IVD TIMING test 1 test at 1 fraction 2 test at 2 fraction 3 test at 3 fraction 4 test during next week 5 test during next week 6 test during next week

IVD TIMING test 1 test at 1 fraction 2 test at 2 fraction 3 test at 3 fraction 4 test during next week 5 test during next week 6 test during next week

Causes of discrepancies due to inadequate quality controls: 1.Patient Set-up 2.Occasional morphological changes 3.Systematic morphological changes 4.Attenuators on the beams (patient supports) 5.TPS implementation 6.CT number implementation 7.Laser misalignments 8.Output dose variations 9.Inaccurate MLC positions

Some frequent warnings obtained in the italian Centers participating at the DISO project are here reported showing the 2 tests

Brest irradiation, at the 3 test an incorrect setup, well evident by the green signal profile,the dose at the isocenter point increase (R= 1.062) off tolerance and. R=1.062

.also the analysis shows the change of setup of about 1.5 cm and the P <1 = 72.6% out of tolerance level, the red area shows an over dosage

ABDOMEN of patient setup, the second test with R = 0.906 is off tolerance and..

..the change of setup is more evident by the gamma analysis where the P <1 = 47.8% Once corrected the setup the R ratios and the P <1 values were within the pass-rate.

Attenuating support not included in the TPS computation, R=0.906 R=0.906

Attenuating support now included in the TPS computation R=0.982 R=0.982

Brest tumor. All the R tests are within the tolerance level of 5% All but.. R= 1.001

.the presence of the couch border on the beam is detected by the analysis that shows a P <1 =80.5% the under dosages can be responsible of recurrences.

the program can estimate an under dosage equal to 8%. 8%.

Pelvic tumor. The R ratios are within the tolerance level of 5% even if the beam at 180 intercept a couch support but..

.the presence of coch -attenuator on the beam is well detected by the analysis that shows a P <1 = 25%. these under dosages (about 10%) can be responsible of recurrences.

in this case dose variations of 10%. are in large area of the field

. Pelvic tumor gas pockets in the TC scan used for planning. The R ratios are within the tolerance but the profiles are irregular, and.

the -analysis P <1 = 75.9%, the signal profiles show dose variations of 10%. In a large area

Pelvic tumor. Large gas pocket in the TC scan used for planning. The R ratios are within aa the tolerance but the profiles are irregular, and.

...the -analysis supplied a P <1 = 76.8%, under dosages up to 15% can be estimated by the profiles, and they are responsible of recurrences.

Prostate TC-scan with small distended rectum, the occasional presence of gas-pocket at the 3th fraction, with R values up to 1.094. Moreover a couch attenuator is present in 1/3 of tha field (under dosage up to 10%)

..the -analysis supplied a P <1 = 93.0% and the dose variations estimated by the profiles are about 10%. The couch-attenuators are always present

Prostate TC-scan without gas pockets, the occasional presence of gas- pocket is during the second fraction, where resulted R= 1.07, but... R= 1.071

..the -analysis supplied a P <1 = 95.5% and the dose delivery can be accepted

Presence of a gas pocket in rectum on the CT-scan used for the planning. During the 1 and 3 tests the rectum is distended, and R ratios are within the tolerance, but at the 2 test the pocket size decreased and R= 0.907 i.e. a underdosage at the tumor of 10%. R= 0.907

...even if the -analysis P <1 = 95.5%, the signal profiles confirmed dose variations of 10% in small areas, but the couch-attenuators are always present

. The distended rectum is stable enough in the sections even if the R values show an under dosage

.even if the -analysis P <1 = 90.5 %, is within the tolerance level dose variations u p to 10%. are due to the presence of a couch attenuator

The presence of a couch attenuator is half field means a large underdosage and the the isocenter dose is over estimated due to a large gas poket.

In the recent years 20.000 IVD tests have been obtained in 8 Italian Centers participating at the DISO Project. Those results are similar to that reported here obtained using the BEST SOFTDISO-3DCRT for 281 patients treated since January 2014 with 3D CRT techniques.

1500 1250 R P <1 R ratio for single test (5603) 89% of tests within 5% 5000 4500 4000 1000 750 Mean R ratio for patient (281) 100% of tests within 5% 3500 3000 2500 2000 Gamma analysis for 5241 test 87% of tests show Pg>90% 500 1500 250 1000 500 0 0.84 0.88 0.92 0.96 1.00 1.04 1.08 1.12 1.16 0 55 65 75 85 95

In conclusion even if 11% of the R tests and 13% of P <1, tests were out-tolerance levels, once removed the causes of the dose discrepancies for each patient the mean value R ratio was within 5% and P <1 90%

SUMMARIZING THE ROLE OF INDEXES R and P <1 We observed cases where R=1.02 (within the tolerance level) and P <1 = 80.5% (outside tolerance level) Attenuator off-axis b) and cases where R=1.08 (outside the tolerance level) and P <1 = 95.5% (within tolerance level) Gas pocket on-axis