapy with rectangular fields is associated with fewer clinical failures than conformal fields in the high-risk prostate cancer subgroup: Results from a randomized trial

ObjectiveHigh-risk prostate cancer patients are at risk for subclinical disease and micro-metastasis at the time of treatment. Nowadays, tight margins reduce dose to periprostatic areas compared to earlier techniques. We investigated whether rectangular fields were associated with fewer failures compared to conformal fields (with lower extraprostatic dose). MethodsWe selected 164 high-risk patients from the trial population of 266 T1-T4N0M0 patients, randomized between rectangular (n=79) and conformal fields (n=85). Prescribed dose was 66Gy to the prostate and seminal vesicles plus 15mm margin. We compared clinical failure rates (in- and excluding local failures), between both arms. Dose differences around the prostate were calculated based on an inter-patient mapping method. ResultsMedian follow-up was 34months. There were 9 clinical failures in the rectangular arm versus 24 in the conformal arm (p=0.012). Number of failures outside the prostate was 7 and 19, respectively (p=0.025). We observed average dose differences of 5–35Gy between the arms in the regions around the prostate. ConclusionsWe found a significantly lower risk of early tumor progression for patients treated with rectangular fields. Treatment failure can probably in part be prevented by irradiation of areas suspected of subclinical disease in high-risk prostate cancer.

Integrating FPWD Measurements With Managed-Pressure Drilling

This article, written by Senior Technology Editor Dennis Denney, contains highlights of paper SPE 156888, ’Demonstrating the Value of Integrating FPWD Measurements With Managed-Pressure Drilling To Drill Narrow Mud-Weight Windows Safely in an HP/HT Environment,’ by L. Umar, SPE, I. Azian, N. Azree, and A.R.M. Ali, Petronas, and A. Waguih, SPE, F. Rojas, SPE, S. Fey, SPE, B. Subroto, SPE, B. Dow, and G. Garcia, SPE, Schlumberger, prepared for the 2012 SPE/IADC Managed Pressure Drilling and Underbalanced Operations Conference and Exhibition, Milan, Italy, 20-21 March. The paper has not been peer reviewed. A high-pressure/high-temperature (HP/HT) exploration field in Block PM on the northern side of the Malay basin, Malaysia, is notorious for a steeply rising pressure ramp, narrow drilling-operation window (only 0.5 to 0.6 lbm/gal in the 14¾ and 9½-in. sections), and interbedded sand/coal and shale formations. Block PM is still in the exploration-and-appraisal stage; therefore, petrophysical information is limited. Well SBD-2 was the second attempt to reach and cross the F and H sands. Formation-pressure-while-drilling (FPWD) and managed-pressure-drilling (MPD) technologies were applied to drill this well. FPWD provided a direct pressure measurement while drilling to set the lower boundary, and formation-integrity tests (FITs) with MPD provided the upper boundary. Introduction The SB field has a relatively high temperature gradient and abnormal-pressure regimes. Challenges in this HP/HT environment include a reduced kick tolerance, narrow drilling margin, higher drilling-fluid densities, high temperature (limitations in formation-evaluation equipment), wellbore ballooning, and availability of personnel experienced in HP/HT drilling. Well SBD-2 had been considered undrillable because of its very narrow safe-drilling margin. The previous attempt to drill through the F and H reservoir sands, Well SBD-1, suffered an influx from the formation that exceeded kick tolerance and compromised the fracture gradient, resulting in total fluid losses. Well SBD-1 failed to reach total depth (TD) despite the use of an MPD system—200 m shy of the geologic target. Well SBD-2 was drilled only 50 m away from Well SBD-1. Given the close proximity, there were offset pressure data for planning Well SBD-2 down to a depth of X240 m, but beyond this depth it would be exploratory drilling. Given the uncertainties that would be encountered drilling past X240 m, the engineering team sought best practices and technologies that would provide the greatest chance of success drilling into such a tight margin at high temperature. The 8½×9½-in. reservoir section would use an automated MPD system to mitigate drilling risk complemented by an FPWD tool in the drilling bottomhole assembly (BHA) to provide direct pressure measurements. The MPD sys-tem was used for early kick detection (EKD), FITs, dynamic flow checks, and constant-bottomhole-pressure (CBHP) control for a safe mud-weight window that was expected to be less than 0.9 lbm/gal. The high mud weight needed to drill this formation resulted in a high equivalent circulating density (ECD) throughout the section, requiring the MPD system to maintain a static condition between 0.2 and 0.4 lbm/gal. The FPWD tool would provide pressure data to establish the lower limit for the MPD fingerprint tests, and to serve as calibration points for the pore-pressure model. The objective in this 8½×9½-in. section was to maintain overbalance in the narrow window between pore pressure and fracture gradient. These tight drilling margins required use of an automated MPD system with software capable of predicting temperature effects and annular-pressure behavior during any well-control situation.